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Tracking solvents in the skin through atomically resolved measurements of molecular mobility in intact stratum corneum. Proc Natl Acad Sci U S A 2016; 114:E112-E121. [PMID: 28028209 DOI: 10.1073/pnas.1608739114] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Solvents are commonly used in pharmaceutical and cosmetic formulations and sanitary products and cleansers. The uptake of solvent into the skin may change the molecular organization of skin lipids and proteins, which may in turn alter the protective skin barrier function. We herein examine the molecular effects of 10 different solvents on the outermost layer of skin, the stratum corneum (SC), using polarization transfer solid-state NMR on natural abundance 13C in intact SC. With this approach it is possible to characterize the molecular dynamics of solvent molecules when present inside intact SC and to simultaneously monitor the effects caused by the added solvent on SC lipids and protein components. All solvents investigated cause an increased fluidity of SC lipids, with the most prominent effects shown for the apolar hydrocarbon solvents and 2-propanol. However, no solvent other than water shows the ability to fluidize amino acids in the keratin filaments. The solvent molecules themselves show reduced molecular mobility when incorporated in the SC matrix. Changes in the molecular properties of the SC, and in particular alternation in the balance between solid and fluid SC components, may have significant influences on the macroscopic SC barrier properties as well as mechanical properties of the skin. Deepened understanding of molecular effects of foreign compounds in SC fluidity can therefore have strong impact on the development of skin products in pharmaceutical, cosmetic, and sanitary applications.
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102
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Opálka L, Kováčik A, Maixner J, Vávrová K. Omega-O-Acylceramides in Skin Lipid Membranes: Effects of Concentration, Sphingoid Base, and Model Complexity on Microstructure and Permeability. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2016; 32:12894-12904. [PMID: 27934529 DOI: 10.1021/acs.langmuir.6b03082] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Omega-O-acylceramides (acylCer), a subclass of sphingolipids with an ultralong N-acyl chain (from 20 to 38 carbons, most usually 30 and 32 carbons), are crucial components of the skin permeability barrier. AcylCer are involved in the formation of the long periodicity lamellar phase (LPP, 12-13 nm), which is essential for preventing water loss from the body. Lower levels of acylCer and LPP accompany skin diseases, such as atopic dermatitis, lamellar ichthyosis, and psoriasis. We studied how the concentration and structure of acylCer influence the organization and permeability barrier properties of model lipid membranes. For simple model membranes composed of the sphingosine-containing acylCer (EOS), N-lignoceroyl sphingosine, lignoceric acid, cholesterol (Chol), and cholesteryl sulfate (CholS), the LPP formed at 10% Cer EOS (of the total Cer) and the short periodicity phase disappeared at 30% Cer EOS. Surprisingly, membranes with the LPP had higher permeabilities than the control membrane without acylCer. In the complex models consisting of acylCer (EOS, phytosphingosine EOP, dihydrosphingosine EOdS, or their mixture; at 10% of the total Cer), a six-component Cer mixture, a free fatty acid mixture, cholesterol (Chol), and cholesteryl sulfate (CholS), acylCer decreased the membrane permeability to model permeants (with the strongest effects for acylCer EOP and EOdS) when compared with the permeability of the control membrane without acylCer. However, in the complex model, only a mixture of acylCer EOS, EOdS, and EOP and not the individual acylCer formed both the LPP and orthorhombic chain packing at the 10% level. Thus, the relationships between acylCer, LPP formation, and permeability barrier function are not trivial. Lipid heterogeneity is essential-only the most complex model with nine Cer subclasses mimicked both the organization and permeability of stratum corneum lipid membranes.
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Affiliation(s)
- Lukáš Opálka
- Faculty of Pharmacy, Charles University , Hradec Králové 500 05, Czech Republic
| | - Andrej Kováčik
- Faculty of Pharmacy, Charles University , Hradec Králové 500 05, Czech Republic
| | - Jaroslav Maixner
- University of Chemistry and Technology Prague , Prague 166 28, Czech Republic
| | - Kateřina Vávrová
- Faculty of Pharmacy, Charles University , Hradec Králové 500 05, Czech Republic
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103
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Gupta R, Dwadasi BS, Rai B. Molecular Dynamics Simulation of Skin Lipids: Effect of Ceramide Chain Lengths on Bilayer Properties. J Phys Chem B 2016; 120:12536-12546. [DOI: 10.1021/acs.jpcb.6b08059] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Affiliation(s)
- Rakesh Gupta
- Engineering & Physical Sciences, TCS Research, Tata Research Development and Design Centre, Tata Consultancy Services, 54B, Hadapsar Industrial Estate, Pune 411013, India
| | - Balarama Sridhar Dwadasi
- Engineering & Physical Sciences, TCS Research, Tata Research Development and Design Centre, Tata Consultancy Services, 54B, Hadapsar Industrial Estate, Pune 411013, India
| | - Beena Rai
- Engineering & Physical Sciences, TCS Research, Tata Research Development and Design Centre, Tata Consultancy Services, 54B, Hadapsar Industrial Estate, Pune 411013, India
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104
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Vidlářová L, Hanuš J, Veselý M, Ulbrich P, Štěpánek F, Zbytovská J. Effect of lipid nanoparticle formulations on skin delivery of a lipophilic substance. Eur J Pharm Biopharm 2016; 108:289-296. [DOI: 10.1016/j.ejpb.2016.07.016] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2016] [Revised: 05/28/2016] [Accepted: 07/15/2016] [Indexed: 12/11/2022]
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105
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The isolated perfused human skin flap model: A missing link in skin penetration studies? Eur J Pharm Sci 2016; 96:334-341. [PMID: 27720898 DOI: 10.1016/j.ejps.2016.10.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2016] [Revised: 09/03/2016] [Accepted: 10/03/2016] [Indexed: 11/22/2022]
Abstract
Development of effective (trans)dermal drug delivery systems requires reliable skin models to evaluate skin drug penetration. The isolated perfused human skin flap remains metabolically active tissue for up to 6h during in vitro perfusion. We introduce the isolated perfused human skin flap as a close-to-in vivo skin penetration model. To validate the model's ability to evaluate skin drug penetration the solutions of a hydrophilic (calcein) and a lipophilic (rhodamine) fluorescence marker were applied. The skin flaps were perfused with modified Krebs-Henseleit buffer (pH7.4). Infrared technology was used to monitor perfusion and to select a well-perfused skin area for administration of the markers. Flap perfusion and physiological parameters were maintained constant during the 6h experiments and the amount of markers in the perfusate was determined. Calcein was detected in the perfusate, whereas rhodamine was not detectable. Confocal images of skin cross-sections shoved that calcein was uniformly distributed through the skin, whereas rhodamine accumulated in the stratum corneum. For comparison, the penetration of both markers was evaluated on ex vivo human skin, pig skin and cellophane membrane. The proposed perfused flap model enabled us to distinguish between the penetrations of the two markers and could be a promising close-to-in vivo tool in skin penetration studies and optimization of formulations destined for skin administration.
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106
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The effects of polar excipients transcutol and dexpanthenol on molecular mobility, permeability, and electrical impedance of the skin barrier. J Colloid Interface Sci 2016; 479:207-220. [DOI: 10.1016/j.jcis.2016.06.054] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2016] [Revised: 06/21/2016] [Accepted: 06/21/2016] [Indexed: 11/16/2022]
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107
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Gupta R, Sridhar DB, Rai B. Molecular Dynamics Simulation Study of Permeation of Molecules through Skin Lipid Bilayer. J Phys Chem B 2016; 120:8987-96. [PMID: 27518707 DOI: 10.1021/acs.jpcb.6b05451] [Citation(s) in RCA: 70] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Stratum Corneum (SC), the outermost layer of skin, is mainly responsible for skin's barrier function. The complex lipid matrix of SC determines these barrier properties. In this study, the lipid matrix is modeled as an equimolar mixture of ceramide (CER), cholesterol (CHOL), and free fatty acid (FFA). The permeation of water, oxygen, ethanol, acetic acid, urea, butanol, benzene, dimethyl sulfoxide (DMSO), toluene, phenol, styrene, and ethylbenzene across this layer is studied using a constrained MD simulations technique. Several long constrained simulations are performed at a skin temperature of 310 K under NPT conditions. The free energy profiles and diffusion coefficients along the bilayer normal have been calculated for each molecule. Permeability coefficients are also calculated and compared with experimental data. The main resistance for the permeation of hydrophilic and hydrophobic permeants has been found to be in the interior of the lipid bilayer and near the lipid-water interface, respectively. The obtained permeability is found to be a few orders of magnitude higher than experimental values for hydrophilic molecules while for hydrophobic molecules more discrepancy was observed. Overall, the qualitative ranking is consistent with the experiments.
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Affiliation(s)
- Rakesh Gupta
- Physical Science Research Area, TCS Research, Tata Research Development and Design Centre, Tata Consultancy Services , 54B, Hadapsar Industrial Estate, Pune - 411013, India
| | - D B Sridhar
- Physical Science Research Area, TCS Research, Tata Research Development and Design Centre, Tata Consultancy Services , 54B, Hadapsar Industrial Estate, Pune - 411013, India
| | - Beena Rai
- Physical Science Research Area, TCS Research, Tata Research Development and Design Centre, Tata Consultancy Services , 54B, Hadapsar Industrial Estate, Pune - 411013, India
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108
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Das C, Olmsted PD. The physics of stratum corneum lipid membranes. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2016; 374:rsta.2015.0126. [PMID: 27298438 PMCID: PMC4920276 DOI: 10.1098/rsta.2015.0126] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 04/15/2016] [Indexed: 05/22/2023]
Abstract
The stratum corneum (SC), the outermost layer of skin, comprises rigid corneocytes (keratin-filled dead cells) in a specialized lipid matrix. The continuous lipid matrix provides the main barrier against uncontrolled water loss and invasion of external pathogens. Unlike all other biological lipid membranes (such as intracellular organelles and plasma membranes), molecules in the SC lipid matrix show small hydrophilic groups and large variability in the length of the alkyl tails and in the numbers and positions of groups that are capable of forming hydrogen bonds. Molecular simulations provide a route for systematically probing the effects of each of these differences separately. In this article, we present the results from atomistic molecular dynamics of selected lipid bilayers and multi-layers to probe the effect of these polydispersities. We address the nature of the tail packing in the gel-like phase, the hydrogen bond network among head groups, the bending moduli expected for leaflets comprising SC lipids and the conformation of very long ceramide lipids in multi-bilayer lipid assemblies.This article is part of the themed issue 'Soft interfacial materials: from fundamentals to formulation'.
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Affiliation(s)
- Chinmay Das
- School of Mathematics, University of Leeds, Leeds LS2 9JT, UK
| | - Peter D Olmsted
- Department of Physics and Institute for Soft Matter Synthesis and Metrology, Georgetown University, Washington, DC 20057, USA
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109
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Di Meo F, Fabre G, Berka K, Ossman T, Chantemargue B, Paloncýová M, Marquet P, Otyepka M, Trouillas P. In silico pharmacology: Drug membrane partitioning and crossing. Pharmacol Res 2016; 111:471-486. [PMID: 27378566 DOI: 10.1016/j.phrs.2016.06.030] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/20/2016] [Revised: 06/30/2016] [Accepted: 06/30/2016] [Indexed: 01/09/2023]
Abstract
Over the past decade, molecular dynamics (MD) simulations have become particularly powerful to rationalize drug insertion and partitioning in lipid bilayers. MD simulations efficiently support experimental evidences, with a comprehensive understanding of molecular interactions driving insertion and crossing. Prediction of drug partitioning is discussed with respect to drug families (anesthetics; β-blockers; non-steroidal anti-inflammatory drugs; antioxidants; antiviral drugs; antimicrobial peptides). To accurately evaluate passive permeation coefficients turned out to be a complex theoretical challenge; however the recent methodological developments based on biased MD simulations are particularly promising. Particular attention is paid to membrane composition (e.g., presence of cholesterol), which influences drug partitioning and permeation. Recent studies concerning in silico models of membrane proteins involved in drug transport (influx and efflux) are also reported here. These studies have allowed gaining insight in drug efflux by, e.g., ABC transporters at an atomic resolution, explicitly accounting for the mandatory forces induced by the surrounded lipid bilayer. Large-scale conformational changes were thoroughly analyzed.
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Affiliation(s)
- Florent Di Meo
- INSERM UMR 850, Univ. Limoges, Faculty of Pharmacy, 2 rue du Dr Marcland, F-87025, Limoges, France
| | - Gabin Fabre
- LCSN, Univ. Limoges, Faculty of Pharmacy, 2 rue du Dr Marcland, F-87025, Limoges, France
| | - Karel Berka
- Regional Centre for Advanced Technologies and Materials, Department of Physical Chemistry, Faculty of Science, Palacky̿ University, Olomouc, Czech Republic
| | - Tahani Ossman
- INSERM UMR 850, Univ. Limoges, Faculty of Pharmacy, 2 rue du Dr Marcland, F-87025, Limoges, France
| | - Benjamin Chantemargue
- INSERM UMR 850, Univ. Limoges, Faculty of Pharmacy, 2 rue du Dr Marcland, F-87025, Limoges, France; Regional Centre for Advanced Technologies and Materials, Department of Physical Chemistry, Faculty of Science, Palacky̿ University, Olomouc, Czech Republic
| | - Markéta Paloncýová
- Regional Centre for Advanced Technologies and Materials, Department of Physical Chemistry, Faculty of Science, Palacky̿ University, Olomouc, Czech Republic
| | - Pierre Marquet
- INSERM UMR 850, Univ. Limoges, Faculty of Pharmacy, 2 rue du Dr Marcland, F-87025, Limoges, France
| | - Michal Otyepka
- Regional Centre for Advanced Technologies and Materials, Department of Physical Chemistry, Faculty of Science, Palacky̿ University, Olomouc, Czech Republic
| | - Patrick Trouillas
- INSERM UMR 850, Univ. Limoges, Faculty of Pharmacy, 2 rue du Dr Marcland, F-87025, Limoges, France; Regional Centre for Advanced Technologies and Materials, Department of Physical Chemistry, Faculty of Science, Palacky̿ University, Olomouc, Czech Republic.
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110
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Egawa G, Kabashima K. Multifactorial skin barrier deficiency and atopic dermatitis: Essential topics to prevent the atopic march. J Allergy Clin Immunol 2016; 138:350-358.e1. [PMID: 27497277 DOI: 10.1016/j.jaci.2016.06.002] [Citation(s) in RCA: 145] [Impact Index Per Article: 18.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2016] [Revised: 06/08/2016] [Accepted: 06/13/2016] [Indexed: 10/21/2022]
Abstract
Atopic dermatitis (AD) is the most common inflammatory skin disease in the industrialized world and has multiple causes. Over the past decade, data from both experimental models and patients have highlighted the primary pathogenic role of skin barrier deficiency in patients with AD. Increased access of environmental agents into the skin results in chronic inflammation and contributes to the systemic "atopic (allergic) march." In addition, persistent skin inflammation further attenuates skin barrier function, resulting in a positive feedback loop between the skin epithelium and the immune system that drives pathology. Understanding the mechanisms of skin barrier maintenance is essential for improving management of AD and limiting downstream atopic manifestations. In this article we review the latest developments in our understanding of the pathomechanisms of skin barrier deficiency, with a particular focus on the formation of the stratum corneum, the outermost layer of the skin, which contributes significantly to skin barrier function.
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Affiliation(s)
- Gyohei Egawa
- Department of Dermatology, Kyoto University Graduate School of Medicine, Kyoto, Japan.
| | - Kenji Kabashima
- Department of Dermatology, Kyoto University Graduate School of Medicine, Kyoto, Japan; Singapore Immunology Network (SIgN) and Institute of Medical Biology, Agency for Science, Technology and Research (A*STAR), Biopolis, Singapore; PRESTO, Japan Science and Technology Agency, Saitama, Japan.
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111
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Mohyeldin SM, Mehanna MM, Elgindy NA. Superiority of liquid crystalline cubic nanocarriers as hormonal transdermal vehicle: comparative human skin permeation-supported evidence. Expert Opin Drug Deliv 2016; 13:1049-64. [PMID: 27167758 DOI: 10.1080/17425247.2016.1182490] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
OBJECTIVES The aim of this investigation was to explore the feasibility of various nanocarriers to enhance progesterone penetration via the human abdominal skin. METHODS Four progesterone-loaded nanocarriers; cubosomes, nanoliposomes, nanoemulsions and nanomicelles were formulated and characterized regarding particle size, zeta potential, % drug encapsulation and in vitro release. Structural elucidation of each nanoplatform was performed using transmission electron microscopy. Ex vivo skin permeation, deposition ability and histopathological examination were evaluated using Franz diffusion cells. RESULTS Each nanocarrier was fabricated with a negative surface, nanometric size (≤ 270 nm), narrow size distribution and reasonable encapsulation efficiency. In vitro progesterone release showed a sustained release pattern for 24 h following a non-Fickian transport diffusion mechanism. All nanocarriers exhibited higher transdermal flux relative to free progesterone. Cubosomes revealed a higher skin penetration with transdermal steady flux of 48.57.10(-2) ± 0.7 µg/cm(2) h. Nanoliposomes offered a higher percentage of skin progesterone deposition compared to other nanocarriers. Based on the histopathological examination, cubosomes and nanoliposomes were found to be biocompatible for transdermal application. Confocal laser scanning microscopy confirmed the ability of fluoro-labeled cubosomes to penetrate through the whole skin layers. CONCLUSION The elaborated cubosomes proved to be a promising non-invasive nanocarrier for transdermal hormonal delivery.
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Affiliation(s)
- Salma M Mohyeldin
- a Department of Industrial Pharmacy, Faculty of Pharmacy , Alexandria University , Alexandria , Egypt
| | - Mohammed M Mehanna
- a Department of Industrial Pharmacy, Faculty of Pharmacy , Alexandria University , Alexandria , Egypt
| | - Nazik A Elgindy
- a Department of Industrial Pharmacy, Faculty of Pharmacy , Alexandria University , Alexandria , Egypt
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112
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Mueller J, Schroeter A, Steitz R, Trapp M, Neubert RHH. Preparation of a New Oligolamellar Stratum Corneum Lipid Model. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2016; 32:4673-4680. [PMID: 27058649 DOI: 10.1021/acs.langmuir.6b00655] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
In this study, we present a preparation method for a new stratum corneum (SC) model system, which is closer to natural SC than the commonly used multilayer models. The complex setup of the native SC lipid matrix was mimicked by a ternary lipid mixture of ceramide [AP], cholesterol, and stearic acid. A spin coating procedure was applied to realize oligo-layered samples. The influence of lipid concentration, rotation speed, polyethylenimine, methanol content, cholesterol fraction, and annealing on the molecular arrangement of the new SC model was investigated by X-ray reflectivity measurements. The new oligo-SC model is closer to native SC in the total number of lipid membranes found between corneocytes. The reduction in thickness provides the opportunity to study the effects of drugs and/or hydrophilic penetration enhancers on the structure of SC in full detail by X-ray or neutron reflectivity. In addition, the oligo-lamellar systems allows one to infer not only the lamellar spacing, but also the total thickness of the oligo-SC model and changes thereof can be monitored. This improvement is most helpful for the understanding of transdermal drug administration on the nanoscale. The results are compared to the commonly used multilamellar lipid model systems and advantages and disadvantages of both models are discussed.
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Affiliation(s)
- Josefin Mueller
- Institute of Pharmacy, Martin Luther University , Wolfgang-Langenbeck-Straße 4, 06120 Halle, Germany
| | - Annett Schroeter
- Institute of Pharmacy, Martin Luther University , Wolfgang-Langenbeck-Straße 4, 06120 Halle, Germany
| | - Roland Steitz
- Institute of Soft Matter and Functional Materials, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH , Hahn-Meitner-Platz 1, 14109 Berlin, Germany
| | - Marcus Trapp
- Institute of Soft Matter and Functional Materials, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH , Hahn-Meitner-Platz 1, 14109 Berlin, Germany
| | - Reinhard H H Neubert
- Institute of Pharmacy, Martin Luther University , Wolfgang-Langenbeck-Straße 4, 06120 Halle, Germany
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113
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Stratum corneum lipid matrix: Location of acyl ceramide and cholesterol in the unit cell of the long periodicity phase. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2016; 1858:1926-34. [PMID: 27169629 DOI: 10.1016/j.bbamem.2016.05.006] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2016] [Accepted: 05/05/2016] [Indexed: 01/04/2023]
Abstract
The extracellular lipid matrix in the skin's outermost layer, the stratum corneum, is crucial for the skin barrier. The matrix is composed of ceramides (CERs), cholesterol (CHOL) and free fatty acids (FFAs) and involves two lamellar phases: the short periodicity phase (SPP) and the long periodicity phase (LPP). To understand the skin barrier thoroughly, information about the molecular arrangement in the unit cell of these lamellar phases is paramount. Previously we examined the molecular arrangement in the unit cell of the SPP. Furthermore X-ray and neutron diffraction revealed a trilayer arrangement of lipids within the unit cell of the LPP [D. Groen et al., Biophysical Journal, 97, 2242-2249, 2009]. In the present study, we used neutron diffraction to obtain more details about the location of lipid (sub)classes in the unit cell of the LPP. The diffraction pattern revealed at least 8 diffraction orders of the LPP with a repeating unit of 129.6±0.5Å. To determine the location of lipid sub(classes) in the unit cell, samples were examined with either only protiated lipids or selectively deuterated lipids. The diffraction data obtained by means of D2O/H2O contrast variation together with a gradual replacement of one particular CER, the acyl CER, by its partly deuterated counterpart, were used to construct the scattering length density profiles. The acyl chain of the acyl CER subclass is located at a position of ~21.4±0.2Å from the unit cell centre of the LPP. The position and orientation of CHOL in the LPP unit cell were determined using tail and head-group deuterated forms of the sterol. CHOL is located with its head-group positioned ~26±0.2Å from the unit cell centre. This allows the formation of a hydrogen bond with the ester group of the acyl CER located in close proximity. Based on the positions of the deuterated moieties of the acyl CER, CHOL and the previously determined location of two other lipid subclasses [E.H. Mojumdar et al., Biophysical Journal, 108, 2670-2679, 2015], a molecular model is proposed for the unit cell of the LPP. In this model CHOL is located in the two outer layers of the LPP, while CER EOS is linking the two outer layers with the central lipid layers. Finally the two other lipid subclasses are predominantly located in the central layer of the LPP.
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114
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Chemical penetration enhancers in stratum corneum - Relation between molecular effects and barrier function. J Control Release 2016; 232:175-87. [PMID: 27108613 DOI: 10.1016/j.jconrel.2016.04.030] [Citation(s) in RCA: 124] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2015] [Revised: 04/14/2016] [Accepted: 04/20/2016] [Indexed: 01/28/2023]
Abstract
Skin is attractive for drug therapy because it offers an easily accessible route without first-pass metabolism. Transdermal drug delivery is also associated with high patient compliance and through the site of application, the drug delivery can be locally directed. However, to succeed with transdermal drug delivery it is often required to overcome the low permeability of the upper layer of the skin, the stratum corneum (SC). One common strategy is to employ so-called penetration enhancers that supposedly act to increase the drug passage across SC. Still, there is a lack of understanding of the molecular effects of so-called penetration enhancers on the skin barrier membrane, the SC. In this study, we provide a molecular characterization of how different classes of compounds, suggested as penetration enhancers, influence lipid and protein components in SC. The compounds investigated include monoterpenes, fatty acids, osmolytes, surfactant, and Azone. We employ natural abundance (13)C polarization transfer solid-state nuclear magnetic resonance (NMR) on intact porcine SC. With this method it is possible to detect small changes in the mobility of the minor fluid lipid and protein SC components, and simultaneously obtain information on the major fraction of solid SC components. The balance between fluid and solid components in the SC is essential to determine macroscopic material properties of the SC, including barrier and mechanical properties. We study SC at different hydration levels corresponding to SC in ambient air and under occlusion. The NMR studies are complemented with diffusion cell experiments that provide quantitative data on skin permeability when treated with different compounds. By correlating the effects on SC molecular components and SC barrier function, we aim at deepened understanding of diffusional transport in SC, and how this can be controlled, which can be utilized for optimal design of transdermal drug delivery formulations.
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115
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Wang J, Liu Y, Liu F, Huang C, Han S, Lv Y, Liu CJ, Zhang S, Qin Y, Ling L, Gao M, Yu S, Li C, Huang M, Liao S, Hu X, Lu Z, Liu X, Jiang T, Tang Z, Zhang H, Guo AY, Liu M. Loss-of-function Mutation in PMVK Causes Autosomal Dominant Disseminated Superficial Porokeratosis. Sci Rep 2016; 6:24226. [PMID: 27052676 PMCID: PMC4823745 DOI: 10.1038/srep24226] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2015] [Accepted: 03/22/2016] [Indexed: 12/26/2022] Open
Abstract
Disseminated superficial porokeratosis (DSP) is a rare keratinization disorder of the epidermis. It is characterized by keratotic lesions with an atrophic center encircled by a prominent peripheral ridge. We investigated the genetic basis of DSP in two five-generation Chinese families with members diagnosed with DSP. By whole-exome sequencing, we sequencing identified a nonsense variation c.412C > T (p.Arg138*) in the phosphomevalonate kinase gene (PMVK), which encodes a cytoplasmic enzyme catalyzing the conversion of mevalonate 5-phosphate to mevalonate 5-diphosphate in the mevalonate pathway. By co-segregation and haplotype analyses as well as exclusion testing of 500 normal control subjects, we demonstrated that this genetic variant was involved in the development of DSP in both families. We obtained further evidence from studies using HaCaT cells as models that this variant disturbed subcellular localization, expression and solubility of PMVK. We also observed apparent apoptosis in and under the cornoid lamella of PMVK-deficient lesional tissues, with incomplete differentiation of keratinocytes. Our findings suggest that PMVK is a potential novel gene involved in the pathogenesis of DSP and PMVK deficiency or abnormal keratinocyte apoptosis could lead to porokeratosis.
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Affiliation(s)
- Jiuxiang Wang
- Key Laboratory of Molecular Biophysics of Ministry of Education, Department of Genetics and Developmental Biology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074, PR China
| | - Ying Liu
- Key Laboratory of Molecular Biophysics of Ministry of Education, Department of Genetics and Developmental Biology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074, PR China
| | - Fei Liu
- Key Laboratory of Molecular Biophysics of Ministry of Education, Department of Genetics and Developmental Biology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074, PR China
| | - Changzheng Huang
- Department of Dermatology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, 430022, PR China
| | - Shanshan Han
- Key Laboratory of Molecular Biophysics of Ministry of Education, Department of Genetics and Developmental Biology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074, PR China
| | - Yuexia Lv
- Key Laboratory of Molecular Biophysics of Ministry of Education, Department of Genetics and Developmental Biology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074, PR China
| | - Chun-Jie Liu
- Department of Bioinformatics and Systems Biology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, 430074, PR China
| | - Su Zhang
- Hubei Polytechnic Institute, Xiaogan, 432000, PR China
| | - Yayun Qin
- Key Laboratory of Molecular Biophysics of Ministry of Education, Department of Genetics and Developmental Biology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074, PR China
| | - Lei Ling
- Department of Dermatology, Chibi People’s Hospital, Hubei, 537300, PR China
| | - Meng Gao
- Key Laboratory of Molecular Biophysics of Ministry of Education, Department of Genetics and Developmental Biology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074, PR China
| | - Shanshan Yu
- Key Laboratory of Molecular Biophysics of Ministry of Education, Department of Genetics and Developmental Biology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074, PR China
| | - Chang Li
- Key Laboratory of Molecular Biophysics of Ministry of Education, Department of Genetics and Developmental Biology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074, PR China
| | - Mi Huang
- Key Laboratory of Molecular Biophysics of Ministry of Education, Department of Genetics and Developmental Biology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074, PR China
| | - Shengjie Liao
- Key Laboratory of Molecular Biophysics of Ministry of Education, Department of Genetics and Developmental Biology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074, PR China
| | - Xuebin Hu
- Key Laboratory of Molecular Biophysics of Ministry of Education, Department of Genetics and Developmental Biology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074, PR China
| | - Zhaojing Lu
- Key Laboratory of Molecular Biophysics of Ministry of Education, Department of Genetics and Developmental Biology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074, PR China
| | - Xiliang Liu
- Key Laboratory of Molecular Biophysics of Ministry of Education, Department of Genetics and Developmental Biology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074, PR China
| | - Tao Jiang
- Key Laboratory of Molecular Biophysics of Ministry of Education, Department of Genetics and Developmental Biology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074, PR China
| | - Zhaohui Tang
- Key Laboratory of Molecular Biophysics of Ministry of Education, Department of Genetics and Developmental Biology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074, PR China
| | - Huiping Zhang
- Division of Human Genetics, Department of Psychiatry, Yale University School of Medicine, New Haven, Connecticut 06511, USA
| | - An-Yuan Guo
- Department of Bioinformatics and Systems Biology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, 430074, PR China
| | - Mugen Liu
- Key Laboratory of Molecular Biophysics of Ministry of Education, Department of Genetics and Developmental Biology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074, PR China
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116
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The molecular assembly of the ionic liquid/aliphatic carboxylic acid/aliphatic amine as effective and safety transdermal permeation enhancers. Eur J Pharm Sci 2016; 86:75-83. [PMID: 26965004 DOI: 10.1016/j.ejps.2016.03.002] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2015] [Revised: 03/04/2016] [Accepted: 03/05/2016] [Indexed: 11/21/2022]
Abstract
In spite of numerous advantages, transdermal drug delivery systems are unfeasible for most drugs because of the barrier effect of the stratum corneum. Ionic liquids were recently used to enhance transdermal drug delivery by improving drug solubility. In the present study, safe and effective ionic liquids for transdermal absorption were obtained as salts generated by a neutralization reaction between highly biocompatible aliphatic carboxylic acids (octanoic acid or isostearic acid) and aliphatic amines (diisopropanolamine or triisopropanolamine) (Medrx Co., Ltd., 2009). The mechanism of skin permeability enhancement by ionic liquids was investigated by hydrophilic phenol red and hydrophobic tulobuterol. Further, the skin permeation enhancing effect was remarkably superior in the acid excess state rather than the neutralization state. Infrared absorption spectrum analysis confirmed that ionic liquids/aliphatic carboxylic acid/aliphatic amine are coexisting at all mixing states. In the acid excess state, ionic liquids interact with aliphatic carboxylic acids via hydrogen bonds. Thus, the skin permeation enhancing effect is not caused by the ionic liquid alone. The "liquid salt mixture," referred to as a complex of ingredients coexisting with ionic liquids, forms a molecular assembly incorporating hydrophilic drug. This molecular assembly was considered an effective and safety enhancer of transdermal drug permeation.
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117
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Stahlberg S, Lange S, Dobner B, Huster D. Probing the Role of Ceramide Headgroup Polarity in Short-Chain Model Skin Barrier Lipid Mixtures by ²H Solid-State NMR Spectroscopy. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2016; 32:2023-2031. [PMID: 26828109 DOI: 10.1021/acs.langmuir.5b04173] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The thermoptropic phase behaviors of two stratum corneum model lipid mixtures composed of equimolar contributions of either Cer[NS18] or Cer[NP18] with stearic acid and cholesterol were compared. Each component of the mixture was specifically deuterated such that the temperature-dependent (2)H NMR spectra allowed disentanglement of the complicated phase polymorphism of these lipid mixtures. While Cer[NS] is based on the sphingosine backbone, Cer[NP] features a phytosphingosine, which introduces an additional hydroxyl group into the headgroup of the ceramide and abolishes the double bond. From the NMR spectra, the individual contributions of all lipids to the respective phases could be determined. The comparison of the two lipid mixtures reveals that Cer[NP] containing mixtures have a tendency to form more fluid phases. It is concluded that the additional hydroxyl group of the phytosphingosine-containing ceramide Cer[NP18] in mixture with chain-matched stearic acid and cholesterol creates a packing defect that destabilizes the orthorhombic phase state of canonical SC mixtures. This steric clash favors the gel phase and promotes formation of fluid phases of Cer[NP] containing lipid mixtures at lower temperature compared to those containing Cer[NS18].
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Affiliation(s)
- Sören Stahlberg
- Institute of Medical Physics and Biophysics, University of Leipzig , Härtelstrasse 16-18, 04107 Leipzig, Germany
| | - Stefan Lange
- Institute of Pharmacy, Martin Luther University Halle-Wittenberg , Wolfgang-Langenbeck-Strasse 4, 06120 Halle, Germany
| | - Bodo Dobner
- Institute of Pharmacy, Martin Luther University Halle-Wittenberg , Wolfgang-Langenbeck-Strasse 4, 06120 Halle, Germany
| | - Daniel Huster
- Institute of Medical Physics and Biophysics, University of Leipzig , Härtelstrasse 16-18, 04107 Leipzig, Germany
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118
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Mojumdar EH, Gooris GS, Barlow DJ, Lawrence MJ, Deme B, Bouwstra JA. Skin lipids: localization of ceramide and fatty acid in the unit cell of the long periodicity phase. Biophys J 2016; 108:2670-9. [PMID: 26039168 DOI: 10.1016/j.bpj.2015.04.030] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2014] [Revised: 03/17/2015] [Accepted: 04/21/2015] [Indexed: 12/22/2022] Open
Abstract
The lipid matrix of the skin's stratum corneum plays a key role in the barrier function, which protects the body from desiccation. The lipids that make up this matrix consist of ceramides, cholesterol, and free fatty acids, and can form two coexisting crystalline lamellar phases: the long periodicity phase (LPP) and the short periodicity phase (SPP). To fully understand the skin barrier function, information on the molecular arrangement of the lipids in the unit cell of these lamellar phases is very desirable. To determine this arrangement in previous studies, we examined the molecular arrangement of the SPP. In this study, neutron diffraction studies were performed to obtain information on the molecular arrangement of the LPP. The diffraction pattern reveals nine diffraction orders attributed to the LPP with a repeating unit of 129.4 ± 0.5 Å. Using D2O/H2O contrast variation, the scattering length density profiles were calculated for protiated samples and samples that included either the perdeuterated acyl chain of the most abundant ceramide or the most abundant perdeuterated fatty acid. Both perdeuterated chains are predominantly located in the central part of the unit cell with substantial interdigitation of the acyl chains in the unit cell center. However, a fraction of the perdeuterated chains is also located near the border of the unit cell with their acyl chains directing toward the center. This arrangement of lipids in the LPP unit cell corresponds with the location of their lipid headgroups at the border and also inside of the unit cell at a well-defined position (±21 Å from the unit cell center), indicative of a three-layer lipid arrangement within the 129.4 ± 0.5 Å repeating unit.
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Affiliation(s)
- Enamul H Mojumdar
- Leiden Academic Centre for Drug Research, Department of Drug Delivery Technology, Gorlaeus Laboratories, University of Leiden, Leiden, the Netherlands
| | - Gert S Gooris
- Leiden Academic Centre for Drug Research, Department of Drug Delivery Technology, Gorlaeus Laboratories, University of Leiden, Leiden, the Netherlands
| | - David J Barlow
- Pharmaceutical Science Division, King's College London, London, United Kingdom
| | - M Jayne Lawrence
- Pharmaceutical Science Division, King's College London, London, United Kingdom
| | - Bruno Deme
- Institute Laue-Langevin, Grenoble, France
| | - Joke A Bouwstra
- Leiden Academic Centre for Drug Research, Department of Drug Delivery Technology, Gorlaeus Laboratories, University of Leiden, Leiden, the Netherlands.
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119
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Dreier J, Sørensen JA, Brewer JR. Superresolution and Fluorescence Dynamics Evidence Reveal That Intact Liposomes Do Not Cross the Human Skin Barrier. PLoS One 2016; 11:e0146514. [PMID: 26751684 PMCID: PMC4709185 DOI: 10.1371/journal.pone.0146514] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2015] [Accepted: 12/19/2015] [Indexed: 02/02/2023] Open
Abstract
In this study we use the combination of super resolution optical microscopy and raster image correlation spectroscopy (RICS) to study the mechanism of action of liposomes as transdermal drug delivery systems in human skin. Two different compositions of liposomes were applied to newly excised human skin, a POPC liposome and a more flexible liposome containing the surfactant sodium cholate. Stimulated emission depletion microscopy (STED) images of intact skin and cryo-sections of skin treated with labeled liposomes were recorded displaying an optical resolution low enough to resolve the 100 nm liposomes in the skin. The images revealed that virtually none of the liposomes remained intact beneath the skin surface. RICS two color cross correlation diffusion measurements of double labeled liposomes confirmed these observations. Our results suggest that the liposomes do not act as carriers that transport their cargo directly through the skin barrier, but mainly burst and fuse with the outer lipid layers of the stratum corneum. It was also found that the flexible liposomes showed a greater delivery of the fluorophore into the stratum corneum, indicating that they functioned as chemical permeability enhancers.
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Affiliation(s)
- Jes Dreier
- Advanced bioimaging group/MEMPHYS Center for membrane biophysics, Department of Biochemistry and Molecular Biology, University of Southern Denmark, Odense, Denmark
| | - Jens A. Sørensen
- Department of reconstructive surgery, Odense University Hospital, Odense, Denmark
| | - Jonathan R. Brewer
- Advanced bioimaging group/MEMPHYS Center for membrane biophysics, Department of Biochemistry and Molecular Biology, University of Southern Denmark, Odense, Denmark
- * E-mail:
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120
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Adaptive Evolution of Skin in Terrestrial Vertebrates and Possible Involvement of Endogenous Retroviruses. Uirusu 2016; 66:31-38. [PMID: 28484176 DOI: 10.2222/jsv.66.31] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
The first terrestrial vertebrates emerged from water and adapted to living on land approximately 360 million years ago (late Devonian). In particular, amphibians are thought to have surface epithelia that changed from multilayered epithelia into keratinized stratified squamous epithelia by acquiring stratum corneum (SC), which is composed of several dead cell layers that serve as an air liquid interface barrier. Then, reptiles appeared and became a major terrestrial vertebrate group approximately 340 million years ago by forming hard SC. About 220 million years ago, mammals radiated by acquiring soft and moisturized SC, and endogenous retroviruses were thought to be actively integrated into mammalian genomes. Skin ASpartic Protease (SASPase)/ASPRV1 is the mammalian-specific endogenous retroviral-derived protease. SASPase-deficient mice had dry skin and aberrant accumulation of profilaggrin, which is another mammalian-specific gene that regulates SC barrier function and is a major predisposing factor for atopic dermatitis. These findings indicate that the retroviral element SASPase was integrated into the first mammalian species and was involved in the adaptive evolution of mammals, as it facilitates moisturization of skin SC. It is possible that other uncharacterized endogenous retroviruses were also involved in epidermal barrier function.
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121
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What happens in the skin? Integrating skin permeation kinetics into studies of developmental and reproductive toxicity following topical exposure. Reprod Toxicol 2015; 58:252-81. [DOI: 10.1016/j.reprotox.2015.10.001] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2014] [Revised: 08/31/2015] [Accepted: 10/07/2015] [Indexed: 02/07/2023]
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122
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Marquês JT, Cordeiro AM, Viana AS, Herrmann A, Marinho HS, de Almeida RFM. Formation and Properties of Membrane-Ordered Domains by Phytoceramide: Role of Sphingoid Base Hydroxylation. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:9410-9421. [PMID: 26262576 DOI: 10.1021/acs.langmuir.5b02550] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Phytoceramide is the backbone of major sphingolipids in fungi and plants and is essential in several tissues of animal organisms, such as human skin. Its sphingoid base, phytosphingosine, differs from that usually found in mammals by the addition of a hydroxyl group to the 4-ene, which may be a crucial factor for the different properties of membrane microdomains among those organisms and tissues. Recently, sphingolipid hydroxylation in animal cells emerged as a key feature in several physiopathological processes. Hence, the study of the biophysical properties of phytosphingolipids is also relevant in that context since it helps us to understand the effects of sphingolipid hydroxylation. In this work, binary mixtures of N-stearoyl-phytoceramide (PhyCer) with palmitoyloleoylphosphatidylcholine (POPC) were studied. Steady-state and time-resolved fluorescence of membrane probes, X-ray diffraction, atomic force microscopy, and confocal microscopy were employed. As for other saturated ceramides, highly rigid gel domains start to form with just ∼5 mol % PhyCer at 24 °C. However, PhyCer gel-enriched domains in coexistence with POPC-enriched fluid present additional complexity since their properties (maximal order, shape, and thickness) change at specific POPC/PhyCer molar ratios, suggesting the formation of highly stable stoichiometric complexes with their own properties, distinct from both POPC and PhyCer. A POPC/PhyCer binary phase diagram, supported by the different experimental approaches employed, is proposed with complexes of 3:1 and 1:2 stoichiometries which are stable at least from ∼15 to ∼55 °C. Thus, it provides mechanisms for the in vivo formation of sphingolipid-enriched gel domains that may account for stable membrane compartments and diffusion barriers in eukaryotic cell membranes.
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Affiliation(s)
- Joaquim T Marquês
- Centro de Química e Bioquímica, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade de Lisboa, Ed. C8, Campo Grande, 1749-016 Lisboa, Portugal
| | - André M Cordeiro
- Centro de Química e Bioquímica, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade de Lisboa, Ed. C8, Campo Grande, 1749-016 Lisboa, Portugal
| | - Ana S Viana
- Centro de Química e Bioquímica, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade de Lisboa, Ed. C8, Campo Grande, 1749-016 Lisboa, Portugal
| | - Andreas Herrmann
- Department of Biology, Molecular Biophysics, Humboldt University , Berlin, Germany
| | - H Susana Marinho
- Centro de Química e Bioquímica, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade de Lisboa, Ed. C8, Campo Grande, 1749-016 Lisboa, Portugal
| | - Rodrigo F M de Almeida
- Centro de Química e Bioquímica, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade de Lisboa, Ed. C8, Campo Grande, 1749-016 Lisboa, Portugal
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123
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Mojumdar EH, Gooris GS, Bouwstra JA. Phase behavior of skin lipid mixtures: the effect of cholesterol on lipid organization. SOFT MATTER 2015; 11:4326-36. [PMID: 25947944 DOI: 10.1039/c4sm02786h] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
The lipid matrix in the stratum corneum (SC), the upper layer of the skin, plays a critical role in the skin barrier. The matrix consists of ceramides (CERs), cholesterol (CHOL) and free fatty acids (FFAs). In human SC, these lipids form two coexisting crystalline lamellar phases with periodicities of approximately 6 and 13 nm. In the studies reported here, we investigated the effect of CHOL on lipid organization in each of these lamellar phases separately. For this purpose, we used lipid model mixtures. Our studies revealed that CHOL is imperative for the formation of each of the lamellar phases. At low CHOL levels, the formation of the lamellar phases was dramatically changed: a minimum 0.2 CHOL level in the CER/CHOL/FFA (1 : 0.2 : 1) mixture is required for the formation of each of the lamellar phases. Furthermore, CHOL enhances the formation of the highly dense orthorhombic lateral packing. The gradual increment of CHOL increases the fraction of lipids forming the very dense orthorhombic lateral packing. Therefore, these studies demonstrate that CHOL is an indispensable component of the SC lipid matrix and is of fundamental importance for appropriate dense lipid organization and thus important for the skin barrier function.
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Affiliation(s)
- E H Mojumdar
- Leiden Academic Center for Drug Research, Department of Drug Delivery Technology, Gorlaeus Laboratories, University of Leiden, Einsteinweg 55, 2333 CC Leiden, The Netherlands.
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124
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Stahlberg S, Školová B, Madhu PK, Vogel A, Vávrová K, Huster D. Probing the role of the ceramide acyl chain length and sphingosine unsaturation in model skin barrier lipid mixtures by (2)H solid-state NMR spectroscopy. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:4906-4915. [PMID: 25870928 DOI: 10.1021/acs.langmuir.5b00751] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We investigated equimolar mixtures of ceramides with lignoceric acid and cholesterol as models for the human stratum corneum by differential scanning calorimetry and (2)H solid-state NMR spectroscopy. Our reference system consisted of lignoceroyl sphingosine (Cer[NS24]), which represents one of the ceramides in the human stratum corneum. Furthermore, the effect of ceramide acyl chain truncation to 16 carbons as in Cer[NS16] and the loss of the C4 trans double bond as in dihydroceramide Cer[NDS24] were studied. Fully relaxed (2)H NMR spectra were acquired for each deuterated component of each mixture separately, allowing the quantitative determination of the individual lipid phases. At skin temperature, the reference system containing Cer[NS24] is characterized by large portions of each component of the mixture in a crystalline phase, which largely restricts the permeability of the skin lipid barrier. The loss of the C4 trans double bond in Cer[NDS24] leads to the replacement of more than 25% of the crystalline phase by an isotropic phase of the dihydroceramide that shows the importance of dihydroceramide desaturation in the formation of the skin lipid barrier. The truncated Cer[NS16] is mostly found in the gel phase at skin temperature, which may explain its negative effect on the transepidermal water loss in atopic dermatitis patients. These significant alterations in the phase behavior of all lipids are further reflected at elevated temperatures. The molecular insights of our study may help us to understand the importance of the structural parameters of ceramides in healthy and compromised skin barriers.
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Affiliation(s)
- Sören Stahlberg
- †Institute of Medical Physics and Biophysics, University of Leipzig, Härtelstr. 16-18, 04107 Leipzig, Germany
| | - Barbora Školová
- †Institute of Medical Physics and Biophysics, University of Leipzig, Härtelstr. 16-18, 04107 Leipzig, Germany
- ‡Faculty of Pharmacy, Charles University in Prague, Heyrovského 1203, 50005 Hradec Králové, Czech Republic
| | - Perunthiruthy K Madhu
- §Department of Chemical Sciences, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400 005, India
- ∥TIFR Centre for Interdisciplinary Sciences, 21 Brundavan Colony, Narsingi, Hyderabad 500 075, India
| | - Alexander Vogel
- †Institute of Medical Physics and Biophysics, University of Leipzig, Härtelstr. 16-18, 04107 Leipzig, Germany
| | - Kateřina Vávrová
- ‡Faculty of Pharmacy, Charles University in Prague, Heyrovského 1203, 50005 Hradec Králové, Czech Republic
| | - Daniel Huster
- †Institute of Medical Physics and Biophysics, University of Leipzig, Härtelstr. 16-18, 04107 Leipzig, Germany
- §Department of Chemical Sciences, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400 005, India
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125
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Boakye CHA, Patel K, Singh M. Doxorubicin liposomes as an investigative model to study the skin permeation of nanocarriers. Int J Pharm 2015; 489:106-16. [PMID: 25910414 DOI: 10.1016/j.ijpharm.2015.04.059] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2015] [Revised: 04/02/2015] [Accepted: 04/19/2015] [Indexed: 12/22/2022]
Abstract
The objectives of this study were to develop an innovative investigative model using doxorubicin as a fluorophore to evaluate the skin permeation of nanocarriers and the impact of size and surface characteristics on their permeability. Different doxorubicin-loaded liposomes with mean particle size <130 nm and different surface chemistry were prepared by ammonium acetate gradient method using DPPC, DOPE, Cholesterol, DSPE-PEG 2000 and 1,1-Di-((Z)-octadec-9-en-1-yl) pyrrolidin-1-ium chloride (CY5)/DOTAP/1,2-dioleoyl-sn-glycero-3-phosphate (DOPA) as the charge modifier. There was minimal release of doxorubicin from the liposomes up to 8h; indicating that fluorescence observed within the skin layers was due to the intact liposomes. Liposomes with particle sizes >600 nm were restricted within the stratum corneum. DOTAP (p<0.01) and CY5 (p<0.05) liposomes demonstrated significant permeation into the skin than DOPA and PEG liposomes. Tape stripping significantly (p<0.01) enhanced the skin permeation of doxorubicin liposomes but TAT-decorated doxorubicin liposomes permeated better (p<0.005). Blockage of the hair follicles resulted in significant reduction in the extent and intensity of fluorescence observed within the skin layers. Overall, doxorubicin liposomes proved to be an ideal fluorophore-based model. The hair follicles were the major route utilized by the liposomes to permeate skin. Surface charge and particle size played vital roles in the extent of permeation.
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Affiliation(s)
- Cedar H A Boakye
- College of Pharmacy and Pharmaceutical Sciences, Florida A&M University, Tallahassee, FL 32307, USA
| | - Ketan Patel
- College of Pharmacy and Pharmaceutical Sciences, Florida A&M University, Tallahassee, FL 32307, USA
| | - Mandip Singh
- College of Pharmacy and Pharmaceutical Sciences, Florida A&M University, Tallahassee, FL 32307, USA.
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126
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Lindberg M. The hand eczema proteome: imbalance of epidermal barrier proteins. Br J Dermatol 2015; 172:852-3. [DOI: 10.1111/bjd.13579] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- M. Lindberg
- Department of Dermatology; University Hospital Örebro; Örebro 70185 Sweden
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127
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Matsui T, Amagai M. Dissecting the formation, structure and barrier function of the stratum corneum. Int Immunol 2015; 27:269-80. [PMID: 25813515 DOI: 10.1093/intimm/dxv013] [Citation(s) in RCA: 212] [Impact Index Per Article: 23.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2015] [Accepted: 03/19/2015] [Indexed: 02/06/2023] Open
Abstract
The skin is the largest organ of the mammalian body. The outermost layer of mammalian skin, the stratum corneum (SC) of the epidermis, consists of piles of dead corneocytes that are the end-products of terminal differentiation of epidermal keratinocytes. The SC performs a crucial barrier function of epidermis. Langerhans cells, when activated, extend their dendrites through tight junctions just beneath the SC to capture external antigens. Recently, knowledge of the biology of corneocytes ('corneobiology') has progressed rapidly and many key factors that modulate its barrier function have been identified and characterized. In this review article on the SC, we summarize its evolution, formation, structure and function. Cornification is an important step of SC formation at the conversion of living epithelial cells to dead corneocytes, and consists of three major steps: formation of the intracellular keratin network, cornified envelopes and intercellular lipids. After cornification, the SC undergoes chemical reactions to form the mature SC with different functional layers. Finally, the SC is shed off at the surface ('desquamation'), mediated by a cascade of several proteases. This review will be helpful to understand our expanding knowledge of the biology of the SC, where immunity meets external antigens.
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Affiliation(s)
- Takeshi Matsui
- Laboratory for Skin Homeostasis, RIKEN Center for Integrative Medical Sciences (IMS), 1-7-22, Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan
| | - Masayuki Amagai
- Laboratory for Skin Homeostasis, RIKEN Center for Integrative Medical Sciences (IMS), 1-7-22, Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan Department of Dermatology, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan
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128
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Sovová Ž, Berka K, Otyepka M, Jurečka P. Coarse-grain simulations of skin ceramide NS with newly derived parameters clarify structure of melted phase. J Phys Chem B 2015; 119:3988-98. [PMID: 25679231 DOI: 10.1021/jp5092366] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Ceramides are lipids that are involved in numerous biologically important structures (e.g., the stratum corneum and ceramide-rich platforms) and processes (e.g., signal transduction and membrane fusion), but their behavior is not fully understood. We report coarse-grain force field parameters for N-lignocerylsphingosine (ceramide NS, also known as ceramide 2) that are consistent with the Martini force field. These parameters were optimized for simulations in the gel phase and validated against atomistic simulations. Coarse-grained simulations with our parameters provide areas per lipid, membrane thicknesses, and electron density profiles that are in good agreement with atomistic simulations. Properties of the simulated membranes are compared with available experimental data. The obtained parameters were used to model the phase behavior of ceramide NS as a function of temperature and hydration. At low water content and above the main phase transition temperature, the bilayer melts into an irregular phase, which may correspond to the unstructured melted-chain phase observed in X-ray diffraction experiments. The developed parameters also reproduce the extended conformation of ceramide, which may occur in the stratum corneum. The parameters presented herein will facilitate studies on important complex functional structures such as the uppermost layer of the skin and ceramide-rich platforms in phospholipid membranes.
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Affiliation(s)
- Žofie Sovová
- Regional Centre of Advanced Technologies and Materials, Department of Physical Chemistry, Faculty of Science, Palacký University , 17 Listopadu 12, 77146 Olomouc, Czech Republic
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129
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Kendall AC, Pilkington SM, Massey KA, Sassano G, Rhodes LE, Nicolaou A. Distribution of bioactive lipid mediators in human skin. J Invest Dermatol 2015; 135:1510-1520. [PMID: 25668241 DOI: 10.1038/jid.2015.41] [Citation(s) in RCA: 75] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2014] [Revised: 12/17/2014] [Accepted: 01/23/2015] [Indexed: 12/30/2022]
Abstract
The skin produces bioactive lipids that participate in physiological and pathological states, including homeostasis, induction, propagation, and resolution of inflammation. However, comprehension of the cutaneous lipid complement, and contribution to differing roles of the epidermal and dermal compartments, remains incomplete. We assessed the profiles of eicosanoids, endocannabinoids, N-acyl ethanolamides, and sphingolipids, in human dermis, epidermis, and suction blister fluid. We identified 18 prostanoids, 12 hydroxy-fatty acids, 9 endocannabinoids and N-acyl ethanolamides, and 21 non-hydroxylated ceramides and sphingoid bases, several demonstrating significantly different expression in the tissues assayed. The array of dermal and epidermal fatty acids was reflected in the lipid mediators produced, whereas similarities between lipid profiles in blister fluid and epidermis indicated a primarily epidermal origin of suction blister fluid. Supplementation with omega-3 fatty acids ex vivo showed that their action is mediated through perturbation of existing species and formation of other anti-inflammatory lipids. These findings demonstrate the diversity of lipid mediators involved in maintaining tissue homeostasis in resting skin and hint at their contribution to signaling, cross-support, and functions of different skin compartments. Profiling lipid mediators in biopsies and suction blister fluid can support studies investigating cutaneous inflammatory responses, dietary manipulation, and skin diseases lacking biomarkers and therapeutic targets.
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Affiliation(s)
- Alexandra C Kendall
- Faculty of Medical and Human Sciences, Manchester Pharmacy School, The University of Manchester, Manchester, UK
| | - Suzanne M Pilkington
- Dermatology Centre, Institute of Inflammation and Repair, Faculty of Medical and Human Sciences, The University of Manchester, Manchester, UK
| | - Karen A Massey
- School of Pharmacy and Centre for Skin Sciences, School of Life Sciences, University of Bradford, Bradford, UK
| | - Gary Sassano
- Safety and Environmental Assurance Centre, Unilever, Sharnbrook, UK
| | - Lesley E Rhodes
- Dermatology Centre, Institute of Inflammation and Repair, Faculty of Medical and Human Sciences, The University of Manchester, Manchester, UK
| | - Anna Nicolaou
- Faculty of Medical and Human Sciences, Manchester Pharmacy School, The University of Manchester, Manchester, UK.
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130
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Paloncýová M, DeVane RH, Murch BP, Berka K, Otyepka M. Rationalization of reduced penetration of drugs through ceramide gel phase membrane. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2014; 30:13942-13948. [PMID: 25354090 DOI: 10.1021/la503289v] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Since computing resources have advanced enough to allow routine molecular simulation studies of drug molecules interacting with biologically relevant membranes, a considerable amount of work has been carried out with fluid phospholipid systems. However, there is very little work in the literature on drug interactions with gel phase lipids. This poses a significant limitation for understanding permeation through the stratum corneum where the primary pathway is expected to be through a highly ordered lipid matrix. To address this point, we analyzed the interactions of p-aminobenzoic acid (PABA) and its ethyl (benzocaine) and butyl (butamben) esters with two membrane bilayers, which differ in their fluidity at ambient conditions. We considered a dioleoylphosphatidylcholine (DOPC) bilayer in a fluid state and a ceramide 2 (CER2, ceramide NS) bilayer in a gel phase. We carried out unbiased (100 ns long) and biased z-constraint molecular dynamics simulations and calculated the free energy profiles of all molecules along the bilayer normal. The free energy profiles converged significantly slower for the gel phase. While the compounds have comparable affinities for both membranes, they exhibit penetration barriers almost 3 times higher in the gel phase CER2 bilayer. This elevated barrier and slower diffusion in the CER2 bilayer, which are caused by the high ordering of CER2 lipid chains, explain the low permeability of the gel phase membranes. We also compared the free energy profiles from MD simulations with those obtained from COSMOmic. This method provided the same trends in behavior for the guest molecules in both bilayers; however, the penetration barriers calculated by COSMOmic did not differ between membranes. In conclusion, we show how membrane fluid properties affect the interaction of drug-like molecules with membranes.
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Affiliation(s)
- Markéta Paloncýová
- Regional Centre of Advanced Technologies and Materials, Department of Physical Chemistry, Faculty of Science, Palacký University Olomouc , tř. 17. listopadu 12, 771 46, Olomouc, Czech Republic
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131
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Boncheva M. The physical chemistry of the stratum corneum lipids. Int J Cosmet Sci 2014; 36:505-15. [PMID: 25230344 DOI: 10.1111/ics.12162] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2014] [Accepted: 09/11/2014] [Indexed: 12/20/2022]
Abstract
This article summarizes the current knowledge of the composition, self-assembly, and molecular organization of the stratum corneum (SC) lipids, reviews the evidence connecting these parameters and the barrier properties of human skin, and outlines the immediate issues in the field of SC lipid research.
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Affiliation(s)
- M Boncheva
- Corporate R&D Division, Firmenich SA, PO Box 239, Route des Jeunes 1, Geneva, CH-1211, Switzerland
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132
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Das C, Noro MG, Olmsted PD. Fast cholesterol flip-flop and lack of swelling in skin lipid multilayers. SOFT MATTER 2014; 10:7346-7352. [PMID: 25079959 DOI: 10.1039/c4sm01161a] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Atomistic simulations were performed on hydrated model lipid multilayers that are representative of the lipid matrix in the outer skin (stratum corneum). We find that cholesterol transfers easily between adjacent leaflets belonging to the same bilayer via fast orientational diffusion (tumbling) in the inter-leaflet disordered region, while at the same time there is a large free energy cost against swelling. This fast flip-flop may play an important role in accommodating the variety of curvatures that would be required in the three dimensional arrangement of the lipid multilayers in skin, and for enabling mechanical or hydration induced strains without large curvature elastic costs.
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Affiliation(s)
- Chinmay Das
- School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, UK.
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133
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Norlén L. Update of technologies for examining the stratum corneum at the molecular level. Br J Dermatol 2014; 171 Suppl 3:13-8. [DOI: 10.1111/bjd.13280] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/09/2014] [Indexed: 11/28/2022]
Affiliation(s)
- L. Norlén
- Department of Cell and Molecular Biology; Karolinska Institutet, and Dermatology Clinic; Karolinska University Hospital; Stockholm Sweden
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134
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Doucet J, Potter A, Baltenneck C, Domanov YA. Micron-scale assessment of molecular lipid organization in human stratum corneum using microprobe X-ray diffraction. J Lipid Res 2014; 55:2380-8. [PMID: 25180243 DOI: 10.1194/jlr.m053389] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Lipid and protein components of the stratum corneum (SC) are organized in complex supramolecular arrangements. Exploring spatial relations between various possible substructures is important for understanding the barrier function of this uppermost layer of epidermis. Here, we report the first study where micro-focus X-ray scattering was used for assessing fine structural variations of the human skin barrier with micrometer resolution. We found that the scattering profiles were unchanged when scanning in the direction parallel to the SC surface. Furthermore, small-angle scattering profiles did not change as a function of depth in the SC, confirming that the lipid lamellar spacings remained the same throughout the SC. However, the wide-angle scattering data showed that the orthorhombic phase was more abundant in the middle layers of the SC, whereas the hexagonal phase dominated in the surface layers both at the external and the lowest part of the SC; i.e., the lipids were most tightly packed in the middle region of the SC. Taken together, our results demonstrate that microprobe X-ray diffraction provides abundant information about spatial variations of the SC lipid structure and thus may be a promising tool for assessing the effects of topical formulations on the barrier function of skin.
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Affiliation(s)
- Jean Doucet
- Laboratoire de Physique des Solides, Université Paris-Sud, Orsay, France Phi-Axis, Antony, France
| | - Anne Potter
- Skin Biophysics Laboratory, L'Oréal Research & Innovation, Aulnay-sous-Bois, France
| | - Carine Baltenneck
- Skin Biophysics Laboratory, L'Oréal Research & Innovation, Aulnay-sous-Bois, France
| | - Yegor A Domanov
- Skin Biophysics Laboratory, L'Oréal Research & Innovation, Aulnay-sous-Bois, France
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135
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Školová B, Hudská K, Pullmannová P, Kováčik A, Palát K, Roh J, Fleddermann J, Estrela-Lopis I, Vávrová K. Different Phase Behavior and Packing of Ceramides with Long (C16) and Very Long (C24) Acyls in Model Membranes: Infrared Spectroscopy Using Deuterated Lipids. J Phys Chem B 2014; 118:10460-70. [DOI: 10.1021/jp506407r] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- Barbora Školová
- Skin
Barrier Research Group, Faculty of Pharmacy in Hradec Králové, Charles University in Prague, Heyrovského 1203, 50005 Hradec Králové, Czech Republic
- Institute
of Medical Physics and Biophysics, University of Leipzig, Härtelstrasse
16-18, 04275 Leipzig, Germany
| | - Klára Hudská
- Skin
Barrier Research Group, Faculty of Pharmacy in Hradec Králové, Charles University in Prague, Heyrovského 1203, 50005 Hradec Králové, Czech Republic
| | - Petra Pullmannová
- Skin
Barrier Research Group, Faculty of Pharmacy in Hradec Králové, Charles University in Prague, Heyrovského 1203, 50005 Hradec Králové, Czech Republic
| | - Andrej Kováčik
- Skin
Barrier Research Group, Faculty of Pharmacy in Hradec Králové, Charles University in Prague, Heyrovského 1203, 50005 Hradec Králové, Czech Republic
| | - Karel Palát
- Skin
Barrier Research Group, Faculty of Pharmacy in Hradec Králové, Charles University in Prague, Heyrovského 1203, 50005 Hradec Králové, Czech Republic
| | - Jaroslav Roh
- Skin
Barrier Research Group, Faculty of Pharmacy in Hradec Králové, Charles University in Prague, Heyrovského 1203, 50005 Hradec Králové, Czech Republic
| | - Jana Fleddermann
- Institute
of Medical Physics and Biophysics, University of Leipzig, Härtelstrasse
16-18, 04275 Leipzig, Germany
| | - Irina Estrela-Lopis
- Institute
of Medical Physics and Biophysics, University of Leipzig, Härtelstrasse
16-18, 04275 Leipzig, Germany
| | - Kateřina Vávrová
- Skin
Barrier Research Group, Faculty of Pharmacy in Hradec Králové, Charles University in Prague, Heyrovského 1203, 50005 Hradec Králové, Czech Republic
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136
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Stachowiak R, Łyżniak M, Grabowska M, Roeske K, Jagielski T, Bielecki J, Budziszewska BK, Hoser G, Kawiak J. Cytotoxicity of purified listeriolysin O on mouse and human leukocytes and leukaemia cells. BMC Biotechnol 2014; 14:77. [PMID: 25134983 PMCID: PMC4149758 DOI: 10.1186/1472-6750-14-77] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2014] [Accepted: 08/07/2014] [Indexed: 11/24/2022] Open
Abstract
Background Listeriolysin O (LLO) is the main virulence factor of Listeria monocytogenes and facilitates the intracellular survival of the pathogen. Some of its characteristics endorse the growing popularity of LLO for use in biotechnology, particularly in the development of novel vaccines. Here, we evaluate the use of LLO to eradicate leukaemia cells. Results A purified LLO preparation was obtained by affinity chromatography. The LLO preparation procedure was optimized and purified LLO was tested for optimal conditions of storage including temperature, application of proteinase inhibitors and serum components. We demonstrated the possibility of regulating LLO activity by adjusting cell membrane cholesterol content. The LLO preparation had haemolytic activity and had a cytotoxic effect on the human T-leukaemia Jurkat cell line as well as mouse and human peripheral blood mononuclear cells. Conclusions LLO has a very potent cytotoxic activity towards human leukocytes. Importantly, the cytotoxic activity was easily regulated in vitro and could be restricted to areas containing malignant cells, raising the possibility of future clinical application of LLO for leukaemia treatment.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Jerzy Kawiak
- Medical Centre of Postgraduate Education, Marymoncka 99/103, 01-813 Warsaw, Poland.
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137
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Coates R, Moran J, Horsburgh MJ. Staphylococci: colonizers and pathogens of human skin. Future Microbiol 2014; 9:75-91. [PMID: 24328382 DOI: 10.2217/fmb.13.145] [Citation(s) in RCA: 92] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Staphylococci are abundant bacteria of the human skin microbiome. Several species, particularly Staphylococcus aureus and Staphylococcus epidermidis, are opportunistic pathogens and cause significant disease. The human skin serves many functions and here we review its role as an antimicrobial barrier and the staphylococcal mechanisms to colonize and counteract the various stresses present in this niche. Successful colonization is achieved using a diversity of adhesins, surface proteins and secreted enzymes to counteract the antimicrobial peptides, enzymes and lipid matrix components present in the acid mantle. Further mechanisms enable these bacteria to overcome osmotic and acid stresses and desiccation in order to survive the exacting demands of an ever-changing landscape.
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Affiliation(s)
- Rosanna Coates
- Microbiology Research Group, Institute of Integrative Biology, University of Liverpool, Liverpool, Merseyside, L69 7ZB, UK
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138
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Björklund S, Andersson JM, Pham QD, Nowacka A, Topgaard D, Sparr E. Stratum corneum molecular mobility in the presence of natural moisturizers. SOFT MATTER 2014; 10:4535-46. [PMID: 24817485 DOI: 10.1039/c4sm00137k] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
The outermost layer of the skin, the stratum corneum (SC), is a lipid-protein membrane that experiences considerable osmotic stress from a dry and cold climate. The natural moisturizing factor (NMF) comprises small and polar substances, which like osmolytes can protect living systems from osmotic stress. NMF is commonly claimed to increase the water content in the SC and thereby protect the skin from dryness. In this work we challenge this proposed mechanism, and explore the influence of NMF on the lipid and protein components in the SC. We employ natural-abundance (13)C solid-state NMR methods to investigate how the SC molecular components are influenced by urea, glycerol, pyrrolidone carboxylic acid (PCA), and urocanic acid (UCA), all of which are naturally present in the SC as NMF compounds. Experiments are performed with intact SC, isolated corneocytes and model lipids. The combination of NMR experiments provides molecularly resolved qualitative information on the dynamics of different SC lipid and protein components. We obtain completely novel molecular information on the interaction of these NMF compounds with the SC lipids and proteins. We show that urea and glycerol, which are also common ingredients in skin care products, increase the molecular mobility of both SC lipids and proteins at moderate relative humidity where the SC components are considerably more rigid in the absence of these compounds. This effect cannot be attributed to increased SC water content. PCA has no detectable effect on SC molecular mobility under the conditions investigated. It is finally shown that the more apolar compound, UCA, specifically influences the mobility of the SC lipid regions. The present results show that the NMF components act to retain the fluidity of the SC molecular components under dehydrating conditions in such a way that the SC properties remain largely unchanged as compared to more hydrated SC. These findings provide a new molecular insight into how small polar molecules in NMF and skin care products act to protect the human skin from drying.
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Affiliation(s)
- Sebastian Björklund
- Division of Physical Chemistry, The Center for Chemistry and Chemical Engineering, Lund University, P.O. Box 124, SE-22100 Lund, Sweden.
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139
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Kováčik A, Roh J, Vávrová K. The chemistry and biology of 6-hydroxyceramide, the youngest member of the human sphingolipid family. Chembiochem 2014; 15:1555-62. [PMID: 24990520 DOI: 10.1002/cbic.201402153] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2014] [Indexed: 11/08/2022]
Abstract
Sphingolipids are crucial for the life of the cell. In land-dwelling mammals, they are equally important outside the cell-in the extracellular space of the skin barrier-because they prevent loss of water. Although a large body of research has elucidated many of the functions of sphingolipids, their extensive structural diversity remains intriguing. A new class of sphingolipids based on 6-hydroxylated sphingosine has recently been identified in human skin. Abnormal levels of these 6-hydroxylated ceramides have repeatedly been observed in atopic dermatitis; however, neither the biosynthesis nor the roles of these unique ceramide subclasses have been established in the human body. In this Minireview, we summarize the current knowledge of 6-hydroxyceramides, including their discovery, structure, stereochemistry, occurrence in healthy and diseased human epidermis, and synthetic approaches to 6-hydroxysphingosine and related ceramides.
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Affiliation(s)
- Andrej Kováčik
- Skin Barrier Research Group, Charles University in Prague, Faculty of Pharmacy in Hradec Králové, Heyrovského 1203, 50005 Hradec Králové (Czech Republic)
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140
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Pullmannová P, Staňková K, Pospíšilová M, Skolová B, Zbytovská J, Vávrová K. Effects of sphingomyelin/ceramide ratio on the permeability and microstructure of model stratum corneum lipid membranes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1838:2115-26. [PMID: 24824073 DOI: 10.1016/j.bbamem.2014.05.001] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/04/2014] [Revised: 04/10/2014] [Accepted: 05/03/2014] [Indexed: 11/27/2022]
Abstract
The conversion of sphingomyelin (SM) to a ceramide (Cer) by acid sphingomyelinase (aSMase) is an important event in skin barrier development. A deficiency in aSMase in diseases such as Niemann-Pick disease and atopic dermatitis coincides with impaired skin barrier recovery after disruption. We studied how an increased SM/Cer ratio influences the barrier function and microstructure of model stratum corneum (SC) lipid membranes. In the membranes composed of isolated human SC Cer (hCer)/cholesterol/free fatty acids/cholesteryl sulfate, partial or full replacement of hCer by SM increased water loss. Partial replacement of 25% and 50% of hCer by SM also increased the membrane permeability to theophylline and alternating electric current, while a higher SM content either did not alter or even decreased the membrane permeability. In contrast, in a simple membrane model with only one type of Cer (nonhydroxyacyl sphingosine, CerNS), an increased SM/Cer ratio provided a similar or better barrier against the permeation of various markers. X-ray powder diffraction revealed that the replacement of hCer by SM interferes with the formation of the long periodicity lamellar phase with a repeat distance of d=12.7nm. Our results suggest that SM-to-Cer processing in the human epidermis is essential for preventing excessive water loss, while the permeability barrier to exogenous compounds is less sensitive to the presence of sphingomyelin.
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Affiliation(s)
- Petra Pullmannová
- Skin Barrier Research Group, Charles University in Prague, Faculty of Pharmacy, Heyrovského 1203, 500 05 Hradec Králové, Czech Republic.
| | - Klára Staňková
- Skin Barrier Research Group, Charles University in Prague, Faculty of Pharmacy, Heyrovského 1203, 500 05 Hradec Králové, Czech Republic
| | - Markéta Pospíšilová
- Skin Barrier Research Group, Charles University in Prague, Faculty of Pharmacy, Heyrovského 1203, 500 05 Hradec Králové, Czech Republic
| | - Barbora Skolová
- Skin Barrier Research Group, Charles University in Prague, Faculty of Pharmacy, Heyrovského 1203, 500 05 Hradec Králové, Czech Republic
| | - Jarmila Zbytovská
- Institute of Chemical Technology Prague, Technická 5, 166 28 Prague, Czech Republic
| | - Kateřina Vávrová
- Skin Barrier Research Group, Charles University in Prague, Faculty of Pharmacy, Heyrovského 1203, 500 05 Hradec Králové, Czech Republic
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141
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142
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Muñoz-Garcia A, Thomas CP, Keeney DS, Zheng Y, Brash AR. The importance of the lipoxygenase-hepoxilin pathway in the mammalian epidermal barrier. BIOCHIMICA ET BIOPHYSICA ACTA 2014; 1841:401-8. [PMID: 24021977 PMCID: PMC4116325 DOI: 10.1016/j.bbalip.2013.08.020] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/16/2013] [Revised: 08/27/2013] [Accepted: 08/30/2013] [Indexed: 01/22/2023]
Abstract
This review covers the background to discovery of the two key lipoxygenases (LOX) involved in epidermal barrier function, 12R-LOX and eLOX3, and our current views on their functioning. In the outer epidermis, their consecutive actions oxidize linoleic acid esterified in ω-hydroxy-ceramide to a hepoxilin-related derivative. The relevant background to hepoxilin and trioxilin biochemistry is briefly reviewed. We outline the evidence that linoleate in the ceramide is the natural substrate of the two LOX enzymes and our proposal for its importance in construction of the epidermal water barrier. Our hypothesis is that the oxidation promotes hydrolysis of the oxidized linoleate moiety from the ceramide. The resulting free ω-hydroxyl of the ω-hydroxyceramide is covalently bound to proteins on the surface of the corneocytes to form the corneocyte lipid envelope, a key barrier component. Understanding the role of the LOX enzymes and their hepoxilin products should provide rational approaches to ameliorative therapy for a number of the congenital ichthyoses involving compromised barrier function. This article is part of a Special Issue entitled The Important Role of Lipids in the Epidermis and their Role in the Formation and Maintenance of the Cutaneous Barrier. Guest Editors: Kenneth R. Feingold and Peter Elias.
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Affiliation(s)
- Agustí Muñoz-Garcia
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, TN 37232, USA; Vanderbilt Institute of Chemical Biology, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Christopher P Thomas
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, TN 37232, USA; Vanderbilt Institute of Chemical Biology, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Diane S Keeney
- Department of Biochemistry, Vanderbilt University Medical Center, Nashville, TN 37232, USA; Vanderbilt Institute of Chemical Biology, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Yuxiang Zheng
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, TN 37232, USA; Vanderbilt Institute of Chemical Biology, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Alan R Brash
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, TN 37232, USA; Vanderbilt Institute of Chemical Biology, Vanderbilt University Medical Center, Nashville, TN 37232, USA.
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143
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Comparative SAXS and DSC study on stratum corneum structural organization in an epidermal cell culture model (ROC): impact of cultivation time. Eur J Pharm Sci 2013; 50:577-85. [PMID: 23770376 DOI: 10.1016/j.ejps.2013.06.003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2013] [Revised: 06/01/2013] [Accepted: 06/02/2013] [Indexed: 11/20/2022]
Abstract
Cell cultured skin equivalents present an alternative for dermatological in vitro evaluations of drugs and excipients as they provide the advantage of availability, lower variability and higher assay robustness compared to native skin. For penetration/permeation studies, an adequate stratum corneum barrier similar to that of human stratum corneum is, however, a prerequisite. In this study, the stratum corneum lipid organization in an epidermal cell culture model based on rat epidermal keratinocytes (REK organotypic culture, ROC) was investigated by small-angle X-ray scattering (SAXS) in dependence on ROC cultivation time and in comparison to native human and rat stratum cornea. In addition, the thermal phase behavior was studied by differential scanning calorimetry (DSC) and barrier properties were checked by measurements of the permeability of tritiated water. The development of the barrier of ROC SC obtained at different cultivation times (7, 14 and 21 days at the air-liquid interface) was connected with an increase in structural order of the SC lipids in SAXS measurements: Already cultivation for 14 days at the air-liquid interface resulted overall in a competent SC permeability barrier and SC lipid organization. Cultivation for 21 days resulted in further minor changes in the structural organization of ROC SC. The SAXS patterns of ROC SC had overall large similarities with that of human SC and point to the presence of a long periodicity phase with a repeat distance of about 122Å, e.g. slightly smaller than that determined for human SC in the present study (127Å). Moreover, SAXS results also indicate the presence of covalently bound ceramides, which are crucial for a proper SC barrier, although the corresponding thermal transitions were not clearly detectable by DSC. Due to the competent SC barrier properties and high structural and organizational similarity to that of native human SC, ROC presents a promising alternative for in vitro studies, particularly as it can be obtained under overall rather straightforward cell culture conditions and thus low assay costs.
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144
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van Smeden J, Janssens M, Gooris GS, Bouwstra JA. The important role of stratum corneum lipids for the cutaneous barrier function. Biochim Biophys Acta Mol Cell Biol Lipids 2013; 1841:295-313. [PMID: 24252189 DOI: 10.1016/j.bbalip.2013.11.006] [Citation(s) in RCA: 334] [Impact Index Per Article: 30.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2013] [Revised: 11/08/2013] [Accepted: 11/10/2013] [Indexed: 01/28/2023]
Abstract
The skin protects the body from unwanted influences from the environment as well as excessive water loss. The barrier function of the skin is located in the stratum corneum (SC). The SC consists of corneocytes embedded in a lipid matrix. This lipid matrix is crucial for the lipid skin barrier function. This paper provides an overview of the reported SC lipid composition and organization mainly focusing on healthy and diseased human skin. In addition, an overview is provided on the data describing the relation between lipid modulations and the impaired skin barrier function. Finally, the use of in vitro lipid models for a better understanding of the relation between the lipid composition, lipid organization and skin lipid barrier is discussed. This article is part of a Special Issue entitled The Important Role of Lipids in the Epidermis and their Role in the Formation and Maintenance of the Cutaneous Barrier. This article is part of a Special Issue entitled The Important Role of Lipids in the Epidermis and their Role in the Formation and Maintenance of the Cutaneous Barrier. Guest Editors: Kenneth R. Feingold and Peter Elias.
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Affiliation(s)
- J van Smeden
- Department of Drug Delivery Technology, Leiden Academic Centre for Drug Research, Leiden University, Leiden, The Netherlands
| | - M Janssens
- Department of Drug Delivery Technology, Leiden Academic Centre for Drug Research, Leiden University, Leiden, The Netherlands
| | - G S Gooris
- Department of Drug Delivery Technology, Leiden Academic Centre for Drug Research, Leiden University, Leiden, The Netherlands
| | - J A Bouwstra
- Department of Drug Delivery Technology, Leiden Academic Centre for Drug Research, Leiden University, Leiden, The Netherlands.
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145
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Bloksgaard M, Brewer JR, Pashkovski E, Ananthapadmanabhan KP, Sørensen JA, Bagatolli LA. Effect of detergents on the physicochemical properties of skin stratum corneum: a two-photon excitation fluorescence microscopy study. Int J Cosmet Sci 2013; 36:39-45. [PMID: 23962033 DOI: 10.1111/ics.12089] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2013] [Accepted: 08/17/2013] [Indexed: 12/20/2022]
Abstract
OBJECTIVE Understanding the structural and dynamical features of skin is critical for advancing innovation in personal care and drug discovery. Synthetic detergent mixtures used in commercially available body wash products are thought to be less aggressive towards the skin barrier when compared to conventional detergents. The aim of this work is to comparatively characterize the effect of a mild synthetic cleanser mixture (SCM) and sodium dodecyl sulphate (SDS) on the hydration state of the intercellular lipid matrix and on proton activity of excised skin stratum corneum (SC). METHOD Experiments were performed using two-photon excitation fluorescence microscopy. Fluorescent images of fluorescence reporters sensitive to proton activity and hydration of SC were obtained in excised skin and examined in the presence and absence of SCM and SDS detergents. RESULTS Hydration of the intercellular lipid matrix to a depth of 10 μm into the SC was increased upon treatment with SCM, whereas SDS shows this effect only at the very surface of SC. The proton activity of SC remained unaffected by treatment with either detergent. CONCLUSION While our study indicates that the SC is very resistant to external stimuli, it also shows that, in contrast to the response to SDS, SCM to some extent modulates the in-depth hydration properties of the intercellular lipid matrix within excised skin SC.
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Affiliation(s)
- M Bloksgaard
- Membrane Biophysics and Biophotonics Group/MEMPHYS-Center, Department of Biochemistry and Molecular Biology, University of Southern Denmark, Campusvej 55, DK-5230, Odense M, Denmark
| | - J R Brewer
- Membrane Biophysics and Biophotonics Group/MEMPHYS-Center, Department of Biochemistry and Molecular Biology, University of Southern Denmark, Campusvej 55, DK-5230, Odense M, Denmark
| | - E Pashkovski
- Unilever R&D, 40 Merritt Blvd., Trumbull, CT, 06611, USA
| | | | - J A Sørensen
- Department of Plastic Surgery, Odense University Hospital, DK-5000, Odense C, Denmark
| | - L A Bagatolli
- Membrane Biophysics and Biophotonics Group/MEMPHYS-Center, Department of Biochemistry and Molecular Biology, University of Southern Denmark, Campusvej 55, DK-5230, Odense M, Denmark
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146
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Das C, Noro MG, Olmsted PD. Lamellar and inverse micellar structures of skin lipids: effect of templating. PHYSICAL REVIEW LETTERS 2013; 111:148101. [PMID: 24138273 DOI: 10.1103/physrevlett.111.148101] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2013] [Indexed: 06/02/2023]
Abstract
The outermost layer of skin comprises rigid nonviable cells (corneocytes) in a layered lipid matrix. Using atomistic simulations we find that the equilibrium phase of the skin lipids is inverse micellar. A model of the corneocyte is used to demonstrate that lamellar layering is induced by the patterned corneocyte wall. The inverse micellar phase is consistent with in vivo observations in regions where corneocyte walls are well separated (lacunar spaces) and in the inner layers of skin, and suggests a functional role in the lipid synthesis pathway in vivo.
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Affiliation(s)
- Chinmay Das
- School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, United Kingdom
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147
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Evenbratt H, Jonsson C, Faergemann J, Engström S, Ericson MB. In vivo study of an instantly formed lipid–water cubic phase formulation for efficient topical delivery of aminolevulinic acid and methyl-aminolevulinate. Int J Pharm 2013; 452:270-5. [DOI: 10.1016/j.ijpharm.2013.05.047] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2013] [Revised: 05/15/2013] [Accepted: 05/16/2013] [Indexed: 11/15/2022]
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148
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Wertz PW. Current understanding of skin biology pertinent to skin penetration: skin biochemistry. Skin Pharmacol Physiol 2013; 26:217-26. [PMID: 23921108 DOI: 10.1159/000351949] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2013] [Accepted: 04/08/2013] [Indexed: 11/19/2022]
Abstract
The purpose of this review is to summarize some of the biochemical or chemical findings that have contributed most significantly to our current understanding of the permeability barrier of the skin. This literature survey covers the period from the 1970s up to the present. This seems appropriate since earlier progress was comprehensively covered in a 1978 review by Bob Scheuplein entitled 'Permeability of the skin: a review of major concepts' and in the earlier review by Scheuplein and Blank entitled 'Permeability of the skin'. Both of these review articles are still being cited, and the earlier one has been cited more than 800 times. Overlap with material covered in these earlier publications will be minimized. The overall significance of findings from some of the most recent years may not yet be determined. The emphasis will be placed on the determination of the composition and structures of the epidermal lipids, especially those of the stratum corneum, key enzymes in the biosynthesis of these lipids and some of the physical chemical properties of these lipids as revealed by X-ray diffraction, infrared spectroscopy and other physical methods.
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Affiliation(s)
- P W Wertz
- Dows Institute, University of Iowa, Iowa City,IA 52242, USA.
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149
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Mitragotri S. Engineering approaches to transdermal drug delivery: a tribute to contributions of prof. Robert Langer. Skin Pharmacol Physiol 2013; 26:263-76. [PMID: 23921113 DOI: 10.1159/000351947] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2013] [Accepted: 04/08/2013] [Indexed: 11/19/2022]
Abstract
Transdermal drug delivery continues to provide an advantageous route of drug administration over injections. While the number of drugs delivered by passive transdermal patches has increased over the years, no macromolecule is currently delivered by the transdermal route. Substantial research efforts have been dedicated by a large number of researchers representing varied disciplines including biology, chemistry, pharmaceutics and engineering to understand, model and overcome the skin's barrier properties. This article focuses on engineering contributions to the field of transdermal drug delivery. The article pays tribute to Prof. Robert Langer, who pioneered the engineering approach towards transdermal drug delivery. Over a period spanning nearly 25 years since his first publication in the field of transdermal drug delivery, Bob Langer has deeply impacted the field by quantitative analysis and innovative engineering. At the same time, he has inspired several generations of engineers by collaborations and mentorship. His scientific insights, innovative technologies, translational efforts and dedicated mentorship have transformed the field.
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Affiliation(s)
- S Mitragotri
- Department of Chemical Engineering, University of California, Santa Barbara, CA 93106, USA.
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150
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Birgersson U, Birgersson E, Nicander I, Ollmar S. A methodology for extracting the electrical properties of human skin. Physiol Meas 2013; 34:723-36. [DOI: 10.1088/0967-3334/34/6/723] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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