Development and skin penetration pathway evaluation of microemulsions for enhancing the dermal delivery of celecoxib

Development of a novel human stratum corneum mimetic phospholipid -vesicle-based permeation assay models for in vitro permeation studies

OBJECTIVES

To develop and evaluate a novel human stratum corneum (SC) mimetic phospholipid vesicle-based permeation assay (PVPASC) model for in vitro permeation studies.

SIGNIFICANCE

Due to the increasing restrictions on the use of human and animal skins, artificial skin models have attracted substantial interest in pharmaceuticals and cosmetic industries. In this study, a modified PVPASC model containing both SC lipids and proteins was developed.

METHODS

The PVPASC model was optimized by altering the lipid composition and adding keratin in the formulation of large liposomes. The barrier properties were monitored by measuring the electrical resistance (ER) and permeability of Rhodamine B (RB). The modified PVPASC model was characterized in terms of the surface topography, solvent influence and storage stability. The permeation studies of the active components in Compound Nanxing Zhitong Plaster (CNZP) were performed to examine the capability of PVPASC in the application of skin penetration.

RESULTS

The ER and Papp values of RB obtained from the optimized PVPASC model indicated a similar barrier property to porcine ear skin. Scanning electron microscope analysis demonstrated a mimic 'brick-and-mortar' structure. The PVPASC model can be stored for three weeks at -20 °C, and withstand the presence of different receptor medium for 24 h. The permeation studies of the active components demonstrated a good correlation (r2 = 0.9136) of Papp values between the drugs' permeation through the PVPASC model and porcine ear skin.

CONCLUSION

Keratin contained composite phospholipid vesicle-based permeation assay models have been proven to be potential skin tools in topical/transdermal permeation studies.

Recent Advances in Nanocarrier-based Approaches to Atopic Dermatitis and Emerging Trends in Drug Development and Design

Atopic dermatitis (AD), commonly known as Eczema, is a non-communicable skin condition that tends to become chronic. The deteriorating immunological abnormalities are marked by mild to severe erythema, severe itching, and recurrent eczematous lesions. Different pharmacological approaches are used to treat AD. The problem with commercial topical preparations lies in the limitation of skin atrophy, systemic side effects, and burning sensation that decreases patient compliance. The carrier-based system promises to eliminate these shortcomings; thus, a novel approach to treating AD is required. Liposomes, microemulsions, solid lipid nanoparticles (SLNs), nanoemulsions, etc., have been developed recently to address this ailment. Despite extensive research in the development method and various techniques, it has been challenging to demonstrate the commercial feasibility of these carrier- based systems, which illustrates a gap among the different research areas. Further, different soft wares and other tools have proliferated among biochemists as part of a cooperative approach to drug discovery. It is crucial in designing, developing, and analyzing processes in the pharmaceutical industry and is widely used to reduce costs, accelerate the development of biologically innovative active ingredients, and shorten the development time. This review sheds light on the compilation of extensive efforts to combat this disease, the product development processes, commercial products along with patents in this regard, numerous options for each step of computer-aided drug design, including in silico pharmacokinetics, pharmacodynamics, and toxicity screening or predictions that are important in finding the drug-like compounds.

Incorporation of Cordia glabrata (Mart.) A.DC. extract in microemulsions and their potential antioxidant, photoprotective and virucidal activities

Abstract Extracts of species from the Cordia genus have been reported with potential biological activities, such as antioxidant, antimicrobial, antiviral, and antiparasitic. The aim of this study was to develop microemulsions containing ethanolic extracts of C. glabrata leaves and to evaluate their stability and biological activities. The five developed microemulsions presented physicochemical stability and presented Newtonian behavior when submitted to rheological analysis. The diameter values of the globules ranged between 225.74 and 273.33 nm and the zeta potential of the formulations remained between -22.40 and -25.08. All phenolic acids of the extract, quantified by HPLC, showed consistency after being microemulsified. The EC50 values for the antioxidant activity by the DPPH scavenging method ranged between 38.13 and 45.54 µgmL-1, and between 34.46 and 39.60 mM for the ABTS+ scavenging method. The virucidal activity presented a CV50 <0.195 µgmL-1 and a selectivity index greater than 20. The photoprotection results ranged between 2.14 to 2.84. The study revealed stable microemulsions and potentiation of the antioxidant effect in the microemulsified extracts.

Nanosizing of Lavender, Basil, and Clove Essential Oils into Microemulsions for Enhanced Antioxidant Potential and Antibacterial and Antibiofilm Activities

Plant essential oils (EOs) possess significant bioactivities (antibacterial and antioxidant) and can be substituted for potentially harmful synthetic preservatives in the food industry. However, limited water solubility, bioavailability, volatility, and stability limit their use. Therefore, the goal of this research was nanosizing lavender essential oil (LEO), basil essential oil (BEO), and clove essential oil (CEO) in a microemulsion (ME) to improve their physicochemical attributes and bioefficacy. Tween 80 and Transcutol P were utilized for construction of pseudoternary phase diagrams. It was observed that the concentration of EOs had a great impact on the physicochemical and biological properties of MEs. A spherical droplet of MEs with a diameter of less than 20 nm with a narrower size distribution (polydispersity index (PDI) = 0.10-0.27) and a ζ potential of -0.27 to -9.03 was observed. ME formulations were also evaluated for viscosity, conductivity, and the refractive index. Moreover, the impact of delivery systems on the antibacterial property of EOs was assessed by determining the zone of inhibition and minimum inhibitory concentration against two distinct pathogen classes (S. aureus and E. coli). Crystal violet assay was used to measure the growth and development of biofilms. According to bioefficacy assays, ME demonstrated more efficient antibacterial activity against microorganisms at concentrations lower than pure EOs. CEO ME had superior activity againstS. aureus and E. coli. Similarly, dose-dependent antioxidant capacity was noted for MEs. Consequently, nanosized EO formulations with improved physicochemical properties and enhanced bioactivities can be employed in the food processing sector as a preservation agent.

Exploring the Versatility of Microemulsions in Cutaneous Drug Delivery: Opportunities and Challenges

Microemulsions are novel drug delivery systems that have garnered significant attention in the pharmaceutical research field. These systems possess several desirable characteristics, such as transparency and thermodynamic stability, which make them suitable for delivering both hydrophilic and hydrophobic drugs. In this comprehensive review, we aim to explore different aspects related to the formulation, characterization, and applications of microemulsions, with a particular emphasis on their potential for cutaneous drug delivery. Microemulsions have shown great promise in overcoming bioavailability concerns and enabling sustained drug delivery. Thus, it is crucial to have a thorough understanding of their formulation and characterization in order to optimize their effectiveness and safety. This review will delve into the different types of microemulsions, their composition, and the factors that affect their stability. Furthermore, the potential of microemulsions as drug delivery systems for skin applications will be discussed. Overall, this review will provide valuable insights into the advantages of microemulsions as drug delivery systems and their potential for improving cutaneous drug delivery.

Boosting the In Vivo Transdermal Bioavailability of Asenapine Maleate Using Novel Lavender Oil-Based Lipid Nanocapsules for Management of Schizophrenia

Lipid nanocapsules (LNCs) are promising for transdermal drug delivery due to their higher permeability-enhancing effects compared to polymeric nanoparticles. Lavender oil is an essential oil consisting of several terpenes (primarily linalool and linalyl acetate) known for their profound permeation-enhancing action. In the present work, we successfully encapsulated asenapine maleate (a second-generation antipsychotic that is highly metabolized by the liver, reducing its oral bioavailability) into biocompatible LNCs for transdermal application using a novel oily phase, i.e., lavender oil (LO-LNCs). A comparative study was conducted to determine the effects of different oily phases (i.e., Miglyol® 812, Labrafil® M1944CS, and Labrafac™ PG) on the LNCs. Surfactant types (Kolliphor® HS15, Kolliphor® EL and Tween80) and oil:surfactant ratios were studied. Blank and asenapine-loaded LNCs were optimized for particle size, polydispersity index, zeta potential, drug content and ex vivo skin permeation. Lavender oil and Labrafil® showed smaller vesicular sizes, while LO-LNCs increased the permeation of ASP across rat skin. In vivo pharmacokinetics revealed that LO-LNCs could increase the ASP Cmax via transdermal application by fourfold compared to oral suspension. They increased the bioavailability of ASP by up to 52% and provided sustained release for three days. The pharmacokinetic profile of the LO-LNCs was compared to ASP-loaded invasomes (discussed in a previous study) to emphasize LNCs' transdermal delivery behavior.

Development and Skin Penetration Pathway Evaluation Using Confocal Laser Scanning Microscopy of Microemulsions for Dermal Delivery Enhancement of Finasteride

This study aimed to develop microemulsions using poloxamer 124 as a surfactant to improve the skin penetration of finasteride and to investigate the skin penetration pathways of these microemulsions by colocalization techniques using confocal laser scanning microscopy (CLSM). The prepared finasteride-loaded microemulsions had average particle sizes ranging from 80.09 to 136.97 nm with particle size distributions within acceptable ranges and exhibited negative surface charges. The obtained microemulsions could significantly increase the skin penetration of finasteride compared to a finasteride solution. According to the skin penetration pathway evaluation conducted with CLSM, the microemulsions were hair follicle-targeted formulations due to penetration via the transfollicular pathway as a major skin penetration pathway. Additionally, this study found that the microemulsions also penetrated via the intercluster pathway more than via the intercellular pathway and transcellular pathway. The intercluster pathway, intercellular pathway, and transcellular pathway were considered only minor pathways.

Development and Evaluation of Ethosomes Loaded with Zingiber zerumbet Linn Rhizome Extract for Antifungal Skin Infection in Deep Layer Skin

Skin fungal infection is still a serious public health problem due to the high number of cases. Even though medicines are available for this disease, drug resistance among patients has increased. Moreover, access to medicine is restricted in some areas. One of the therapeutic options is herbal medicine. This study aims to develop an ethosome formulation loaded with Zingiber zerumbet (L.) Smith. rhizome extract for enhanced antifungal activity in deep layer skin, which is difficult to cure. Ethosomes were successfully prepared by the cold method, and the optimized formulation was composed of 1% (w/v) phosphatidylcholine and 40% (v/v) ethanol. Transmission electron microscope (TEM) images revealed that the ethosomes had a vesicle shape with a diameter of 205.6-368.5 nm. The entrapment of ethosomes was 31.58% and could inhibit the growth of Candida albicans at a concentration of 312.5 μg/mL. Finally, the ethosome system significantly enhanced the skin penetration and retention of the active compound (zerumbone) compared with the liquid extract. This study showed that Z. zerumbet (L.) rhizome extract could be loaded into ethosomes. The findings could be carried over to the next step for clinical application by conducting further in vivo penetration and permeation tests.

Transdermal delivery of inflammatory factors regulated drugs for rheumatoid arthritis

Rheumatoid arthritis is a chronic autoimmune disease, with the features of recurrent chronic inflammation of synovial tissue, destruction of cartilage, and bone erosion, which further affects joints tissue, organs, and systems, and eventually leads to irreversible joint deformities and body dysfunction. Therapeutic drugs for rheumatoid arthritis mainly reduce inflammation through regulating inflammatory factors. Transdermal administration is gradually being applied to the treatment of rheumatoid arthritis, which can allow the drug to overcome the skin stratum corneum barrier, reduce gastrointestinal side effects, and avoid the first-pass effect, thus improving bioavailability and relieving inflammation. This paper reviewed the latest research progress of transdermal drug delivery in the treatment of rheumatoid arthritis, and discussed in detail the dosage forms such as gel (microemulsion gel, nanoemulsion gel, nanomicelle gel, sanaplastic nano-vesiclegel, ethosomal gel, transfersomal gel, nanoparticles gel), patch, drug microneedles, nanostructured lipid carrier, transfersomes, lyotropic liquid crystal, and drug loaded electrospinning nanofibers, which provide inspiration for the rich dosage forms of transdermal drug delivery systems for rheumatoid arthritis.

Topical Semisolid Products-Understanding the Impact of Metamorphosis on Skin Penetration and Physicochemical Properties

Recently, the United States Food and Drug Administration published a series of product-specific guidance for the development of topical drugs, with in vitro options consisting of qualitative sameness (Q1) and quantitative sameness (Q2) assessment of formulations, physiochemical and structural characterization of formulations (Q3), and, potentially, in vitro drug release and permeation tests. In these tests, the topical semisolid product's critical quality attributes (CQAs), such as rheological properties, thermodynamic activity, particle size, globule size, and rate/extent of drug release/permeation, are evaluated to ensure the desired product quality. However, alterations in these CQAs of the drug products may occur under 'in use' conditions because of various metamorphosis events, such as evaporation that leads to supersaturation and crystallization, which may eventually result in specific failure modes of semisolid products. Under 'in use' conditions, a limited amount of formulation is applied to the skin, where physicochemical characteristics of the formulation are substantially altered from primary state to secondary and, eventually, tertiary state on the skin. There is an urgent need to understand the behavior of topical semisolid products under 'in use' conditions. In this review, we attempt to cover a series of metamorphosis events and their impact on CQAs (Q3 attributes), such as viscosity, drug activity, particle size, globule size, and drug release/permeation of topical semisolid products.

Ex vivo permeation parameters and skin deposition of melatonin-loaded microemulsion for treatment of alopecia

Background

Melatonin (MEL) is a powerful antioxidant molecule with anti-androgenic property. A microemulsion (ME) system loaded with MEL was designed for treatment of androgenic alopecia. Pseudo-ternary phase diagram was constructed, and ME formulae were developed using coconut oil, Tween 80 and PEG 400. In the present study, MEL ME was characterized and evaluated for droplet size, polydispersity index, zeta potential, morphology using TEM imaging. MEL ex vivo permeation study through rat skin followed by tape stripping for stratum corneum (SC) was performed for different ME formulae, to determine skin permeation parameters and detect SC-MEL deposition.

Results

Spherical and uniform particles of MEL-loaded microemulsion were formulated with high stability. In ex vivo permeation study, MEL ME exhibited low steady-state skin flux along with pronounced SC deposition which prevailed a controlled release manner.

Conclusion

The results suggested that MEL ME could be a promising candidate for further permeation and in vivo studies for androgenic alopecia treatment.

Hair follicle-targeting drug delivery strategies for the management of hair follicle-associated disorders

The hair follicle is not only a critical penetration route in percutaneous absorption but also has been recognized to be a target for hair follicle-associated disorders, such as androgenetic alopecia (AGA) and acne vulgaris. Hair follicle-targeting drug delivery systems allow for controlled drug release and enhance therapeutic efficacy with minimal side effects, exerting a promising method for the management of hair follicle-associated dysfunctions. Therefore, they have obtained much attention in several fields of research in recent years. This review gives an overview of potential follicle-targeting drug delivery formulations currently applied based on the particularities of the hair follicles, including a comprehensive assessment of their preclinical and clinical performance.

DPD Simulation on the Transformation and Stability of O/W and W/O Microemulsions

The dissipative particle dynamics simulation method is adopted to investigate the microemulsion systems prepared with surfactant (H1T1), oil (O) and water (W), which are expressed by coarse-grained models. Two topologies of O/W and W/O microemulsions are simulated with various oil and water ratios. Inverse W/O microemulsion transform to O/W microemulsion by decreasing the ratio of oil-water from 3:1 to 1:3. The stability of O/W and W/O microemulsion is controlled by shear rate, inorganic salt and the temperature, and the corresponding results are analyzed by the translucent three-dimensional structure, the mean interfacial tension and end-to-end distance of H1T1. The results show that W/O microemulsion is more stable than O/W microemulsion to resist higher inorganic salt concentration, shear rate and temperature. This investigation provides a powerful tool to predict the structure and the stability of various microemulsion systems, which is of great importance to developing new multifunctional microemulsions for multiple applications.

Optimization and Transfollicular Delivery of Finasteride-Loaded Proniosomes for Hair Growth Stimulation in C57BL/6Mlac Mice

The study aimed to develop the finasteride-loaded proniosome (FLP) to enhance the transfollicular delivery of finasteride (FN). The response surface methodology (RSM) combined with central composite design (CCD) with three independent variables (FN concentrations, total lipid content, and cholesterol content) was used to optimize the FLP preparation. The particles size, zeta potential, entrapment efficiency, and drug loading capacity of the FLP were analyzed. The transfollicular delivery of the optimum formulation was investigated in vitro. In vivo hair growth stimulation study was performed on C57BL/6Mlac mice dorsal areas. The Draize primary skin irritation test for erythema and edema was performed in the New Zealand white rabbit skin. The optimum FLP consists of 5.0 mM of FN, 10.1 mM of total lipid content, and 50.0% of the cholesterol in the total lipid. The prepared proniosome delivered the FN significantly (p < 0.05), compared to the naked finasteride solution in a dose- and time-dependent manner. The FLP treatment significantly increases the number and size of hair follicles in a dose-dependent manner. The efficiency of 1% FLP was comparable to the 2% minoxidil solution. The FLP exhibited no skin irritation after 72 h. Therefore, the results demonstrated that the FLP could stimulate hair growth via a transfollicular delivery system.

Topical transdermal chemoprevention of breast cancer: where will nanomedical approaches deliver us?

Despite the high incidence of breast cancer, there are few pharmacological prevention strategies for the high-risk population and those that are available have low adherence. Strategies that deliver drugs directly to the breasts may increase drug local concentrations, improving efficacy, safety and acceptance. The skin of the breast has been proposed as an administration route for local transdermal therapy, which may improve drug levels in the mammary tissue, due to both deep local penetration and percutaneous absorption. In this review, we discuss the application of nanotechnology-based strategies for the delivery of well established and new agents as well as drug repurposing using the topical transdermal route to improve the outcomes of preventive therapy for breast cancer.

A Recent Update on Drug Delivery Systems for Pain Management

Pain remains a global health challenge affecting approximately 1.5 billion people worldwide. Pain has been an implicit variable in the equation of human life for many centuries considering different types and the magnitude of pain. Therefore, developing an efficacious drug delivery system for pain management remains an open challenge for researchers in the field of medicine. Lack of therapeutic efficacy still persists, despite high throughput studies in the field of pain management. Research scientists have been exploiting different alternatives to curb the adverse side effects of pain medications or attempting a more substantial approach to minimize the prevalence of pain. Various drug delivery systems have been developed such as nanoparticles, microparticles to curb adverse side effects of pain medications or minimize the prevalence of pain. This literature review firstly provides a brief introduction of pain as a sensation and its pharmacological interventions. Second, it highlights the most recent studies in the pharmaceutical field for pain management and serves as a strong base for future developments. Herein, we have classified drug delivery systems based on their sizes such as nano, micro, and macro systems, and for each of the reviewed systems, design, formulation strategies, and drug release performance has been discussed.

Combined effect of sonophoresis and a microemulsion on the dermal delivery of celecoxib

The aim of this study was to evaluate the intensity of sonophoresis at which the skin penetration of celecoxib was enhanced and to study the combined effects of sonophoresis and microemulsion application on the dermal delivery of celecoxib. The sonophoresis intensity that provided the highest skin penetration enhancement of celecoxib was 30 Watts/cm². However, the combination of sonophoresis and the microemulsion resulted in a decrease in celecoxib skin penetration. The results of a confocal laser scanning microscopy study using the colocalization analysis of multifluorescently labeled particles revealed that the reduction in skin penetration of celecoxib from the combination of sonophoresis and a microemulsion resulted from a decrease in transfollicular penetration, which is the major skin absorption pathway of the microemulsion.

Design and evaluation of microemulsion-based efinaconazole formulations for targeted treatment of onychomycosis through transungual route: Ex vivo and nail clipping studies

The onychomycosis treatment remains a big challenge for onychologist due to the shorter nail residence time of topical formulations and the lack of availability of novel formulations in markets for new generation antifungal drugs. The objective of this work was to design, develop, optimize, and evaluate microemulsion formulations for effective delivery of efinaconazole through transungual route in onychomycosis treatment. Capmul® MCM (Glyceryl Caprylate/Caprate) as oil, Labrasol® (caprylocaproyl polyoxyl-8 glycerides) as a surfactant, and Transcutol® P (diethylene glycol monoethyl ether) as co-surfactant exhibited higher solubility of efinaconazole and surfactant-cosurfactant mixture (Smix) in a ratio of 1:1 rendered higher microemulsion region in the pseudo-ternary phase diagram. The optimized microemulsion formulation containing 6%w/w oil phase, 22.5%w/w surfactant, 22.5%w/w co-surfactant, and 49%w/w demineralized water was converted into gel formulation using 1.0%w/w Carbopol® 934 P gelling agent and evaluated for stability of 6 months. The optimized microemulsion formulation globule size was less than 100 nm. The ex vivo permeation confirmed improved permeation of efinaconazole from microemulsion formulations (346.36±12.90μgcm^-2) in comparison to reference formulation without observing any lag in drug permeation through the nail plate. The in vitro antifungal study data indicated increased antifungal efficacy relative to efinaconazole topical solution against Trichophyton rubrum, Trichophyton mentagrophytes, and Candida albicans species. Further, an in vitro cell cytotoxicity study exhibited no toxic effect for any excipients used in the formulation while applied on nail cells. Hence, the efinaconazole loaded microemulsion formulations could be considered as an effective therapy in the treatment of onychomycosis.

Development of Ultradeformable Liposomes with Fatty Acids for Enhanced Dermal Rosmarinic Acid Delivery

This study aimed to develop ultradeformable liposomes (ULs) with fatty acids, namely, oleic, linoleic, and linolenic acid, to improve the skin penetration of rosmarinic acid. This study also investigated the vesicle-skin interaction and skin penetration pathway of ULs with fatty acids using the co-localization technique of multifluorescently labeled particles. The prepared ULs were characterized in terms of size, surface charge, size distribution, shape, % entrapment efficiency (% EE), and % loading efficiency (% LE). The prepared ULs with fatty acids had an average particle size between 50.37 ± 0.3 and 59.82 ± 17.3 nm with a size distribution within an acceptable range and exhibited a negative surface charge. The average % EE and % LE were 9 and 24.02, respectively. The in vitro skin penetration study found that ULs with oleic acid could significantly increase the skin penetration of rosmarinic acid compared to ULs. According to confocal laser scanning microscopy observations, this study suggested that UL vesicles attach to the skin before releasing the entrapped drug to penetrate the skin. These findings suggested that ULs with oleic acid penetrated the skin via the transfollicular pathway as a major penetration pathway.

Microemulsion-Based Media in Nose-to-Brain Drug Delivery

Nose-to-brain drug delivery has recently attracted enormous attention as an alternative to other delivery routes, including the most popular oral one. Due to the unique anatomical features of the nasal cavity, drugs administered intranasally can be delivered directly to the central nervous system. The most important advantage of this approach is the ability to avoid the blood-brain barrier surrounding the brain and blocking the entry of exogenous substances to the central nervous system. Moreover, selective brain targeting could possibly avoid peripheral side effects of pharmacotherapy. The challenges associated with nose-to-brain drug delivery are mostly due to the small volume of the nasal cavity and insufficient drug absorption from nasal mucosa. These issues could be minimized by using a properly designed drug carrier. Microemulsions as potential drug delivery systems offer good solubilizing properties and the ability to enhance drug permeation through biological membranes. The aim of this review is to summarize the current status of the research focused on microemulsion-based systems for nose-to-brain delivery with special attention to the most extensively investigated neurological and psychiatric conditions, such as neurodegenerative diseases, epilepsy, and schizophrenia.

Biological Evaluation of Oil-in-Water Microemulsions as Carriers of Benzothiophene Analogues for Dermal Applications

During the last decade, many studies have been reported on the design and formulation of novel drug delivery systems proposed for dermal or transdermal administration. The efforts focus on the development of biocompatible nanodispersions that can be delivered to the skin and treat severe skin disorders, including cancer. In this context, oil-in-water (O/W) microemulsions have been developed to encapsulate and deliver lipophilic bioactive molecules for dermal application. An O/W biocompatible microemulsion composed of PBS buffer, Tween 80, and triacetin was assessed for its efficacy as a drug carrier of DPS-2, a lead compound, initially designed in-house to inhibit BRAF^V600E oncogenic kinase. The system was evaluated through both in vitro and ex vivo approaches. The cytotoxic effect, in the presence and absence of DPS-2, was examined through the thiazolyl blue tetrazolium bromide (MTT) cell proliferation assay using various cell lines. Further investigation through Western blotting revealed that cells died of necrosis. Porcine ear skin was used as a skin model to evaluate the degree of permeation of DPS-2 through skin and assess its retention. Through the ex vivo experiments, it was clarified that encapsulated DPS-2 was distributed within the full thickness of the stratum corneum (SC) and had a high affinity to hair follicles.

Repurposing INCI-registered compounds as skin prebiotics for probiotic Staphylococcus epidermidis against UV-B

Repurposing existing compounds for new indications may facilitate the discovery of skin prebiotics which have not been well defined. Four compounds that have been registered by the International Nomenclature of Cosmetic Ingredients (INCI) were included to study their abilities to induce the fermentation of Staphylococcusepidermidis (S. epidermidis), a bacterial species abundant in the human skin. Liquid coco-caprylate/caprate (LCC), originally used as an emollient, effectively initiated the fermentation of S. epidermidis ATCC 12228, produced short-chain fatty acids (SCFAs), and provoked robust electricity. Application of LCC plus electrogenic S. epidermidis ATCC 12228 on mouse skin significantly reduced ultraviolet B (UV-B)-induced injuries which were evaluated by the formation of 4-hydroxynonenal (4-HNE), cyclobutane pyrimidine dimers (CPD), and skin lesions. A S. epidermidis S2 isolate with low expressions of genes encoding pyruvate dehydrogenase (pdh), and phosphate acetyltransferase (pta) was found to be poorly electrogenic. The protective action of electrogenic S. epidermidis against UV-B-induced skin injuries was considerably suppressed when mouse skin was applied with LCC in combination with a poorly electrogenic S. epidermidis S2 isolate. Exploring new indication of LCC for promoting S. epidermidis against UV-B provided an example of repurposing INCI-registered compounds as skin prebiotics.

Development of Microemulsions Containing Glochidion wallichianum Leaf Extract and Potential for Transdermal and Topical Skin Delivery of Gallic Acid

Glochidion wallichianum (GW) is a good source of antioxidants, including gallic acid, promoting its development as a microemulsion. We constructed five pseudo-ternary phase diagrams comprising isopropyl myristate (IPM), water, and surfactant mixture (Smix)—i.e., Labrasol®:HCO-40® (1:1) with Transcutol® (1:1, 2:1, 3:1), and Tween80:Span80 (3:2) with Transcutol® or propylene glycol:ethanol (1:1). Additionally, blank and GW extract-loaded microemulsions were prepared at an IPM:Water:Smix ratio of 10:30:60 (high water content) and 30:10:60 (high oil content) from each Smix. The physical characteristics, skin permeation, and disposition were evaluated. The formulations with high water content and conductivities provided higher gallic acid permeation and disposition than those with high oil content. The Smix of Labrasol®:HCO-40® (1:1) and Transcutol® (1:1) promoted the highest gallic acid permeation (enhancement ratio 1.78 ± 0.12) and was suitable for transdermal delivery. However, the 1% hydroxypropyl methylcellulose control gel, the microemulsion with Smix of Labrasol®:HCO-40® (1:1) with Transcutol® (2:1), and Smix of Tween80:Span80 (3:2) with propylene glycol:ethanol (1:1) could provide higher skin accumulation of gallic acid than that with other formulations. The microstructures, ratio of surfactant:cosurfactant, and compositions of microemulsions were found to affect the skin permeation and disposition of gallic acid and require optimization to act as transdermal or topical delivery carriers.