Enhancement of Topical Delivery from Biodegradable Nanoparticles

Nanoparticle Skin Penetration: Depths and Routes Modeled In-Silico

Nanoparticles (NPs) are increasingly explored for targeted skin penetration, particularly for pharmaceutical and cosmetic applications. However, the complex system between NP properties, skin structure, and experimental conditions poses significant challenges in predicting their penetration depth and pathways. To what depth do NPs penetrate the skin, and which pathways do they follow? These are the questions which we tried to answer in this paper. A n in-silico human skin model based on 20 years of literature on NPs skin penetration is developed. The model incorporates 19 independent parameters, including a wide range of NP properties, skin across species, and test conditions. Using random forest analysis coupled with Kennard-Stone sorting, the model achieves a high predictive accuracy of 95%. The study identifies hair follicle diameter as the most critical factor influencing NP penetration across skin layers, surpassing other skin properties, NP properties, or experimental variables. Pig and rabbit skin are the most suitable models for simulating human skin in NP penetration studies. Additionally, the in-silico model reveals that NPs in emulsions and oil-based media predominantly follow the intercellular and transappendageal route. In contrast, those embedded in aqueous media favor the intracellular route. These findings offer insights for optimizing NP-based drug delivery systems.

Enhancement of Transdermal Drug Delivery: Integrating Microneedles with Biodegradable Microparticles

This investigation aimed to enhance transdermal methotrexate delivery through human skin by employing Dr. Pen microneedles and poly(d,l-lactide-co-glycolide) acid microparticles formulated from eight polymer grades (Expansorb DLG 95-4A, DLG 75-5A, DLG 50-2A, DLG 50-5A, DLG 50-8A, DLG 50-6P, DLG 50-7P, and DLL 10-15A). A comprehensive characterization of the microparticles was performed, encompassing various parameters such as size, charge, morphology, microencapsulation efficiency, yield, release kinetics, and chemical composition. The efficacy of microneedles in disrupting skin integrity was demonstrated by scanning electron microscopy, dye binding, histological examination, confocal laser microscopy, and pore size analysis. Microneedle-mediated skin microporation led to a substantial reduction in skin electrical resistance and a concomitant increase in transepidermal water loss. In vitro permeation experiments using human skin delivered microparticles into microporated skin and demonstrated a considerable difference in methotrexate delivery among the polymer groups. Microneedle treatment significantly amplified cumulative drug delivery, steady-state flux, diffusion coefficient, permeability coefficient, and drug concentration within skin layers while concurrently diminishing lag time (p < 0.05). Furthermore, a robust correlation was established between microparticle properties (cumulative release, release rate, encapsulation efficiency) and drug deposition in the skin. In conclusion, the synergistic combination of Dr. Pen microneedles and PLGA microparticles facilitated enhanced and regulated transdermal methotrexate delivery.

The Impact of Anesthesia on Dermatological Outcomes: A Narrative Review

Anesthesia is an essential component of dermatologic procedures, influencing pain management and patient outcomes, including wound healing, infection control, and cosmetic appearance. This review examines the impact of various anesthetic techniques, topical, local, regional, and general, on dermatological outcomes. The findings reveal that while local anesthesia is preferred due to its efficacy and safety, specialized considerations are necessary for pediatric, geriatric, and high-risk patients. Anesthesia-related complications, such as allergic reactions, systemic toxicity, and delayed healing, require careful selection of agents and techniques. Innovations in anesthetic technology, including nanotechnology, microneedle patches, and cryoanesthesia, promise to improve pain management and minimize complications. Personalized anesthesia approaches, informed by genetic and proteomic analyses, offer the potential to optimize individual patient care. However, further research is needed to understand the long-term effects of anesthetic agents on wound healing and scarring, especially in patients with comorbidities. Overall, this review emphasizes the evolving role of anesthesia in dermatology and highlights the need for ongoing innovation to enhance patient care, minimize risks, and improve procedural outcomes.

The Other Side of Plastics: Bioplastic-Based Nanoparticles for Drug Delivery Systems in the Brain

Plastics have changed human lives, finding a broad range of applications from packaging to medical devices. However, plastics can degrade into microscopic forms known as micro- and nanoplastics, which have raised concerns about their accumulation in the environment but mainly about the potential risk to human health. Recently, biodegradable plastic materials have been introduced on the market. These polymers are biodegradable but also bioresorbable and, indeed, are fundamental tools for drug formulations, thanks to their transient ability to pass through biological barriers and concentrate in specific tissues. However, this "other side" of bioplastics raises concerns about their toxic potential, in the form of micro- and nanoparticles, due to easier and faster tissue accumulation, with unknown long-term biological effects. This review aims to provide an update on bioplastic-based particles by analyzing the advantages and drawbacks of their potential use as components of innovative formulations for brain diseases. However, a critical analysis of the literature indicates the need for further studies to assess the safety of bioplastic micro- and nanoparticles despite they appear as promising tools for several nanomedicine applications.

Development of Essential Oil-Loaded Polymeric Nanocapsules as Skin Delivery Systems: Biophysical Parameters and Dermatokinetics Ex Vivo Evaluation

Essential oils (EOs) are natural antioxidant alternatives that reduce skin damage. However, EOs are highly volatile; therefore, their nanoencapsulation represents a feasible alternative to increase their stability and favor their residence time on the skin to guarantee their effect. In this study, EOs of Rosmarinus officinalis and Lavandula dentata were nanoencapsulated and evaluated as skin delivery systems with potential antioxidant activity. The EOs were characterized and incorporated into polymeric nanocapsules (NC-EOs) using nanoprecipitation. The antioxidant activity was evaluated using the ferric thiocyanate method. The ex vivo effects on pig skin were evaluated based on biophysical parameters using bioengineering techniques. An ex vivo dermatokinetic evaluation on pig skin was performed using modified Franz cells and the tape-stripping technique. The results showed that the EOs had good antioxidant activity (>65%), which was maintained after nanoencapsulation and purification. The nanoencapsulation of the EOs favored its deposition in the stratum corneum compared to free EOs; the highest deposition rate was obtained for 1,8-cineole, a major component of L. dentata, at 1 h contact time, compared to R. officinalis with a major deposition of the camphor component. In conclusion, NC-EOs can be used as an alternative antioxidant for skin care.

Size-Dependence of the Skin Penetration of Andrographolide Nanosuspensions: In Vitro Release-Ex Vivo Permeation Correlation and Visualization of the Delivery Pathway

Particle size is a key parameter to determine the capacity of nanoparticles to overcome the skin barrier; however, such effect and the possible mechanism remain only partially understood for nanosuspensions. In this work, we examined the skin delivery performance of andrographolide nanosuspensions (AG-NS) ranging in diameter from 250 nm to 1000 nm and analyzed the role of particle size in influencing their ability of skin penetration. The AG-NS with particle sizes of about 250 nm (AG-NS250), 450 nm (AG-NS450), and 1000 nm (AG-NS1000) were successfully prepared by ultrasonic dispersion method and characterized by transmission electron microscopy. The drug release and penetration via the intact and barrier-removed skin were compared by the Franz cell method, and the related mechanisms were probed using laser scanning confocal microscopy (LSCM) via visualization of penetration routes and histopathological study via observation of structural change of the skin. Our finding revealed that drug retention in the skin or its sub-layers was increased with the reduction of particle size, and the drug permeability through the skin also exhibited an obvious dependence on the particle size from 250 nm to 1000 nm. The linear relationship between the in vitro drug release and ex vivo permeation through the intact skin was well established among different preparations and in each preparation, indicating the skin permeation of the drug was mainly determined by the release process. The LSCM indicated that all these nanosuspensions could deliver the drug into the intercellular lipid space, as well as block the hair follicle in the skin, where a similar size dependence was also observed. The histopathological investigation showed that the formulations could make the stratum corneum of the skin loose and swelling without severe irritation. In conclusion, the reduction of particle size of nanosuspension would facilitate topical drug retention mainly via the modulation of drug release.

Nanocrystals as an emerging nanocarrier for the management of dermatological diseases

Skin conditions are amongst the most prevalent health issues in the world and come with a heavy economic, social, and psychological burden. Incurable and chronic skin conditions like eczema, psoriasis, fungal infections are linked to major morbidity in the manner of physical pain and a reduction in quality life of patients. Several drugs have difficulties for penetrating the skin due to the barrier mechanism of the skin layers and the incompatible physicochemical characteristics of the drugs. This has led to the introduction of innovative drug delivery methods. Currently, formulations depend on nanocrystals have indeed been researched for topical administration of drugs and have resulted in enhanced skin penetration. This review focuses on skin penetration barriers, modern methods to enhance topical distribution, and the use of nanocrystals to overcome these barriers. By means of mechanisms such as adherence to skin, creation of diffusional corona, targeting of hair follicles, and the generation of a greater concentration gradient throughout the skin, nanocrystals could enhance transport across the skin. Scientists working on product formulations incorporating chemicals that are "challenging-to-deliver" topically may find the most current findings to be of relevance.

Assessing the Dermal Penetration Efficacy of Chemical Compounds with the Ex-Vivo Porcine Ear Model

(1) Background: The ex vivo porcine ear model is often used for the determination of the dermal penetration efficacy of chemical compounds. This study investigated the influence of the post-slaughter storage time of porcine ears on the dermal penetration efficacy of chemical compounds. (2) Methods: Six different formulations (curcumin and different fluorescent dyes in different vehicles and/or nanocarriers) were tested on ears that were (i) freshly obtained, (ii) stored for 24 or 48 h at 4 °C after slaughter before use and (iii) freshly frozen and defrosted 12 h before use. (3) Results: Results showed that porcine ears undergo post-mortem changes. The changes can be linked to rigor mortis and all other well-described phenomena that occur with carcasses after slaughter. The post-mortem changes modify the skin properties of the ears and affect the penetration efficacy. The onset of rigor mortis causes a decrease in the water-holding capacity of the ears, which leads to reduced penetration of chemical compounds. The water-holding capacity increases once the rigor is released and results in an increased penetration efficacy for chemical compounds. Despite different absolute penetration values, no differences in the ranking of penetration efficacies between the different formulations were observed between the differently aged ears. (4) Conclusions: All different types of ears can be regarded to be suitable for dermal penetration testing of chemical compounds. The transepidermal water loss (TEWL) and/or skin hydration of the ears were not correlated with the ex vivo penetration efficacy because both an impaired skin barrier and rigor mortis cause elevated skin hydration and TEWL values but an opposite penetration efficacy. Other additional values (for example, pH and/or autofluorescence of the skin) should, therefore, be used to select suitable and non-suitable skin areas for ex vivo penetration testing. Finally, data from this study confirmed that smartFilms and nanostructured lipid carriers (NLC) represent superior formulation strategies for efficient dermal and transdermal delivery of curcumin.

Mathematical modelling of nanoparticle-mediated topical drug delivery to skin tissue

Nanoparticles have been extensively studied to improve drug delivery outcomes, however, their use in topical delivery remains controversial. Although the feasibility to cross the human skin barrier has been demonstrated in experiments, the risk of low drug concentration in deep tissue still limits the application. In this study, mathematical modelling is employed to examine the performance of nanoparticle-mediated topical delivery for sending drugs into the deep skin tissue. The pharmacokinetic effect is evaluated based on the drug exposure over time. As compared to the delivery using plain drugs, nanoparticle-mediated topical delivery has the potential to significantly improve the drug exposure in deep skin tissue. Modelling predictions denote that the importance of sufficient long-term drug-skin contact in achieving effective drug deposition in the deep skin tissue. The delivery outcomes are highly sensitive to the release rate. Accelerating the release from nanoparticles in stratum corneum is able to improve the drug exposure in stratum corneum and viable epidermis while resulting in the reductions in dermis and blood. The release rate in stratum corneum and viable epidermis should be well-designed below a threshold for generating effective drug accumulation in dermis and blood. A more localised drug accumulation can be achieved in the capillary-rich region of dermis by increasing the local release rate. The release rate in dermis needs to be optimised to increase the drug exposure in the dermis region where there are fewer blood and lymphatics capillaries. Results from this study can be used to improve the regimen of topical delivery for localised treatment.

The Factors Determining the Skin Penetration and Cellular Uptake of Nanocarriers: New Hope for Clinical Development

The skin provides a protective barrier against toxic environments and also offers a valuable route for topical drug delivery. The stratum corneum (SC) is the outermost layer of the skin and serves as the major barrier to chemical transfer through the skin. The human skin barrier is particularly difficult to overcome because of the complex composition and structure of the SC. Nanoparticulate carriers have gained widespread attention in topical drug delivery due to their tunable and versatile properties. The present review summarizes the main factors involved in skin penetration of nanocarriers containing the drug. Employment of nanotechnology in topical delivery has grown progressively during recent years; however, it is important to monitor the skin penetration of nanocarriers prior to their use to avoid possible toxic effects. Nanocarriers can act as a means to increase skin permeation of drugs by supporting direct interaction with the SC and increasing the period of permanence on the skin. Skin penetration is influenced by the physicochemical characteristics of nanocarriers such as composition, size, shape, surface chemistry, as well as skin features. Considering that the target of topical systems based on nanocarriers is the penetration of therapeutic agents in the skin layers, so a detailed understanding of the factors influencing skin permeability of nanocarriers is essential for safe and efficient therapeutic applications.

Challenges of nanotechnology in cosmetic permeation with caffeine

The evolution of beauty market and personal care is constant in Brazil as well in the rest of the world. Technological advances have brought up nanotechnology to the cosmetological field, employing active principles at atoms enveloped by vesicles, in order to take the active principle precisely to the target tissue to optimize the results achieved because of the considerable ease to cross skin barriers. Manufacturing of nanotechnology cosmetics is confronted with low absorption capacity. One of the many active principle found in cosmetic industry is caffeine, a pseudoalkaloid from the xanthine group used as a stimulant with the mechanism of the lipolytic action. This active is widely used in ​​a esthetics and cosmetics field in treatments involving dysfunctions such as localized fat and fibroedema geloid. To work out perfectly, the principle active need to interact and create a set of factors that includes lipolysis intensification. The caffeine encapsulation in gel-based nanocosmetics has the purpose of taking this active up to the adipocyte, the target cell, for mentioned dysfunctions treatment. Thus, we aim to present a review of how has been, the use of caffeine in the production of cosmetics.

Toward Precisely Controllable Acoustic Response of Shell-Stabilized Nanobubbles: High Yield and Narrow Dispersity

Understanding the pressure dependence of the nonlinear behavior of ultrasonically excited phospholipid-stabilized nanobubbles (NBs) is important for optimizing ultrasound exposure parameters for implementations of contrast enhanced ultrasound, critical to molecular imaging. The viscoelastic properties of the shell can be controlled by the introduction of membrane additives, such as propylene glycol as a membrane softener or glycerol as a membrane stiffener. We report on the production of high-yield NBs with narrow dispersity and different shell properties. Through precise control over size and shell structure, we show how these shell components interact with the phospholipid membrane, change their structure, affect their viscoelastic properties, and consequently change their acoustic response. A two-photon microscopy technique through a polarity-sensitive fluorescent dye, C-laurdan, was utilized to gain insights on the effect of membrane additives to the membrane structure. We report how the shell stiffness of NBs affects the pressure threshold (P_t) for the sudden amplification in the scattered acoustic signal from NBs. For narrow size NBs with 200 nm mean size, we find P_t to be between 123 and 245 kPa for the NBs with the most flexible membrane as assessed using C-Laurdan, 465-588 kPa for the NBs with intermediate stiffness, and 588-710 kPa for the NBs with stiff membranes. Numerical simulations of the NB dynamics are in good agreement with the experimental observations, confirming the dependence of acoustic response to shell properties, thereby substantiating further the development in engineering the shell of ultrasound contrast agents. The viscoelastic-dependent threshold behavior can be utilized for significantly and selectively enhancing the diagnostic and therapeutic ultrasound applications of potent narrow size NBs.

Development and Evaluation of Polymeric Nanosponge Hydrogel for Terbinafine Hydrochloride: Statistical Optimization, In Vitro and In Vivo Studies

Terbinafine hydrochloride, although one of the prominent antifungal agents, suffers from low drug permeation owing to its hydrophobic nature. The approach of nanosponge formulation may thus help to resolve this concern. Thus, the present research was envisioned to fabricate the nanosponge hydrogel of terbinafine hydrochloride for topical delivery since nanosponge augments the skin retentivity of the drug. The optimized formulation was obtained using Box Behnken Design. The dependent and independent process parameters were also determined wherein polyvinyl alcohol (%), ethylcellulose (%), and tween 80 (%) were taken as independent process parameters and particle size, polydispersity index (PDI), and entrapment efficiency (EE) were the dependent parameters. The nanosponge was then incorporated into the hydrogel and characterized. In-vitro drug release from the hydrogel was 90.20 ± 0.1% which was higher than the drug suspension and marketed formulation. In vitro permeation potential of the developed formulation through rat skin showed a flux of 0.594 ± 0.22 µg/cm²/h while the permeability coefficient was 0.059 ± 0.022 cm/s. Nanosponge hydrogel was evaluated for non-irritancy and antifungal activity against C. albicans and T. rubrum confirming the substantial outcome. Tape stripping studies exhibited ten times stripping off the skin quantified 85.6 ± 0.21 μg/cm². The confocal analysis justified the permeation potential of the prepared hydrogel. The mean erythemal score was 0.0, confirming that the prepared hydrogel did not cause erythema or oedema. Therefore, based on results obtained, nanosponge hydrogel formulation is a potential carrier for efficient topical delivery of terbinafine hydrochloride.

Targeting of the Pilosebaceous Follicle by Liquid Crystal Nanocarriers: In Vitro and In Vivo Effects of the Entrapped Minoxidil

The topical administration of active compounds represents an advantageous strategy to reach the various skin components as well as its appendages. Pilosebaceous follicles are skin appendages originating in the deeper skin layers. They are very difficult to target, and hence higher active dosages are generally required to achieve effective biological responses, thus favoring the rise of side effects. The aim of this work was to design a supramolecular colloidal carrier, i.e., a liquid crystal nanocarrier, for the selective delivery of active compounds into the pilosebaceous follicle. This nanocarrier showed mean sizes of ~80 nm, a good stability, a negative surface charge, and great safety properties. In vitro studies highlighted its ability to contain and release different substances and to successfully permeate the skin. Minoxidil was encapsulated in the nanocarriers and the in vivo biological effect was compared with a conventional dosage form. Minoxidil-loaded liquid crystal nanocarrier was able to selectively reach the pilosebaceous follicle, thus allowing an increased biological effectiveness of the delivered active in terms of biological response, duration of the biological effects, and reduction of collaterals. Our investigation showed that liquid crystal nanocarriers represent a promising device for the treatment of different pilosebaceous follicular impairments/diseases.

Allergic contact dermatitis to immobilization mask used in radiation therapy

Thermoplastic masks made of polyester resin are used to immobilize patients receiving radiation therapy. We describe a case of allergic contact dermatitis (ACD) to a thermoplastic mask worn by a child receiving proton beam therapy for treatment of medulloblastoma. ACD to a thermoplastic mask in an adult was first reported in 2018. (J Med Case Rep. 2018;12:181) To our knowledge, ACD to a thermoplastic mask has not been reported previously in the pediatric population.

Nanogels for Skin Cancer Therapy via Transdermal Delivery: Current Designs

BACKGROUND

Recently, several strategies have been proposed for skin cancer therapy by transdermal delivery, and particularly the use of nanotechnology.

METHODS

This process disrupts the stratum corneum to deliver a drug through the skin, allowing it to accumulate at the tumor site.

RESULTS

Nanogels are drug delivery systems that can be applied to many diseases. Nanogel engineering has been widely studied for use in drug delivery, particularly in cancer theranostics. This review summarizes specific strategies for using nanogels to treat skin cancer, a topic that is limited in recent literature.

CONCLUSION

Advanced techniques for effective skin cancer therapy based on the nanogel's penetration and cellular uptake abilities will be discussed. Moreover, techniques for penetrating the skin, as well as drug release, permeation studies, and microscopic observations, will also be discussed.

Recent advances in follicular drug delivery of nanoparticles

Introduction: The improvement of percutaneous absorption represents a clear dermatopharmaceutical aim. Recently, the hair follicle was recognized to be an important penetration pathway. Especially nanoparticles show an enhanced intrafollicular penetration and can be utilized to target specific cell populations within the hair follicle.Areas covered: The present review briefly summarizes the recent advances in follicular drug delivery of nanoparticles. Moreover, the particularities of the hair follicle as a penetration pathway are summarized which include its structure and specific barrier properties. Recently, the mechanism of the follicular penetration process has been clarified.In the meantime, different strategies have been developed to successfully improve follicular drug delivery of nanoparticles. One approach is to equip the nanocarriers with a triggered release system enabling them to release their drug load at the right time and place.Expert opinion: Follicular drug delivery with smart nanocarrier-based drug delivery systems represents a promising approach to increase the percutaneous absorption of topically applied substances. Although technical achievements and efficacy proofs concerning an increased penetration of substances are already available, the practical implementation into clinical application still represents an additional challenge and should be in the focus of interest in future research.

Permeation-enhancing effects and mechanisms of O-acylterpineol on isosorbide dinitrate: mechanistic insights based on ATR-FTIR spectroscopy, molecular modeling, and CLSM images

The present study aimed to evaluate the penetration activity of O-acylterpineol derivatives both in vitro and in vivo, and to investigate the enhancing mechanism of O-acylterpineol derivatives which were synthesized by α-terpineol and fatty acid. The promoting activities on the isosorbide dinitrate patch were tested across full thickness rabbit skin both in vitro and in vivo. In order to elucidate the permeation mechanism, attenuated total reflection Fourier transform infrared spectroscopy, molecular modeling, and confocal laser scanning microscopy were introduced to investigate the regulation of enhancers in the skin permeability and biophysical properties. With in vitro cytotoxicity test and in vivo erythema model, the skin irritation of enhancers was also evaluated. Permeation studies showed 2-(4-methylcyclohex-3-en-l-yl) propan-2-yl tetradecanoate produced the obvious enhancement activity for ISDN both in vitro and in vivo from patches. These results were supported by ATR-FTIR, molecular modeling, and CLSM studies which revealed that O-acylterpineol could decrease the order of the alkyl chains in the skin lipids. Additionally, it was found that TER-C14 produced a relatively low skin irritation, compared with the TER which was assumed to be a safe compound. The present research suggested that some newly designed acylterpineol derivatives are shown to be suitable permeation enhancers for transdermal drug delivery, and the chain length of C14 seem to be safe and more favorable for the penetration of ISDN from DIA patches.

Nanocarriers and Microcarriers for Enhancing the UV Protection of Sunscreens: An Overview

This review addresses a major question of importance to pharmaceutical scientists: how can novel drug delivery systems play a role in maximizing the UV protection of sunscreens? Because more and more people are being diagnosed with skin cancer each year than all other cancers combined, adequate sun protective measures are pivotal. In this context, the present review is to give an up-to-date overview on the different nanocarrier systems that have been explored so far for encapsulating different types of UV filters present on the market. The aim of these carrier systems is to prevent skin penetration and to enhance the photoprotective potential of sunscreen actives. For each supramolecular system, a brief description along with the studies, achievements, and pitfalls, on the type of UV actives inside them, ranging from classical UV filters to new generation of UV actives is given. A brief overview of UV filters encapsulated in microcarriers is also discussed.

Contrast enhanced ultrasound imaging by nature-inspired ultrastable echogenic nanobubbles

Advancement of ultrasound molecular imaging applications requires not only a reduction in size of the ultrasound contrast agents (UCAs) but also a significant improvement in the in vivo stability of the shell-stabilized gas bubble. The transition from first generation to second generation UCAs was marked by an advancement in stability as air was replaced by a hydrophobic gas, such as perfluoropropane and sulfur hexafluoride. Further improvement can be realized by focusing on how well the UCAs shell can retain the encapsulated gas under extreme mechanical deformations. Here we report the next generation of UCAs for which we engineered the shell structure to impart much better stability under repeated prolonged oscillation due to ultrasound, and large changes in shear and turbulence as it circulates within the body. By adapting an architecture with two layers of contrasting elastic properties similar to bacterial cell envelopes, our ultrastable nanobubbles (NBs) withstand continuous in vitro exposure to ultrasound with minimal signal decay and have a significant delay on the onset of in vivo signal decay in kidney, liver, and tumor. Development of ultrastable NBs can potentially expand the role of ultrasound in molecular imaging, theranostics, and drug delivery.

In Vitro Drug Dissolution/Permeation Testing of Nanocarriers for Skin Application: a Comprehensive Review

This review highlights in vitro drug dissolution/permeation methods available for topical and transdermal nanocarriers that have been designed to modulate the propensity of drug release, drug penetration into skin, and permeation into systemic circulation. Presently, a few of USFDA-approved in vitro dissolution/permeation methods are available for skin product testing with no specific application to nanocarriers. Researchers are largely utilizing the in-house dissolution/permeation testing methods of nanocarriers. These drug release and permeation methods are pending to be standardized. Their biorelevance with reference to in vivo plasma concentration-time profiles requires further exploration to enable translation of in vitro data for in vivo or clinical performance prediction.

Core-multishell nanocarriers enhance drug penetration and reach keratinocytes and antigen-presenting cells in intact human skin

In reconstructed skin and diffusion cell studies, core-multishell nanocarriers (CMS-NC) showed great potential for drug delivery across the skin barrier. Herein, we investigated penetration, release of dexamethasone (DXM), in excised full-thickness human skin with special focus on hair follicles (HF). Four hours and 16 h after topical application of clinically relevant dosages of 10 μg DXM/cm² skin encapsulated in CMS-NC (12 nm diameter, 5.8% loading), presence of DXM in the tissue as assessed by fluorescence microscopy of anti-DXM-stained tissue sections as well as ELISA and HPLC-MS/MS in tissue extracts was enhanced compared to standard LAW-creme but lower compared to DXM aqueous/alcoholic solution. Such enhanced penetration compared to conventional cremes offers high potential for topical therapies, as recurrent applications of corticosteroid solutions face limitations with regard to tolerability and fast drainage. The findings encourage more detailed investigations on where and how the nanocarrier and drug dissociate within the skin and what other factors, e.g. thermodynamic activity, influence the penetration of this formulations. Microscopic studies on the spatial distribution within the skin revealed accumulation in HF and furrows accompanied by limited cellular uptake assessed by flow cytometry (up to 9% of total epidermal cells). FLIM clearly visualized the presence of CMS-NC in the viable epidermis and dermis. When exposed in situ a fraction of up to 25% CD1a⁺ cells were found within the epidermal CMS-NC⁺ population compared to approximately 3% CD1a⁺/CMS-NC⁺ cells after in vitro exposure in short-term cultures of epidermal cell suspensions. The latter reflects the natural percentage of Langerhans cells (LC) in epidermis suspensions and indicated that CMS-NC were not preferentially internalized by one cell type. The increased CMS-NC⁺ LC proportion after exposure within the tissue is in accordance with the strategic suprabasal LC-localization. More specifically we postulate that the extensive dendrite meshwork, their position around HF orifices and their capacity to modulate tight junctions facilitated a preferential uptake of CMS-NC by LC within the skin. This newly identified aspect of CMS-NC penetration underlines the potential of CMS-NC for dermatotherapy and encourages further investigations of CMS-NC for the delivery of other molecule classes for which intracellular delivery is even more crucial.

An Evaluation of Curcumin-Encapsulated Chitosan Nanoparticles for Transdermal Delivery

Curcumin-loaded chitosan nanoparticles were synthesised and evaluated in vitro for enhanced transdermal delivery. Zetasizer® characterisation of three different formulations of curcumin nanoparticles (Cu-NPs) showed the size ranged from 167.3 ± 3.8 nm to 251.5 ± 5.8 nm, the polydispersity index (PDI) values were between 0.26 and 0.46 and the zeta potential values were positive (+ 18.1 to + 20.2 mV). Scanning electron microscopy (SEM) images supported this size data and confirmed the spherical shape of the nanoparticles. All the formulations showed excellent entrapment efficiency above 80%. FTIR results demonstrate the interaction between chitosan and sodium tripolyphosphate (TPP) and confirm the presence of curcumin in the nanoparticle. Differential scanning calorimetry (DSC) studies of Cu-NPs indicate the presence of curcumin in a disordered crystalline or amorphous state, suggesting the interaction between the drug and the polymer. Drug release studies showed an improved drug release at pH 5.0 than in pH 7.4 and followed a zero order kinetics. The in vitro permeation studies through Strat-M® membrane demonstrated an enhanced permeation of Cu-NPs compared to aqueous curcumin solution (p ˂ 0.05) having a flux of 0.54 ± 0.03 μg cm^-2 h^-1 and 0.44 ± 0.03 μg cm^-2 h^-1 corresponding to formulations 5:1 and 3:1, respectively. The cytotoxicity assay on human keratinocyte (HaCat) cells showed enhanced percentage cell viability of Cu-NPs compared to curcumin solution. Cu-NPs developed in this study exhibit superior drug release and enhanced transdermal permeation of curcumin and superior percentage cell viability. Further ex vivo and in vivo evaluations will be conducted to support these findings.

Simultaneous GC-FID Quantification of Main Components of Rosmarinus officinalis L. and Lavandula dentata Essential Oils in Polymeric Nanocapsules for Antioxidant Application

The essential oils (EO) of R. officinalis and L. dentata have been widely used due to their antioxidant activity. However, due to their high volatility, the loading of EO into polymeric nanocapsules (NC) represents an efficient way of retaining their effect in future topical administration. In this way, the quantitative determination of EO incorporated into NC is necessary for simultaneous monitoring of the main components of the EO during the nanoencapsulation process as well as for precise and exact dosing of the components used during the performance of in vitro and in vivo biological tests. In this study, EO were isolated by hydrodistillation in a Clevenger-type apparatus and characterized by GC-MS and GC-FID analyses. The major constituents of EO-R. officinalis were camphor (39.46%) and 1,8-cineole (14.63%), and for EO-L. dentata were 1,8-cineole (68.59%) and β-pinene (11.53%). A new analytical method based on GC-FID for quantification of free and encapsulated EO was developed and validated according to ICH. Linearity, limit of detection and quantification, and intra- and interday precision parameters were determined. The methods were linear and precise for the quantification of the main components of EO. The EO were encapsulated by nanoprecipitation and were analyzed by the GC-FID method validated for their direct quantification. The NC size was 200 nm with homogeneous size distribution. The quantification of the incorporated EO within a NC is an important step in NC characterization. In this way, an encapsulation efficiency of at least 59.03% and 41.15% of total EO-R. officinalis and EO-L. dentata, respectively, was obtained. Simple, repeatable, and reproducible methods were developed as an analytical tool for the simultaneous quantification of the main components of EO loaded in polymeric nanocapsules as well as their monitoring in biological assays.

Recent development in biodegradable nanovehicle delivery system-assisted immunotherapy

A schematic illustration of BNDS biodegradation and release antigen delivery for assisting immunotherapy.

Coated microneedles mediated intradermal delivery of octaarginine/BRAF siRNA nanocomplexes for anti-melanoma treatment

BRAF is the most frequently mutated gene in skin melanoma. Applying BRAF siRNA (siBraf) to silencing BRAF gene is a current frontline therapy for melanoma. However, delivery of macromolecular siRNA into the tumor site and introduction of siRNA into the tumor cells remain as challenges. In this study, we for the first time developed a siBraf delivery system based on cell penetrating peptide octaarginine (R8) nanocomplexes combined with coated microneedles (MNs), i.e. R8/siBraf coated MNs, for targeted anti-melanoma treatment. The R8/siBraf nanocomplexes were optimized based on the internalization of siBraf by A375 cells. In vitro A375 cell experiments presented that R8/siBraf can enhance siBraf transfection, silence BRAF gene, and inhibit tumor cells growth, comparable to polyethylenimine (PEI)/siBraf. R8/siBraf coated MNs can effectively deliver R8/siBraf into the disease site. In vivo anti-melanoma experiments indicated that R8/siBraf coated MNs can significantly inhibit the melanoma development, induce the tumor cells apoptosis, and suppress their proliferation. The BRAF gene in tumor were also significantly silenced in vivo. SiBraf intradermal delivery via combining MNs and R8 nanocomplexes is a promising approach for skin melanoma treatment, which exploited both virtues of MNs and cell penetrating peptide to obtain the targeting inhibition efficacy on skin melanoma.

Nanocrystal: a novel approach to overcome skin barriers for improved topical drug delivery

INTRODUCTION

Skin is an important route of drug delivery for the treatment of various dermatological conditions. The advent of nanotechnology is paving the roadmaps for topical drug delivery by providing sustained release as well as maintaining a localized effect, outweighing the toxicity concern.

AREAS COVERED

This review highlighted the morphology of skin, its barrier nature as well as drug penetration pathways after topical application of formulations. The existing methods to improve topical drug delivery, by infringing or permeating the skin barriers, are discussed. This context concretes the foundation to accentuate the need for the development of nanocrystal-based topical formulation. The mechanism of drug release, immediate as well as sustained release, after topical administration of drug nanocrystals is also elaborated. The special emphasis is given on the breakthrough achieved, in topical drug delivery using drug nanocrystals, so far in the plethora of literature, patents, and products, under clinical trial as well as in the market.

EXPERT OPINION

The current research on nanocrystals for topical drug delivery is highlighting the breakthroughs achieved so far. The output of these research envisages that topical nanocrystals based formulations can be a novel strategy for the drugs which are facing solubility, bioavailability and toxicity concerns.

Combined use of nanocarriers and physical methods for percutaneous penetration enhancement

Dermal and transdermal drug delivery (due to its non-invasiveness, avoidance of the first-pass metabolism, controlling the rate of drug input over a prolonged time, etc.) have gained significant acceptance. Several methods are employed to overcome the permeability barrier of the skin, improving drug penetration into/through skin. Among chemical penetration enhancement methods, nanocarriers have been extensively studied. When applied alone, nanocarriers mostly deliver drugs to skin and can be used to treat skin diseases. To achieve effective transdermal drug delivery, nanocarriers should be applied with physical methods, as they act synergistically in enhancing drug penetration. This review describes combined use of frequently used nanocarriers (liposomes, novel elastic vesicles, lipid-based and polymer-based nanoparticles and dendrimers) with the most efficient physical methods (microneedles, iontophoresis, ultrasound and electroporation) and demonstrates superiority of the combined use of nanocarriers and physical methods in drug penetration enhancement compared to their single use.

Methacrylate-Stitched β-Cyclodextrin Embedded with Nanogold/Nanotitania: A Skin Adhesive Device for Enhanced Transdermal Drug Delivery

Transdermal (TD) drug delivery is a more attractive technique for drug delivery compared to oral and intravenous injection. However, the permeation of drug molecules across the skin is difficult due to the presence of highly ordered lipid barrier. This study details the development of a novel TD system, which has the potential to simultaneously enhance the skin permeability and adhesion behavior. Ibuprofen (IP) was selected as model drug. The ability of gold nanoparticle (AuNP) and hydrophobic titanium nanotube (TNT) to enhance the skin permeability was explored. Additionally, β-cyclodextrin (βCD), which can exceptionally encapsulate poorly water-soluble drugs, is grafted with methacrylates to improve the skin adhesion property. Finally, Au-TNT nanocomposite was deposited onto methacrylate-grafted βCD matrix. The developed material was characterized through NMR spectroscopy, infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and Raman spectroscopy. The characteristics of the film, including water vapor permeability (WVP), thermomechanical properties, etc., were examined in terms of Au-TNT content. The TD delivery of IP with different concentrations of Au-TNT was evaluated via an in vitro skin permeation study through rat skin. It is revealed that the prepared TD film exhibited an improved drug-delivery performance due to the synergistic action of AuNP and hydrophobic TNT. The cumulative percent of IP delivered across the skin is extremely depending on nanofiller content, lipophilicity, and thickness of the membrane, and the device incorporated with 4.0% Au-TNT displayed the best performance. In addition, a study on storage stability was performed by storing the films for 2 months at different temperatures. The study revealed that the device possessed excellent storage stability when stored at low temperature. The developed film offers excellent WVP, drug encapsulation efficiency, thermomechanical properties, and skin adhesion behavior. Moreover, the device was cosmetically attractive, noncytotoxic, and resistant to microbial growth and hence extremely reliable for skin application. The developed skin permeation strategy may open new avenues in TD drug delivery.

Skin-penetrating polymeric nanoparticles incorporated in silk fibroin hydrogel for topical delivery of curcumin to improve its therapeutic effect on psoriasis mouse model

A poor percutaneous penetration capability for most topical anti-inflammatory drugs is one of the main causes compromising their therapeutic effects on psoriatic skin. Even though curcumin has shown a remarkable efficacy in the treatment of psoriasis, its effective penetration through the stratum corneum is still a major challenge during transdermal delivery. The aim of our study was to design skin-permeating nanoparticles (NPs) to facilitate delivery of curcumin to the deeper layers of the skin. A novel amphiphilic polymer, RRR-α-tocopheryl succinate-grafted-ε-polylysine conjugate (VES-g-ε-PLL) was synthesized and self-assembled into polymeric nanoparticles. The nanoparticles of VES-g-ε-PLL exhibiting an ultra-small hydrodynamic diameter (24.4nm) and a positive Zeta potential (19.6mV) provided a strong skin-penetrating ability in vivo. Moreover, curcumin could effectively be encapsulated in the polymeric nanoparticles with a drug loading capacity of 3.49% and an encapsulating efficiency of 78.45%. In order to prolong the retention time of the ultra-small curcumin-loaded nanoparticles (CUR-NPs) in the skin, silk fibroin was used as a hydrogel-based matrix to further facilitate topical delivery of the model drug. In vitro studies showed that CUR-NPs incorporated in silk fibroin hydrogel (CUR-NPs-gel) exhibited a slower release profile of curcumin than the plain CUR-gel, without compromising the skin penetration ability of CUR-NPs. In vivo studies on miquimod-induced psoriatic mice showed that CUR-NPs-gel exhibited a higher therapeutic effect than CUR-NPs as the former demonstrated a more powerful skin-permeating capability and a more effective anti-keratinization process. CUR-NPs-gel was therefore able to inhibit the expression of inflammatory cytokines (TNF-α, NF-κB and IL-6) to a greater extent. In conclusion, the permeable nanoparticle-gel system may be a potential carrier for the topical delivery of lipophilic anti-psoriatic drugs.

Evaluation of Transdermal Drug Permeation as Modulated by Lipoderm and Pluronic Lecithin Organogel

The transdermal delivery of 2 fluorescent probes with similar molecular weight but different lipophilicity, into and through the skin from 2 commercially available transdermal bases, pluronic lecithin organogel, and Lipoderm^® has been evaluated. First, in vitro penetration of fluorescein sodium and fluorescein (free acid) through porcine skin was evaluated. Retention and depth distribution profiles in skin were obtained by tape stripping and then followed by optical sectioning using multiphoton microscopy. The results showed that Lipoderm^® led to an enhanced penetration of the hydrophilic compound, fluorescein sodium. For the lipophilic compound fluorescein (free acid), Lipoderm^® performed similar to pluronic lecithin organogel base, where minimal drug was detected in either receptor phase. The skin retention and depth distribution results also showed that the hydrophilic fluorescein sodium had high skin retention with Lipoderm^®, whereas fluorescein (free acid) had very low penetration and retention with increasing skin depth. Moreover, optical sectioning by multiphoton microscopy revealed an uneven distribution of probes across the skin in the x-y plane for both transdermal bases. This work showed that a hydrophilic compound has significantly increased skin penetration and retention when formulated with Lipoderm^®, and the skin retention of the probe was the main determinant of its skin flux.

Pickering emulsions stabilized by biodegradable block copolymer micelles for controlled topical drug delivery

Surfactant-free biocompatible and biodegradable Pickering emulsions were investigated as vehicles for skin delivery of hydrophobic drugs. O/w emulsions of medium-chain triglyceride (MCT) oil droplets loaded with all-trans retinol as a model hydrophobic drug were stabilized by block copolymer nanoparticles: either poly(lactide)-block-poly(ethylene glycol) (PLA-b-PEG) or poly(caprolactone)-block-poly(ethylene glycol) (PCL-b-PEG). Those innovative emulsions were prepared using two different processes allowing drug loading either inside oil droplets or inside both oil droplets and non-adsorbed block copolymer nanoparticles. Skin absorption of retinol was investigated in vitro on pig skin biopsies using the Franz cell method. Supplementary experiments by confocal fluorescence microscopy allowed the visualization of skin absorption of the Nile Red dye on histological sections. Retinol and Nile Red absorption experiments showed the large accumulation of hydrophobic drugs in the stratum corneum for the Pickering emulsions compared to the surfactant-based emulsion and an oil solution. Loading drug inside both oil droplets and block copolymer nanoparticles enhanced again skin absorption of drugs, which was ascribed to the supplementary contribution of free block copolymer nanoparticles loaded with drug. Such effect allowed tuning drug delivery to skin over a wide range by means of a suitable selection of either the formulation or the drug loading process.

Biodegradable Core⁻Multishell Nanocarriers: Influence of Inner Shell Structure on the Encapsulation Behavior of Dexamethasone and Tacrolimus

We here present the synthesis and characterization of a set of biodegradable core⁻multishell (CMS) nanocarriers. The CMS nanocarrier structure consists of hyperbranched polyglycerol (hPG) as core material, a hydrophobic (12, 15, 18, 19, and 36 C-atoms) inner and a polyethylene glycol monomethyl ether (mPEG) outer shell that were conjugated by ester bonds only to reduce the toxicity of metabolites. The loading capacities (LC) of the drugs, dexamethasone and tacrolimus, and the aggregate formation, phase transitions, and degradation kinetics were determined. The intermediate inner shell length (C15) system had the best overall performance with good LCs for both drugs as well as a promising degradation and release kinetics, which are of interest for dermal delivery.

Lipid- and Polymer-Based Nanostructures for Cutaneous Delivery of Curcumin

It is well-known that nanoencapsulation may overcome biopharmaceutical limitations of curcumin (CUR), but studies regarding the contribution of the vesicular nature of CUR-loaded nanoparticles on skin permeation are still scarce. Therefore, the effect of three colloidal systems (solid lipid nanoparticles (SLN), nanoemulsion (NE), and polymeric nanoparticles (NP)) on the control of cutaneous permeation of CUR was investigated in porcine ear skin/Franz diffusion cells. Colloidal suspensions were designed to present a similar particle size (±170 nm), narrow size distribution (PdI < 0.2), and high entrapment efficiency (>99%). Zeta potential values were -0.13, -9.68 and -36.7 mV for the CUR-loaded NP, SLN and NE, respectively. Nanoencapsulation resulted in a cumulative amount of CUR in the more superficial layers of the skin. NP significantly enhanced the compound retention in the epidermis, which was approximately 2.49- and 3.32-fold more than SLN and NE, respectively. The CUR levels into the dermis were significantly increased after treatment with NE, which may be associated with repulsion phenomena in surface skin. Therefore, a more superficial or deeper action of CUR on the skin may be obtained depending on nanostructure type. While NPs are more effective in upper skin layers, NE should be prioritized when a dermal action for the CUR is required.

Degradability and Clearance of Silicon, Organosilica, Silsesquioxane, Silica Mixed Oxide, and Mesoporous Silica Nanoparticles

The biorelated degradability and clearance of siliceous nanomaterials have been questioned worldwide, since they are crucial prerequisites for the successful translation in clinics. Typically, the degradability and biocompatibility of mesoporous silica nanoparticles (MSNs) have been an ongoing discussion in research circles. The reason for such a concern is that approved pharmaceutical products must not accumulate in the human body, to prevent severe and unpredictable side-effects. Here, the biorelated degradability and clearance of silicon and silica nanoparticles (NPs) are comprehensively summarized. The influence of the size, morphology, surface area, pore size, and surface functional groups, to name a few, on the degradability of silicon and silica NPs is described. The noncovalent organic doping of silica and the covalent incorporation of either hydrolytically stable or redox- and enzymatically cleavable silsesquioxanes is then described for organosilica, bridged silsesquioxane (BS), and periodic mesoporous organosilica (PMO) NPs. Inorganically doped silica particles such as calcium-, iron-, manganese-, and zirconium-doped NPs, also have radically different hydrolytic stabilities. To conclude, the degradability and clearance timelines of various siliceous nanomaterials are compared and it is highlighted that researchers can select a specific nanomaterial in this large family according to the targeted applications and the required clearance kinetics.

Efficient delivery of nanoparticles to deep skin layers using dissolvable microneedles with an extended-length design

Dissolvable microneedles with an extended-length design can efficiently deliver NPs to the deep skin layers and prolong the skin retention time of NPs up to 5 days.

Design of an Inflammation-Sensitive Polyelectrolyte-Based Topical Drug Delivery System for Arthritis

The most successful treatment strategy for arthritis is intra-articular injections that are costly and have reduced patient compliance. The purpose of the current study was to develop an inflammation-sensitive system for topical drug administration. Multi-macromolecular alginate-hyaluronic acid-chitosan (A-H-C) polyelectrolyte complex nanoparticles, loaded with indomethacin were developed employing pre-gel and post-gel techniques in the presence of dodecyl-L-pyroglutamate (DLP). In addition to in vitro studies, in silico simulations were performed to affirm and associate the molecular interactions inherent to the formulation of core all-natural multi-component biopolymeric architectures composed of an anionic (alginate), a cationic (chitosan), and an amphi-ionic polyelectrolytic (hyaluronic acid) macromolecule. The results demonstrated that DLP significantly influenced the size of the synthesized nanoparticles. Drug-content analysis revealed higher encapsulation efficiency (77.3%) in the presence of DLP, irrespective of the techniques used. Moreover, in vitro drug release studies showed that indomethacin release from the nanosystem was significantly improved (98%) in Fenton's reagent. Drug permeation across a cellulose membrane using a Franz diffusion cell system showed an initial surge flux (0.125 mg/cm(-2)/h), followed by sustained release of indomethacin for the post-gel nanoparticles revealing its effective skin permeation efficiency. In conclusion, the study presents novel nanoparticles which could effectively encapsulate and deliver hydrophobic drugs to the target site, particularly for arthritis.

Comparison of different in vitro release methods used to investigate nanocarriers intended for dermal application

In vitro drug release measurement is one of the most important methods used to assess the quality of a nanocarrier and estimate it́s in vivo performance. Different in vitro drug release methods have been used to investigate the drug release from nanocarriers, however, little information is available with regard to a comparison of these methods (e.g. discriminative power, reproducibility). Thus, drug release from four nanocarriers (nanocrystals, lipid nanoparticles, Eudragit^® RS and ethyl cellulose nanoparticles) was investigated under sink and non-sink conditions with three drug release methods: an in situ method using Sirius^® inForm and two in vitro methods using dialysis bags and Franz diffusion cells. Dexamethasone was used as the model drug. The in situ measurement was a simple and fast method but not adequately discriminating because of a too rapid drug dissolution/release. Franz diffusion cells and dialysis bags were in most cases discriminative for the different nanocarriers with the drug dissolution/release being in the order of nanocrystals>Eudragit^® RS nanoparticles>lipid nanoparticles>ethyl cellulose nanoparticles. Drug release experiments with Franz diffusion cells had the highest reproducibility. The Franz diffusion cells could also be easily used with semisolid dosage forms.