Transdermal drug delivery: overcoming the skin's barrier function

Iontophoresis and electroporation-assisted microneedles: advancements and therapeutic potentials in transdermal drug delivery

Transdermal drug delivery (TDD) using electrically assisted microneedle (MN) systems has emerged as a promising alternative to traditional drug administration routes. This review explores recent advancements in this technology across various therapeutic applications. Integrating iontophoresis (IP) and electroporation (EP) with MN technology has shown significant potential in improving treatment outcomes for various conditions. Studies demonstrate their effectiveness in enhancing vaccine and DNA delivery, improving diabetes management, and increasing efficacy in dermatological applications. The technology has also exhibited promise in delivering nonsteroidal anti-inflammatory drugs (NSAIDs), treating multiple sclerosis, and advancing obesity and cancer therapy. These systems offer improved drug permeation, targeted delivery, and enhanced therapeutic effects. While challenges remain, including safety concerns and technological limitations, ongoing research focuses on optimizing these systems for broader clinical applications. The future of electrically assisted MN technologies in TDD appears promising, with potential advancements in personalized medicine, smart monitoring systems, and expanded therapeutic applications.

Evaluation of Drug Permeation Enhancement by Using In Vitro and Ex Vivo Models

Drugs administered by means of extravascular routes of drug administration must be absorbed into the systemic circulation, which involves the movement of the drug molecules across biological barriers such as epithelial cells that cover mucosal surfaces or the stratum corneum that covers the skin. Some drugs exhibit poor permeation across biological membranes or may experience excessive degradation during first-pass metabolism, which tends to limit their bioavailability. Various strategies have been used to improve drug bioavailability. Absorption enhancement strategies include the co-administration of chemical permeation enhancers, enzymes, and/or efflux transporter inhibitors, chemical changes, and specialized dosage form designs. Models with physiological relevance are needed to evaluate the efficacy of drug absorption enhancement techniques. Various in vitro cell culture models and ex vivo tissue models have been explored to evaluate and quantify the effectiveness of drug permeation enhancement strategies. This review deliberates on the use of in vitro and ex vivo models for the evaluation of drug permeation enhancement strategies for selected extravascular drug administration routes including the nasal, oromucosal, pulmonary, oral, rectal, and transdermal routes of drug administration.

Liposomal Nanocarriers to Enhance Skin Delivery of Chemotherapeutics in Cancer Therapy

Cancer chemotherapeutics administered to cancer patients via traditional oral or parenteral routes often encounter poor bioavailability and severe systemic side effects. Skin delivery is a promising alternative route with reduced side effects and improved therapeutic efficacy and has gained significant attention in recent years. With conventional or deformable liposomal nanocarriers as a skin permeation strategy, cancer chemotherapeutics can be delivered via skin route, offering an option for more efficient therapy. This review summarizes the recent advances in liposome nanocarrier efficacy to enhance the skin delivery of chemotherapeutics with a wide range of physicochemical properties (log Poct from -0.89 to 5.93, MW from 130 to 1415) in targeting local skin cancer, breast cancer, and tumor metastasis and delivering the drug to systemic circulation to treat distal cancers. The potential mechanisms of skin permeation enhancement by different type of liposomes are also discussed in this review.

Establishing a General Atomistic Model for the Stratum Corneum Lipid Matrix Based on Experimental Data for Skin Permeation Studies

Understanding the permeation of drugs through the intercellular lipid matrix of the stratum corneum layer of skin is crucial for effective transdermal delivery. Molecular dynamics simulations can provide molecular insights into the permeation process. In this study, we developed a new atomistic model representing the multilamellar arrangement of lipids in the stratum corneum intercellular space for permeation studies. The model was built using ceramides in extended conformation as the backbone along with free fatty acids and cholesterol. The properties of the equilibrated model were in agreement with the neutron scattering data and hydration behavior previously reported in the literature. The permeability of molecules, such as water, benzene and estradiol, and the molecular mechanism of action of permeation enhancers, such as eucalyptol and limonene, were evaluated using the model. The new model can be reliably used for studying the permeation of small molecules and for gaining mechanistic insights into the action of permeation enhancers.

Effect of the barrier function of stratum corneum and viable epidermis and dermis on the skin concentration of topically applied chemicals

Three-dimensional cultured skin (3D skin) models have been utilized for in vitro skin permeation tests to evaluate the skin permeation rate and local effects (efficacy and toxicity) of applied chemicals, particularly from the perspective of the 3Rs (reduction, replacement, refinement) approach. The steady-state concentration of applied chemicals at different depths in the viable epidermis and dermis (VED) is affected by their skin permeation parameters, such as permeability coefficient (Kp) and partition coefficient (K) from the donor solution to the skin of the chemicals. In the present study, the steady-state concentration of chemicals in the VED of EpiDerm 606X (EpiDerm) as representative of a 3D skin model were compared with hairless rat skin. The VED concentrations of chemicals in EpiDerm were higher than those in hairless rat skin when a model hydrophilic compound, antipyrine, and a model lipophilic compound, flurbiprofen, were applied, suggesting that the barrier functions of the VED against the whole skin were higher in EpiDerm than in hairless rat skin. When an ester compound, ethyl nicotinate, was applied, the VED concentration of nicotinic acid, a metabolite of ethyl nicotinate, was lower in EpiDerm than in hairless rat skin. These differences in the VED concentrations of applied chemicals might be related to false-positives and -negatives of topical effects evaluated with 3D skin models. It is important to pay particular attention to differences in VED concentration in 3D skin models and real skin when evaluating local efficacy and toxicity using 3D skin models.

Enhanced transdermal delivery of insulin by choline-based ionic liquids

Ionic liquids (ILs) show promises as chemical penetration enhancers (CPEs) for transdermal delivery of macromolecular drugs. However, their high viscosity and strong drug-IL affinity may limit drug diffusion and release from the drug-loaded IL (one-step strategy). Herein, a two-step strategy was used by applying choline-based ILs as pretreatment agents followed by insulin solution to improve penetration. Insulin remained stable in the ILs and are released slowly from the IL matrices. In vitro and in vivo studies showed that two-step treatment enhanced insulin penetration compared to one-step treatment, with choline citrate ([Ch][Ci]) and choline geranate ([Ch][Ge]) performing the best. In a diabetic rat model, two-step treatment with [Ch][Ge] reduced blood glucose levels to below 80% within 8 h, while one-step treatment only maintained for 12 h. Trans-epidermal water loss and molecular dynamics simulations suggested that variations in release rates and skin condition accounted for the differences between the two strategies. Physical characterization confirmed that ILs enhanced transdermal delivery of insulin by permeabilizing stratum corneum and opening tight junctions. Preliminary safety assessment indicated mild irritation by [Ch][Ge], whereas [Ch][Ci] showed good biocompatibility. It is concluded that ILs hold potential in enhancing transdermal delivery of insulin.

Effect of gelatin nanoparticles' size and charge on iontophoretic targeted deposition to the hair follicles

Hair follicles (HFs) represent a route of interest to drug delivery for treating several skin conditions. Iontophoresis, on the other hand, is a physical method to enhance drug permeation by applying a low electrical current to the formulation. HFs can be targeted following topical iontophoretic application, as they represent a pathway of lower electrical resistance, as well as a drug reservoir, in particular useful for nanoparticles (NPs), which can preferably accumulate in these structures. Combining both strategies may provide optimal results, but the literature still lacks evidence of the ideal NP characteristics for the iontophoretic drug delivery targeting the HFs. Here, we aimed to evaluate the effect of gelatin NPs' size and charge under iontophoresis application on NPs' deposition into the HFs. Four gelatin NP formulations were produced with varying gelatin concentrations and gelatin types (positively charged type A and negatively charged type B), with sizes ranging from 220 to 770 nm. A fluorescent dye, TRITC-dextran 150 kDa, was encapsulated for monitoring NPs deposition. Cutaneous penetration experiments were performed in vitro with and without iontophoresis for 6 h with pig ear skin. The deposition profile was assessed by confocal laser scanning microscopy. Photomicrographs showed a higher accumulation of the larger positively charged NPs (AL), reaching deeper portions of HFs, and showed iontophoresis further increased their deposition, resulting in the highest signal. In conclusion, these findings shed light on the applications of NPs and bring novel treatment opportunities for several diseases compromising the hair follicles.

Advancements in microneedle technology: current status and next-generation innovations

Microneedle technology is a pivotal component of third-generation transdermal drug delivery systems featuring tiny needles that create temporary microscopic channels in the stratum corneum which facilitate drug penetration in the dermis. This review offers a detailed examination of the current types of microneedles, including solid, coated, dissolving, hollow, and swelling microneedles, along with their preparation techniques as well as their benefits and challenges. Use of 3D printing technology is especially gaining significant attention due to its ability to achieve the high dimensional accuracy required for precise fabrication. Additionally, its customisability presents significant potential for exploring new designs and creating personalised microneedles products. Furthermore, this review explores next generation microneedles, especially stimuli-responsive microneedle, bioinspired microneedle and microneedles combined with other transdermal technology like sonophoresis, electroporation and iontophoresis. Regulatory aspects, characterisation techniques, safety considerations, and cost factors have also been addressed which are crucial for translation from lab to the market.

Formulation and Ex Vivo Evaluation of Ivermectin Within Different Nano-Drug Delivery Vehicles for Transdermal Drug Delivery

Background/Objectives: Ivermectin gained widespread attention as the "miracle drug" during the coronavirus disease 2019 (COVID-19) pandemic. Its inclusion in the 21st World Health Organization (WHO) List of Essential Medicines is attributed to its targeted anti-helminthic response, high efficacy, cost-effectiveness and favorable safety profile. Since the late 2000s, this bio-inspired active pharmaceutical ingredient (API) gained renewed interest for its diverse therapeutic capabilities. However, producing ivermectin formulations does remain challenging due to its poor water solubility, resulting in low bioavailability after oral administration. Therefore, the transdermal drug delivery of ivermectin was considered to overcome these challenges, which are observed after oral administration. Methods: Ivermectin was incorporated in a nano-emulsion, nano-emulgel and a colloidal suspension as ivermectin-loaded nanoparticles. The nano-drug delivery vehicles were optimized, characterized and evaluated through in vitro membrane release studies, ex vivo skin diffusion studies and tape-stripping to determine whether ivermectin was successfully released from its vehicle and delivered transdermally and/or topically throughout the skin. This study concluded with cytotoxicity tests using the methyl thiazolyl tetrazolium (MTT) and neutral red (NR) assays on both human immortalized epidermal keratinocytes (HaCaT) and human immortalized dermal fibroblasts (BJ-5ta). Results: Ivermectin was successfully released from each vehicle, delivered transdermally and topically throughout the skin and demonstrated little to no cytotoxicity at concentrations that diffused through the skin. Conclusions: The type of nano-drug delivery vehicle used to incorporate ivermectin influences its delivery both topically and transdermally, highlighting the dynamic equilibrium between the vehicle, the API and the skin.

Design Principles and Applications of Ionic Liquids for Transdermal Drug Delivery

Ionic liquids (ILs) are salts with melting points typically <100 °C, composed of specific anions and cations. Recently, IL application has expanded into material engineering and biomedicine. Due to their unique properties, ILs have garnered significant interest in pharmacological research as solubilizers, transdermal absorption enhancers, antibacterial agents, and stabilizers of insoluble pharmaceutical active ingredients. The improvement of skin permeability by ILs is closely associated with their specific physicochemical characteristics, which are identified by their ionic composition. However, the existing literature on transdermal medication administration is insufficient in terms of a comprehensive knowledge base. This review provides a comprehensive assessment of the design principles involved in IL synthesis. Additionally, it discusses the methods utilized to assess skin permeability and provides a focused outline of IL application in transdermal drug administration.

Development of Minodronic Acid-Loaded Dissolving Microneedles for Enhanced Osteoporosis Therapy: Influence of Drug Loading on the Bioavailability of Minodronic Acid

Osteoporosis is a metabolic bone disorder with impaired bone microstructure and increased bone fractures, seriously affecting the quality of life of patients. Among various bisphosphonates prescribed for managing osteoporosis, minodronic acid (MA) is the most potent inhibitor of bone context resorption. However, oral MA tablet is the only commercialized dosage form that has extremely low bioavailability, severe adverse reactions, and poor patient compliance. To tackle these issues, we developed MA-loaded dissolving microneedles (MA-MNs) with significantly improved bioavailability for osteoporosis therapy. We investigated the influence of drug loading on the physicochemical properties, transdermal permeation behavior, and pharmacokinetics of MA-MNs. The drug loading of MA-MNs exerted almost no effect on their morphology, mechanical property, and skin insertion ability, but it compromised the transdermal permeability and bioavailability of MA-MNs. Compared with oral MA, MA-MNs with the lowest drug loading (224.9 μg/patch) showed a 9-fold and 25.8-fold increase in peak concentration and bioavailability, respectively. This may be ascribed to the reason that the increased drug loading can generate higher burst release, higher drug residual rate, and drug supersaturation effect in skin tissues, eventually limiting drug absorption into the systemic circulation. Moreover, MA-MNs prolonged the half-life of MA and provided more steady plasma drug concentrations than intravenously injected MA, which helps to reduce dosing frequency and side effects. Therefore, dissolving MNs with optimized drug loading provides a promising alternative for bisphosphonate drug delivery.

The Design Features, Quality by Design Approach, Characterization, Therapeutic Applications, and Clinical Considerations of Transdermal Drug Delivery Systems-A Comprehensive Review

Transdermal drug delivery systems (TDDSs) are designed to administer a consistent and effective dose of an active pharmaceutical ingredient (API) through the patient's skin. These pharmaceutical preparations are self-contained, discrete dosage forms designed to be placed topically on intact skin to release the active component at a controlled rate by penetrating the skin barriers. The API provides the continuous and prolonged administration of a substance at a consistent rate. TDDSs, or transdermal drug delivery systems, have gained significant attention as a non-invasive method of administering APIs to vulnerable patient populations, such as pediatric and geriatric patients. This approach is considered easy to administer and helps overcome the bioavailability issues associated with conventional drug delivery, which can be hindered by poor absorption and metabolism. A TDDS has various advantages compared to conventional methods of drug administration. It is less intrusive, more patient-friendly, and can circumvent first pass metabolism, as well as the corrosive acidic environment of the stomach, that happens when drugs are taken orally. Various approaches have been developed to enhance the transdermal permeability of different medicinal compounds. Recent improvements in TDDSs have enabled the accurate administration of APIs to their target sites by enhancing their penetration through the stratum corneum (SC), hence boosting the bioavailability of drugs throughout the body. Popular physical penetration augmentation methods covered in this review article include thermophoresis, iontophoresis, magnetophoresis, sonophoresis, needle-free injections, and microneedles. This review seeks to provide a concise overview of several methods employed in the production of TDDSs, as well as their evaluation, therapeutic uses, clinical considerations, and the current advancements intended to enhance the transdermal administration of drugs. These advancements have resulted in the development of intelligent, biodegradable, and highly efficient TDDSs.

PAMAM dendrimers as mediators of dermal and transdermal drug delivery: a review

OBJECTIVES

Poly(amidoamine) dendrimers have been widely investigated as potential nanomaterials that can enhance the skin permeation of topically applied drugs. This article reviews the studies that have used dendrimers as penetration enhancers and examines the mechanisms by which enhancement is claimed.

KEY FINDINGS

A wide range of studies have demonstrated that, in certain circumstances and for certain drugs, the incorporation of dendrimers into a topically applied formulation can significantly increase the amount of drug passing into and through the skin. In some cases, dendrimers offered little or no enhancement of skin permeation, suggesting that the drug-dendrimer interaction and the selection of a specific dendrimer were central to ensuring optimal enhancement of skin permeation. Significant interactions between dendrimers and other formulation components were also reported in some cases.

SUMMARY

Dendrimers offer substantial potential for enhancing drug delivery into and across the skin, putatively by mechanisms that include occlusion and changes to surface tension. However, most of these studies are conducted in vitro and limited progress has been made beyond such laboratory studies, some of which are conducted using membranes of limited relevance to humans, such as rodent skin. Thus, the outcomes and claims of such studies should be treated with caution.

Network pharmacology, molecular docking, and untargeted metabolomics reveal molecular mechanisms of multi-targets effects of Qingfei Tongluo Plaster improving respiratory syncytial virus pneumonia

Objective

Qingfei Tongluo Plaster (QFP), an improved Chinese medicine hospital preparation, is an attractive treatment option due to its well clinical efficacy, convenience, economy, and patient compliance in the treatment of respiratory syncytial virus (RSV) pneumonia. The aim of this study was to investigate the efficacy mechanism of QFP on RSV rats from the perspective of alleviating lung inflammation and further explore the changes of serum metabolites and metabolic pathways in RSV rats under the influence of QFP.

Methods

This study used network pharmacological methods and molecular docking combined with molecular biology and metabolomics from multi-dimensional perspectives to screen and verify the therapeutic targets. Open online databases were used to speculate the gene targets of efficient ingredients and diseases. Then, we used the String database to examine the fundamental interaction of common targets of drugs and diseases. An online enrichment analysis was performed to predict the functional pathways. Molecular docking was applied to discover the binding modes between essential ingredients and crucial gene targets. Finally, we demonstrated the anti-inflammatory ability of QFP in the RSV-evoked pneumonia rat model and explained the mechanism in combination with the metabolomics results.

Results

There were 19 critical targets defined as the core targets: tumor necrosis factor (TNF), inducible nitric oxide synthase 2 (NOS2), mitogen-activated protein kinase 14 (MAPK14), g1/S-specific cyclin-D1 (CCND1), signal transducer and activator of transcription 1-alpha/beta (STAT1), proto-oncogene tyrosine-protein kinase Src (SRC), cellular tumor antigen p53 (TP53), interleukin-6 (IL6), hypoxia-inducible factor 1-alpha (HIF1A), RAC-alpha serine/threonine-protein kinase (AKT1), signal transducer and activator of transcription 3 (STAT3), heat shock protein HSP 90-alpha (HSP90AA1), tyrosine-protein kinase JAK2 (JAK2), cyclin-dependent kinase inhibitor 1 (CDKN1A), mitogen-activated protein kinase 3 (MAPK3), epidermal growth factor receptor (EGFR), myc proto-oncogene protein (MYC), protein c-Fos (FOS) and transcription factor p65 (RELA). QFP treated RSV pneumonia mainly through the phosphatidylinositol 3-kinase (PI3K)/RAC AKT pathway, HIF-1 pathway, IL-17 pathway, TNF pathway, and MAPK pathway. Animal experiments proved that QFP could effectively ameliorate RSV-induced pulmonary inflammation. A total of 28 metabolites underwent significant changes in the QFP treatment, and there are four metabolic pathways consistent with the KEGG pathway analyzed by network pharmacology, suggesting that they may be critical processes related to treatment.

Conclusion

These results provide essential perspicacity into the mechanisms of action of QFP as a promising anti-RSV drug.

A compact and low-frequency drive ultrasound transducer for facilitating cavitation-assisted drug permeation via skin

Low-frequency sonophoresis has emerged as a promising minimally invasive transdermal drug delivery method. However, effectively inducing cavitation on the skin surface with a compact, low-frequency ultrasound transducer poses a significant challenge. This paper presents a modified design of a low-frequency ultrasound transducer capable of generating ultrasound cavitation on the skin surfaces. The transducer comprises a piezoelectric ceramic disk and a bowl-shaped acoustic resonator. A conical slit structure was incorporated into the modified transducer design to amplify vibration displacement and enhance the maximum sound pressure. The FEM-based simulation results confirmed that the maximum sound pressure at the resonance frequency of 78 kHz was increased by 1.9 times that of the previous design. Ultrasound cavitation could be experimentally observed on the gel surface. Moreover, 3 min of ultrasound treatment significantly improved the caffeine permeability across an artificial membrane. These results demonstrated that this transducer holds promise for enhancing drug permeation by generating ultrasound cavitation on the skin surface.

Unraveling the Potential of Vitamin B3-Derived Salts with a Salicylate Anion as Dermal Active Agents for Acne Treatment

This study is focused on the utilization of naturally occurring salicylic acid and nicotinamide (vitamin B3) in the development of novel sustainable Active Pharmaceutical Ingredients (APIs) with significant potential for treating acne vulgaris. The study highlights how the chemical structure of the cation significantly influences surface activity, lipophilicity, and solubility in aqueous media. Furthermore, the new ionic forms of APIs, the synthesis of which was assessed with Green Chemistry metrics, exhibited very good antibacterial properties against common pathogens that contribute to the development of acne, resulting in remarkable enhancement of biological activity ranging from 200 to as much as 2000 times when compared to salicylic acid alone. The molecular docking studies also revealed the excellent anti-inflammatory activity of N-alkylnicotinamide salicylates comparable to commonly used drugs (indomethacin, ibuprofen, and acetylsalicylic acid) and were even characterized by better IC50 values than common anti-inflammatory drugs in some cases. The derivative, featuring a decyl substituent in the pyridinium ring of nicotinamide, exhibited efficacy against Cutibacterium acnes while displaying favorable water solubility and improved wettability on hydrophobic surfaces, marking it as particularly promising. To investigate the impact of the APIs on the biosphere, the EC50 parameter was determined against a model representative of crustaceans─Artemia franciscana. The majority of compounds (with the exception of the salt containing the dodecyl substituent) could be classified as "Relatively Harmless" or "Practically Nontoxic", indicating their potential low environmental impact, which is essential in the context of modern drug development.

Topical drug delivery by Sepineo P600 emulgel: Relationship between rheology, physical stability, and formulation performance

The objective of this present work was to develop and optimize oil-in-water (O/W) emulsion-based gels, namely emulgels that allow maximum topical drug delivery while having desired microstructure and acceptable physical stability. Emulgels containing 2.0 wt% lidocaine were prepared using various concentrations (0.75-5.0 wt%) of Sepineo P600. Their droplet size distribution, physical stability, rheological behaviors, in vitro drug release, and skin permeation profiles were evaluated. Results show that the concentration of Sepineo P600 significantly influenced the microstructure, rheology, and physical stability of the emulgel formulations. The physico-chemical properties also reveals that at least 1.0 wt% Sepineo P600 was needed to produce stable emulgel formulations. All formulations exhibited non-Newtonian shear-thinning properties which are desirable for topical applications. Both the release and permeation rates decreased with increasing viscosity and rigidity of the formulation. The lower the complex modulus of the emulgels, the higher the steady-state flux of the drug through the skin. Adding Sepineo P600 to emulgel systems resulted in increased rheological properties, which in turn slowed the diffusion of the drug for in vitro release. Although as expected skin permeation was rate limiting since in vitro release was 3 to 4 log-fold faster than skin flux. However, an interesting finding was that the derived skin/vehicle partition coefficient suggested the ionic interaction between lidocaine and Sepineo polymer reducing the free drug, i.e., thermodynamic activity and hence the flux with increasing Sepineo P600 concentration. Overall, this study has provided us with valuable insights into understanding the relationship between the microstructure (rheology), physical stability and skin drug delivery properties which will help to design and optimize topical emulgel formulations.

Evaluation of Emulgel and Nanostructured Lipid Carrier-Based Gel Formulations for Transdermal Administration of Ibuprofen: Characterization, Mechanical Properties, and Ex-Vivo Skin Permeation

In transdermal applications of nonsteroidal anti-inflammatory drugs, the rheological and mechanical properties of the dosage form affect the performance of the drug. The aim of this study to develop emulgel and nanostructured lipid carrier NLC-based gel formulations containing ibuprofen, evaluate their mechanical properties, bioadhesive value and ex-vivo rabbit skin permeability. All formulations showed non-Newtonian pseudoplastic behavior and their viscosity values are suitable for topical application. The particle size of the nanostructured lipid carrier system was found to be 468 ± 21 nm, and the encapsulation efficiency was 95.58 ± 0.41%. According to the index of viscosity, consistency, firmness, and cohesiveness values obtained as a result of the back extrusion study, E2 formulation was found to be more suitable for transdermal application. The firmness and work of shear values of the E2 formulation, which has the highest viscosity value, were also found to be the highest and it was chosen as the most suitable formulation in terms of the spreadability test. The work of bioadhesion values of NLC-based gel and IBU-loaded NLC-based gel were found as 0.226 ± 0.028 and 0.181 ± 0.006 mJ/cm2 respectively. The percentages of IBU that penetrated through rabbit skin from the Ibuactive-Cream and the E2 were 87.4 ± 2.11% and 93.4 ± 2.72% after 24 h, respectively. When the penetration of ibuprofen through the skin was evaluated, it was found that the E2 formulation increased penetration due to its lipid and nanoparticle structure. As a result of these findings, it can be said that the NLC-based gel formulation will increase the therapeutic efficacy and will be a good alternative transdermal formulation.

Revolutionizing transdermal drug delivery: unveiling the potential of cubosomes and ethosomes

The area of drug delivery systems has witnessed significant advancements in recent years, with a particular focus on improving efficacy, stability, and patient compliance. Transdermal drug delivery offers numerous benefits compared to conventional methods of drug administration through the skin. It helps in avoiding gastric irritation, hepatic first-pass metabolism, and gastric degradation of the drug. It bypasses the gastrointestinal tract, eliminating the risk of first-pass metabolism and allowing drugs to be administered without being affected by pH, enzymes, or intestinal bacteria. Additionally, it allows for sustained release of the drug, is noninvasive, and enhances patient adherence to the treatment regimen. The transdermal drug delivery system (TDDS) can serve as an alternative route for drug administration in individuals who cannot tolerate oral medications, experience nausea, or are unconscious. When compared to intravenous, hypodermic, and other parenteral routes, TDDS stands out due to its ability to eliminate pain, reduce the risk of infection, and prevent disease transmission associated with needle reuse. Consequently, the overall patient compliance is significantly improved with the utilization of TDDS. Among the noteworthy developments are cubosomes and ethosomes, two distinct yet promising carriers that have garnered attention for their unique properties. In conclusion, this review synthesizes the current knowledge on cubosomes and ethosomes, shedding light on their individual strengths and potential synergies. The exploration of their application in various therapeutic areas underscores their versatility and establishes them as key players in the evolving landscape of drug delivery systems.

Non-Invasive Delivery of Negatively Charged Nanobodies by Anodal Iontophoresis: When Electroosmosis Dominates Electromigration

Iontophoresis enables the non-invasive transdermal delivery of moderately-sized proteins and the needle-free cutaneous delivery of antibodies. However, simple descriptors of protein characteristics cannot accurately predict the feasibility of iontophoretic transport. This study investigated the cathodal and anodal iontophoretic transport of the negatively charged M7D12H nanobody and a series of negatively charged variants with single amino acid substitutions. Surprisingly, M7D12H and its variants were only delivered transdermally by anodal iontophoresis. In contrast, transdermal permeation after cathodal iontophoresis and passive diffusion was Collapse

Key Words

• anti-EGFR 7D12 nanobody
• electroosmosis
• iontophoresis
• nanobodies
• protein expression and purification
• skin topical and transdermal delivery

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Affiliation(s)

Phedra Firdaws Sahraoui School of Pharmaceutical Sciences, University of Geneva, CMU-1 Rue Michel Servet, 1211 Geneva, Switzerland; Institute of Pharmaceutical Sciences of Western Switzerland, University of Geneva, CMU-1 Rue Michel Servet, 1211 Geneva, Switzerland
Oscar Vadas Department of Microbiology and Molecular Medicine, Faculty of Medicine, University of Geneva, CMU-1 Rue Michel Servet, 1211 Geneva, Switzerland;
Yogeshvar N. Kalia School of Pharmaceutical Sciences, University of Geneva, CMU-1 Rue Michel Servet, 1211 Geneva, Switzerland; Institute of Pharmaceutical Sciences of Western Switzerland, University of Geneva, CMU-1 Rue Michel Servet, 1211 Geneva, Switzerland

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CFD simulation of cannabidiol delivery through microneedle patches

This study investigates the efficiency and influence of microneedle parameters, specifically Needle Point Angle (a) and Needle Height (h), on the diffusion of Cannabidiol (CBD) across varying skin depths. Utilizing the Latin Hypercube Sampling method, twelve distinct cases were analyzed. Observations reveal a consistent high concentration of CBD delivered via the microneedle patch, with a notable decrease in concentration as the depth increases, displaying a non-linear trend. Multivariate polynomial regression offers a quantitative relationship between the variables, with the third-order bivariate fitting providing the most accurate representation. Compared to other CBD delivery mechanisms, microneedle patches present enhanced CBD concentrations, circumventing challenges faced by other methods such as dosage inaccuracy, systemic absorption issues, and CBD degradation. The results highlight the potential of microneedle patches as a promising avenue for optimized transdermal drug delivery.

Development of a hierarchical support vector regression-based in silico model for the prediction of the cysteine depletion in DPRA

Topical and transdermal treatments have been dramatically growing recently and it is crucial to consider skin sensitization during the drug discovery and development process for these administration routes. Various tests, including animal and non-animal approaches, have been devised to assess the potential for skin sensitization. Furthermore, numerous in silico models have been created, providing swift and cost-effective alternatives to traditional methods such as in vivo, in vitro, and in chemico methods for categorizing compounds. In this study, a quantitative structure-activity relationship (QSAR) model was developed using the innovative hierarchical support vector regression (HSVR) scheme. The aim was to quantitatively predict the potential for skin sensitization by analyzing the percent of cysteine depletion in Direct Peptide Reactivity Assay (DPRA). The results demonstrated accurate, consistent, and robust predictions in the training set, test set, and outlier set. Consequently, this model can be employed to estimate skin sensitization potential of novel or virtual compounds.

Do the chitosan nanoparticles really augment the drugs' transdermal fluxes: ending the debate using meta-analysis

INTRODUCTION

Transdermal delivery has been extensively investigated as a successful alternative to the oral and parenteral routes of administration. The use of polymeric nanoparticles as drug delivery systems through this route has always been controversial. The use of meta-analyses is a useful quantitative means to decide upon the efficiency of this type of vehicles transporting drugs through the skin.

AREAS COVERED

In this meta-analysis study, polymeric nanoparticles were quantitatively compared to conventional formulations in order to investigate the feasibility of using these particles in transdermal delivery. Natural versus synthetic polymeric sub-groups were also contrasted to determine the most efficient class for transdermal drug enhancement.

EXPERT OPINION

Meta-analyses are gaining ground in the drug delivery field as they can exploit the mines of the literature and pick up by statistical evidence the superior formulations administered through several routes of administration. This is the first study that utilized the transdermal fluxes as the meta-analysis study effect and could prove the superiority of natural polymeric nanoparticles in transdermal delivery. In our opinion, there is paucity in research work regarding this type of nanocarriers, specifically on chitosan nanoparticles. More studies are warranted for full exploitation of its benefits.

Fabrication of controlled-release polymeric microneedles containing progesterone-loaded self-microemulsions for transdermal delivery

Progesterone (PG) has been approved for hormone replacement therapy to mitigate the risk of endometrial carcinoma. However, there has been a lack of success in oral PG due to its rapid degradation. Transdermal PG has advantages but lacks efficacy due to its poor solubility (Log p = 3.9). Therefore, this study aimed to evaluate how combining self-microemulsifying drug delivery systems (SMEDDS) and polymeric microneedles (MNs) could improve the transdermal delivery of PG in a controlled-release manner. Among PG-SMEDDS, PG-SME5 was selected for its desirable properties and stability. The two-layer polymeric MNs formulation incorporating PG-SME5 (PG-SMEDDS-tMNs) was formulated from aqueous blends of polymers as a first layer and 20% PCL as a second layer. It successfully penetrated neonatal porcine skin with the dissolution of the first layer observed within 15 min after application. In vitro skin permeation revealed that the percentage of PG which permeated the skin over 82 h using PG-SMEDDS-tMNs was higher than a PG-suspension and PG-SMEDDS. The Higuchi kinetic showed controlled release over 15 days of PG from PG-SMEDDS-tMNs. These studies suggested that incorporating PG-SMEDDS into controlled-release two-layer polymeric MNs could be a promising approach for improving the transdermal delivery of PG.

Non-invasive transdermal delivery of biomacromolecules with fluorocarbon-modified chitosan for melanoma immunotherapy and viral vaccines

Transdermal drug delivery has been regarded as an alternative to oral delivery and subcutaneous injection. However, needleless transdermal delivery of biomacromolecules remains a challenge. Herein, a transdermal delivery platform based on biocompatible fluorocarbon modified chitosan (FCS) is developed to achieve highly efficient non-invasive delivery of biomacromolecules including antibodies and antigens. The formed nanocomplexes exhibits effective transdermal penetration ability via both intercellular and transappendageal routes. Non-invasive transdermal delivery of immune checkpoint blockade antibodies induces stronger immune responses for melanoma in female mice and reduces systemic toxicity compared to intravenous injection. Moreover, transdermal delivery of a SARS-CoV-2 vaccine in female mice results in comparable humoral immunity as well as improved cellular immunity and immune memory compared to that achieved with subcutaneous vaccine injection. Additionally, FCS-based protein delivery systems demonstrate transdermal ability for rabbit and porcine skins. Thus, FCS-based transdermal delivery systems may provide a compelling opportunity to overcome the skin barrier for efficient transdermal delivery of bio-therapeutics.

Advances in the transdermal delivery of antiretroviral drugs

Antiretroviral therapy regimens are successful in stopping the advancement of human immunodeficiency virus infection to acquired immunodeficiency syndrome, and other opportunistic infections. However, they do have significant disadvantages, including long-term treatment, limited oral bioavailability, inaccessibility to organs, non-adherence by patients, and the development of medication resistance. Because of the listed drawbacks of available routes and the availability of curative medicines for human immunodeficiency virus/acquired immunodeficiency syndrome, advanced solutions are required. Antiretroviral therapy transdermal delivery is one of the current strategies that have attracted much attention from many researchers. In this narrative review, various in vitro, in vivo, and ex vivo transdermal antiretroviral therapy delivery strategies were reviewed, such as transdermal patches and films, lipid-based nano-delivery systems, microneedles, chemical penetration enhancers, and iontophoresis, which showed promising results. Although the majority of studies on Antiretroviral transdermal delivery have produced hopeful findings, additional in-depth research on passive and physical enhancement techniques, both existing and new, is necessary to fully understand the potential of this route and to make it accessible to human immunodeficiency virus patients.

Advanced Formulation Approaches for Proteins

Proteins and peptides are highly desirable as therapeutic agents, being highly potent and specific. However, there are myriad challenges with processing them into patient-friendly formulations: they are often unstable and have a tendency to aggregate or degrade upon storage. As a result, the vast majority of protein actives are delivered parenterally as solutions, which has a number of disadvantages in terms of cost, accessibility, and patient experience. Much work has been undertaken to develop new delivery systems for biologics, but to date this has led to relatively few products on the market. In this chapter, we review the challenges faced when developing biologic formulations, discuss the technologies that have been explored to try to overcome these, and consider the different delivery routes that can be applied. We further present an overview of the currently marketed products and assess the likely direction of travel in the next decade.

Confocal Raman Spectroscopic Characterization of Dermatopharmacokinetics Ex Vivo

Confocal Raman spectroscopy is being assessed as a tool with which to quantify the rate and extent of drug uptake to and its clearance from target sites of action within the viable epidermis below the skin's stratum corneum (SC) barrier. The objective of this research was to confirm that Raman can interrogate drug disposition within the living layers of the skin (where many topical drugs elicit their pharmacological effects) and to identify procedures by which Raman signal attenuation with increasing skin depth may be corrected and normalized so that metrics descriptive of topical bioavailability may be identified. It was first shown in experiments on skin cross-sections parallel to the skin surface that the amide I signal, originating primarily from keratin, was quite constant with depth into the skin and could be used to correct for signal attenuation when confocal Raman data were acquired in a "top-down" fashion. Then, using 4-cyanophenol (CP) as a model skin penetrant with a strong Raman-active C≡N functionality, a series of uptake and clearance experiments, performed as a function of time, demonstrated clearly that normalized spectroscopic data were able to detect the penetrant to at least 40-80 μm into the skin and to distinguish the disposition of CP from different vehicles. Metrics related to local bioavailability (and potentially bioequivalence) included areas under the normalized C≡N signal versus depth profiles and elimination rate constants deduced post-removal of the formulations. Finally, Raman measurements were made with an approved dermatological drug, crisaborole, for which delivery from a fully saturated formulation into the skin layers just below the SC was detectable.

Novel drug delivery strategies for antidepressant active ingredients from natural medicinal plants: the state of the art

Depression is a severe mental disorder among public health issues. Researchers in the field of mental health and clinical psychiatrists have long been faced with difficulties in slow treatment cycles, high recurrence rates, and lagging efficacy. These obstacles have forced us to seek more advanced and effective treatments. Research has shown that novel drug delivery strategies for natural medicinal plants can effectively improve the utilization efficiency of the active molecules in these plants and therefore improve their efficacy. Currently, with the development of treatment technologies and the constant updating of novel drug delivery strategies, the addition of natural medicinal antidepressant therapy has given new significance to the study of depression treatment against the background of novel drug delivery systems. Based on this, this review comprehensively evaluates and analyses the research progress in novel drug delivery systems, including nanodrug delivery technology, in intervention research strategies for neurological diseases from the perspective of natural medicines for depression treatment. This provided a new theoretical foundation for the development and application of novel drug delivery strategies and drug delivery technologies in basic and clinical drug research fields.

Liposome-Derived Nanosystems for the Treatment of Behavioral and Neurodegenerative Diseases: The Promise of Niosomes, Transfersomes, and Ethosomes for Increased Brain Drug Bioavailability

Psychiatric and neurodegenerative disorders are amongst the most prevalent and debilitating diseases, but current treatments either have low success rates, greatly due to the low permeability of the blood-brain barrier, and/or are connected to severe side effects. Hence, new strategies are extremely important, and here is where liposome-derived nanosystems come in. Niosomes, transfersomes, and ethosomes are nanometric vesicular structures that allow drug encapsulation, protecting them from degradation, and increasing their solubility, permeability, brain targeting, and bioavailability. This review highlighted the great potential of these nanosystems for the treatment of Alzheimer's disease, Parkinson's disease, schizophrenia, bipolar disorder, anxiety, and depression. Studies regarding the encapsulation of synthetic and natural-derived molecules in these systems, for intravenous, oral, transdermal, or intranasal administration, have led to an increased brain bioavailability when compared to conventional pharmaceutical forms. Moreover, the developed formulations proved to have neuroprotective, anti-inflammatory, and antioxidant effects, including brain neurotransmitter level restoration and brain oxidative status improvement, and improved locomotor activity or enhancement of recognition and working memories in animal models. Hence, albeit being relatively new technologies, niosomes, transfersomes, and ethosomes have already proven to increase the brain bioavailability of psychoactive drugs, leading to increased effectiveness and decreased side effects, showing promise as future therapeutics.

Stimuli-Responsive Hydrogels for Protein Delivery

Proteins and peptides are potential therapeutic agents, but their physiochemical properties make their use as drug substances challenging. Hydrogels are hydrophilic polymeric networks that can swell and retain high amounts of water or biological fluids without being dissolved. Due to their biocompatibility, their porous structure, which enables the transport of various peptides and proteins, and their protective effect against degradation, hydrogels have gained prominence as ideal carriers for these molecules' delivery. Particularly, stimuli-responsive hydrogels exhibit physicochemical transitions in response to subtle modifications in the surrounding environment, leading to the controlled release of entrapped proteins or peptides. This review is focused on the application of these hydrogels in protein and peptide delivery, including a brief overview of therapeutic proteins and types of stimuli-responsive polymers.

Investigation and Evaluation of the Transdermal Delivery of Ibuprofen in Various Characterized Nano-Drug Delivery Systems

The aim was to assess the suitability of three nano-based transdermal drug delivery systems containing ibuprofen: a nano-emulsion, a nano-emulgel, and a colloidal suspension with ibuprofen-loaded nanoparticles. Understanding the transdermal delivery of ibuprofen using nano-based drug delivery systems can lead to more effective pain relief and improved patient compliance. Characterization tests assessed the suitability of the developed drug delivery systems. Membrane release and skin diffusion studies, along with tape stripping, were performed to determine drug release and skin permeation of ibuprofen. In vitro cytotoxicity studies on HaCaT cells were conducted using MTT and neutral red assays to evaluate the safety of the developed drug delivery systems. Characterization studies confirmed stable drug delivery systems with ideal properties for transdermal delivery. Membrane release studies demonstrated the successful release of ibuprofen. In vitro skin diffusion experiments and tape stripping, detecting ibuprofen in the receptor phase, stratum corneum-epidermis, and epidermis-dermis, indicating successful transdermal and topical delivery. The in vitro cytotoxicity studies observed only minor cytotoxic effects on HaCaT cells, indicating the safety of the developed drug delivery systems. The investigation demonstrated promising results for the transdermal delivery of ibuprofen using the developed drug delivery systems, which contributes to valuable insights that may lead to improved pain management strategies.

A shea butter-based ketamine ointment: The antidepressant effects of transdermal ketamine in rats

The delayed onset of monoaminergic antidepressants and disadvantages of traditional administration routes created the need for alternative non-invasive delivery methods with rapid onset therapeutic effect. Ketamine attracted attention as a fast-acting glutamatergic antidepressant with ideal physiochemical properties for alternative routes of administration. However, there is no sufficient data for its transdermal use in depression. In this proof-of-concept study, we investigated the antidepressant effects of transdermal ketamine delivered via a novel ointment with skin protective, emulsifying and permeation enhancing properties. A shea butter-based 5% (w/w) ketamine ointment or a drug-free vehicle ointment were applied to the shaved dorsal skin of male Wistar rats for 2 days, twice a day. Behavioral despair, locomotor activity and anxiety-like behavior were respectively assessed in the forced swim test (FST), open field test (OFT), and elevated plus maze (EPM). The pharmacokinetic profile of the ointment was analyzed with high-performance liquid chromatography. Transdermal ketamine ameliorated behavioral despair without altering general locomotor activity and anxiety-like behavior, showing that skin-friendly drug carriers like shea butter may constitute promising alternatives to current routes of delivery for ketamine. Tested transdermal method aims to provide more sustainable drug delivery for long-term treatment schedules. Future studies can investigate its long-term use, side effects and abuse liability.

Effects of Intradermal Administration Volume Using a Hollow Microneedle on the Pharmacokinetics of Fluorescein Isothiocyanate Dextran (M.W. 4,000)

PURPOSE

Hollow microneedles (hMNs) have been gaining attention as a tool to enable the intradermal (i.d.) administration of pharmaceutical products. However, few reports have examined the effect of administration volume on distribution in the skin and pharmacokinetics parameters after i.d. injection. In the present study, a model middle molecular weight compound, fluorescein isothiocyanate dextran (M.W. 4,000, FD-4), was selected, and blood concentration-time profiles after i.d. and subcutaneous (s.c.) injections with different administration volumes were compared.

METHODS

FD-4 solution was injected i.d. using a hMN or injected s.c. with a 27 G needle. Pharmacokinetics and dermatokinetics of FD-4 were analyzed using a compartment model. The skin distribution of iodine, as an X ray tracer, was used to evaluate drug disposition.

RESULTS

With the administered drug assumed to be absorbed from the broad injection site into blood vessels in the upper and lower dermis by rapid (krapid) and slow (kslow) first-order absorption rate constants, respectively, better agreement of observed and theoretical values was obtained. Furthermore, the fraction, F, of the administered dose absorbed with krapid decreased with the increase in injection volume after i.d. injection, although the pharmacokinetics parameters were almost the same regardless of administration volume after s.c. injection.

CONCLUSION

The drug distribution in the skin may be related to the obtained pharmacokinetics parameters suggested that the number of needles in the MN system and the total administration volume should be considered in designing hMN systems. The present results provide useful information that may support effective drug delivery with hMNs.

New Insights in Topical Drug Delivery for Skin Disorders: From a Nanotechnological Perspective

Skin, the largest organ in humans, is an efficient route for the delivery of drugs as it circumvents several disadvantages of the oral and parenteral routes. These advantages of skin have fascinated researchers in recent decades. Drug delivery via a topical route includes moving the drug from a topical product to a locally targeted region with dermal circulation throughout the body and deeper tissues. Still, due to the skin's barrier function, delivery through the skin can be difficult. Drug delivery to the skin using conventional formulations with micronized active components, for instance, lotions, gels, ointments, and creams, results in poor penetration. The use of nanoparticulate carriers is one of the promising strategies, as it provides efficient delivery of drugs through the skin and overcomes the disadvantage of traditional formulations. Nanoformulations with smaller particle sizes contribute to improved permeability of therapeutic agents, targeting, stability, and retention, making nanoformulations ideal for drug delivery through a topical route. Achieving sustained release and preserving a localized effect utilizing nanocarriers can result in the effective treatment of numerous infections or skin disorders. This article aims to evaluate and discuss the most recent developments of nanocarriers as therapeutic agent vehicles for skin conditions with patent technology and a market overview that will give future directions for research. As topical drug delivery systems have shown great preclinical results for skin problems, for future research directions, we anticipate including in-depth studies of nanocarrier behavior in various customized treatments to take into account the phenotypic variability of the disease.

Iontophoresis for the cutaneous delivery of nanoentraped drugs

INTRODUCTION

The skin is an attractive route for drug delivery. However, the stratum corneum is a critical limiting barrier for drug permeation. Nanoentrapment is a way to enhance cutaneous drug delivery, by diverse mechanisms, with a notable trend of nanoparticles accumulating into the hair follicles when topically applied. Iontophoresis is yet another way of increasing drug transport by applying a mild electrical field that preferentially passes through the hair follicles, for being the pathway of lower resistance. So, iontophoresis application to nanocarriers could further increase actives accumulation into the hair follicles, impacting cutaneous drug delivery.

AREAS COVERED

In this review, the authors aimed to discuss the main factors impacting iontophoretic skin transport when combining nanocarriers with iontophoresis. We further provide an overview of the conditions in which this combination has been studied, the characteristics of nanosystems employed, and hypothesize why the association has succeeded or failed to enhance drug permeation.

EXPERT OPINION

Nanocarriers and iontophoresis association can be promising to enhance cutaneous drug delivery. For better results, the electroosmotic contribution to the iontophoretic transport, mainly of negatively charged nanocarriers, charge density, formulation pH, and skin models should be considered. Moreover, the transfollicular pathway should be considered, especially when designing the nanocarriers.

Potentials of a Plasma-Aerosol System for Wound Healing Advanced by Drug Introduction: An In Vitro Study

Cold plasmas have found their application in a wide range of biomedical fields by virtue of their high chemical reactivity. In the past decades, many attempts have been made to use cold plasmas in wound healing, and within this field, many studies have focused on plasma-induced cell proliferation mechanisms. In this work, one step further has been taken to demonstrate the advanced role of plasma in wound healing. To this end, the simultaneous ability of plasma to induce cell proliferation and permeabilize treated cells has been examined in the current study. The driving force was to advance the wound healing effect of plasma with drug delivery. On this subject, we demonstrate in vitro the healing effect of Ar, Ar+N₂ plasma, and their aerosol counterparts. A systematic study has been carried out to study the role of reactive oxygen species (ROS) and reactive nitrogen species (RNS) in cell adhesion, signaling, differentiation, and proliferation. An additional investigation was also performed to study the permeabilization of cells and the delivery of the modeled drug carrier fluorescein isothiocyanate (FITC) labeled dextran into cells upon plasma treatment. Short 35 s plasma treatments were found to promote fibroblast adhesion, migration, signaling, proliferation, and differentiation by means of reactive oxygen and nitrogen species (RONS) created by plasma and deposited into the cell environment. The impact of the plasma downstream products NO₂^- and NO₃^- on the expressions of the focal adhesion's genes, syndecans, and collagens was observed to be prominent. On the other hand, the differentiation of fibroblasts to myofibroblasts was mainly initiated by ROS produced by the plasma. In addition, the ability of plasma to locally permeabilize fibroblast cells was demonstrated. During proliferative cell treatment, plasma can simultaneously induce cell membrane permeabilization (d ∼ 7.3 nm) by the species OH and H₂O₂. The choice for a plasma or a plasma-aerosol configuration thus allows the possibility to change the spatial chemistry of drug delivery molecules and thus to locally deliver drugs. Accordingly, this study offers a pivotal step toward plasma-assisted wound healing advanced by drug delivery.

Quantification of Chemical Uptake into the Skin by Vibrational Spectroscopies and Stratum Corneum Sampling

Evaluation of the bioavailability of drugs intended to act within the skin following the application of complex topical products requires the application of multiple experimental tools, which must be quantitative, validated, and, ideally and ultimately, sufficiently minimally invasive to permit use in vivo. The objective here is to show that both infrared (IR) and Raman spectroscopies can assess the uptake of a chemical into the stratum corneum (SC) that correlates directly with its quantification by the adhesive tape-stripping method. Experiments were performed ex vivo using excised porcine skin and measured chemical disposition in the SC as functions of application time and formulation composition. The quantity of chemicals in the SC removed on each tape-strip was determined from the individually measured IR and Raman signal intensities of a specific molecular vibration at a frequency where the skin is spectroscopically silent and by a subsequent conventional extraction and chromatographic analysis. Correlations between the spectroscopic results and the chemical quantification on the tape-strips were good, and the effects of longer application times and the use of different vehicles were clearly delineated by the different measurement techniques. Based on this initial investigation, it is now possible to explore the extent to which the spectroscopic approach (and Raman in particular) may be used to interrogate chemical disposition deeper in the skin and beyond the SC.

Hyaluronidase-powered microneedles for significantly enhanced transdermal delivery efficiency

Microneedles (MNs) with enhanced delivery efficiency have revolutionized the transdermal drug delivery system for treating systemic illness. However, the bioavailability of MNs was still far from the clinical requirements by only overcoming the stratum corneum barrier. Herein, hyaluronidase (HAase)-powered MNs were developed as a top-down permeation-enhancement strategy to hijack the sequential transdermal barriers for improved bioavailability. HAase MNs with robust mechanical strength showed excellent skin penetration ability and significantly enhanced the transdermal delivery efficacy of macromolecular drugs as compared to that of HAase-absent MNs, resulting in considerable effect to subcutaneous injection in terms of biodistribution, bioavailability, and therapeutical efficacy. As evidenced from the distribution of trypan blue and fluorescence underlying skin, the positive effects exerted by HAase MNs could be ascribed to the depolymerization of HA that would loosen the subcutaneous space and destruct the extracellular matrix barrier to promote drug diffusion and permeation in larger area and greater depth. Notably, the transient interconversion of keratin from α-helix to β-sheet that might assist the drug residues on the skin surface permeate across the stratum corneum during administration might be another reason not to be ignored. As a labor-saving strategy, HAase-powered MNs offers a promising and painless administration route for macromolecules.

Formulation of tizanidine hydrochloride-loaded provesicular system for improved oral delivery and therapeutic activity employing a 23 full factorial design

Tizanidine hydrochloride (TZN) is one of the most effective centrally acting skeletal muscle relaxants. The objective of this study is to prepare TZN-loaded proniosomes (TZN-PN) aiming at enhanced oral delivery and therapeutic activity. TZN-PN were prepared by coacervation phase separation method. The developed vesicles were characterized via entrapment efficiency percentage (EE%), vesicular size (VS), and zeta potential (ZP). A 2³ full factorial design was employed to attain an optimized TZN-PN formulation. The optimized TZN-PN were further characterized via in vitro release study and transmission electron microscopy (TEM). In vivo rotarod test was employed for determination of the muscle relaxant activities of rats and levels of GABA and EAAT2 were detected. The developed TZN-PN exhibited relatively high EE% (75.78-85.45%), a VS ranging between (348-559 nm), and a ZP (-26.47 to -59.64). In vitro release profiles revealed sustained release of TZN from the optimized TZN-PN, compared to free drug up to 24 h. In vivo rotarod study revealed that the elevation in coordination was in the following order: normal control < free TZN < market product < TZN-PN (F6). Moreover, the optimized TZN-PN exhibited significant elevated coordination activity by 39% and 26% compared to control group and market product group, respectively. This was accompanied with an elevation in both GABA and EAAT2 serum levels. Thus, it could be concluded that encapsulation of TZN in the provesicular nanosystem proniosomes has enhanced the anti-nociceptive effect of the drug and consequently its therapeutic activity.

Electrospun fibers as carriers for topical drug delivery and release in skin bandages and patches for atopic dermatitis treatment

The skin is a complex layer system and the most important barrier between the environment and the organism. In this review, we describe some widespread skin problems, with a focus on eczema, which are affecting more and more people all over the world. Most of treatment methods for atopic dermatitis (AD) are focused on increasing skin moisture and protecting from bacterial infection and external irritation. Topical and transdermal treatments have specific requirements for drug delivery. Breathability, flexibility, good mechanical properties, biocompatibility, and efficacy are important for the patches used for skin. Up to today, electrospun fibers are mostly used for wound dressing. Their properties, however, meet the requirements for skin patches for the treatment of AD. Active agents can be incorporated into fibers by blending, coaxial or side-by-side electrospinning, and also by physical absorption post-processing. Drug release from the electrospun membranes is affected by drug and polymer properties and the technique used to combine them into the patch. We describe in detail the in vitro release mechanisms, parameters affecting the drug transport, and their kinetics, including theoretical approaches. In addition, we present the current research on skin patch design. This review summarizes the current extensive know-how on electrospun fibers as skin drug delivery systems, while underlining the advantages in their prospective use as patches for atopic dermatitis. This article is categorized under: Implantable Materials and Surgical Technologies > Nanomaterials and Implants Implantable Materials and Surgical Technologies > Nanotechnology in Tissue Repair and Replacement Therapeutic Approaches and Drug Discovery > Emerging Technologies.

Comparative study on the topical and transdermal delivery of diclofenac incorporated in nano-emulsions, nano-emulgels, and a colloidal suspension

Transdermal delivery of active pharmaceutical ingredients (APIs) can be challenging, since the skin possesses a rate-limiting barrier, which may be overcome when APIs possess certain ideal physicochemical properties. The lack thereof would require that APIs be included in drug delivery vehicles to enhance skin permeation. Hence, diclofenac was incorporated into various drug delivery vehicles (i.e., nano-emulsions, nano-emulgels, and a colloidal suspension containing drug-loaded nanoparticles) to investigate the transdermal delivery thereof, while nano-emulsions and nano-emulgels had varying concentrations of evening primrose oil (EPO). The aim of the study was to compare the topical and transdermal diclofenac delivery from the different types of vehicles and to investigate the influence the different EPO concentrations had on diclofenac delivery. After characterization, membrane release studies were performed (to determine whether the API was successfully released from the vehicle) followed by in vitro skin diffusion studies and tape stripping (to establish whether the vehicles assisted the API in reaching the target site (transdermal delivery)). Lastly, cytotoxicity studies were conducted via methyl thiazolyl tetrazolium (MTT) and neutral red (NR) assays on human keratinocyte (HaCaT) cells. Results showed minimal cytotoxic effects at concentrations equivalent to that which had permeated through the skin, while the membrane release and in vitro skin diffusion studies indicated that the nano-emulsions and the 10% EPO vehicles increased API release and diffusion when compared to the other vehicles. However, the colloidal suspension had the highest concentrations of API within the skin. Hence, all the vehicles were non-toxic and effectively delivered diclofenac through the transdermal route.

Enhanced Micro-Channeling System via Dissolving Microneedle to Improve Transdermal Serum Delivery for Various Clinical Skincare Treatments

Topical liquid formulations, dissolving microneedles (DMNs), and microscale needles composed of biodegradable materials have been widely used for the transdermal delivery of active compounds for skincare. However, transdermal active compound delivery by topical liquid formulation application is inhibited by skin barriers, and the skincare efficacy of DMNs is restricted by the low encapsulation capacity and incomplete insertion. In this study, topical serum application via a dissolvable micro-channeling system (DMCS) was used to enhance serum delivery through micro-channels embedded with DMNs. Transdermal serum delivery was evaluated after the topical-serum-only application and combinatorial serum application by assessing the intensity of allophycocyanin (APC) loaded with the serum in the porcine skin. APC intensity was significantly higher in the skin layer at a depth of 120-270 μm upon combinatorial serum application as compared to topical-serum-only application. In addition, the combinatorial serum application showed significantly improved efficacy in the clinical assessment of skin hydration, depigmentation, improvement of wrinkles, elasticity, dermal density, skin pores, and skin soothing without any safety issues compared to the serum-only application. The results indicate that combinatorial serum application with DMCS is a promising candidate for improving skincare treatments with optimal transdermal delivery of active compounds.

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.

A reliable quantitative method for determining CBD content and release from transdermal patches in Franz cells

INTRODUCTION

There are several cannabidiol (CBD) transdermal patches available on the market. However, none are FDA-approved. Furthermore, not much evidence has been published about CBD release and skin permeation from such patches, so the effectiveness and reliability remain unclear.

OBJECTIVES

We aimed to develop a method to determine the in vitro release and skin permeation of CBD from transdermal patches using Franz cell diffusion in combination with quantitative ¹ H-NMR (qNMR).

MATERIALS AND METHODS

The study was conducted on CBD patches with known CBD content and six different commercially available or market-ready CBD patches using a Franz cell with a Strat-M™ membrane and with samples taken directly from the transdermal patch for qNMR analysis.

RESULTS

The use of qNMR yielded an average recovery of 100% ± 7% when samples with known CBD content were tested. Results from the testing of six commercially available patches indicated that five out of six patches did not contain the CBD amount stated by the manufacturer according to a ± 10% variance margin, of which four patches were under-labeled and one was over-labeled. The release rate of patches was determined, and significant differences between the patches were shown. Maximum release of CBD was calculated to occur after 39 to 70 h.

CONCLUSION

The established method was proven to be a reliable means of determining the quantity and release of CBD from transdermal patches and can be used to verify CBD content and release rate in transdermal patches.

Treating allergies via skin - Recent advances in cutaneous allergen immunotherapy

Subcutaneous allergen immunotherapy has been practiced clinically for decades to treat airborne allergies. Recently, the cutaneous route, which exploits the immunocompetence of the skin has received attention, which is evident from attempts to use it to treat peanut allergy. Delivery of allergens into the skin is inherently impeded by the barrier imposed by stratum corneum, the top layer of the skin. While the stratum corneum barrier must be overcome for efficient allergen delivery, excessive disruption of this layer can predispose to development of allergic inflammation. Thus, the most desirable allergen delivery approach must provide a balance between the level of skin disruption and the amount of allergen delivered. Such an approach should aim to achieve high allergen delivery efficiency across various skin types independent of age and ethnicity, and optimize variables such as safety profile, allergen dosage, treatment frequency, application time and patient compliance. The ability to precisely quantify the amount of allergen being delivered into the skin is crucial since it can allow for allergen dose optimization and can promote consistency and reproducibility in treatment response. In this work we review prominent cutaneous delivery approaches, and offer a perspective on further improvisation in cutaneous allergen-specific immunotherapy.

Study on the effect of Pogostemon cablin Benth on skin aging based on network pharmacology

BACKGROUND

At present, there is still little research on the anti-aging effect of Pogostemon cablin Benth (PCB) on human skin. In this paper, the mechanism of anti-aging effect of PCB on human skin was studied by using network pharmacology and molecular docking methods.

OBJECTIVE

To analyze the pharmacological mechanism of PCB in the treatment of skin aging, so as to provide reference for new drug development and clinical application.

METHODS

Active ingredients and related targets of PCB and skin aging-related disease targets are obtained through public databases, and the "drug-disease-target" and protein-protein interaction (PPI) network diagrams were constructed with the help of software to screen the core targets; Then GO analysis and KEGG pathway analysis were performed on the target; Finally, the molecular docking between the components and the targets were verified.

RESULTS

After screening, 112 intersection targets of active compounds of skin aging and PCB were obtained. Through GO and KEGG enrichment analysis, it is found that these biological processes mainly focus on epithelial cell proliferation, aging, growth factors, longevity regulation pathway, cancer pathway, AGE-RAGE signal pathway, PI3K Akt signal pathway and IL-17 signal pathway. The molecular docking results showed that quercetin, apigenin, irisnepalensis isoflavone, 3,23-dihydroxy-12-oleorene-28-oleic acid, 5-hydroxy-7,4'- dimethoxyflavone and other major compounds were connected with TP53, JUN, HSP90AAL, AKT1 and MAPK1 through hydrogen bonds, and there was high binding energy between them.

CONCLUSION

Through multi-target prediction and molecular docking verification, it shows that PCB provides a strong effect in the treatment of skin aging, which provides a reference for its further research.

Proniosome: A Promising Approach for Vesicular Drug Delivery

Different types of drug delivery systems are intended to deliver therapeutic agents to the appropriate site of interest to get desired pharmacological effect. In the field of drug delivery, the advancement of nanotechnology helps develop novel dosage forms such as liposome, noisome, and proniosome. Proniosomes are promising drug carriers, that are dry formulations, and after hydration, are converted to noisome dispersion. Dry proniosomal powder can deliver a unit dose of the drug with improved drug stability and solubility. By using this formulation, both the hydrophilic and lipophilic drugs can be delivered through different routes like oral, topical, transdermal, vaginal, etc. This review revolves on different features of proniosomes such as their structure, formulation materials of proniosomes, preparation methods, evaluation, and application.

Green synthesis of silver nanoparticles through oil: Promoting full-thickness cutaneous wound healing in methicillin-resistant Staphylococcus aureus infections

Due to the emergence of multi-drug resistant microorganisms, the development and discovery of alternative eco-friendly antimicrobial agents have become a top priority. In this study, a simple, novel, and valid green method was developed to synthesize Litsea cubeba essential oil-silver nanoparticles (Lceo-AgNPs) using Lceo as a reducing and capping agent. The maximum UV absorbance of Lceo-AgNPs appeared at 423 nm and the size was 5-15 nm through transmission electron microscopy result. The results of Fourier transform infrared and DLS showed that Lceo provided sufficient chemical bonds for Lceo-AgNPs to reinforce its stability and dispersion. The in vitro antibacterial effects of Lceo-AgNPs against microbial susceptible multidrug-resistant Escherichia coli (E. coli) and methicillin-resistant Staphylococcus aureus (MRSA) were determined. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of Lceo-AgNPs against E. coli were 25 and 50 μg/ml. The MIC and MBC of Lceo-AgNPs against MRSA were 50 and 100 μg/ml, respectively. The results of scanning electron microscopy showed that the amount of bacteria obviously decreased and the bacteria cells were destroyed by Lceo-AgNPs. In vivo research disclosed significant wound healing and re-epithelialization effects in the Lceo-AgNPs group compared with the self-healing group and the healing activity was better than in the sulfadiazine silver group. In this experiment, Lceo-AgNPs has been shown to have effects on killing multidrug-resistant bacteria and promoting wound healing. This study suggested Lceo-AgNPs as an excellent new-type drug for wound treatment infected with multidrug-resistant bacteria, and now expects to proceed with clinical research.

Effect of squalane-based emulsion on polyphenols skin penetration: Ex vivo skin study

Polyphenols have gained attractiveness as ingredients in cosmetic formulations as result of their ability to delay the aging process. However, different factors limit their use, including low solubility and poor skin permeability. In this sense, this study describes the potential of squalane to increase the polyphenols ex vivo skin penetration, incorporated into a water-in-oil emulsion. Polyphenols skin permeation followed the Fick's first law and, p-coumaric acid, vitexin, schaftoside and ferulic acid had the higher permeability coefficients (Kp = 6.0-8.0 × 10^-3 cm^-2 h^-1). Addition of squalane to phenolic compounds decreased the permeability coefficients (Kp = 4.1-5.9 × 10^-3 cm^-2 h^-1), indicating that squalane increased the retention of polyphenols in the skin. Gentisic acid, ferulic acid, and p-coumaric acid were the only compounds permeating from water-in-oil emulsion, in the first 8 h of study and, according Krosmeyer-Peppas model, its n value was > 1 indicating a high transport resistance from the formulation and throughout the skin. Results suggest squalane as an efficient vehicle to increase the dermal availability increasing phenolic compounds physiological functions, by enhancing the skin retention time where they should exert antiaging effect.