Topical delivery of siRNA into skin using SPACE-peptide carriers

Breaking barriers: Innovative approaches for skin delivery of RNA therapeutics

RNA therapeutics represent a rapidly expanding platform with game-changing prospects in personalized medicine. The disruptive potential of this technology will overhaul the standard of care with reference to both primary and specialty care. To date, RNA therapeutics have mostly been delivered parenterally via injection, but topical administration followed by intradermal or transdermal delivery represents an attractive method that is convenient to patients and minimally invasive. The skin barrier, particularly the lipid-rich stratum corneum, presents a significant hurdle to the uptake of large, charged oligonucleotide drugs. Therapeutic oligonucleotides need to be engineered for stability and specificity and formulated with state-of-the-art delivery strategies for efficient uptake. This review will cover various passive and active strategies deployed to enhance permeation through the stratum corneum and achieve effective delivery of RNA therapeutics to treat both local skin disorders and systemic diseases. Some strategies to achieve selectivity between local and systemic administration will also be discussed.

Exploring the Therapeutic Potential of Natural Compounds in Psoriasis and Their Inclusion in Nanotechnological Systems

Psoriasis is a chronic inflammatory disease that affects around 2-3% of the world's population. The treatment for this autoimmune disease still remains centered around conventional methods using synthetic substances, even though more recent advancements focus on biological therapies. Given the numerous side effects of such treatments, current research involves plant extracts and constituents that could prove useful in treating psoriasis. The aim of this narrative review is to highlight the most known representatives belonging to classes of natural compounds such as polyphenols (e.g., astilbin, curcumin, hesperidin, luteolin, proanthocyanidins, and resveratrol), alkaloids (e.g., berberine, capsaicin, and colchicine), coumarins (psoralen and 8-methoxypsoralen), and terpenoids (e.g., celastrol, centelloids, and ursolic acid), along with plants used in traditional medicine that could present therapeutic potential in psoriasis. The paper also provides an overview of these compounds' mechanisms of action and current inclusion in clinical studies, as well as an investigation into their potential incorporation in various nanotechnological systems, such as lipid-based nanocarriers or polymeric nanomaterials, that may optimize their efficacy during treatment.

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.

Advancing immunotherapy using biomaterials to control tissue, cellular, and molecular level immune signaling in skin

Immunotherapies have been transformative in many areas, including cancer treatments, allergies, and autoimmune diseases. However, significant challenges persist in extending the reach of these technologies to new indications and patients. Some of the major hurdles include narrow applicability to patient groups, transient efficacy, high cost burdens, poor immunogenicity, and side effects or off-target toxicity that results from lack of disease-specificity and inefficient delivery. Thus, there is a significant need for strategies that control immune responses generated by immunotherapies while targeting infection, cancer, allergy, and autoimmunity. Being the outermost barrier of the body and the first line of host defense, the skin presents a unique immunological interface to achieve these goals. The skin contains a high concentration of specialized immune cells, such as antigen-presenting cells and tissue-resident memory T cells. These cells feature diverse and potent combinations of immune receptors, providing access to cellular and molecular level control to modulate immune responses. Thus, skin provides accessible tissue, cellular, and molecular level controls that can be harnessed to improve immunotherapies. Biomaterial platforms - microneedles, nano- and micro-particles, scaffolds, and other technologies - are uniquely capable of modulating the specialized immunological niche in skin by targeting these distinct biological levels of control. This review highlights recent pre-clinical and clinical advances in biomaterial-based approaches to target and modulate immune signaling in the skin at the tissue, cellular, and molecular levels for immunotherapeutic applications. We begin by discussing skin cytoarchitecture and resident immune cells to establish the biological rationale for skin-targeting immunotherapies. This is followed by a critical presentation of biomaterial-based pre-clinical and clinical studies aimed at controlling the immune response in the skin for immunotherapy and therapeutic vaccine applications in cancer, allergy, and autoimmunity.

Effects of imidazolium ionic liquids on skin barrier lipids - Perspectives for drug delivery

Ionic liquids (ILs) have great potential to facilitate transdermal and topical drug delivery. Here, we investigated the mechanism of action of amphiphilic ILs 1-methyl-3-octylimidazolium bromide (C8MIM) and 3-dodecyl-1-methylimidazolium bromide (C12MIM) in skin barrier lipid models in comparison to their complex effects in human skin. C8MIM incorporated in a skin lipid model was a better permeation enhancer than C12MIM for water and model drugs, theophylline and diclofenac. Solid state 2H NMR and X-ray diffraction indicated that both ILs prefer the cholesterol-rich regions in skin lipids without significantly perturbing their lamellar arrangement and that C8MIM induces the formation of an isotropic lipid phase to a greater extent compared to C12MIM. C12MIM applied topically to the lipid model or human skin as a pretreatment was more potent than C8MIM. When co-applied with the drugs to human skin, aqueous C12MIM was more potent than C8MIM in enhancing theophylline permeation, but neither IL affected (even decreased) diclofenac permeation. Thus, the IL's ability to permeabilize skin lipid barrier is strongly modulated by its ability to reach the site of action and its interactions with drug and solvent. Such an interplay is far from trivial and requires detailed investigation to realize the full potential of ILs.

Nanotechnology strategies to address challenges in topical and cellular delivery of siRNAs in skin disease therapy

Gene therapy is one of the most advanced therapies in current medicine. In particular, interference RNA-based therapy by small interfering RNA (siRNA) has gained attention in recent years as it is a highly versatile, selective and specific therapy. In dermatological conditions, topical delivery of siRNA offers numerous therapeutic advantages, mainly by inhibiting the expression of target transcripts directly in the skin. However, crossing the stratum corneum and overcoming intracellular barriers is an inherent challenge. Substantial efforts by scientists have moved towards the use of multimodal and multifunctional nanoparticles to overcome these barriers and achieve greater bioavailability in their site of action, the cytoplasm. In this review the most innovative strategies based on nanoparticle and physical methods are presented, as well as the design principles and the main factors that contribute to the performance of these systems. This review also highlights the synergistic contributions of medicine, nanotechnology, and molecular biology to advancing translational research into siRNA-based therapeutics for skin diseases.

5,10,15,20-Tetrakis(pentafluorophenyl)porphyrin as a Functional Platform for Peptide Stapling and Multicyclisation

Polyfluorinated aromatic reagents readily react with thiolates via nucleophilic aromatic substitution (SN Ar) and provide excellent scaffolds for peptide cyclisation. Here we report a robust and versatile platform for peptide stapling and multicyclisation templated by 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin, opening the door to the next generation of functional scaffolds for 3D peptide architectures. We demonstrate that stapling and multicyclisation occurs with a range of non-protected peptides under peptide-compatible conditions, exhibiting chemoselectivity and wide-applicability. Peptides containing two cysteine residues are readily stapled, and the remaining perfluoroaryl groups permit the introduction of a second peptide in a modular fashion to access bicyclic peptides. Similarly, peptides with more than two cysteine residues can afford multicyclic products containing up to three peptide 'loops'. Finally, we demonstrate that a porphyrin-templated stapled peptide containing the Skin Penetrating and Cell Entering (SPACE) peptide affords a skin cell penetrating conjugate with intrinsic fluorescence.

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.

Quantitative Ratiometric Biosensors Based on Fluorescent Ferrocene-Modified Histidine Dipeptide Nanoassemblies

Fluorescent proteins (FPs) provide a ratiometric readout for quantitative assessment of the destination of internalized biomolecules. FP-inspired peptide nanostructures that can compete with FPs in their capacity are the most preferred building blocks for the synthesis of fluorescent soft matter. However, realizing a ratiometric emission from a single peptide fluorophore remains exclusive since multicolor emission is a rare property in peptide nanostructures. Here, we describe a bioinspired peptidyl platform for ratiometric intracellular quantitation by employing a single ferrocene-modified histidine dipeptide. The intensiometric ratio of green to blue fluorescence correlates linearly with the concentration of the peptide by three orders of magnitude. The ratiometric fluorescence of the peptide is an assembly-induced emission originating from hydrogen bonds and aromatic interactions. Additionally, modular design enables ferrocene-modified histidine dipeptides to use as a general platform for the construction of intricate peptides that retain the ratiometric fluorescent properties. The ratiometric peptide technique promises flexibility in the design of a wide spectrum of stoichiometric biosensors for quantitatively understanding the trafficking and subcellular fate of biomolecules.

Novel Pharmaceutical Strategies for Enhancing Skin Penetration of Biomacromolecules

Skin delivery of biomacromolecules holds great advantages in the systemic and local treatment of multiple diseases. However, the densely packed stratum corneum and the tight junctions between keratinocytes stand as formidable skin barriers against the penetration of most drug molecules. The large molecular weight, high hydrophilicity, and lability nature of biomacromolecules pose further challenges to their skin penetration. Recently, novel penetration enhancers, nano vesicles, and microneedles have emerged as efficient strategies to deliver biomacromolecules deep into the skin to exert their therapeutic action. This paper reviews the potential application and mechanisms of novel skin delivery strategies with emphasis on the pharmaceutical formulations.

Strategies for improving the safety and RNAi efficacy of noncovalent peptide/siRNA nanocomplexes

In the past decades, the striking development of cationic polypeptides and cell-penetrating peptides (CPPs) tailored for small interfering RNA (siRNA) delivery has been fuelled by the conception of nuclear acid therapy and precision medicine. Owing to their amino acid compositions, inherent secondary structures as well as diverse geometrical shapes, peptides or peptide-containing polymers exhibit good biodegradability, high flexibility, and bio-functional diversity as nonviral siRNA vectors. Also, a variety of noncovalent nanocomplexes could be built via self-assembling and electrostatic interactions between cationic peptides and siRNAs. Although the peptide/siRNA nanocomplex-based RNAi therapies, STP705 and MIR-19, are under clinical trials, a guideline addressing the current bottlenecks of peptide/siRNA nanocomplex delivery is in high demand for future research and development. In this review, we present strategies for improving the safety and RNAi efficacy of noncovalent peptide/siRNA nanocomplexes in the treatment of genetic disorders. Through thorough analysis of those RNAi formulations using different delivery strategies, we seek to shed light on the rationale of peptide design and modification in constructing robust siRNA delivery systems, including targeted and co-delivery systems. Based on this, we provide a timely and comprehensive understanding of how to engineer biocompatible and efficient peptide-based siRNA vectors.

Liposomal siRNA Formulations for the Treatment of Herpes Simplex Virus-1: In Vitro Characterization of Physicochemical Properties and Activity, and In Vivo Biodistribution and Toxicity Studies

Herpes simplex virus-1 (HSV-1) is highly contagious, and there is a need for a therapeutic means to eradicate it. We have identified an siRNA (siHSV) that knocks down gene expression of the infected cell protein 0 (ICP0), which is important in the regulation of HSV infection. The selected siHSV was encapsulated in liposomes to overcome its poor stability, increase cell permeability, and prolonging siRNA circulation time. Several siRNAs against ICP0 have been designed and identified. We examined the role of various parameters, including formulation technique, lipids composition, and ratio. An optimal liposomal siHSV formulation (LipDOPE-siHSV) was characterized with desirable physiochemical properties, in terms of nano-size, low polydispersity index (PDI), neutral surface charge, high siHSV loading, spherical shape, high stability in physiologic conditions in vitro, and long-term shelf-life stability (>1 year, 4 °C). The liposomes exhibited profound internalization by human keratinocytes, no cytotoxicity in cell cultures, no detrimental effect on mice liver enzymes, and a gradual endo-lysosomal escape. Mice biodistribution studies in intact mice revealed accumulation, mainly in visceral organs but also in the trigeminal ganglion. The therapeutic potential of siHSV liposomes was demonstrated by significant antiviral activity both in the plaque reduction assay and in the 3D epidermis model, and the mechanism of action was validated by the reduction of ICP0 expression levels.

Nanoparticle Delivery Platforms for RNAi Therapeutics Targeting COVID-19 Disease in the Respiratory Tract

Since December 2019, a pandemic of COVID-19 disease, caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has rapidly spread across the globe. At present, the Food and Drug Administration (FDA) has issued emergency approval for the use of some antiviral drugs. However, these drugs still have limitations in the specific treatment of COVID-19, and as such, new treatment strategies urgently need to be developed. RNA-interference-based gene therapy provides a tractable target for antiviral treatment. Ensuring cell-specific targeted delivery is important to the success of gene therapy. The use of nanoparticles (NPs) as carriers for the delivery of small interfering RNA (siRNAs) to specific tissues or organs of the human body could play a crucial role in the specific therapy of severe respiratory infections, such as COVID-19. In this review, we describe a variety of novel nanocarriers, such as lipid NPs, star polymer NPs, and glycogen NPs, and summarize the pre-clinical/clinical progress of these nanoparticle platforms in siRNA delivery. We also discuss the application of various NP-capsulated siRNA as therapeutics for SARS-CoV-2 infection, the challenges with targeting these therapeutics to local delivery in the lung, and various inhalation devices used for therapeutic administration. We also discuss currently available animal models that are used for preclinical assessment of RNA-interference-based gene therapy. Advances in this field have the potential for antiviral treatments of COVID-19 disease and could be adapted to treat a range of respiratory diseases.

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.

Emerging landscape of cell-penetrating peptide-mediated nucleic acid delivery and their utility in imaging, gene-editing, and RNA-sequencing

The safety issues like immunogenicity and unacceptable cancer risk of viral vectors for DNA/mRNA vaccine delivery necessitate the development of non-viral vectors with no toxicity. Among the non-viral strategies, cell-penetrating peptides (CPPs) have been a topic of interest recently because of their ability to cross plasma membranes and facilitate nucleic acids delivery both in vivo and in vitro. In addition to the application in the field of gene vaccine and gene therapy, CPPs based nucleic acids delivery have been proved by its potential application like gene editing, RNA-sequencing, and imaging. Here, we focus on summarizing the recent applications and progress of CPPs-mediated nucleic acids delivery and discuss the current problems and solutions in this field.

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.

Efficient and safe small RNA delivery to macrophage using peptide-based nanocomplex

As one of the gene therapies, RNA interference (RNAi) effectively suppresses only specific genes, targeting various diseases in which they are involved. For the successful process of RNAi, efficient and safe delivery of small RNAs, including small interfering RNA and short hairpin RNA, is essential. Herein, an S-R11 fusion peptide, SPACE peptide conjugated with poly-arginine, was introduced to deliver small RNAs into immune cells that are difficult to transfect. This S-R11 peptide stably formed a spontaneous self-assembling nanocomplex through electrostatic attraction and hydrogen bonding with small RNAs. The nanocomplex showed about 5.3-fold better permeation efficiency than the conventional Lipofectamine™ 2000 for RAW 264.7 macrophage cells. Moreover, it induced about 66.2% silencing effect of the target gene in the cells activated with polyinosinic:polycytidylic acid (poly (I:C)). In addition, the cell viability of fusion peptide was ensured even in a concentration range exceeding the concentration used in the nanocomplex. Based on these results, it is expected that the nanocomplex in this study can be used as a new gene delivery system that can overcome the challenge of gene therapies to immune cells.

Formulation-based approaches for dermal delivery of vaccines and therapeutic nucleic acids: Recent advances and future perspectives

A growing variety of biological macromolecules are in development for use as active ingredients in topical therapies and vaccines. Dermal delivery of biomacromolecules offers several advantages compared to other delivery methods, including improved targetability, reduced systemic toxicity, and decreased degradation of drugs. However, this route of delivery is hampered by the barrier function of the skin. Recently, a large body of research has been directed toward improving the delivery of macromolecules to the skin, ranging from nucleic acids (NAs) to antigens, using noninvasive means. In this review, we discuss the latest formulation-based efforts to deliver antigens and NAs for vaccination and treatment of skin diseases. We provide a perspective of their advantages, limitations, and potential for clinical translation. The delivery platforms discussed in this review may provide formulation scientists and clinicians with a better vision of the alternatives for dermal delivery of biomacromolecules, which may facilitate the development of new patient-friendly prophylactic and therapeutic medicines.

Transdermal delivery of heparin using low-frequency sonophoresis in combination with sponge spicules for venous thrombosis treatment

This study reports that the use of low-frequency sonophoresis (LFS) in combination with sponge Haliclona sp. spicules (SHS), referred to as cSoSp (combined Sonophoresis and Spicules), can enhance the transdermal drug delivery in a synergistic manner. The topical application of cSoSp in vitro significantly enhanced the skin absorption of Fluorescent-Dextrans (4000 Da, FD-4K), a model drug of low-molecular-weight heparin (LMWH). The utilization of cSoSp dramatically increased the transdermal flux of FD-4K (188.6 ± 93.7 ng cm^-2 h^-1) compared to LFS (5.8 ± 3.1 ng cm^-2 h^-1) and SHS (3.2 ± 1.2 ng cm^-2 h^-1) among others. The mechanism of action of cSoSp could be attributed to the synergism between plenty of long-lasting nano-channels created by SHS and the disorders of SC lipids made by shock waves of LFS, which improves the homogeneity of the cavitation effects. Furthermore, LMWH (3000 Da) was transdermally delivered by using cSoSp to treat both superficial venous thrombosis (SVT) and deep venous thrombosis (DVT) in the marginal ear vein of rabbits with a good therapeutic effect. Furthermore, skin irritation and toxicity studies using guinea pigs indicated that cSoSp was nonirritating without any morphological changes in the keratinocytes. cSoSp offers a promising strategy to enhance the transdermal delivery of hydrophilic macromolecules such as heparin.

Suppression of FGF5 and FGF18 Expression by Cholesterol-Modified siRNAs Promotes Hair Growth in Mice

FGF5 and FGF18 are key factors in the regulation of the hair follicle cycle. FGF5 is overexpressed during the late anagen phase and serves as a crucial regulatory factor that promotes the anagen-to-catagen transition in the hair follicle cycle. FGF18, which is overexpressed during the telogen phase, mainly regulates the hair follicle cycle by maintaining the telogen phase and inhibiting the entry of hair follicles into the anagen phase. The inhibition of FGF5 may prolong the anagen phase, whereas the inhibition of FGF18 may promote the transition of the hair follicles from the telogen phase to the anagen phase. In the present study, we used siRNA to suppress FGF5 or FGF18 expression as a way to inhibit the activity of these genes. Using qPCR, we showed that FGF5-targeting siRNA modified by cholesterol was more effective than the same siRNA bound to a cell-penetrating peptide at suppressing the expression of FGF5 both in vitro and in vivo. We then investigated the effects of the cholesterol-modified siRNA targeting either FGF5 or FGF18 on the hair follicle cycle in a depilated area of the skin on the back of mice. The cholesterol-modified siRNA, delivered by intradermal injection, effectively regulated the hair follicle cycle by inhibiting the expression of FGF5 and FGF18. More specifically, intradermal injection of a cholesterol-modified FGF5-targeted siRNA effectively prolonged the anagen phase of the hair follicles, whereas intradermal injection of the cholesterol-modified FGF18-targeted siRNA led to the mobilization of telogen follicles to enter the anagen phase earlier. The inhibitory effect of the cholesterol-modified FGF18-targeted siRNA on FGF18 expression was also evaluated for a topically applied siRNA. Topical application of a cream containing the cholesterol-modified FGF18-targeted siRNA on a depilated area of the skin of the back of mice revealed comparable inhibition of FGF18 expression with that observed for the same siRNA delivered by intradermal injection. These findings suggested that alopecia could be prevented and hair regrowth could be restored either through the intradermal injection of cholesterol-modified siRNA targeting FGF5 or FGF18 or the topical application of FGF18 siRNA.

Advances in siRNA delivery strategies for the treatment of MDR cancer

RNA interference (RNAi) represents a promising therapeutic method that uses siRNA for cancer treatment. Although the RNAi technique has been increasingly used for clinical trials, systemic siRNA delivery into targeted cells is still challenging. The barriers impeding siRNA therapeutics delivery and impacting the treatment outcome must overcome with negligible systemic toxicity for a desirable and successful delivery of siRNA to MDR cancer cells. Nano delivery strategies have been investigated for nanocarrier functionalization, cancer immunotherapy and cancer targeting. Lipid nanoparticles (LNPs), dynamic polyconjugates (DPC™), GalNAc-siRNA conjugates, exosome and RBC systems have shown potential for efficient delivery of siRNA to cancer cells. Delivery of siRNA to tumor cells, immune cells to regulate T cell functions for immunotherapy are promising approaches.

Spherical Nucleic Acids for Topical Treatment of Hyperpigmentation

Oligonucleotide-based materials such as spherical nucleic acid (SNA) have been reported to exhibit improved penetration through the epidermis and the dermis of the skin upon topical application. Herein, we report a self-assembled, skin-depigmenting SNA structure, which is based upon a bifunctional oligonucleotide amphiphile containing an antisense oligonucleotide and a tyrosinase inhibitor prodrug. The two components work synergistically to increase oligonucleotide cellular uptake, enhance drug solubility, and promote skin penetration. The particles were shown to reduce melanin content in B16F10 melanoma cells and exhibited a potent antimelanogenic effect in an ultraviolet B-induced hyperpigmentation mouse model.

Downregulation of CR6-interacting factor 1 suppresses keloid fibroblast growth via the TGF-β/Smad signaling pathway

Keloids are a type of aberrant skin scarring characterized by excessive accumulation of collagen and extracellular matrix (ECM), arising from uncontrolled wound healing responses. While typically non-pathogenic, keloids are occasionally regarded as a form of benign tumor. CR6-interacting factor 1 (CRIF1) is a well-known CR6/GADD45-interacting protein, that has both nuclear and mitochondrial functions, and also exerts regulatory effects on cell growth and apoptosis. In this study, cell proliferation, cell migration, collagen production and TGF-β signaling was compared between normal fibroblasts (NFs) and keloid fibroblasts (KFs). Subsequently, the effects of CRIF1 deficiency were investigated in both NFs and KFs. Cell proliferation, cell migration, collagen production and protein expressions of TGF-β, phosphorylation of Smad2 and Smad3 were all found to be higher in KFs compared to NFs. CRIF1 deficiency in NFs and KFs inhibited cell proliferation, migration, and collagen production. In addition, phosphorylation of Smad2 and Smad3, which are transcription factors of collagen, was decreased. In contrast, mRNA expression levels of Smad7 and SMURF2, two important inhibitory proteins of Smad2/3, were increased, suggesting that CRIF1 may regulate collagen production. CRIF1 deficiency decreases the proliferation and migration of KFs, thereby inhibiting their overgrowth via the transforming growth factor-β (TGF-β)/Smad pathway. CRIF1 may therefore represent a potential therapeutic target in keloid pathogenesis.

Importance of microRNAs in Skin Oncogenesis and Their Suitability as Agents and Targets for Topical Therapy

Skin cancer is the most common cancer worldwide, with rapidly increasing incidence and consistent mortality. Skin cancer encompasses melanoma and non-melanoma skin cancer, which in turn is mainly divided into cutaneous squamous cell carcinoma and basal cell carcinoma. Small noncoding micro-RNAs (miRNAs) regulate protein expression after transcription and play a role in the development and progression of skin cancer. Deregulated expression of miRNAs in skin cancer is associated with cell proliferation, angiogenesis, metastasis, apoptosis, immune response, and drug resistance. Specific patterns of miRNAs in specific skin cancer types can be used as diagnostic markers. For therapeutic purposes, both miRNA and chemically modified variants thereof as well as miRNA antagonists (antagomiRs) or RNA inhibitors may be applied topically. Due to their specific physicochemical properties, physical or chemical diffusion promoters are used with varying degrees of success. There is no question by now that such preparations have a high potential for the treatment of epithelial skin tumors in particular.

Direct Delivery of Apatite Nanoparticle-Encapsulated siRNA Targeting TIMP-1 for Intractable Abnormal Scars

Hypertrophic scars (HSs) and keloids are histologically characterized by excessive extracellular matrix (ECM) deposition. ECM deposition depends on the balance between matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteases (TIMPs). TIMP-1 has been linked to ECM degradation and is therefore a promising therapeutic strategy. In this study, we generated super carbonate apatite (sCA) nanoparticle-encapsulated TIMP-1 small interfering RNA (siRNA) (siTIMP1) preparations and examined the effect of local injections on mouse HSs and on ex vivo-cultured keloids. The sCA-siTIMP1 injections significantly reduced scar formation, scar cross-sectional areas, collagen densities, and collagen types I and III levels in the lesions. None of the mice died or exhibited abnormal endpoints. Apatite accumulation was not detected in the other organs. In an ex vivo keloid tissue culture system, sCA-siTIMP1 injections reduced the thickness and complexity of collagen bundles. Our results showed that topical sCA-siTIMP1 injections during mechanical stress-induced HS development reduced scar size. When keloids were injected three times with sCA-siTIMP1 during 6 days, keloidal collagen levels decreased substantially. Accordingly, sCA-siRNA delivery may be an effective approach for keloid treatment, and further investigations are needed to enable its practical use.

Treatment of psoriasis with NFKBIZ siRNA using topical ionic liquid formulations

Systemic antibodies targeting tumor necrosis factor-α (TNF-α) and interleukin-17A (IL-17A) are effective in plaque psoriasis. Despite their popularity, safety concerns pose a challenge for systemic biologics. While anti-TNF-α and anti-IL-17A antibodies effectively inhibit respective proteins, we hypothesize that an approach based on local silencing of an upstream target such as NFKBIZ can be advantageous for treating psoriasis. However, effective delivery of small interfering RNA (siRNA) into the skin is a substantial hurdle due to skin's barrier function and poor stability of siRNA. Using ionic liquids as an enabling technology, we report on the effective delivery of NFKBIZ siRNA into the skin and its therapeutic efficacy in a psoriasis model. Treatment with IL-siRNA suppressed aberrant gene expression and resulted in down-regulation of psoriasis-related signals including TNF-α and IL-17A. These results provide a framework for a topical delivery platform for siRNA.

Topical delivery of siRNA into skin using ionic liquids

Skin diseases such as lupus, cancer, psoriasis, and hyperhidrosis can potentially be treated effectively by suppressing allele-specific genes using small interfering RNA (siRNA). Injections of siRNA into skin, though effective, are painful and cover small surface areas and thus are not suitable as a long-term treatment option. Topical delivery of siRNA is an attractive alternative option to mediate RNA interference (RNAi). However, the barrier function of the epidermis impedes effective permeation of siRNA into the skin. Herein, we describe topical delivery of siRNA using ionic liquids (ILs) capable of complexing with siRNA non-covalently and delivering it effectively. Using complementary and synergistic strategies of ionic liquids, we report delivery of effective doses of siRNA into skin. The first strategy involved the use of hydrophobic cations to robe the siRNA and the second strategy involved the use of choline-geranic acid ionic liquid (CAGE) to enhance its dermal penetration. In vitro studies in porcine skin confirmed the synergistic effect of these strategies in enhancing epidermal and dermal penetration. In vivo application of siRNA formulation to SKH-1E hairless mice significantly suppressed GAPDH expression with no clinical evidence of toxicity. This is a simple, personalized, and scalable platform for effective topical delivery of siRNA for treating genetic skin diseases.

Skin Delivery of siRNA Using Sponge Spicules in Combination with Cationic Flexible Liposomes

We report the topical administration of sponge Haliclona sp. Spicules (SHS) combined with cationic flexible liposomes (CFL) to increase the delivery of small interfering RNA (siRNA) into viable skin cells in vitro and in vivo. SHS can be applied topically as novel microneedles to overcome skin barrier by creating plenty of new microchannels in stratum corneum. Subsequently, well-designed CFL can be also utilized topically as nanocarriers to overcome skin cells membrane by delivering siRNA to skin deep layers through these microchannels and thereby facilitating their cell internalization. The topical application of SHS in combination with CFL (0.05% of lipids, w/v), referred to as CFL(0.05%), enhanced siRNA skin penetration in vitro by 72.95 ± 2.97-fold compared to control group (p < 0.001). Further, the topical application of SHS in combination with CFL(0.05%) on female BALB/c mice skin resulted in 29.21% ± 1.41% of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) knockdown at all application area in vivo, which was not significantly different from the GAPDH protein knockdown rate in the subcutaneous injection center. However, the high knockdown rate only appears in the vicinity (<0.5 cm) of the injection center. In sum, this study provides a promising strategy of topical delivery of siRNA by the combined used of SHS and well-designed CFL.

Skin delivery of hyaluronic acid by the combined use of sponge spicules and flexible liposomes

We demonstrated that the topical combined use of sponge Haliclona sp. spicules (SHS) and flexible liposomes (FL), referred to as SFLS (SHS-Flexible Liposomes combined System), can result in synergy to improve the skin absorption and deposition of hyaluronic acid (HA), especially in deep skin layers, both in vitro and in vivo. SHS treatment can result in skin micro-channels which are continuous, deep enough (48.6 ± 13.5 μm) and available in large quantities (850 ± 125 micro-channels per mm2). These micro-channels gradually closed up in 120 h and also allowed the intact vesicles of flexible liposomes and vesicle-bound or vesicle-encapsulated HA to penetrate into the skin-deep layers under the driving force of transdermal osmotic gradients. Specifically, SFLS topical application enhanced the penetration of FITC-HA (MW: 250 kDa) into porcine skin in vitro up to 23.2 ± 3.7%, which is 19.4 ± 3.1-fold (p < 0.001) that of a Phosphate Buffered Saline (PBS) group, 3.4 ± 0.5-fold (p < 0.01) that of an SHS group and 3.6 ± 0.6-fold (p < 0.01) that from the combined use of a Dermaroller and flexible liposomes. Moreover, SFLS can lead to significantly enhanced skin deposition of HA in all skin layers, especially in deep skin layers: up to 86.8 ± 4.1% of HA absorbed by skin was accumulated in deep skin layers. The effectiveness of SFLS topical application was also confirmed in vivo by using BALB/c mice. In addition, a skin irritation and toxicity study showed that the SFLS treatment may cause very minimal redness and the skin can recover in a short time. In sum, the combined use of SHS and FL (SFLS) offers a promising strategy to safely and effectively improve the skin delivery of hydrophilic biomacromolecules such as HA.

Bacteriophage-based biomaterials for tissue regeneration

Bacteriophage, also called phage, is a human-safe bacteria-specific virus. It is a monodisperse biological nanostructure made of proteins (forming the outside surface) and nucleic acids (encased in the protein capsid). Among different types of phages, filamentous phages have received great attention in tissue regeneration research due to their unique nanofiber-like morphology. They can be produced in an error-free format, self-assemble into ordered scaffolds, display multiple signaling peptides site-specifically, and serve as a platform for identifying novel signaling or homing peptides. They can direct stem cell differentiation into specific cell types when they are organized into proper patterns or display suitable peptides. These unusual features have allowed scientists to employ them to regenerate a variety of tissues, including bone, nerves, cartilage, skin, and heart. This review will summarize the progress in the field of phage-based tissue regeneration and the future directions in this field.

Non-invasive delivery strategies for biologics

Biologics now constitute a significant element of available medical treatments. Owing to their clinical and commercial success, biologics are a rapidly growing class and have become a dominant therapeutic modality. Although most of the successful biologics to date are drugs that bear a peptidic backbone, ranging from small peptides to monoclonal antibodies (~500 residues; 150 kDa), new biologic modalities, such as nucleotide-based therapeutics and viral gene therapies, are rapidly maturing towards widespread clinical use. Given the rise of peptides and proteins in the pharmaceutical landscape, tremendous research and development interest exists in developing less-invasive or non-invasive routes for the systemic delivery of biologics, including subcutaneous, transdermal, oral, inhalation, nasal and buccal routes. This Review summarizes the current status, latest updates and future prospects for such delivery of peptides, proteins and other biologics.

Transdermal applications of ethosomes - a detailed review

Skin, the largest organ of the body serves as a potential route of drug delivery for local and systemic effects. However, the outermost layer of skin, the stratum corneum (SC) acts as a tough barrier that prevents penetration of hydrophilic and high molecular weight drugs. Ethosomes are a novel phospholipid vesicular carrier containing high ethanol concentrations and offer improved skin permeability and efficient bioavailability due to their structure and composition. This article gives a review of ethosomes including their compositions, types, mechanism of drug delivery, stability, and safety behaviour. This article also provides a detailed overview of drug delivery applications of ethosomes in various diseases.

In Vitro TyRP-1 Knockdown Based on siRNA Carried by Liquid Crystalline Nanodispersions: an Alternative Approach for Topical Treatment of Vitiligo

PURPOSE

Vitiligo is a skin disease characterized by depigmentation and the presence of white patches that are associated with the loss of melanocytes. The most common explanation for the cause of this condition is that it is an autoimmune condition. TyRP-1 is involved in melanin pigment synthesis but can also function as a melanocyte differentiation antigen. This protein plays a role in the autoimmune destruction of melanocytes, which results in the depigmentation, characteristic of this disease. In this study, we evaluated liquid crystalline nanodispersions as non-viral vectors to deliver siRNA-TyRP-1 as an alternative for topical treatment of vitiligo.

METHODS

Liquid crystalline nanodispersions were obtained and characterized with respect to their physical-chemical parameters including size, PdI and zeta potential, as well as Small Angle X-ray Scattering and complexing to siRNA. The effects of the liquid crystalline nanodispersions on the cellular viability, cell uptake and levels of the knockdown target TyRP-1 were evaluated in melan-A cells after 24 h of treatment.

RESULTS

The liquid crystalline nanodispersions demonstrated adequate physical-chemical parameters including nanometer size and a PdI below 0.38. These systems promoted a high rate of cell uptake and an impressive TyRP-1 target knockdown (> 80%) associated with suitable loading of TyRp-1 siRNA.

CONCLUSIONS

We demonstrated that the liquid crystalline nanodispersions showed promising alternative for the topical treatment of vitiligo due to their physical parameters and ability in knockdown the target protein involved with autoimmune destruction of melanocytes.

Current and future technological advances in transdermal gene delivery

Transdermal gene delivery holds significant advantages as it is able to minimize the problems of systemic administration such as enzymatic degradation, systemic toxicity, and poor delivery to target tissues. This technology has the potential to transform the treatment and prevention of a range of diseases. However, the skin poses a great barrier for gene delivery because of the "bricks-and-mortar" structure of the stratum corneum and the tight junctions between keratinocytes in the epidermis. This review systematically summarizes the typical physical and chemical approaches to overcome these barriers and facilitate gene delivery via skin for applications in vaccination, wound healing, skin cancers and skin diseases. Next, the advantages and disadvantages of different approaches are discussed and the insights for future development are provided.

Towards topical microRNA-directed therapy for epidermal disorders

There remains an unmet dermatological need for innovative topical agents that achieve better longterm outcomes with fewer side effects. Modulation of the expression and activity of microRNA (miRNAs) represents an emerging translational framework for the development of such innovative therapies because changes in the expression of one miRNA can have wide-ranging effects on diverse cellular processes associated with disease. In this short review, the roles of miRNA in epidermal development, psoriasis, cutaneous squamous cell carcinoma and re-epithelisation are highlighted. Consideration is given to the delivery of oligonucleotides that mimic or inhibit miRNA function using vehicles such as cell penetrating peptides, spherical nucleic acids, deformable liposomes and liquid crystalline nanodispersions. Formulation of miRNA-directed oligonucleotides with such skin-penetrating epidermal agents will drive the development of RNA-based cutaneous therapeutics for deployment as primary or adjuvant therapies for epidermal disorders.

Reductive nanocomplex encapsulation of cRGD-siRNA conjugates for enhanced targeting to cancer cells

In this study, through covalent conjugation and lipid material entrapment, a combined modification strategy was established for effective delivery of small interfering RNA (siRNA). Single strands of siRNA targeting to BRAF^V600E gene (siMB3) conjugated with cRGD peptide at 3'-terminus or 5'-terminus via cleavable disulfide bond was synthesized and then annealed with corresponding strands to obtain single and bis-cRGD-siRNA conjugates. A cationic lipid material (CLD) developed by our laboratory was mixed with the conjugates to generate nanocomplexes; their uniformity and electrical property were revealed by particle size and zeta potential measurement. Compared with CLD/siBraf, CLD/cRGD-siBraf achieved higher cell uptake and more excellent tumor-targeting ability, especially 21 (sense-5'/antisense-3″-cRGD-congjugate) nanocomplex. Moreover, they can regulate multiple pathways to varying degree and reduce acidification of endosome. Compared with the gene silencing of different conjugates, single or bis-cRGD-conjugated siRNA showed little differences except 22 (5/5) which cRGD was conjugated at 5'-terminus of antisense strand and sense strand. However bis-cRGD conjugate 21 nanocomplex exhibited better specific target gene silencing at multiple time points. Furthermore, the serum stabilities of the bis-cRGD conjugates were higher than those of the single-cRGD conjugates. In conclusion, all these data suggested that CLD/bis-conjugates, especially CLD/21, can be an effective system for delivery of siRNA to target BRAF^V600E gene for therapy of melanoma.

Advances in the Application and Impact of MicroRNAs as Therapies for Skin Disease

The advent of RNA interference (RNAi) technology has profoundly impacted molecular biology research and medicine but has also advanced the field of skin care. Both effector molecules of RNAi, short-interfering RNA molecules and microRNAs (miRNAs), have been explored for their relative impact and utility for treating a variety of skin conditions. These post-transcriptional RNA regulatory molecules down-modulate protein expression through targeting of the 3' untranslated regions of messenger RNAs, leading to their degradation or repression through sequestration. As researchers hunt for genetic linkages to skin diseases, miRNA regulators have emerged as key players in the biology of keratinocytes, fibroblasts, melanocytes, and other cells of the skin. Herein, we attempt to coalesce the current efforts to combat various skin disorders and diseases through the development of miRNA-based technologies.

Can Simple Interaction Models Explain Sequence-Dependent Effects in Peptide Homodimerization?

The development of rapid methods to explain and predict peptide interactions, aggregation, and self-assembly has become important to understanding amyloid disease pathology, the shelf stability of peptide therapeutics, and the design of novel peptide materials. Although experimental aggregation databases have been used to develop correlative and statistical models, molecular simulations offer atomic-level details that potentially provide greater physical insight and allow one to single out the most explanatory simple models. Here, we outline one such approach using a case study that develops homodimerization models for serine-glycine peptides with various hydrophobic leucine mutations. Using detailed all-atom simulations, we calculate reference dimerization free energy profiles and binding constants for a small peptide library. We then use statistical methods to systematically assess whether simple interaction models, which do not require expensive simulations and free energy calculation, can capture them. Surprisingly, some combinations of a few simple scaling laws well recapitulate the detailed, all-atom results with high accuracy. Specifically, we find that a recently proposed phenomenological hydrophobic force law and coarse measures of entropic effects in binding offer particularly high explanatory power, underscoring the physical relevance to association that these driving forces can play.

Prospects of siRNA applications in regenerative medicine

Small interfering RNA (siRNA) has established its reputation in the field of tissue engineering owing to its ability to silence the proteins that inhibit tissue regeneration. siRNA is capable of regulating cellular behavior during tissue regeneration processes. The concept of using siRNA technology in regenerative medicine derived from its ability to inhibit the expression of target genes involved in defective tissues and the possibility to induce the expression of tissue-inductive factors that improve the tissue regeneration process. To date, siRNA has been used as a suppressive biomolecule in different tissues, such as nervous tissue, bone, cartilage, heart, kidney, and liver. Moreover, various delivery systems have been applied in order to deliver siRNA to the target tissues. This review will provide an in-depth discussion on the development of siRNA and their delivery systems and mechanisms of action in different tissues.

Novel lipoproteoplex delivers Keap1 siRNA based gene therapy to accelerate diabetic wound healing

Therapeutics utilizing siRNA are currently limited by the availability of safe and effective delivery systems. Cutaneous diseases, specifically ones with significant genetic components are ideal candidates for topical siRNA based therapy but the anatomical structure of skin presents a considerable hurdle. Here, we optimized a novel liposome and protein hybrid nanoparticle delivery system for the topical treatment of diabetic wounds with severe oxidative stress. We utilized a cationic lipid nanoparticle (CLN) composed of 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) and the edge activator sodium cholate (NaChol), in a 6:1 ratio of DOTAP:NaChol (DNC). Addition of a cationic engineered supercharged coiled-coil protein (CSP) in a 10:1:1 ratio of DNC:CSP:siRNA produced a stable lipoproteoplex (LPP) nanoparticle, with optimal siRNA complexation, minimal cytotoxicity, and increased transfection efficacy. In a humanized murine diabetic wound healing model, our optimized LPP formulation successfully delivered siRNA targeted against Keap1, key repressor of Nrf2 which is a central regulator of redox mechanisms. Application of LPP complexing siKeap1 restored Nrf2 antioxidant function, accelerated diabetic tissue regeneration, and augmented reduction-oxidation homeostasis in the wound environment. Our topical LPP delivery system can readily be translated into clinical use for the treatment of diabetic wounds and can be extended to other cutaneous diseases with genetic components.

A Theoretical Study on Inhibition of Melanoma with Controlled and Targeted Delivery of siRNA via Skin Using SPACE-EGF

Melanoma is a potentially lethal skin cancer with high mortality rate. Recently, the peptide-mediated transdermal delivery of small interference RNA (siRNA) emerges as a promising strategy to treat melanoma by inducing the apoptosis of tumor cells, but the related theoretical model describing the delivery of siRNA under the effect of SPACE-EGF, the growth inhibition of melanoma and the dynamic expanding of the bump on the skin due to the growth of melanoma has not been reported yet. In this article, a theoretical model is developed to describe the percutaneous siRNA delivery mediated by SPACE-EGF to melanoma and the growth inhibition of melanoma. The results present the spatial-temporal distribution of siRNA and the growth of melanoma under the inhibition of siRNA, which shows a good consistency with the experimental results. In addition, this model represents the uplift process of tumors on the skin surface. The model presented here is a useful tool to understand the whole process of the SPACE-EGF-mediated delivery of the siRNA to melanoma through skin, to predict the therapeutic effect, and to optimize the therapeutic strategy, providing valuable references for the treatment of melanoma.