Current and future technological advances in transdermal gene delivery

Transdermal gene delivery

Gene delivery has revolutionized conventional medical approaches to vaccination, cancer, and autoimmune diseases. However, current gene delivery methods are limited to either intravenous administration or direct local injections, failing to achieve well biosafety, tissue targeting, drug retention, and transfection efficiency for desired therapeutic outcomes. Transdermal drug delivery based on various delivery strategies can offer improved therapeutic potential and superior patient experiences. Recently, there has been increased foundational and clinical research focusing on the role of the transdermal route in gene delivery and exploring its impact on the efficiency of gene delivery. This review introduces the recent advances in transdermal gene delivery approaches facilitated by drug formulations and medical devices, as well as discusses their prospects.

Clinical perspective on topical vaccination strategies

Vaccination is one of the most successful measures in modern medicine to combat diseases, especially infectious diseases, and saves millions of lives every year. Vaccine design and development remains critical and involves many aspects, including the choice of platform, antigen, adjuvant, and route of administration. Topical vaccination, defined herein as the introduction of a vaccine to any of the three layers of the human skin, has attracted interest in recent years as an alternative vaccination approach to the conventional intramuscular administration because of its potential to be needle-free and induce a superior immune response against pathogens. In this review, we describe recent progress in developing topical vaccines, highlight progress in the development of delivery technologies for topical vaccines, discuss potential factors that might impact the topical vaccine efficacy, and provide an overview of the current clinical landscape of topical vaccines.

Effect of ion pair strategy on transdermal delivery of guanfacine: Which factor dominates drug permeation?

Ion pair is an effective chemical approach to promoting drug transdermal permeation, and the traditional interpretation for its enhanced permeation effect is mainly attributed to counterions altering the physicochemical properties of the drug (lipophilicity, melting point, etc.). In this work, guanfacine (GFC), a non-stimulant for anti-attention deficit and hyperactivity disorder (ADHD), was used as a model drug, and several organic or inorganic acids were designed thereby successfully constructing ion pairs. The transdermal permeation ability of ion pairs through isolated porcine skin was observed and ranked as follows: guanfacine caprylate (GFC-CA) > GFC > guanfacine laurate (GFC-LA) > guanfacine fumarate (GFC-FA) > guanfacine hydrochloride (GFC-HA) > guanfacine palmitate (GFC-PA). The effect of key physicochemical properties (octanol-water partition coefficient, molecular volume, melting point) on the transdermal permeation rate of the model drug was analyzed in detail. In addition, GFC-CA was observed to alter the lipid structure of the skin, suggesting the traditional explanation of the action of ion pair may be inadequate and underrated, and ion pair may also enhance permeation by disrupting skin structure. The intriguing phenomenon is expected to provide a novel approach to achieving precise transdermal drug delivery.

Regulating Size and Charge of Liposomes in Microneedles to Enhance Intracellular Drug Delivery Efficiency in Skin for Psoriasis Therapy

The stratum corneum (SC) and cell membrane are two major barriers that hinder the therapeutic outcomes of transdermal drug delivery for the treatment of skin diseases. While microneedles (MNs) can efficiently penetrate the SC to deliver nanomedicines, the optimization of physicochemical properties of nanomedicines in MNs to enhance their in vivo cellular delivery efficiency remains unclear. Here, how the size and surface charge of drug-loaded liposomes in MNs influence the retention time and cellular delivery in psoriatic skin is systematically investigated. The results indicate that while 100 nm negatively-charged liposomes in MNs show higher cellular uptake in vitro, 250 and 450 nm liposomes could enhance skin retention and the long-term in vivo cellular delivery efficiency of drugs. Moreover, 250 nm cationic liposomes with a stronger positive charge show an extraordinarily long skin retention time of 132 h and significantly higher in vivo cellular internalization. In the treatment study, dexamethasone (dex)-loaded cationic liposomes-integrated MNs show better therapeutic outcomes than dex-loaded anionic liposomes-integrated MNs in a psoriasis-like animal model. The design principles of liposomes in MN drug delivery systems explored in the study hold the potential for enhancing the therapeutic outcomes of psoriasis and are instrumental for successful translation.

Transcutaneous Immunotherapy for RNAi: A Cascade-Responsive Decomposable Nanocomplex Based on Polyphenol-Mediated Framework Nucleic Acid in Psoriasis

Skin is the first barrier against external threats, and skin immune dysfunction leads to multiple diseases. Psoriasis is an inflammatory, chronic, common, immune-related skin disease that affects more than 125 million people worldwide. RNA interference (RNAi) therapy is superior to traditional therapies, but rapid degradation and poor cell uptake are the greatest obstacles to its clinical transformation. The transdermal delivery of siRNA and controllable assembly/disassembly of nanodrug delivery systems can maximize the therapeutic effect. Tetrahedral framework nucleic acid (tFNA) is undoubtedly the best carrier for the transdermal transport of genes due to its excellent noninvasive transdermal effect and editability. The authors combine acid-responsive tannic acid (TA), RNase H-responsive sequences, siRNA, and tFNA into a novel transdermal RNAi drug with controllable assembly and disassembly: STT. STT has heightened resistance to enzyme, serum, and lysosomal degradation, and its size is similar to that of tFNA, enabling easy transdermal transport. After transdermal administration, STT can specifically silence nuclear factor kappa-B (NF-κB) p65, thereby maintaining the stability of the skin's microenvironment and reshaping normal skin immune defense. This work demonstrates the advantages of STT in RNAi therapy and the potential for future treatment of skin-related diseases.

The Use of Nanoneedles in Drug Delivery: an Overview of Recent Trends and Applications

Nanoneedles (NN) are growing rapidly as a means of navigating biological membranes and delivering therapeutics intracellularly. Nanoneedle arrays (NNA) are among the most potential resources to achieve therapeutic effects by administration of drugs through the skin. Although this is based on well-established approaches, its implementations are rapidly developing as an important pharmaceutical and biological research phenomenon. This study intends to provide a broad overview of current NNA research, with an emphasis on existing approaches, applications, and types of compounds released by these systems. A nanoneedle-based delivery device with great spatial and temporal accuracy, minimal interference, and low toxicity could transfer biomolecules into living organisms. Due to its vast potential, NN has been widely used as a capable transportation system of many therapeutic active substances, from cancer therapy, vaccine delivery, cosmetics, and bio-sensing nanocarrier drugs to genes. The use of nanoneedles for drug delivery offers new opportunities for the rapid, targeted, and exact administration of biomolecules into cell membranes for high-resolution research of biological systems, and it can treat a wide range of biological challenges. As a result, the literature has analyzed existing patents to emphasize the status of NNA in biological applications.

Prediction of the penetration depth of multi-lamellar liposomes in artificial skin. Application to the vectorization of corticosteroid in human skin

Our previous work showed that the size, elasticity and charge of multi-lamellar liposomes (MLLs) could not be considered separately to predict the fate of MLLs in the skin [1]. Based on this study, we developed several MLLs formulations containing a corticosteroid, betamethasone 17-valerate (B17) to transport the drug into the stratum corneum, living epidermis, dermis or through the skin. MLLs encapsulation efficiency was found to exceed 74 ± 3 % in all cases. In addition, we showed that MLLs protected the corticosteroid from thermal degradation. Comparing the penetration depth of all MLLs within artificial skin measured by Raman imaging, we established an equation for its determination, given the MLLs elasticity and size. This equation was verified experimentally on human explants: quantification of B17 in each skin layer, as well as its transdermal passage by ultra-high performance liquid chromatography, confirmed that B17 was predominantly and significantly transported in the desired layer. Eventually, we showed the benefits in using B17-loaded MLLs instead of a B17-containing pharmaceutical cream in terms of B17 penetration and thermal degradation.

Advances in transdermal siRNAs delivery: A review of current research progress

Small interfering RNA (siRNAs) is a double-stranded RNA molecule which can hybridize with a specific mRNA sequence and block the translation of numerous genes to regulate endogenous genes and to defend the genome from invasive nucleic acids. The use of siRNAs has been studied as a treatment option for various skin conditions. One of the main obstacles in the dermal or transdermal delivery of this compound is low skin permeability, and application is limited by its negative charge, high polarity, susceptibility to degradation by nucleases, and difficulty in penetrating the skin barrier. Effective delivery of therapeutic biomolecules to their target is a challenging issue, which can be solved by innovations in drug delivery systems and lead to improvement of the efficiency of many new biopharmaceuticals. Designing of novel transdermal delivery systems garnered tremendous attention in both cosmeceutical and pharmaceutical research and industries, which offers a number of advantages. Developing safe and efficient siRNAs delivery vectors is essential for effective treatment of skin diseases. In recent years, significant progress has been made in the creation of delivery systems using lipids, polymers, cell-penetrating peptides, nanoparticles and other biologically active agents. In this review we will focus on the recent advancements in transdermal siRNAs delivery vectors, such as liposomes, dendrimers, cell-penetrating peptides, and spherical nucleic acid nanoparticles.

A comprehensive review on novel targeted therapy methods and nanotechnology-based gene delivery systems in melanoma

Melanoma, a malignant form of skin cancer, has been swiftly increasing in recent years. Although there have been significant advancements in clinical treatment underlying a well-understanding of melanoma-susceptible genes and the molecular basis of melanoma pathogenesis, the permanency of response to therapy is frequently constrained by the emergence of acquired resistance and systemic toxicity. Conventional therapies, including surgical resection, chemotherapy, radiotherapy, and immunotherapy, have already been used to treat melanoma and are dependent on the cancer stage. Nevertheless, ineffective side effects and the heterogeneity of tumors pose major obstacles to the therapeutic treatment of malignant melanoma through such strategies. In light of this, advanced therapies including nucleic acid therapies (ncRNA, aptamers), suicide gene therapies, and gene therapy using tumor suppressor genes, have lately gained immense attention in the field of cancer treatment. Furthermore, nanomedicine and targeted therapy based on gene editing tools have been applied to the treatment of melanoma as potential cancer treatment approaches nowadays. Indeed, nanovectors enable delivery of the therapeutic agents into the tumor sites by passive or active targeting, improving therapeutic efficiency and minimizing adverse effects. Accordingly, in this review, we summarized the recent findings related to novel targeted therapy methods as well as nanotechnology-based gene systems in melanoma. We also discussed current issues along with potential directions for future research, paving the way for the next-generation of melanoma treatments.

Recent Advances in Oral and Transdermal Protein Delivery Systems

Protein and peptide drugs are predominantly administered by injection to achieve high bioavailability, but this greatly compromises patient compliance. Oral and transdermal drug delivery with minimal invasiveness and high adherence represent attractive alternatives to injection administration. However, oral and transdermal administration of bioactive proteins must overcome biological barriers, namely the gastrointestinal and skin barriers, respectively. The rapid development of new materials and technologies promises to address these physiological obstacles. This review provides an overview of the latest advances in oral and transdermal protein delivery, including chemical strategies, synthetic nanoparticles, medical microdevices, and biomimetic systems for oral administration, as well as chemical enhancers, physical approaches, and microneedles in transdermal delivery. We also discuss challenges and future perspectives of the field with a focus on innovation and translation.

Transdermal delivery of colchicine using dissolvable microneedle arrays for the treatment of acute gout in a rat model

Colchicine (Col) is used to prevent and treat acute gout flare; however, its therapeutic use is strictly limited owing to severe gastrointestinal side effects after oral administration. Therefore, we developed a dissolvable Col-loaded microneedle (MN) with hyaluronic acid to deliver Col via the transdermal route. We studied the preparation, mechanical properties, skin insertion, skin irritation, drug content, and transdermal release of the Col-loaded MN. The pharmacokinetics of Col after Col-loaded MN application were compared with those of Col solution gavage over 24 h. Knee joint edema evaluation and the hindfoot mechanical threshold test were conducted to determine the pharmacodynamic profile. The dissolvable Col-loaded MN possessed sufficient mechanical strength to penetrate the skin and release the loaded drug. No skin irritation was observed for 3 days after application. We found that 3.36-fold more Col contained in MNs was delivered through the skin compared with that in gel in vitro, and moderate relative bioavailability in vivo. The Col-loaded MN significantly relieved swollen knee joints and mechanical hypernociception in an acute gout model in rats. The dissolvable Col-loaded MN array reduced inflammation and pain via topical administration when acute gout occurred. Reducing the gastrointestinal side effects of Col-loaded MNs is expected to optimize the therapeutic effects of Col and improve patient compliance.

Skin Microbiome, Metabolome and Skin Phenome, from the Perspectives of Skin as an Ecosystem

Skin is a complex ecosystem colonized by millions of microorganisms, including bacteria, fungi, and viruses. Skin microbiota is believed to exert critical functions in maintaining host skin health. Profiling the structure of skin microbial community is the first step to overview the ecosystem. However, the community composition is highly individualized and extremely complex. To explore the fundamental factors driving the complexity of the ecosystem, namely the selection pressures, we review the present studies on skin microbiome from the perspectives of ecology. This review summarizes the following: (1) the composition of substances/nutrients in the cutaneous ecological environment that are derived from the host and the environment, highlighting their proposed function on skin microbiota; (2) the features of dominant skin commensals to occupy ecological niches, through self-adaptation and microbe-microbe interactions; (3) how skin microbes, by their structures or bioactive molecules, reshape host skin phenotypes, including skin immunity, maintenance of skin physiology such as pH and hydration, ultraviolet (UV) protection, odor production, and wound healing. This review aims to re-examine the host-microbe interactions from the ecological perspectives and hopefully to give new inspiration to this field.

Designing electrospun fiber platforms for efficient delivery of genetic material and genome editing tools

Electrospun fibers are versatile biomaterial platforms with great potential to support regeneration. Electrospun fiber characteristics such as fiber diameter, degree of alignment, rate of degradation, and surface chemistry enable the creation of unique, tunable scaffolds for various drug or gene delivery applications. The delivery of genetic material and genome editing tools via viral and non-viral vectors are approaches to control cellular protein production. However, immunogenicity, off-target effects, and low delivery efficiencies slow the progression of gene delivery strategies to clinical settings. The delivery of genetic material from electrospun fibers overcomes such limitations by allowing for localized, tunable delivery of genetic material. However, the process of electrospinning is harsh, and care must be taken to retain genetic material bioactivity. This review presents an up-to-date summary of strategies to incorporate genetic material onto or within electrospun fiber platforms to improve delivery efficiency and enhance the regenerative potential of electrospun fibers for various tissue engineering applications.

Ionic Liquids for Enhanced Drug Delivery: Recent Progress and Prevailing Challenges

Ionic liquids (ILs) are a class of nonmolecular compounds composed only of ions. Compared with traditional organic solvents, ILs have the advantages of wide chemical space, diverse and flexible structures, negligible vapor pressure, and high thermal stability, which make them widely used in many fields of modern science, such as chemical synthesis and catalytic decomposition, electrochemistry, biomass conversion, and biotransformation biotechnology. Because of their special characteristics, ILs have been favored in the pharmaceutical field recently, especially for the development of efficient drug delivery systems. So far, ILs have been successfully designed to promote the dissolution of poorly soluble drugs and the destruction of physiological barriers, such as the tight junction between the stratum corneum and the intestinal epithelium. In addition, ILs can also be combined with other drug strategies to stabilize the structure of small molecules. This Review mainly introduces the application of ILs in drug delivery, emphasizes the potential mechanism of ILs, and presents the key research directions of ILs in the future.

Transdermal delivery for gene therapy

Gene therapy is a critical constituent of treatment approaches for genetic diseases and has gained tremendous attention. Treating and preventing diseases at the genetic level using genetic materials such as DNA or RNAs could be a new avenue in medicine. However, delivering genes is always a challenge as these molecules are sensitive to various enzymes inside the body, often produce systemic toxicity, and suffer from off-targeting problems. In this regard, transdermal delivery has emerged as an appealing approach to enable a high efficiency and low toxicity of genetic medicines. This review systematically summarizes outstanding transdermal gene delivery methods for applications in skin cancer treatment, vaccination, wound healing, and other therapies.

Transdermal Drug delivery: A step towards treatment of cancer

BACKGROUND

Transdermal drug delivery is an emerging and tempting system over oral and hypodermic drug delivery system. With the new developments in skin penetration techniques, anticancer drugs ranging from hydrophilic macromolecules to lipophilic drugs can be administered via transdermal route to treat cancer.

OBJECTIVE

In the present review, various approaches to enhance the transdermal delivery of drugs is discussed including the micro and nanotechnology based transdermal formulations like chemotherapy, gene therapy, immunotherapy, phototherapy, vaccines and medical devices. Limitations and advantages of various transdermal technologies is also elaborated.

METHOD

In this review, patent applications and recent literature of transdermal drug delivery systems employed to cure mainly cancer are covered.

RESULTS

Transdermal drug delivery systems have proved their potential to cure cancer. They increase the bioavailability of drug by site specific drug delivery and can reduce the side effects/toxicity associated with anticancer drugs.

CONCLUSION

The potential of transdermal drug delivery systems to carry the drug may unclutter novel ways for therapeutic intercessions in various tumors.

Oleic acid-reinforced PEGylated polymethacrylate transdermal film with enhanced antidyslipidemic activity and bioavailability of atorvastatin: A mechanistic ex-vivo/in-vivo analysis

To enhance the poor bioavailability and extensive liver metabolism of atorvastatin calcium (ATC), we have developed an oleic acid-reinforced PEGylated polymethacrylate (OLA-PEG-E-RLPO) transdermal film as a convenient and alternative delivery system. The effect of varying levels of Eudragit RLPO, PEG 400, and oleic acid on the target product profile was optimized through Quality by Design (QbD) approach. The ATC-loaded OLA-PEG-E-RLPO transdermal films were evaluated in ex-vivo experiments using full thickness skin, utilizing Franz cell studies, and undergone in-vivo pharmacokinetics/pharmacodynamics (PK/PD) assessment, using poloxamer-induced dyslipidemic Sprague-Dawley rats. At 2 and 12 h, the optimized ATC films with a thickness of 0.79 mm showed permeation of 37.34% and 97.23% into the receptor compartment, respectively. Steady-state flux was 0.172 mg/cm²h, with 7.01 × 10^-4 cm/h permeability coefficient, and 0.713 × 10^-3 cm²/h diffusion coefficient. In-vivo PK results indicated that the absorption profiles (AUC_0-∞) of the optimized film in pre-treated group of animals were 8.6-fold and 2.8-fold greater than controls pre-treated with non-PEGylated non-oleic acid film and orally administered ATC, respectively. PD assessment of the lipid panel indicated that the lipid profile of the optimized film pre-treated group reached normal levels after 12 h, along with the significant enhancement over the non-PEGylated non-oleic acid film and the oral marketed tablet groups. The histopathological findings revealed near-normal hepatocyte structure for the optimized film pre-treated animal group. Our results further indicate that transdermal delivery films based on an optimized ATC-loaded OLA-PEG-E-RLPO were successfully developed and their assessment in both ex-vivo and in-vivo suggests enhanced permeability and improvement in bioavailability and antidyslipidemic activity of ATC. This approach can provide several advantages, especially during chronic administration of ATC, including improvement in patient compliance, therapeutic benefits, bioavailability, and feasibility for commercialization and as a platform for other drug classes.

Nanocarriers for Skin Applications: Where Do We Stand?

Skin penetration of active molecules for treatment of diverse diseases is a major field of research owing to the advantages associated with the skin like easy accessibility, reduced systemic‐derived side effects, and increased therapeutic efficacy. Despite these advantages, dermal drug delivery is generally challenging due to the low skin permeability of therapeutics. Although various methods have been developed to improve skin penetration and permeation of therapeutics, they are usually aggressive and could lead to irreversible damage to the stratum corneum. Nanosized carrier systems represent an alternative approach for current technologies, with minimal damage to the natural barrier function of skin. In this Review, the use of nanoparticles to deliver drug molecules, genetic material, and vaccines into the skin is discussed. In addition, nanotoxicology studies and the recent clinical development of nanoparticles are highlighted to shed light on their potential to undergo market translation.

Molecular perspective of efficiency and safety problems of chemical enhancers: bottlenecks and recent advances

Chemical penetration enhancer (CPE) is a preferred approach to improve drug permeability through the skin, due to its unique advantages of simple use and high compatibility. However, CPEs efficiency and safety problems frequently arise, which greatly restrains the further application in transdermal drug delivery systems (TDDS). To get access to the root of problems, the efficiency and safety of CPEs are reviewed especially from molecular perspectives, which include (1) the possible factors of CPEs low efficiency; (2) the possible contribution of CPEs in the evolution of safety problems such as skin irritation and allergic reaction; (3) the interactive relationship between CPEs efficiency and safety, as well as the bottlenecks of achieving their balance. More importantly, based on these, recent advances are summarized in improving efficiency or safety of CPEs, which offers a guidance of rationally selecting CPEs in future research.

Cell-Penetrating Peptides-Based Liposomal Delivery System Enhanced Immunogenicity of Peptide-Based Vaccine against Group A Streptococcus

Peptide-based vaccine development represents a highly promising strategy for preventing Group A Streptococcus (GAS) infection. However, these vaccines need to be administered with the help of a delivery system and/or immune adjuvant. Cell-penetrating peptides (CPPs) have been used as a powerful tool for delivering various therapeutic agents, including peptides, as they can overcome the permeability barrier of cell membranes. Here, we used CPPs to deliver our lead lipopeptide-based vaccine (LCP-1). CPPs were anchored through a spacer to LCP-1-bearing multilamellar and unilamellar liposomes and administered to Swiss outbred mice. Tat47-57 conjugated to two palmitic acids via a (Gly)6 spacer (to form a liposome-anchoring moiety) was the most efficient system for triggering immune responses when combined with multilamellar liposomes bearing LCP-1. The immunostimulatory potential of a variety of other CPPs was examined following intranasal administration in mice. Among them, LCP-1/liposomes/Tat47-57 and LCP-1/liposomes/KALA induced the highest antibody titers. The antibodies produced showed high opsonic activity against clinically isolated GAS strains D3840 and GC2 203. The use of the CPP-liposome delivery system is a promising strategy for liposome-based GAS vaccine development.

The varied influences of cell adhesion and spreading on gene transfection of mesenchymal stem cells on a micropatterned substrate

Transmembrane transport of exogenous genes is widely investigated because of high demand for gene therapy. Both gene carriers and cellular conditions can affect gene transfection efficiency. Although cell morphology has been reported to affect cell functions, the influence of cell adhesion area and cell spreading area on the transfection of exogenous genes remains unclear because it is difficult to separate the individual influence of these areas during normal cell culture. In this study, micropatterns were prepared to separately control the adhesion and spreading areas of human bone marrow-derived mesenchymal stem cells (hMSCs). Transfection efficiency of the green fluorescent protein gene to hMSCs cultured on the micropatterns was compared. Cells with a larger adhesion area showed higher transfection efficiency, while cell spreading area hardly affected gene transfection efficiency. Cell adhesion area had dominant influence on gene transfection. Microparticle uptake and BrdU staining showed that the cellular uptake capacity and DNA synthesis activity increased with the increase in cell adhesion area, but were not affected by cell spreading area. The different influence of cell adhesion area and cell spreading area on gene transfection was correlated with their influence on cellular uptake capacity, DNA synthesis activity, focal adhesion formation, cytoskeletal mechanics, and mechanotransduction signal activation. The results suggest that cell adhesion area and cell spreading area had different influence on gene transfection; this finding should provide useful information for the manipulation of cell functions in gene therapy, protein modification, and cell reprogramming. STATEMENT OF SIGNIFICANCE: Cell adhesion and spreading are important morphological factors during the interaction of cells with biomaterial surfaces or interfaces. However, the predominant morphological factor that affects cellular functions such as gene transfection remains unclear. In the present study, special micropatterns were used to precisely control cell adhesion and spreading areas independently. Mesenchymal stem cells cultured on the micropatterns were transfected with the green fluorescent protein gene to compare the different influence of cell adhesion and spreading areas on gene transfection efficiency. Cell adhesion area showed dominant influence on gene transfection, while cell spreading area did not affect gene transfection. The dominant influence of cell adhesion area could be explained by cellular uptake capacity and DNA synthesis activity through the formation of FAs, cytoskeletal mechanics, and YAP/TAZ nuclear localization. The results provide new insights of correlation between cell morphology and cellular functions for designing functional biomaterials.

Functional Transdermal Nanoethosomes Enhance Photodynamic Therapy of Hypertrophic Scars via Self-Generating Oxygen

Photodynamic therapy (PDT) is a new therapeutic strategy for hypertrophic scars (HSs), and nanoethosomes (ES) have attracted considerable attention as an efficient transdermal delivery system for PDT of HSs (HS-PDT). However, the delivery of photosensitizers and the hypoxic microenvironment of HSs limit HS-PDT efficacy. Consequently, functional transdermal ES (A/A-ES) that are loaded with the photosensitizer, 5-aminolevulinic acid (ALA), and immobilized nanoenzyme Au nanoclusters (ANCs) within the ES surface have been developed that exhibit superior co-delivery characteristics and produce catalase that enhances HS-PDT efficacy. The unique structure of A/A-ES enables them to co-deliver ALA and ANCs into the HS tissue and to efficiently decompose the endogenous hydrogen peroxide in the HS to generate oxygen. The findings from in vitro and in vivo experiments demonstrated that A/A-ES efficiently co-delivered ALA and ANCs into the HS tissue and that they improved the hypoxic microenvironment of the HS. Systematic assessments reveal that A/A-ES enhance HS-PDT efficacy and that they are highly effective at improving the morphology and promoting HS fibroblast apoptosis and the rearrangement of collagen. These works give rise to an effective treatment option for HSs that integrates the transdermal co-delivery of ALA and nanoenzymes, thereby enabling them to exert their respective beneficial effects, and they highlight the enhancement of HS-PDT efficacy via self-generating oxygen.

Harnessing pH-Sensitive Polycation Vehicles for the Efficient siRNA Delivery

pH-sensitive hydrophobic segments have been certificated to facilitate siRNA delivery efficiency of amphiphilic polycation vehicles. However, optimal design concepts for these vehicles remain unclear. Herein, by studying the library of amphiphilic polycations mPEG-PAMA50-P(DEAx-r-D5Ay) (EAE5x/y), we concluded a multifactor matching concept (pKa values, "proton buffering capacities" (BCs), and critical micelle concentrations (CMCs)) for polycation vehicles to improve siRNA delivery efficiency in vitro and in vivo. We identified that the stronger BCs in a pH 5.5-7.4 subset induced by EAE548/29 (pKa = 6.79) and EAE539/37 (pKa = 6.20) are effective for siRNA delivery in vitro. Further, the stronger BCs occurred in a narrow subset of pH 5.5-6.5 and the lower CMC attributed to higher siRNA delivery capacity of EAE539/37 in vivo than EAE548/29 after intravenous administration and subcutaneous injection. More importantly, 87.2% gene knockdown efficacy was achieved by EAE539/37 via subcutaneous injection, which might be useful for an mRNA vaccine adjuvant. Furthermore, EAE539/37 also successfully delivered siRRM2 to tumor via intravenous administration and received highly efficient antitumor activity. Taken together, the suitable pKa values, strong BCs occurred in pH 5.5-6.5, and low CMCs were probably the potential solution for designing efficient polycationic vehicles for siRNA delivery.

Microneedle Arrays Combined with Nanomedicine Approaches for Transdermal Delivery of Therapeutics

Organic and inorganic nanoparticles (NPs) have shown promising outcomes in transdermal drug delivery. NPs can not only enhance the skin penetration of small/biomacromolecule therapeutic agents but can also impart control over drug release or target impaired tissue. Thanks to their unique optical, photothermal, and superparamagnetic features, NPs have been also utilized for the treatment of skin disorders, imaging, and biosensing applications. Despite the widespread transdermal applications of NPs, their delivery across the stratum corneum, which is the main skin barrier, has remained challenging. Microneedle array (MN) technology has recently revealed promising outcomes in the delivery of various formulations, especially NPs to deliver both hydrophilic and hydrophobic therapeutic agents. The present work reviews the advancements in the application of MNs and NPs for an effective transdermal delivery of a wide range of therapeutics in cancer chemotherapy and immunotherapy, photothermal and photodynamic therapy, peptide/protein vaccination, and the gene therapy of various diseases. In addition, this paper provides an overall insight on MNs' challenges and summarizes the recent achievements in clinical trials with future outlooks on the transdermal delivery of a wide range of nanomedicines.

Cucurbituril-Oriented Nanoplatforms in Biomedical Applications

Cucucrbituril (CB) belongs to a family of macrocycles that are easily accessible. Their structural specificity provides excellent molecular recognition capabilities, with the ability to be readily chemically modified. Because of these properties, researchers have found CB to be a useful molecular carrier for delivering drug molecules and therapeutic biomolecules. Their significance lies in the fact that CB not only increases the solubility and stability of an encapsulated guest but also provides the possibility to achieve targeted delivery of the guest molecule. Therefore, the emergence of CB undoubtedly provides opportunities for the development of targeted drug delivery in an era where intelligent drugs have attracted considerable attention. It has also been found that CB can enhance fluorescent dyes, allowing the preparation of biosensors with enhanced sensitivity for use in clinical settings. In the present review, the acquisition, properties, and structural modifications of CB are first comprehensively described, and then the value of this macrocycle in applications within the medical field is discussed. In addition, we have also summarized patent applications of CB in this field over recent years, aiming to illustrate the current status of developments of this molecule. Finally, we discuss the challenges faced by CB in the medical field and future trends in its development.

A Novel Eutectic-Based Transdermal Delivery System for Risperidone

This paper reports for the first time the possible formation of a novel room temperature therapeutic deep eutectic solvent (THEDES) of risperidone (RIS) with some fatty acids, namely capric acid (C10; CA), lauric acid (C12; LA), and myristic acid (C14; MA). All mixtures of RIS and MA yielded a solid or pasty-like solid and were readily discarded. Some of the prepared THEDESs from RIS and CA or LA have spontaneously transformed into a transparent liquid, without any precipitate at room temperature by simple physical mixing of the components. From the DSC thermograms, phase diagrams of the eutectic systems were constructed and the lowest obtained melting point for a RIS:CA mixture was 17°C at 40:60% w/w ratio. While 22°C was recorded as the lowest melting point for RIS:LA at a ratio of 30:70% w/w, solubility improvement of RIS was up to 70,000-fold compared with water. Freeze-drying microscopy provided valuable information regarding the phase change and transitions the drug undergoes as a function of temperature and it clarifies the interpretation of the DSC results and provides valuable evidence of drug crystals co-melting within the fatty acid base. The presence of natural fatty acid as one component of THEDES and the depression in the melting point significantly (P < 0.05) enhanced RIS skin permeation. Rheological studies showed a viscosity temperature dependency of the DES and well fitted to the Arrhenius equation. Application of the obtained THEDES on the shaved skin of rats revealed the absence of any irritation or edema effects.

Influence of a combination of triptolide and ferulic acid on the activities of CYP450 enzymes and oxidative stress in HaCaT cells

Topical administration of triptolide (TP) is effective in the treatment of rheumatoid arthritis (RA), but it can also induce skin irritation. Previous studies have used data mining strategies to analyze the application of Tripterygium wilfordii in the treatment of RA and have shown that TP and ferulic acid (FA) can be used in combination due to their component compatibility. The aims of the present study were to investigate the mechanisms underlying the effects of TP treatment and to identify its effects on metabolism and oxidative damage in the skin. MTT assay results suggested that the HaCaT cell survival rate was significantly increased when the compatibility ratio of TP to FA was 1:100. Moreover, the combination of TP with FA (TP + FA) did not significantly affect the activities of the cytochrome P40 (CYP) enzymes CYP family 1 subfamily A member 2 (CYP1A2), CYP2E1 and CYP3A4, when used as a 'cocktail'. It was found that TP + FA significantly decreased the production levels of reactive oxygen species (ROS), superoxide dismutase and malondialdehyde in HaCaT cells, while significantly increasing levels of glutathione and catalase. In addition, TP + FA significantly increased nuclear factor erythroid 2-related factor 2 protein expression, compared with TP alone. Thus, the present results indicated that the underlying mechanism of TP + FA efficacy may be related to decreased ROS production level in HaCaT cells, increased production levels of key antioxidant factors and increased antioxidant activity of the epidermis, all of which were correlated with a protective effect against oxidative damage.

Progress and perspective of microneedle system for anti-cancer drug delivery

Transdermal drug delivery exhibited encouraging prospects, especially through superficial drug administration routes. However, only a few limited lipophilic drug molecules could cross the skin barrier, those are with low molecular weight and rational Log P value. Microneedles (MNs) can overcome these limitations to deliver numerous drugs into the dermal layer by piercing the outermost skin layer of the body. In the case of superficial cancer treatments, topical drug administration faces severely low transfer efficiency, and systemic treatments are always associated with side effects and premature drug degradation. MN-based systems have achieved excellent technical capabilities and been tested for pre-clinical chemotherapy, photothermal therapy, photodynamic therapy, and immunotherapy. In this review, we will focus on the features, progress, and opportunities of MNs in the anticancer drug delivery system. Then, we will discuss the strategies and advantages in these works and summarize challenges, perspectives, and translational potential for future applications.

Synergistic transdermal delivery of nanoethosomes embedded in hyaluronic acid nanogels for enhancing photodynamic therapy

Photodynamic therapy (PDT) is a new therapeutic strategy for hypertrophic scars (HS), but it is limited by low drug utilization. Transdermal delivery based on nanoethosomes (ES) has attracted considerable attention as a potential clinical strategy in PDT treating HS. However, free ES are unsatisfactory due to their instability and non-targeting, which causes non-effective delivery and low drug utilization. Herein, 5-aminolevulinic acid (ALA)-loaded ES (ES-ALA) embedded in hyaluronic acid (HA) meshes (HA/ES-ALA), a novel synergistic transdermal delivery nanogel, are developed for enhancing PDT of HS. HA/ES-ALA has a unique structure and property to protect unilaminar ES-ALA with HA meshes and actively target hypertrophic scar fibroblasts (HSFs) with HA receptors. Both in vitro and in vivo experiments demonstrate that HA/ES-ALA has a remarkable transdermal delivery ability with penetrating channels and a membrane-fusion mechanism. Meanwhile, the synergistic delivery mechanism is visually characterized as three stages: synergistic penetration, targeting aggregation and transmembrane delivery. With the synergistic effect, HA/ES-ALA can realize a targeted transdermal delivery, and significantly improve ALA utilization and enhance PDT efficacy. The results demonstrate an effective transdermal delivery route to enhance therapy for HS as well as other skin diseases.

Transcutaneous delivery of DNA/mRNA for cancer therapeutic vaccination

Therapeutic vaccination is a promising strategy for the immunotherapy of cancers. It eradicates cancer cells by evoking and strengthening the patient's own immune system. Because of the easy access and sophisticated immune networks, the skin becomes an ideal target organ for vaccination. Genetic vaccines have been widely investigated, with the advantages of the delivery of multiple antigens and a lower cost for production compared to protein/peptide vaccines. This review summarizes the advances made with respect to the transcutaneous delivery of DNA/mRNA for cancer therapeutic vaccination and also gives a brief description of the immunological milieu of the skin and the importance of dendritic cell-targeting in vaccine delivery, as well as the technologies that aim to facilitate antigen delivery and modulate antigen-presenting cells, thus improving cellular responses. The applications of genetic vaccines encoding tumor antigens delivered through the skin route, both in preclinical and clinical trials, are outlined.

Skin Electrical Resistance Measurement of Oxygen-Containing Terpenes as Penetration Enhancers: Role of Stratum Corneum Lipids

The measurement of skin electrical resistance (SER) has drawn a great deal of attention for the rapid screening of transdermal penetration enhancers (PEs). However, the mechanisms underlying the SER measurement are still unclear. This study was to investigate the effects and mechanisms of seven oxygen-containing terpenes on the SER kinetics. Stratum corneum (SC) lipids were proved to play a key role in SER measurement. Then, the factors affecting the SER measurement were optimized. By the determination of SER kinetics, cyclic terpenes (1,8-cineole, terpinen-4-ol, menthol and α-terpineol) were demonstrated to possess higher enhancement ratio (ER) values compared with linear terpenes (linalool, geraniol and citral). For the first time, the linear correlation was found between ER of terpenes and the interaction energy of terpene⁻ceramide complexes revealed by molecular simulation. The attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) analysis revealed that the effect of cyclic terpenes on SC lipid arrangement was obviously stronger than that of linear terpenes. In addition, by evaluating HaCaT skin cell viability, little difference was found between the toxicities of cyclic and linear terpenes. In conclusion, measurement of SER could be a feasible approach for the efficient evaluation of the PEs that mainly act on SC lipids.

Advances in transdermal insulin delivery

Insulin therapy is necessary to regulate blood glucose levels for people with type 1 diabetes and commonly used in advanced type 2 diabetes. Although subcutaneous insulin administration via hypodermic injection or pump-mediated infusion is the standard route of insulin delivery, it may be associated with pain, needle phobia, and decreased adherence, as well as the risk of infection. Therefore, transdermal insulin delivery has been widely investigated as an attractive alternative to subcutaneous approaches for diabetes management in recent years. Transdermal systems designed to prevent insulin degradation and offer controlled, sustained release of insulin may be desirable for patients and lead to increased adherence and glycemic outcomes. A challenge for transdermal insulin delivery is the inefficient passive insulin absorption through the skin due to the large molecular weight of the protein drug. In this review, we focus on the different transdermal insulin delivery techniques and their respective advantages and limitations, including chemical enhancers-promoted, electrically enhanced, mechanical force-triggered, and microneedle-assisted methods.

Cell-penetrating Peptides: Efficient Vectors for Vaccine Delivery

Subunit vaccines are composed of pathogen fragments that, on their own, are generally poorly immunogenic. Therefore, the incorporation of an immunostimulating agent, e.g. adjuvant, into vaccine formulation is required. However, there are only a limited number of licenced adjuvants and their immunostimulating ability is often limited, while their toxicity can be substantial. To overcome these problems, a variety of vaccine delivery systems have been proposed. Most of them are designed to improve the stability of antigen in vivo and its delivery into immune cells. Cell-penetrating peptides (CPPs) are especially attractive component of antigen delivery systems as they have been widely used to enhance drug transport into the cells. Fusing or co-delivery of antigen with CPPs can enhance antigen uptake, processing and presentation by antigen presenting cells (APCs), which are the fundamental steps in initiating an immune response. This review describes the different mechanisms of CPP intercellular uptake and various CPP-based vaccine delivery strategies.

Hydrogel-forming microneedles enhance transdermal delivery of metformin hydrochloride

We investigated, for the first time, the potential for a hydrogel-forming microneedle (MN) patch to deliver the high-dose drug metformin HCl transdermally in a sustained manner. This may minimize some gastrointestinal side effects and small intestine absorption variations associated with oral delivery. Patches (two layers) were assembled from a lyophilised drug reservoir layer, with the MN layer made from aqueous blend of 20% w/w poly (methylvinylether-co-maleic acid) crosslinked by esterification with 7.5% w/w poly (ethylene glycol) 10,000 Da. >90% of metformin was recovered from homogeneous drug reservoirs. Drug reservoir dissolution time in PBS (pH 7.4) was <10 min. MN penetrated a validated skin model Parafilm® M consistently. Permeation of metformin HCl across dermatomed neonatal porcine skin in vitro was enhanced by using MN. The combined MN and metformin HCl reservoir patch (containing 75 mg or 50 mg metformin HCl, respectively) delivered 9.71 ± 2.22 mg and 10.04 ± 1.92 mg at 6 h, respectively, and 28.15 ± 2.37 mg and 23.25 ± 3.58 mg at 24 h, respectively.In comparison, 0.34 ± 0.39 mg and 0.85 ± 0.68 mg was delivered at 6 h, respectively, and 0.39 ± 0.39 mg and 1.01 ± 0.84 mg was delivered at 24 h, respectively, from a control set-up employing only the drug reservoirs. In vivo, metformin HCl was detected in rat plasma at 1 h post MN application at a concentration of 0.62 ± 0.51 μg/mL, increasing to 3.76 ± 2.58 μg/ml at 3 h. A maximal concentration of 3.77 ± 2.09 μg/ml was achieved at 24 h. Css was 3.2 μg/mL. Metformin transdermal bioavailability using MNs was estimated as 30%.Hydrogel-forming MN are a promising technology that has demonstrated successful transdermal delivery of metformin HCl. Potential clearly exists for administration of other high-dose drugs using this system.