Retinyl palmitate flexible polymeric nanocapsules: characterization and permeation studies

PEGylated and functionalized polylactide-based nanocapsules: An overview

Polymeric nanocapsules (NC) are versatile mixed vesicular nanocarriers, generally containing a lipid core with a polymeric wall. They have been first developed over four decades ago with outstanding applicability in the cosmetic and pharmaceutical fields. Biodegradable polyesters are frequently used in nanocapsule preparation and among them, polylactic acid (PLA) derivatives and copolymers, such as PLGA and amphiphilic block copolymers, are widely used and considered safe for different administration routes. PLA functionalization strategies have been developed to obtain more versatile polymers and to allow the conjugation with bioactive ligands for cell-targeted NC. This review intends to provide steps in the evolution of NC since its first report and the recent literature on PLA-based NC applications. PLA-based polymer synthesis and surface modifications are included, as well as the use of NC as a novel tool for combined treatment, diagnostics, and imaging in one delivery system. Furthermore, the use of NC to carry therapeutic and/or imaging agents for different diseases, mainly cancer, inflammation, and infections is presented and reviewed. Constraints that impair translation to the clinic are discussed to provide safe and reproducible PLA-based nanocapsules on the market. We reviewed the entire period in the literature where the term "nanocapsules" appears for the first time until the present day, selecting original scientific publications and the most relevant patent literature related to PLA-based NC. We presented to readers a historical overview of these Sui generis nanostructures.

Binding Affinity of Concanavalin A to Native and Acid-Hydrolyzed Phytoglycogen Nanoparticles

Phytoglycogen (PG) is a polysaccharide produced in the kernels of sweet corn as soft, highly branched, compact nanoparticles. Its tree-like or dendritic architecture, combined with a high-safety profile, makes PG nanoparticles attractive for use in biological applications, many of which rely on the association or binding of small biomolecules. We have developed a methodology to functionalize surface plasmon resonance (SPR) sensor surfaces with PG nanoparticles, and we demonstrate the utility of the PG-functionalized SPR sensor by measuring the binding affinity of the tetrameric concanavalin A (ConA) protein to both native PG nanoparticles and smaller, softer acid-hydrolyzed PG nanoparticles. We measure comparable values of the equilibrium association constant K for native and acid-hydrolyzed PG, with a slightly smaller value for the acid-hydrolyzed particles that we attribute to unfavorable lateral interactions between the tetrameric subunits of ConA due to the increase in surface curvature of the smaller acid-hydrolyzed PG particles. We also use infrared reflection-absorption spectroscopy (IRRAS) to show that ConA maintains a large fraction of its native conformation, and thus its bioactivity, upon binding to PG, representing an important step toward the realization of PG as a novel bioactive delivery vehicle.

Integrated approaches to testing and assessment for grouping nanomaterials following dermal exposure

Exposure to different nanoforms (NFs) via the dermal route is expected in occupational and consumer settings and thus it is important to assess their dermal toxicity and the contribution of dermal exposure to systemic bioavailability. We have formulated four grouping hypotheses for dermal toxicity endpoints which allow NFs to be grouped to streamline and facilitate risk assessment. The grouping hypotheses are developed based on insight into how physicochemical properties of NFs (i.e. composition, dissolution kinetics, size, and flexibility) influence their fate and hazard following dermal exposure. Each hypothesis is accompanied by a tailored Integrated Approach to Testing and Assessment (IATA) that is structured as a decision tree and tiered testing strategies (TTS) for each relevant question (at decision nodes) that indicate what information is needed to guide the user to accept or reject the grouping hypothesis. To develop these hypotheses and IATAs, we gathered and analyzed existing information on skin irritation, skin sensitization, and dermal penetration of NFs from the published literature and performed experimental work to generate data on NF dissolution in sweat simulant fluids. We investigated the dissolution of zinc oxide and silicon dioxide NFs in different artificial sweat fluids, demonstrating the importance of using physiologically relevant conditions for dermal exposure. All existing and generated data informed the formulation of the grouping hypotheses, the IATAs, and the design of the TTS. It is expected that the presented IATAs will accelerate the NF risk assessment for dermal toxicity via the application of read-across.

Transition in the Glassy Dynamics of Melts of Acid-Hydrolyzed Phytoglycogen Nanoparticles

The deformability, responsiveness, and tunability of soft nanoparticles (NPs) offer unique opportunities to learn about their complex properties and the interactions between particles. In the present study, we provide new insights into the physical properties of phytoglycogen (PG) NPs, which are soft, compact particles with a dendritic architecture that are produced in the kernels of sweet corn. In particular, we study PG NPs modified using acid hydrolysis, which not only reduces their diameter but also alters their stiffness, internal structure, and the interactions between particles in aqueous dispersions. We used steady shear rheology to determine the dependence of the relative zero-shear viscosity η_r of aqueous dispersions of acid-hydrolyzed PG NPs on the effective volume fraction ϕ_eff, which indicated a reduction in stiffness of the particles relative to that of native PG NPs. We quantified this difference by analyzing the nature of the colloidal glasses formed at high ϕ_eff. We measured a smaller value of the fragility index m for acid-hydrolyzed PG NP glasses than that for native PG NP glasses, indicating that acid-hydrolyzed PG NPs form stronger glasses and are therefore softer than native PG NPs. Unlike the native PG NPs, we observed a distinctive change in the character of the glass transition of the acid-hydrolyzed PG NPs as ϕ_eff was increased above ϕ_eff∼1: a crossover in the dependence of η_r on ϕ_eff from Vogel-Fulcher-Tammann behavior to a more gradual, Arrhenius-like behavior. By expressing the steady shear and oscillatory rheology data in terms of generalized Péclet numbers, we obtained collapse of the data onto master curves. We interpret this result in terms of the acid-hydrolyzed PG NPs predominantly interpenetrating neighboring particles at large ϕ_eff, for which fluctuations of the outer chains enhance the mobility of the particles and make α-relaxation times τ_α experimentally accessible.

Nano intervention in topical delivery of corticosteroid for psoriasis and atopic dermatitis-a systematic review

Atopic dermatitis (AD) and psoriasis are highly prevalent, complex, chronic inflammatory skin diseases that immensly affect the patient's quality of life. While there is no definitive cure for these conditions, suppressive medications aim at managing the symptoms of these diseases. The application of emollients accompanied by symptomatic anti-inflammatory therapy consisting of topical corticosteroids (TCS) is extensively employed for controlling the symptoms among general practitioners making this therapeutic class an indispensable pillar of dermatotherapeutics. The first TCS, hydrocortisone (HC) introduced in the early 1950s led to the development of different steroidal moieties of varying potencies by inducing chemical modifications to the basic steroid structure. The wide spectrum of the available range of formulations and potency provides flexibility to treat all patient groups, different phases of the diseases, and different anatomical sites. Conventional TCS therapy suffers from drawbacks such as low drug permeation and retention rate. Thus, novel nanoformulations have been developed to overcome these problems. This review provides an insight into the current state of nanocarrier-mediated topical delivery of corticosteroids monotherapy and combination therapy with special emphasis on targeting psoriasis and AD.

Force Spectroscopy Mapping of the Effect of Hydration on the Stiffness and Deformability of Phytoglycogen Nanoparticles

Phytoglycogen is a naturally occurring glucose polymer that is produced by sweet corn in the form of compact nanoparticles with a dendritic or tree-like architecture. The soft and porous nature of the nanoparticles, combined with their biodegradability and lack of toxicity, makes them ideal for a broad range of applications in personal care, nutrition, and biomedicine. To fully exploit these applications, it is necessary to understand the complex properties of the soft, hydrated nanoparticles in detail. In the present study, we have used atomic force microscopy (AFM) force spectroscopy to collect high-resolution force-distance maps of a large number of individual phytoglycogen nanoparticles, providing unique insights into the morphology and mechanical stiffness of the nanoparticles at the single-particle level. Our measurements performed in water on nanoparticles covalently bonded to gold surfaces revealed an inner branched structure and high deformability of the nanoparticles at modest values of the applied force. These measurements also allowed us to determine the spatial distribution of Young's modulus values within individual nanoparticles. Drying of the nanoparticles resulted in a dramatic increase in Young's modulus, quantifying the effect of hydration on their mechanical stiffness. We obtained excellent agreement between AFM and osmotic pressure measurements of the mechanical properties of hydrated phytoglycogen nanoparticles; the ratio of the average Young's modulus measured using AFM to the bulk modulus measured using osmotic pressure was in close agreement with that expected for a material with Poisson's ratio ν = 0. The soft, deformable nature of phytoglycogen nanoparticles revealed by our measurements provides new insights at the single-nanoparticle level and suggests their suitability for biomedical applications such as transdermal and targeted drug delivery.

New pectin-based hydrogel containing imiquimod-loaded polymeric nanocapsules for melanoma treatment

We developed a pectin-based hydrogel containing nanocapsules as a new strategy for melanoma treatment. Our first objective was to evaluate the nanoencapsulation effect of imiquimod on melanoma. Imiquimod-loaded polymeric nanocapsules (NCimiq) showed significant time-dependent decrease in cell viability after treatment at 3 μmol L^-1 (79% viable cells in 24 h and 55% in 72 h), which was not observed in cells treated with the solution of the drug (IMIQ) (99% viable cells in 24 h and 91% in 72 h). The second objective was to develop the hydrogel containing the drug-loaded nanocapsules (PEC-NCimiq). In vitro release study showed that 63% of imiquimod was released from the pectin-based hydrogel containing the drug (PEC-imiq) after 2 h, while 60% of the drug was released from PEC-NCimiq after 8 h. In the permeation study, 2.5 μg of imiquimod permeated the skin within 8 h after the initial contact of PEC-NCimiq, whereas only 2.1 μg of drug permeated after 12 h of contact when PEC-imiq was assayed. Pectin-based hydrogels enabled the drug penetration in all skin layers, especially the dermis (PEC-NCimiq = 6.8 μg and PEC-imiq = 4.3 μg). In the adhesion study, PEC-NCimiq showed the highest adhesiveness (42% removed from the skin) in comparison to PEC-imiq (71% removed from the skin). In conclusion, the nanoencapsulation provided a higher cytotoxic effect of imiquimod in SK-MEL-28, and the incorporation of the drug-loaded nanocapsules in pectin-based hydrogel showed higher adhesiveness and deeper penetration of the drug into the skin. Graphical abstract.

Epidermal Delivery of Retinyl Palmitate Loaded Transfersomes: Penetration and Biodistribution Studies

The alteration of retinoids levels in the skin can cause different disorders in the maturation of epithelial skin cells. Topical administration of these lipophilic molecules is a challenge that can be addressed by encapsulation into drug delivery systems. In this study, retinyl palmitate transferosomes formulated in cream were developed and the increases in the penetration of the active ingredients as well as the biodistribution were evaluated in vitro and in vivo. Transfersomes demonstrated a significant increase in the administration of retinyl palmitate to the epidermis by quantification of the active ingredients in the different layers of the skin, as well as by fluorescence microscopy of biopsies of non-dermatomized pig-ear skin. These results suggest that transfersomes may be an efficient vehicle for the delivery of retinoids to inner layers of the skin, such as the epidermis.

Pharmacotherapeutic approaches for transportation of anticancer agents via skin

Cancer is the largest family of diseases that involve abnormal uncontrolled cell growth which metastasizes to other parts of the body. The most common type of cancers includes lung, liver, colorectal, prostate, stomach, breast and cervical cancer with skin cancer excluding melanoma (contribute up to 40% of the cases). The conventional treatment approaches like surgery, chemotherapy, etc., have several side effects such as severe inflammation and pain. Hence, pharmacotherapeutic approaches of antineoplastic agents can be advantageous for treating various forms of cancer through the skin. Novel transdermal techniques and preparations have been emerged to overcome the limitations of skin and to penetrate inside the cancerous cells by transporting through the deeper tissues of the skin. The transdermal penetration of drugs using different formulations such as nanocarriers, physical penetration enhancement techniques, chemical penetration enhancers and newer technologies such as gels, dendrimers, needle-free injection jet etc., show improved patient compliance, abolition of scars and economic value. The topical delivery of antineoplastic agents is an attractive choice for increasing site-specific delivery, reducing side effects and improving therapeutic effects. The objective of this review is to present insights into pharmacotherapeutic techniques, which can be used for transdermal delivery of anticancer agents through skin due to its potential to create a new frontier in treatment of cancer.

Understanding the prospective of nano-formulations towards the treatment of psoriasis

Psoriasis is a consistently recurring, inflammatory, autoimmune disorder of the skin, affecting about 2-5% of the world population. Abundant therapeutic agents are accessible for the treatment of psoriasis. Nevertheless, none of them are entirely secure and effective to treat the disease without compromising patient compliance. Furthermore, already existing drugs are supposed to restrain the ailment and alleviate the sign and symptoms with no complete cure. However, they focus on restraining the disease and alleviating the symptoms without providing an absolute cure. Therefore there remains a vital challenge, to explore a new drug moiety or delivery system which could safely and effectively manage psoriasis without compromising patient compliance. Furthermore, conventional formulations offer reduced benefit/risk ratio of anti-psoriatic drugs, which limits the use of existing conventional formulations. Novel formulations based on nanocarriers are a promising prospect to overcome the limitation of conventional formulations by offering a reduction in dose, dosing frequency, dose-dependent, side effects with enhanced efficacy. Presently nano-formulations have gained widespread application for effective and safe treatment of psoriasis. The present review primarily focuses on conventional therapeutic strategy and recent advances in lipid-based, polymer-based and metallic nano-formulations of a variety of anti-psoriatic drugs. The practicability of various nanocarrier systems including liposomes, nanostructured lipid carriers, ethosomes, solid lipid nanoparticles, nanocapsules, micelles, dendrimers, gold nanoparticles and silver nanoparticles have been discussed in detail. The review also traces related patents to exemplify the role of various nanoparticles in psoriasis treatment. In a nutshell, nano-formulations remain established as a promising modality for treating psoriasis treatment as they propose better penetration, targeted delivery, enhanced safety, and efficacy.

Potential enhancement and targeting strategies of polymeric and lipid-based nanocarriers in dermal drug delivery

Nanocarriers used for alternative drug-delivery strategies have gained interest due to improved penetration and delivery of drugs into specific regions of the skin in recent years. Dermal drug delivery via polymeric-based nanocarriers (polymeric nanoparticles, micelles, dendrimers) and lipid-based nanocarriers (solid–lipid nanoparticles and nanostructured lipid carriers, vesicular nanocarriers including liposomes, niosomes, transfersomes and ethosomes) has been widely investigated. Although penetration of nanocarriers through the intact skin could be restricted, these carriers are particularly considered as feasible for the treatment of dermatological diseases in which the skin barrier is disrupted and also for follicular delivery of drugs for management of skin disorders such as acne. This review mainly highlights the recent approaches on potential penetration enhancement and targeting mechanisms of these nanocarriers.

Advances in the bioanalytical study of drug delivery across the skin

The study of a drug's dermal penetration profile provides important pharmaceutical data for the rational development of topical and transdermal delivery systems because the skin is a broadly used delivery route for local and systemic drugs and a potential route for gene therapy and vaccines. Monitoring drug penetration across the skin and quantifying its levels in different skin layers have been constant challenges due to the detection limitations of the available techniques, as well as the inherent interference in this tissue. This review explores and discusses several bionalytical methods that are indispensable tools to study drugs across the skin. In addressing the main topic, we structure the review highlighting the skin as an important route of drug administration and its structure, skin membrane models most used and its properties, in vitro and in vivo assays most used in the study of drug delivery to the skin, the techniques for processing the skin for subsequent analysis by bioanalytical methods that have a theoretical and practical approach showing its applicability, limitations and also including examples of its use. This review has a comprehensive approach in order to help researchers design their experiments and update the applicability and advances in this area of expertise.

Lipid nanoparticles for the topical delivery of retinoids and derivatives

Retinoids are lipophilic compounds that are highly used in cosmetics/therapeutics for skin disorders. Conventional formulations are limited by poor water solubility, high chemical/photochemical instability and the irritation of retinoids. Interestingly, lipid nanoparticles enable the administration of retinoids in aqueous media, providing drug stabilization and controlled release. Recently, it has been demonstrated that retinoids in solid lipid nanoparticles, nanostructured lipid carriers, nanoemulsions and nanocapsules can decrease degradation, improve targeting and enhance efficacy for the treatment of skin disorders. This article focuses on the formulation, fabrication, characterization and in vitro/in vivo evaluation of solid lipid nanoparticles, nanostructured lipid carriers, nanoemulsions and nanocapsules loaded with retinoids for skin administration. Furthermore, the incorporation of these lipid nanoparticles into secondary vehicles is discussed.

Nanoemulsions (NEs), liposomes (LPs) and solid lipid nanoparticles (SLNs) for retinyl palmitate: effect on skin permeation

The aim of this study was to develop biocompatible lipid-based nanocarriers for retinyl palmitate (RP) to improve its skin delivery, photostability and biocompatibility, and to avoid undesirable topical side effects. RP loaded nanoemulsions (NEs), liposomes (LPs) and solid lipid nanoparticles (SLNs) were characterized in terms of size, surface electrical charge, pH, drug encapsulation efficiency and morphology. Spherical-shaped nanocarriers with a negatively charged surface (>|40|mV) and mean size lower than 275 nm were produced with adequate skin compatibility. The rheological properties showed that aqueous dispersions of SLNs followed a non-Newtonian behavior, pseudoplastic fluid adjusted to Herschel-Bulkley equation, whereas LPs and NEs exhibited a Newtonian behavior. SLNs offered significantly better photoprotection than LPs and NEs for RP. The cumulative amount of drug permeated through human skin at the end of 38 h was 6.67 ± 1.58 μg, 4.36 ± 0.21 μg and 3.64 ± 0.28 μg for NEs, LPs and SLNs, respectively. NEs flux was significantly higher than SLNs and LPs: NEs (0.37 ± 0.12 μg/h) > LPs (0.15 ± 0.09 μg/h) > SLNs (0.10 ± 0.05 μg/h). LPs offered significant higher skin retention than NEs and SLNs. Finally, even though all developed nanocarriers were found to be biocompatible, according to histological studies, NE was the system that most disrupted the skin. These encouraging findings can guide in proper selection of topical carriers among the diversity of available lipid-based nanocarriers, especially when a dermatologic or cosmetic purpose is desired.

Drug delivery nanoparticles in skin cancers

Nanotechnology involves the engineering of functional systems at nanoscale, thus being attractive for disciplines ranging from materials science to biomedicine. One of the most active research areas of the nanotechnology is nanomedicine, which applies nanotechnology to highly specific medical interventions for prevention, diagnosis, and treatment of diseases, including cancer disease. Over the past two decades, the rapid developments in nanotechnology have allowed the incorporation of multiple therapeutic, sensing, and targeting agents into nanoparticles, for detection, prevention, and treatment of cancer diseases. Nanoparticles offer many advantages as drug carrier systems since they can improve the solubility of poorly water-soluble drugs, modify pharmacokinetics, increase drug half-life by reducing immunogenicity, improve bioavailability, and diminish drug metabolism. They can also enable a tunable release of therapeutic compounds and the simultaneous delivery of two or more drugs for combination therapy. In this review, we discuss the recent advances in the use of different types of nanoparticles for systemic and topical drug delivery in the treatment of skin cancer. In particular, the progress in the treatment with nanocarriers of basal cell carcinoma, squamous cell carcinoma, and melanoma has been reported.

Enhanced In Vitro Skin Deposition Properties of Retinyl Palmitate through Its Stabilization by Pectin

The purpose of this study was to examine the effect of stabilization of retinyl palmitate (RP) on its skin permeation and distribution profiles. Skin permeation and distribution study were performed using Franz diffusion cells along with rat dorsal skin, and the effect of drug concentration and the addition of pectin on skin deposition profiles of RP was observed. The skin distribution of RP increased in a concentration dependent manner and the formulations containing 0.5 and 1 mg of pectin demonstrated significantly increased RP distributions in the epidermis. Furthermore, it was found that skin distribution of RP could be further improved by combined use of pectin and ascorbyl palmitate (AP), due largely to their anti-oxidative effect. These results clearly demonstrate that the skin deposition properties of RP can be improved by stabilizing RP with pectin. Therefore, it is strongly suggested that pectin could be used in the pharmaceutical and cosmetic formulations as an efficient stabilizing agent and as skin penetration modulator.

Improved percutaneous delivery of ketoprofen using combined application of nanocarriers and silicon microneedles

Objectives

The aim of our study was to evaluate the effect of designing ketoprofen-loaded nanosized spheres and combining them with solid silicon microneedles for enhanced and sustained percutaneous drug delivery.

Methods

Ketoprofen-loaded nanoparticles (KET-NP) were designed by modified solvent displacement method, using poly (D, L-lactic acid) (PDLLA). All prepared nanoparticles were characterised with regard to their particle size distribution, morphology, surface properties, thermal behaviour, drug content, drug release and stability. In-vitro skin permeation studies were conducted on Franz-type diffusion cells using porcine skin treated with ImmuPatch silicon microneedles (Tyndall Nation Institute, Cork, Ireland).

Key findings

The study showed that uniform nanospheres were prepared with high encapsulation efficiency and retained stable for 2 months. After an initial burst release, the PDLLA nanoparticles were capable of sustaining and controlling ketoprofen release that followed Korsmeyer–Peppas kinetics. An enhanced flux of ketoprofen was observed in the skin treated with silicon microneedles over a prolonged period of time.

Conclusions

Following application of silicon microneedle arrays, KET-NP were able to enhance ketoprofen flux and supply the porcine skin with drug over a prolonged (24 h) period of time. Our findings indicate that the delivery strategy described here could be used for the further development of effective and painless administration systems for sustained percutaneous delivery of ketoprofen.

Retinyl palmitate–loaded poly(lactide-co-glycolide) nanoparticles for the topical treatment of skin diseases

Nanoparticles were prepared with poly(lactide- co-glycolide), Pluronic F127, and phospholipids and loaded with retinyl palmitate. Morphology and physicochemical properties of these nanoparticles were determined by atomic force microscopy, light scattering, and zeta potential. The elasticity and deformability of the nanoparticles were correlated to Tg values measured by differential scanning calorimetry. The in vitro cytotoxicity and genotoxicity of the nanosystems were determined using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, cell membrane asymmetry, and Ames tests with BALB/3T3 mouse embryo fibroblasts and HaCaT human keratinocytes cell lines. The reactive oxygen species levels and cytokine production in response to the exposure of cells to these nanoparticles were investigated, as well as the penetration in human skin culture.