Beneath the Skin: A Review of Current Trends and Future Prospects of Transdermal Drug Delivery Systems

Future Prospects and Regulatory Pathways for Invasome Technologies in Transdermal Drug Delivery

Skin is one of the largest organs in the human body. It acts as an outer protective cover and comprises the epidermis, dermis, and hypodermis. Liposomes are formed by phospholipids and have a vesicular character that improves the encapsulation of lipophilic, hydrophilic, and amphiphilic drugs. The invasome structure is flexible as opposed to regular liposomes; this is due to the presence of ethanol and terpene that increases lipid fluidity in the vesicle structure. Terpenes, ethanol, or terpene mixes are potential carriers that invasomes' tiny liposomal vesicles used to improve skin penetration. Terpenes that are primarily derived from natural sources are the most efficient and secure kind of penetration enhancers (PEs). There are some methods for the preparation of invasomes, but mostly the techniques used for the preparation of invasomes are mechanical dispersion and film hydration methods. Although PEs are effective when applied topically, only a small number are clinically approved due to concerns about skin irritation and toxicity. Invasomes exhibit a higher rate of skin penetration than liposomes and ethosomes. This review examines the structure, components, preparation methods, and applications of invasomes in pharmaceutical formulations, focusing on their potential to treat skin disorders and improve therapeutic outcomes. The primary objective is to assess the future potential of invasome technologies in transdermal drug delivery, alongside an exploration of the regulatory challenges and pathways for their development and approval. Graphical abstract illustrating the composition, mechanism of action, and therapeutic applications of invasomes in transdermal drug delivery systems.

Carbohydrate-based polymer nanocarriers for environmentally friendly applications

Effective delivery of active substances and drugs is an important part of treatment. In order for a drug to work at the right place in the body, it must be transported there in the right way. For this reason, new carriers are being sought for active substances and drugs that can effectively deliver drugs to the target site without causing additional side effects. These include nanoparticles, microneedles, cubosomes and nanogels, among others. Recently, carriers based on biodegradable polymers such as hyaluronic acid or chitosan are becoming popular. In addition, modern carriers are designed to release the active ingredient in response to a specific agent. This paper reviews the literature from the past 5 years on novel delivery systems with medical, agricultural, food and cosmetic applications, with a special emphasis on the use of carbohydrate-based nanocarriers.

Skin-penetrating peptides (SKPs): Enhancing skin permeation for transdermal delivery of pharmaceuticals and cosmetic compounds

Skin-penetrating peptides (SKPs) are emerging as a promising class of permeation enhancers that can facilitate macromolecule delivery across the skin. Although their pharmaceutical applications are under extensive study, SKPs are crucial for enhancing skin permeability, enabling larger molecules to penetrate the stratum corneum. This review explores the transformative role of SKPs in non-invasive transdermal drug delivery. Drawing from an extensive collection of literature, it provides insights into the current usage and application of SKPs as tools to enhance skin permeability and facilitate the delivery of larger molecules. Additionally, it highlights the opportunities, challenges, and future directions for SKP applications in transdermal drug delivery.

Topical gel formulations as potential dermal delivery carriers for green-synthesized zinc oxide nanoparticles

This study aimed to incorporate green-synthesized zinc oxide nanoparticles (ZnO NPs), functionalized with polyethylene glycol (PEG) and linked to doxorubicin (DOX), into various topical gel formulations (hydrogel, oleogel, and bigel) to enhance their dermal delivery. The ZnO NPs were produced using the aqueous extract of the root hair of Phoenix dactylifera. The optimized green-synthesized ZnO NPs, PEGylated and conjugated to DOX, demonstrated a particle size below 100 nm, low polydispersity index, and zeta potential between - 11 and - 19 mV. The UV-Vis spectroscopy analysis confirmed characteristic absorption peaks at 351 and 545 nm for ZnO and DOX, respectively. The transmission electron microscope (TEM) images revealed well-dispersed spherical nanoparticles without aggregation. Additionally, ZnO NPs-loaded gels exhibited uniformity, cohesion, no phase separation, pseudoplastic flow, and viscoelastic properties. The in vitro release studies showed that DOX-PEG-ZnO NPs hydrogel released 99.5% of DOX after 5 h of starting the release. Moreover, the penetration of DOX-PEG-ZnO NPs through excised rat skin was visualized by TEM. In conclusion, the hydrogel formulation containing green-synthesized DOX-PEG-ZnO NPs holds great promise for dermal administration in skin cancer treatment. Furthermore, the release rate and skin penetration of DOX from gels were varied based on the type of gel matrix and corroborated with their corresponding rheological properties.

Hyaluronic acid-liposomes hybridized with HucMSC exosomes for enhanced exosomes transdermal delivery and acute skin photodamage repair

Long-term exposure to ultraviolet (UV) radiation can damage human skin, resulting in photodamage. Repairing photodamaged skin has been a major focus of research in recent years. Extensive research has shown that human umbilical cord mesenchymal stem cell-derived exosomes (Exo) possess anti-inflammatory, pro-angiogenic, and wound healing properties, holding great potential for treating skin damage. However, due to the limitations of exosomes alone, such as poor transdermal penetration, instability, and low utilization, there is an urgent need for new delivery strategies. We designed a hybrid nanovesicle (HL@Exo) by combining ultrasonic incubation with membrane extrusion to fuse Exo with HL. HL@Exo capitalizes on the advantages of liposomal carriers and the permeation-enhancing properties of hyaluronic acid to effectively facilitate transdermal delivery of Exo. The successful fusion of HL@Exo and its skin penetration were verified by methods such as fluorescent labeling, western blotting, Transwell assays, and in vivo imaging. In vitro studies on photodamaged keratinocytes and endothelial cells demonstrated HL@Exo ability to promote cell proliferation, repair, angiogenesis, and reduce inflammation. In a laser-induced skin photodamage model, HL@Exo enhanced collagen regeneration, accelerated wound healing, and demonstrated significant anti-inflammatory effects, indicating its potential as a non-invasive treatment and offering a novel strategy for the clinical application of Exo.

Targeted delivery systems of siRNA based on ionizable lipid nanoparticles and cationic polymer vectors

As an emerging therapeutic tool, small interfering RNA (siRNA) had the capability to down-regulate nearly all human mRNAs via sequence-specific gene silencing. Numerous studies have demonstrated the substantial potential of siRNA in the treatment of broad classes of diseases. With the discovery and development of various delivery systems and chemical modifications, six siRNA-based drugs have been approved by 2024. The utilization of siRNA-based therapeutics has significantly propelled efforts to combat a wide array of previously incurable diseases and advanced at a rapid pace, particularly with the help of potent targeted delivery systems. Despite encountering several extracellular and intracellular challenges, the efficiency of siRNA delivery has been gradually enhanced. Currently, targeted strategies aimed at improving potency and reducing toxicity played a crucial role in the druggability of siRNA. This review focused on recent advancements on ionizable lipid nanoparticles (LNPs) and cationic polymer (CP) vectors applied for targeted siRNA delivery. Based on various types of targeted modifications, we primarily described delivery systems modified with receptor ligands, peptides, antibodies, aptamers and amino acids. Finally, we discussed the challenges and opportunities associated with siRNA delivery systems based on ionizable LNPs and CPs vectors.

Bacterial cellulose in transdermal drug delivery systems: Expanding horizons in multi-scale therapeutics and patient-centric approach

This review explores the transformative potential of Bacterial cellulose (BC) in an increasingly vital avenue of transdermal drug delivery systems (TDDS) for multi-scale therapeutic applications with patient-centric approach. In this review, we have not only highlighted the role of BC as the main matrix material for TDDS but emphasized the other possible role that BC can play in TDDS. For this purpose, we have delved into the avenues of the physico-chemical interactions that BC can offer in governing the incorporation of different length-scales of therapeutics as well as tuning their extent of loading. Furthermore, this review underscores BC's potential in developing need-specific drug release profiles and stimuli-responsive release platforms, enabling their application in TDDS for wound healing, pain management, and targeted delivery for chronic diseases. Apart from the existing literature, this review focuses on patient comfort, which is an often-overlooked aspect, and highlights how BC's unique physicochemical properties enhance user experience. Additionally, this review justifies the potential of BC in compliance with the other parameters of the TDDS, including shelf-life, design requirements, and evaluation strategies in ensuring their clinical translation and user acceptance. To harness BC's potential in the new era of personalized TDDS, this review also sheds light on the challenges of standardizing BC production processes with appropriate data disclosure, ensuring adhesion and anti-microbial actions, along with the integration of passive and active technologies.

AI-Driven Innovation in Skin Kinetics for Transdermal Drug Delivery: Overcoming Barriers and Enhancing Precision

Transdermal drug delivery systems (TDDS) offer an alternative to conventional oral and injectable drug administration by bypassing the gastrointestinal tract and liver metabolism, improving bioavailability, and minimizing systemic side effects. However, widespread adoption of TDDS is limited by challenges such as the skin's permeability barrier, particularly the stratum corneum, and the need for optimized formulations. Factors like skin type, hydration levels, and age further complicate the development of universally effective solutions. Advances in artificial intelligence (AI) address these challenges through predictive modeling and personalized medicine approaches. Machine learning models trained on extensive molecular datasets predict skin permeability and accelerate the selection of suitable drug candidates. AI-driven algorithms optimize formulations, including penetration enhancers and advanced delivery technologies like microneedles and liposomes, while ensuring safety and efficacy. Personalized TDDS design tailors drug delivery to individual patient profiles, enhancing therapeutic precision. Innovative systems, such as sensor-integrated patches, dynamically adjust drug release based on real-time feedback, ensuring optimal outcomes. AI also streamlines the pharmaceutical process, from disease diagnosis to the prediction of drug distribution in skin layers, enabling efficient formulation development. This review highlights AI's transformative role in TDDS, including applications of models such as Deep Neural Networks (DNN), Artificial Neural Networks (ANN), BioSIM, COMSOL, K-Nearest Neighbors (KNN), and Set Covering Machine (SVM). These technologies revolutionize TDDS for both skin and non-skin diseases, demonstrating AI's potential to overcome existing barriers and improve patient care through innovative drug delivery solutions.

Application of microarray patches for the transdermal administration of psychedelic drugs in micro-doses

Throughout history, psychedelic compounds have been used for religious, spiritual and recreational purposes. A plethora of studies have reported the use of psychedelic compounds in the treatment of various conditions, such as alcoholism, addictions, depressive state to borderline schizophrenia, personality disorder, among other mental disorders. Psychedelic microdosing, a common technique in recent years, involves the consumption of small doses of psychedelic drugs for therapeutic purposes. This study investigated the potential of hydrogel-forming microarray patches (HF-MAPs) to deliver N,N-dimethyltryptamine (DMT), 5-methoxy-N,N-dimethyltryptamine (5-MeO-DMT), and mescaline (MES) in small doses through the skin. To this purpose, HF-MAPs were prepared using poly(vinyl alcohol) (PVA) and poly(vinyl pyrrolidone) (PVP), using citric acid as the crosslinker. Two different reservoirs, containing PVP and PVA as the main components and poly(ethylene)glycol 400 (PEG400) and glycerol as plasticising agents, were used to deliver all the drugs from the HF-MAPs. Franz cells studies in excised neonatal porcine skin demonstrated that the permeation of DMT, 5-MeO-DMT and MES was better from the PEG400 reservoir, showing a permeation of 60.71 %, 59.61 % and 41.85 % respectively. Pharmacokinetic studies in rats showed that HF-MAP technology as a strategy for microdosing psychedelic compounds was also demonstrated with DMT. AUCt0-final for the HF-MAP cohort (7186 ± 1296 ng/mL*h) was significantly greater than the IM cohort (1803 ± 53.25 ng/mL*h) (p = 0.0020), with a relative bioavailability of ∼ 72 %. Considering their pharmacokinetic profile, the frequency of DMT dosing could be reduced with HF-MAP when compared to the IM route.

Fabrication and Evaluation of Dissolving Hyaluronic Acid Microneedle Patches for Minimally Invasive Transdermal Drug Delivery by Nanoimprinting

Transdermal drug delivery minimizes pain and provides a controlled, stable release of drugs, but its effectiveness is limited by the skin's natural barriers. Microneedles overcome this problem, enabling minimally invasive drug delivery. Microneedle patches (MNPs) with 80 µm-tall needles composed of hyaluronic acid (HA) were developed and evaluated for their formability, structural integrity, dissolution rate, skin penetration ability, and drug transmission capacity. The influence of the molecular weight of HA on these properties was also investigated. MNPs made from low-molecular-weight HA (30 kDa-50 kDa) demonstrated 12.5 times superior drug permeability in ex vivo human skin compared to needleless patches (NLPs). Furthermore, in the same test, low-molecular-weight HA MNPs had 1.7 times higher drug permeability than high-molecular-weight HA MNPs, suggesting superior transdermal administration. The molecular weight of HA significantly influenced its solubility and permeability, highlighting the potential effectiveness of MNPs as drug delivery systems. Puncture tests demonstrated a penetration depth of 50-60 µm, indicating minimal nerve irritation in the dermis and effective drug delivery to the superficial dermal layer. These results present a manufacturing technique for MNPs incorporating model drug compounds and highlight their potential as a novel and minimally invasive drug delivery method for the biomedical applications of soft gels.

Microneedles: multifunctional devices for drug delivery, body fluid extraction, and bio-sensing

Microneedles represent a miniaturized mechanical structure with versatile applications, including transdermal drug delivery, vaccination, body-fluid extraction, and bio-sensing. Over the past two decades, microneedle-based devices have garnered considerable attention in the biomedicine field, exhibiting the potential for mitigating patient discomfort, enhancing treatment adherence, avoiding first-pass effects, and facilitating precise therapeutic interventions. As an application-oriented technology, the innovation of microneedles is generally carried out in response to a specific demand. Currently, three most common applications of microneedles are drug delivery, fluid extraction, and bio-sensing. This review focuses on the progress in the materials, fabrication techniques, and design of microneedles in recent years. On this basis, the progress and innovation of microneedles in the current research stage are introduced in terms of their three main applications.

Overcoming Skin Barrier with Transfersomes: Opportunities, Challenges, and Applications

BACKGROUND

Transdermal drug delivery systems (TDDS) offer several advantages over traditional methods such as injections and oral administration. These advantages include preventing first-pass metabolism, providing consistent and sustained activity, reducing side effects, enabling the use of short half-life drugs, improving physiological response, and enhancing patient convenience. However, the permeability of skin poses a challenge for TDDS, as it is impermeable to large molecules and hydrophilic drugs but permeable to small molecules and lipophilic drug. To overcome this barrier, researchers have investigated vesicular systems, such as transfersomes, liposomes, niosomes, and ethosomes. Among these vesicular systems, transfersomes are particularly promising for noninvasive drug administration due to their deformability and flexible membrane. They have been extensively studied for delivering anticancer drugs, insulin, corticosteroids, herbal medicines, and NSAIDs through the skin. Transfersomes have demonstrated efficacy in treating skin cancer, improving insulin delivery, enhancing site-specific corticosteroid delivery, and increasing the permeation and therapeutic effects of herbal medicines. They have also been effective in delivering pain relief with minimal side effects using NSAIDs and opioids. Transfersomes have been used for transdermal immunization and targeted drug delivery, offering site-specific release and minimizing adverse effects. Overall, transfersomes are a promising approach for transdermal drug delivery in various therapeutic applications.

OBJECTIVE

The aim of the present review is to discuss the various advantages and limitations of transfersomes and their mechanism to penetration across the skin, as well as their application for the delivery of various drugs like anticancer, antidiabetic, NSAIDs, herbal drugs, and transdermal immunization.

METHODS

Data we searched from PubMed, Google Scholar, and ScienceDirect.

RESULTS

In this review, we have explored the various methods of preparation of transfersomes and their application for the delivery of various drugs like anticancer, antidiabetic, NSAIDs, herbal drugs, and transdermal immunization.

CONCLUSION

In comparison to other vesicular systems, transfersomes are more flexible, have greater skin penetration capability, can transport systemic medicines, and are more stable. Transfersomes are capable of delivering both hydrophilic and hydrophobic drugs, making them suitable for transdermal drug delivery. The developed transfersomal gel could be used to improve medicine delivery through the skin.

Novel drug delivery systems for hirudin-based product development and clinical applications

Hirudin, a natural biological polypeptide macromolecule secreted by the salivary glands of medicinal leech, is a specific thrombin inhibitor with multiple favourable bioactivities, including anti-coagulation, anti-fibrotic, and anti-tumour. Despite several anticoagulants have been widely applied in clinic, hirudin shows advantages in reducing the incidence of bleeding side effects by virtue of its high specificity in binding to thrombin. As a result, hirudin has been tested in clinical practice to prevent and treat several complex diseases. However, the application of this polypeptide macromolecule is compromised by its low bioavailability and bioactivity due to poor serum stability and susceptibility to protease degradation in vivo. To overcome these drawbacks, several studies have proposed novel drug delivery systems (NDDSs) to prevent the degradation and increase the targeting efficiency of hirudin. This systematic review summarises the clinical research on hirudin, including its classification and bioactivities, and highlights the opportunities and challenges in the clinical use of hirudin. The NDDSs designed to enhance the bioavailability and bioactivity of hirudin are discussed to explore its application in the treatment of related diseases. This review may considerably contribute to the advancement of delivery science and technology, particularly in the context of polypeptide-based therapeutics.

Microneedles as an Emerging Platform for Transdermal Delivery of Phytochemicals

Phytochemicals, which are predominantly found in plants, hold substantial medicinal value. Despite their potential, challenges such as poor oral bioavailability and instability in the gastrointestinal tract have limited their therapeutic use. Traditional intra/transdermal drug delivery systems offer some advantages over oral administration but still suffer from issues such as limited penetration depth, slow drug release rates, and inconsistent drug absorption. In contrast, microneedles (MNs) represent a significant advancement in intra/transdermal drug delivery by providing precise control over phytochemical delivery and enhanced penetration capabilities. By circumventing skin barriers, MNs directly access dermal layers rich in blood vessels and lymphatics, thus facilitating efficient phytochemical delivery. This review extensively discusses the obstacles of traditional oral delivery and the benefits of intra/transdermal delivery routes with a particular focus on the transformative potential of MNs for phytochemical delivery. This review explores the complexities of delivering phytochemicals through intra/transdermal routes, the development and types of MNs as innovative delivery tools, and the optimal design and properties of MNs for effective phytochemical delivery. Additionally, this review examines the versatile applications of MN-mediated phytochemical delivery, including its role in administering phytophotosensitizers for photodynamic therapy, and concludes with insights into relevant patents and future perspectives.

Advancing burn wound treatment: exploring hydrogel as a transdermal drug delivery system

Burn injuries are prevalent and life-threatening forms that contribute significantly to mortality rates due to associated wound infections. The management of burn wounds presents substantial challenges. Hydrogel exhibits tremendous potential as an ideal alternative to traditional wound dressings such as gauze. This is primarily attributed to its three-dimensional (3D) crosslinked polymer network, which possesses a high water content, fostering a moist environment that supports effective burn wound healing. Additionally, hydrogel facilitates the penetration of loaded therapeutic agents throughout the wound surface, combating burn wound pathogens through the hydration effect and thereby enhancing the healing process. However, the presence of eschar formation on burn wounds obstructs the passive diffusion of therapeutics, impairing the efficacy of hydrogel as a wound dressing, particularly in cases of severe burns involving deeper tissue damage. This review focuses on exploring the potential of hydrogel as a carrier for transdermal drug delivery in burn wound treatment. Furthermore, strategies aimed at enhancing the transdermal delivery of therapeutic agents from hydrogel to optimize burn wound healing are also discussed.

Transdermal Drug Delivery Systems (TDDS): Recent Advances and Failure Modes

Transdermal drug delivery systems (TDDS), commonly refered to as "patches", present a nonintrusive technique to provide medication without the need for invasive procedures. These products adhere to the skin and gradually release a specific dosage of medicine at a defined rate into the bloodstream. Compared with other methods of drug delivery, TDDS offer benefits such as reduced invasiveness, convenience for patients, and avoidance of the metabolic processes that occur when drugs are orally consumed. Throughout time, TDDS have been used to provide medications for various medical conditions (such as nicotine, fentanyl, nitroglycerin, and clonidine), and their potential for delivering biologics is currently being explored. This review investigates the current literature on the drug delivery efficacy of medical TDDS through the transdermal route. Additionally, the review addresses potential risks and failure modes associated with TDDS design and development as well as strategies for mitigating such risks. A thorough understanding of failure modes provides a blueprint to mitigate failure and produce high-quality efficacious therapeutics.

Design Principles and Applications of Ionic Liquids for Transdermal Drug Delivery

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

Advancements in Drug Delivery Systems for the Treatment of Sarcopenia: An Updated Overview

Since sarcopenia is a progressive condition that leads to decreased muscle mass and function, especially in elderly people, it is a public health problem that requires attention from researchers. This review aims to highlight drug delivery systems that have a high and efficient therapeutic potential for sarcopenia. Current as well as future research needs to consider the barriers encountered in the realization of delivery systems, such as the route of administration, the interaction of the systems with the aggressive environment of the human body, the efficient delivery and loading of the systems with therapeutic agents, and the targeted delivery of therapeutic agents into the muscle tissue without creating undesirable adverse effects. Thus, this paper sets the framework of existing drug delivery possibilities for the treatment of sarcopenia, serving as an inception point for future interdisciplinary studies.

Microneedles mediated-dermal delivery of Vitamin C: Formulation, characterization, cytotoxicity, and enhancement of stability

Vitamin C (VIT C) is an antioxidant that prevents skin aging. Although dermal delivery is one of the most effective routes to transport VIT C to the skin, the impact of this route can be limited by the barrier function of the stratum corneum (SC). Additionally, VIT C rapidly oxidized and degraded under light and temperature. Therefore, this study provides an approach to utilizing microneedles (MNs) to improve the dermal delivery of VIT C and enhance its stability by incorporating a stabilizing system of ethylenediaminetetraacetic acid (EDTA) and sodium metabisulfite (Meta) within the MNs. Vitamin C microneedles (VIT C MNs) were fabricated using different biodegradable polymers and various concentrations of EDTA/Meta. VIT C MNs were evaluated for morphology, VIT C content, mechanical properties, dissolution rate, needles' insertion, physicochemical properties, ex vivo permeation, viscosity of VIT C polymeric solutions, cytotoxicity, and stability. The results showed that VIT C MNs were uniform and mechanically strong. The recovery of VIT C in MNs was 88.3-90.0 %. The dissolution rate of MNs was <30 min. The flux of VIT C varied based on the composition of MNs. VIT C MNs demonstrated safety against human dermal fibroblasts. VIT C MNs with EDTA/Meta (0.1/0.3 %) were stable under different storage conditions for two months. In conclusion, VIT C MNs were successfully developed using biodegradable polymers, and the stabilizing system (EDTA/META) provided a stable dermal delivery system for VIT C to protect skin from aging.

Formulation and Evaluation of Turmeric- and Neem-Based Topical Nanoemulgel against Microbial Infection

The combination of nanoemulgel and phytochemistry has resulted in several recent discoveries in the field of topical delivery systems. The present study aimed to prepare nanoemulgel based on turmeric (Curcuma longa) and neem (Azadirachta indica) against microbial infection as topical drug delivery. Olive oil (oil phase), Tween 80 (surfactant), and PEG600 (co-surfactant) were used for the preparation of nanoemulsion. Carbopol 934 was used as a gelling agent to convert the nanoemulsion to nanoemulgel and promote the control of the release of biological properties of turmeric and neem. The nanoemulsion was characterized based on particle size distribution, PDI values, and compatibility using FTIR analysis. In contrast, the nanoemulgel was evaluated based on pH, viscosity, spreadability, plant extract and excipient compatibility or physical state, in vitro study, ex vivo mucoadhesive study, antimicrobial properties, and stability. The resulting nanoemulsion was homogeneous and stable during the centrifugation process, with the smallest droplets and low PDI values. FTIR analysis also confirmed good compatibility and absence of phase separation between the oil substance, surfactant, and co-surfactant with both plant extracts. The improved nanoemulgel also demonstrated a smooth texture, good consistency, good pH, desired viscosity, ex vivo mucoadhesive strength with the highest spreadability, and 18 h in vitro drug release. Additionally, it exhibited better antimicrobial properties against different microbial strains. Stability studies also revealed that the product had good rheological properties and physicochemical state for a period of over 3 months. The present study affirmed that turmeric- and neem-based nanoemulgel is a promising alternative for microbial infection particularly associated with microorganisms via topical application.

Development of Transdermal Formulation Integrating Polymer-Based Solid Microneedles and Thermoresponsive Gel Fucoidan for Antiaging: Proof of Concept Study

Skin can be damaged by intense and prolonged exposure to ultraviolet (UV) radiation. Photoaging and acute damage from sun exposure result in collagen degradation and enzymatic activity decline in the skin. Fucoidan (FUC) exhibits potential antiaging properties, including collagen synthesis promotion and enzyme activity inhibition. However, FUC's limited ability to penetrate the skin layers due to its large molecular weight makes it a challenge for topical application. In this study, we successfully developed a new approach by integrating thermoresponsive gel (TRG) containing FUC with solid microneedles (SMNs) as a delivery system. TRG is formulated using a combination of Pluronic F127 (PF127) and Pluronic F68 (PF68) polymers, while SMNs are made from a mixture of poly(vinyl alcohol) (PVA) and poly(vinylpyrrolidone) (PVP) polymers with a variety of cross-linkers. Based on the results of ex vivo testing, it was shown that more than 80% of FUC can be delivered using the optimized formula. Furthermore, the results of the in vitro blood hemolytic test showed that TRG-FUC-SMNs were relatively biocompatible. In vivo antiaging activity tests using a rat model exposed to UV for 14 days showed that histological assessment, skin elasticity measurement, wrinkle evaluation, and skin moisture content had no significant differences (p < 0.05) compared to the positive control group. In contrast, a significant difference (p < 0.05) was observed when comparing the TRG-FUC-SMNs group with the group that received only TRG-FUC without pretreatment and negative controls. These findings suggest that FUC has potential to be delivered using the TRG system in combination with SMNs to harness its antiaging properties.

Inorganic nanoparticles incorporated with transdermal drug delivery systems

INTRODUCTION

Transdermal drug delivery (TDD) is becoming more recognized as a noninvasive method particularly suitable for vulnerable populations. TDD offers an alternative to oral drug delivery, bypassing issues related to poor absorption and metabolism. However, the application of TDD is limited to a few drugs due to the skin's barrier. Various techniques, including passive methods like nanoparticles (NPs), are being explored to enhance drug permeability through the skin.

AREAS COVERED

This review shows the benefit of incorporating inorganic NPs with TDD in improving drug delivery through the skin. Despite the potential of these techniques, there are currently only a few research studies that utilize them. This review addresses the scarcity of research incorporating inorganic NPs with TDD. It also aims to summarize both inorganic NPs and TDD in the pharmaceutical industry, highlighting the advantages of incorporating these novel drug delivery systems with each other.

EXPERT OPINION

Given the potential benefits of incorporating inorganic NPs into TDD systems, there is a need for increased research and attention in this area. The review encourages scientists to address the existing research gap and explore the advantages of combining these innovative drug delivery systems to advance the field.

Beyond Skin Deep: Phospholipid-Based Nanovesicles as Game-Changers in Transdermal Drug Delivery

Transdermal administration techniques have gained popularity due to their advantages over oral and parenteral methods. Noninvasive, self-administered delivery devices improve patient compliance and control drug release. Transdermal delivery devices struggle with the skin's barrier function. Molecules over 500 Dalton (Da) and ionized compounds don't permeate through the skin. Drug encapsulation in phospholipid-based vesicular systems is the most effective skin delivery technique. Vesicular carriers include bi-layered liposomes, ultra-deformable liposomes, ethanolic liposomes, transethosomes, and invasomes. These technologies enhance skin drug permeation by increasing formula solubilization, partitioning into the skin, and fluidizing the lipid barrier. Phospholipid-based delivery systems are safe and efficient, making them a promising pharmaceutical and cosmeceutical drug delivery technique. Still, making delivery systems requires knowledge about the physicochemical properties of the drug and carrier, manufacturing and process variables, skin delivery mechanisms, technological advances, constraints, and regulatory requirements. Consequently, this review covers recent research achievements addressing the mentioned concerns.

Transdermal Delivery System of Doxycycline-Loaded Niosomal Gels: Toward Enhancing Doxycycline Stability

Doxycycline (DOX) is an antimicrobial agent that is susceptible to photosensitivity and thermal degradation. It addition, it causes gastrointestinal side effects when taken orally. Therefore, the development of alternative formulations is necessary to improve drug stability and promote patient compliance. The aim of the present study was to encapsulate DOX in niosomes as a nanocarrier to deliver DOX transdermally and enhance its stability in the formulation. DOX niosomes were prepared using nonionic surfactants, cholesterol, and dihexadecyl phosphate (DCP). After that, niosomes were characterized in terms of practical size (PS), zeta potential (ZP), morphology, and entrapment efficacy (EE%). DOX niosomal gels were then prepared using Carbopol and penetration enhancers (poly(ethylene glycol) 400 (PEG 400) and propylene glycol (PG)). The flux of DOX from the optimized formula was 322.86 μg/cm2/h over 5 h, which equates to 71.2% of DOX. Furthermore, neither the DOX niosomal gel (D3) nor the comparable blank niosomal gel had a negative influence on human dermal fibroblast (HDF) cells. The findings of the antimicrobial effectiveness of DOX niosomes indicated that the niosomal formulation improved the antibacterial activity of DOX against E. coli. Permeation studies demonstrated significantly higher DOX permeation when the niosomal gel was applied to rat skin, compared to the conventional gel. Permeability parameters such as flux and the permeability coefficient increased more than 10-fold using the niosomal gels compared with those of conventional gels. In conclusion, a new niosomal gel formulation could serve as an effective alternative for the commercially available form of DOX.

Sustained release microneedle patch for pronounced systemic delivery of doxazosin mesylate

Introduction

Microneedle patch is one of the fascinating drug delivery approaches that offers low invasiveness and a painless physical application to enhance the delivery of micro and macro-molecules into the skin.

Methods

Variable contents of chitosan and polyvinyl alcohol were used for the development of doxazosin mesylate containing sustained release microneedle patches via solvent casting technique. The prepared patches were evaluated for microscopic evaluation, mechanical strength, drug loading (%) and Fourier transform infrared spectroscopy (FTIR) etc. The skin penetration study was performed by using pig ear skin and results were captured through confocal microscopy. Ex-vivo release study and pharmacokinetic evaluation were also performed.

Results

Sharp needle tips with a height of 600µm and a base of 200µm were confirmed through microscopic examination. Optimized formulation (SRF-6) exhibited loading of 92.11% doxazosin mesylate with appreciable strength up to 1.94N force. Ex-vivo release studies revealed 87.24% release within 48 hours. Moreover, the pharmacokinetic parameters in case of optimized patch formulation (SRF-6) were markedly improved i.e. MRT (19.46 h), AUC (57.12 μg.h /mL), Cmax (2.16 µg /mL), tmax (10.10 h) and t1/2 (6.32 h) as compared to commercially available tablet. Biocompatibility of the developed patches was validated from skin irritation studies.

Conclusion

Results confirmed the successful fabrication of microneedle patch having sufficient strength and effective penetration ability into the skin to ensure controlled release of incorporated drug for the intended duration. It can be employed as an efficient carrier system for other therapeutics those are prone to bioavailability issues due to first pass effect after their oral administration.

High-Intensity Focused Ultrasound Enhances Drug Penetration into the Human Skin in the Franz Diffusion Cell

Purpose

High-intensity focused ultrasound (HIFU)-assisted drug delivery is a non-invasive tool to deliver drugs to targeted areas, currently used mainly for treating cancer and cardiovascular diseases. However, in terms of transdermal drug delivery, HIFU technology is still poorly understood. Accordingly, this study sought to investigate the effectiveness of HIFU on drug penetration into the skin using human skin tissues.

Methods

Gel-type drugs whose ingredient is glutathione were labelled with fluorescein isothiocyanate, in turn the drugs were allowed to penetrate to the human skin tissue in the Franz diffusion cell for 24 hours in control and HIFU treatment groups, and their fluorescence intensity was measured using a multiple microplate reader at one, two, six, and 24 hours after drug application. In addition, tissue slice analysis was performed in each tissue slice at 24 hours post-drug application. The % area, fluorescence intensity per area, and penetration depth of the drug were measured using a fluorescence microscope.

Results

The fluorescence intensity increased with time in all groups. Specifically, at 24 hours after drug application, the fluorescence intensity (a.u). of the 10-shot HIFU treatment group was significantly enhanced compared to that of the control group (p < 0.05). The tissue slice analysis demonstrated that the % area of fluorescent drug and the fluorescence intensity per area (a.u.) were all significantly increased in both HIFU treatment groups compared to the control group (p < 0.05, p < 0.001). In addition, the penetration depth (μm) also markedly rose in both HIFU treatment groups compared to the control group (p < 0.01, p < 0.05).

Conclusion

It was demonstrated for the first time that HIFU significantly facilitated topical drug penetration into the human skin, strongly implying that HIFU can be a useful option for transdermal drug delivery.

Long-acting transdermal drug delivery formulations: Current developments and innovative pharmaceutical approaches

Transdermal administration remains an active research and development area as an alternative route for long-acting drug delivery. It avoids major drawbacks of conventional oral (gastrointestinal side effects, low drug bioavailability, and need for multiple dosing) or parenteral routes (invasiveness, pain, and psychological stress and bio-hazardous waste generated from needles), thereby increasing patient appeal and compliance. This review focuses on the current state of long-acting transdermal drug delivery, including adhesive patches, microneedles, and molecularly imprinted polymeric systems. Each subsection describes an approach including key considerations in formulation development, design, and process parameters with schematics. An overview of commercially available conventional (adhesive) patches for long-acting drug delivery (longer than 24 h), the reservoir- and matrix-type systems under preclinical evaluation, as well as the advanced transdermal formulations, such as the core-shell, nanoformulations-incorporated and stimuli-responsive microneedles, and 3D-printed and molecularly imprinted polymers that are in development, is also provided. Finally, we elaborated on translational aspects, challenges in patch formulation development, and future directions for the clinical advancement of new long-acting transdermal products.

High molecular weight hyaluronic acid-liposome delivery system for efficient transdermal treatment of acute and chronic skin photodamage

Photodamage is one of the most common causes of skin injury. High molecular weight hyaluronic acid (HHA) has shown immense potential in the treatment of skin photodamage by virtue of its anti-inflammatory, reparative, and antioxidative properties. However, due to its large molecular structure of HHA, HHA solution could only form a protective film on the skin surface in conventional application, failing to effectively penetrate the skin, which necessitates the development of new delivery strategies. Liposomes, with a structure similar to biological membranes, have garnered extensive attention as transdermal drug delivery carriers because of their advantages in permeability, dermal compatibility, and biosafety. Herein, we have developed a HHA-liposome transdermal system (HHL) by embedding HHA into the liposome structure using reverse evaporation, high-speed homogenization, and micro-jet techniques. The effective penetration and long-term residence of HHA in skin tissue were multidimensionally verified, and the kinetics of HHA in the skin were extensively studied. Moreover, it was demonstrated that HHL significantly strengthened the activity of human keratinocytes and effectively inhibits photo-induced cellular aging in vitro. Furthermore, a murine model of acute skin injury induced by laser ablation was established, where the transdermal system showed significant anti-inflammatory and immunosuppressive properties, promoting skin proliferation and scar repair, thereby demonstrating immense potential in accelerating skin wound healing. Meanwhile, HHL significantly ameliorated skin barrier dysfunction caused by simulated sunlight exposure, inhibited skin erythema, inflammatory responses, and oxidative stress, and promoted collagen expression in a chronic photodamage skin model. Therefore, this transdermal delivery system with biocompatibility represents a promising new strategy for the non-invasive application of HHA in skin photodamage, revealing the significant potential for clinical translation and broad application prospects. STATEMENT OF SIGNIFICANCE: The transdermal system utilizing hyaluronic acid-based liposomes enhances skin permeability and retains high molecular weight hyaluronic acid (HHL). In vitro experiments with human keratinocytes demonstrate significant skin repair effects of HHL and its effective inhibition of cellular aging. In an acute photodamage model, HHL exhibits stronger anti-inflammatory and immunosuppressive properties, promoting skin proliferation and scar repair. In a chronic photodamage model, HHL significantly improves skin barrier dysfunction, reduces oxidative stress induced by simulated sunlight, and enhances collagen expression.

Spatiotemporal fate of nanocarriers-embedded dissolving microneedles: the impact of needle dissolving rate

OBJECTIVE

Dissolving microneedles (DMNs) have shown great potential for transdermal drug delivery due to their excellent skin-penetrating ability and combination with nanocarriers (NCs) can realize targeted drug delivery. The objective of this study was to investigate the impact of microneedle dissolving rate on the in vivo fate of NC-loaded DMNs, which would facilitate the clinical translation of such systems.

METHODS

Solid lipid nanoparticles (SLNs) were selected as the model NC for loading in DMNs, which were labeled by P4 probes with aggregation-quenching properties. Sodium hyaluronate acid (HA) and chitosan (CS), with different aqueous dissolving rates, were chosen as model tip materials. The effects of needle dissolving rate on the in vivo fate of NC-loaded DMNs was investigated by tracking the distribution of fluorescence signals after transdermal exposure.

RESULTS

P4 SLNs achieved a deeper diffusion depth of 180 μm in DMN-HA with a faster dissolution rate, while the diffusion depth in DMN-CS with a slower dissolution rate was lower (140 μm). The in vivo experiments demonstrated that P4 SLNs had a T1/2 value of 12.14 h in DMN-HA, whilst a longer retention time was found in DMN-CS, with a T1/2 of 13.12 h.

CONCLUSIONS

This study confirmed that the in vivo diffusion rate of NC-loaded DMNs was determined by the dissolving rate of DMNs materials and provided valuable guidance for the design and development of NC-loaded DMNs in the future.

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.

Models of the Three-Component Bilayer of Stratum Corneum: A Molecular Simulation Study

The construction of the stratum corneum (SC) is crucial to the problems of transdermal drug delivery. SC consists of the keratinocyte layers and the lipid matrix surrounding it. Among them, the lipid matrix is the barrier for many exogenous molecules, mainly composed of ceramides (CERs), free fatty acids (FFA), and cholesterol (CHOL). In this work, we developed single-component (CERs, CER-NS, and CER-EOS) and six three-component models, and each model was simulated by using the GROMOS-54A7 force field. Short-period phase (SPP) and long-period phase (LPP) systems were established separately, and area per lipid (APL), thickness, order of carbon chain (SCD), and density distribution were analyzed. The transition of CER-NS and CER-EOS in LPP was observed. The results of hydrogen bonds in the lipid systems indicated that a strong hydrogen-bond network was formed between the skin-lipid bilayers. Umbrella sampling method simulations were performed to calculate the free energy change of ethanol moving into the skin-lipid bilayer. The results revealed that ethanol molecules pulled some water molecules into the membrane when they passed through SPP-1. Our findings provided some insights and models of the stratum corneum that could be used for the subsequent mechanism of macromolecule permeation through membranes in drugs, cosmetics, and so on.

Minoxidil Nanosuspension-Loaded Dissolved Microneedles for Hair Regrowth

Minoxidil (MIN) is used topically to treat alopecia. However, its low absorption limits its use, warranting a new strategy to enhance its delivery into skin layers. The objective of this study was to evaluate the dermal delivery of MIN by utilizing dissolved microneedles (MNs) loaded with MIN nanosuspension (MIN-NS) for hair regrowth. MIN-NS was prepared by the solvent-antisolvent precipitation technique. The particle size of MIN-NS was 226.7 ± 9.3 nm with a polydispersity index of 0.29 ± 0.17 and a zeta potential of -29.97 ± 1.23 mV. An optimized formulation of MIN-NS was selected, freeze-dried, and loaded into MNs fabricated with sodium carboxymethyl cellulose (Na CMC) polymeric solutions (MIN-NS-loaded MNs). MNs were evaluated for morphology, dissolution rate, skin insertion, drug content, mechanical properties, ex vivo permeation, in vivo, and stability studies. MNs, prepared with 14% Na CMC, were able to withstand a compression force of 32 N for 30 s, penetrate Parafilm M® sheet at a depth of 374-504 µm, and dissolve completely in the skin within 30 min with MIN %recovery of 95.1 ± 6.5%. The release of MIN from MIN-NS-loaded MNs was controlled for 24 h. MIN-NS-loaded MNs were able to maintain their mechanical properties and chemical stability for 4 weeks, when kept at different storage conditions. The in vivo study of the freeze-dried MIN-NS and MIN-NS-loaded MNs proved hair regrowth on rat skin after 11 and 7 days, respectively. These results showed that MIN-NS-loaded MNs could potentially improve the dermal delivery of MIN through the skin to treat alopecia.

Predictive modeling of skin permeability for molecules: Investigating FDA-approved drug permeability with various AI algorithms

The transdermal route of drug administration has gained popularity for its convenience and bypassing the first-pass metabolism. Accurate skin permeability prediction is crucial for successful transdermal drug delivery (TDD). In this study, we address this critical need to enhance TDD. A dataset comprising 441 records for 140 molecules with diverse LogKp values was characterized. The descriptor calculation yielded 145 relevant descriptors. Machine learning models, including MLR, RF, XGBoost, CatBoost, LGBM, and ANN, were employed for regression analysis. Notably, LGBM, XGBoost, and gradient boosting models outperformed others, demonstrating superior predictive accuracy. Key descriptors influencing skin permeability, such as hydrophobicity, hydrogen bond donors, hydrogen bond acceptors, and topological polar surface area, were identified and visualized. Cluster analysis applied to the FDA-approved drug dataset (2326 compounds) revealed four distinct clusters with significant differences in molecular characteristics. Predicted LogKp values for these clusters offered insights into the permeability variations among FDA-approved drugs. Furthermore, an investigation into skin permeability patterns across 83 classes of FDA-approved drugs based on the ATC code showcased significant differences, providing valuable information for drug development strategies. The study underscores the importance of accurate skin permeability prediction for TDD, emphasizing the superior performance of nonlinear machine learning models. The identified key descriptors and clusters contribute to a nuanced understanding of permeability characteristics among FDA-approved drugs. These findings offer actionable insights for drug design, formulation, and prioritization of molecules with optimum properties, potentially reducing reliance on costly experimental testing. Future research directions include offering promising applications in pharmaceutical research and formulation within the burgeoning field of computer-aided drug design.

Multilayered Microneedles for Triphasic Controlled Delivery of Small Molecules and Proteins

Transdermal delivery is an attractive delivery method that increases bioavailability, is suitable for a wide variety of therapeutics, and offers stable delivery outcomes. However, many therapeutics are unable to readily cross the stratum corneum. Microneedles mechanically disrupt the cutaneous barrier to deliver small molecules, proteins, and vaccines. To date, microneedles have not been used in conjunction with coacervate, a liquid-liquid phase separation that protects unstable proteins. A three-layer microneedle for the controlled release of three different molecules is designed. Through micromolding, microneedles are efficiently generated, which benefits product scalability. The microneedles have good mechanical integrity and effectively penetrate porcine skin ex vivo. The three layers, in the microneedles, release the cargo in a three-phase manner. The released protein maintains its structure well. Moreover, layer thickness can be controlled by varying fabrication parameters. The microneedles can incorporate both small molecule drugs and protein therapeutics, thus promising uses in multi-drug therapies through a single treatment.

ATP-adenosine axis regulation combined with microneedle assisted photoimmunotherapy to boost the immunotherapy efficiency

Immunogenic cell death (ICD) is associated with the release of damage-associated molecular patterns, including ATP, to promote an effective immune cycle against tumors. However, tumors have evolved an effective strategy for degrading extracellular immunostimulatory ATP via the ATP-adenosine axis, allowing the sequential action of the ectonucleotidases CD39 to degrade accumulated immunostimulatory ATP into pleiotropic immunosuppressive adenosine. Here, an ingenious dissolving microneedle patch (DMNs) is designed for the intralesional delivery of CD39 inhibitor (sodium polyoxotungstate, POM-1) and ICD inducer (IR780) co-encapsulated solid lipid nanoparticles (P/I SLNs) for antitumor therapy. Upon insertion into the tumor site, IR780 induces ICD modalities with the release of damage-associated molecular patterns from endogenous tissues, which activates the antitumor immune cycle. Simultaneously, POM-1 promotes the liberation of immunostimulatory ATP and lowers the level of immunosuppressive extracellular adenosine, which supported immune control of tumors via recruiting CD39-expressing immune cells. In vivo antitumor studies prove that this platform can effectively eliminate mice melanoma (tumor growth inhibitory rate of 96.5%) and colorectal adenocarcinoma (tumor growth inhibitory rate of 93.5%). Our results shed light on the immunological aspects of combinatorial phototherapy and ATP-adenosine regulation, which will broaden the scope of synergistic antitumor immunotherapy.

The Necessity to Investigate In Vivo Fate of Nanoparticle-Loaded Dissolving Microneedles

Transdermal drug delivery systems are rapidly gaining prominence and have found widespread application in the treatment of numerous diseases. However, they encounter the challenge of a low transdermal absorption rate. Microneedles can overcome the stratum corneum barrier to enhance the transdermal absorption rate. Among various types of microneedles, nanoparticle-loaded dissolving microneedles (DMNs) present a unique combination of advantages, leveraging the strengths of DMNs (high payload, good mechanical properties, and easy fabrication) and nanocarriers (satisfactory solubilization capacity and a controlled release profile). Consequently, they hold considerable clinical application potential in the precision medicine era. Despite this promise, no nanoparticle-loaded DMN products have been approved thus far. The lack of understanding regarding their in vivo fate represents a critical bottleneck impeding the clinical translation of relevant products. This review aims to elucidate the current research status of the in vivo fate of nanoparticle-loaded DMNs and elaborate the necessity to investigate the in vivo fate of nanoparticle-loaded DMNs from diverse aspects. Furthermore, it offers insights into potential entry points for research into the in vivo fate of nanoparticle-loaded DMNs, aiming to foster further advancements in this field.

The Use of Data Mining for Obtaining Deeper Insights into the Fabrication of Prednisolone-Loaded Chitosan Nanoparticles

The present work explores a data mining approach to study the fabrication of prednisolone-loaded chitosan nanoparticles and their properties. Eight PLC formulations were prepared using an automated adaptation of the antisolvent precipitation method. The PLCs were characterized using dynamic light scattering, infrared spectroscopy, and drug release studies. Results showed that that the effective diameter, loading capacity, encapsulation efficiency, zeta potential, and polydispersity of the PLCs were influenced by the concentration and molecular weight of chitosan. The drug release studies showed that PLCs exhibited significant dissolution enhancement compared to pure prednisolone crystals. Principal components analysis and partial least squares regression were applied to the infrared spectra and the DLS data to extract higher-order interactions and correlations between the critical quality attributes and the diameter of the PLCs. Principal components revealed that the spectra clustered according to the type of material, with PLCs forming a separate cluster from the raw materials and the physical mix. PLS was successful in predicting the ED of the PLCs from the FTIR spectra with R2 = 0.98 and RMSE = 27.18. The present work demonstrates that data mining techniques can be useful tools for obtaining deeper insights into the fabrication and properties of PLCs, and for optimizing their quality and performance. It also suggests that FTIR spectroscopy can be a rapid and non-destructive method for predicting the ED of PLCs.

Delivery Strategies for Colchicine as a Critical Dose Drug: Reducing Toxicity and Enhancing Efficacy

Colchicine (COL), a widely used natural drug, has potent anti-inflammatory effects; however, as a narrow therapeutic index drug, its clinical application is limited by its serious gastrointestinal adverse effects, and only oral formulations are currently marketed worldwide. Recent studies have shown that transdermal, injection, and oral drug delivery are the three main delivery strategies for COL. This article elaborates on the research progress of different delivery strategies in terms of toxicity reduction and efficacy enhancement, depicting that the transdermal drug delivery route can avoid the first-pass effect and the traumatic pain associated with the oral and injection routes, respectively. Therefore, such a dosage form holds a significant promise that requires the development of further research to investigate effective COL delivery formulations. In addition, the permeation-promoting technologies utilized for transdermal drug delivery systems are briefly discussed. This article is expected to provide scientific ideas and theoretical guidance for future research and the exploration of COL delivery strategies.

Cell-penetrating peptides for transmucosal delivery of proteins

Enabling non-invasive delivery of proteins across the mucosal barriers promises improved patient compliance and therapeutic efficacies. Cell-penetrating peptides (CPPs) are emerging as a promising and versatile tool to enhance protein and peptide permeation across various mucosal barriers. This review examines the structural and physicochemical attributes of the nasal, buccal, sublingual, and oral mucosa that hamper macromolecular delivery. Recent development of CPPs for overcoming those mucosal barriers for protein delivery is summarized and analyzed. Perspectives regarding current challenges and future research directions towards improving non-invasive transmucosal delivery of macromolecules for ultimate clinical translation are discussed.

An Updated Review on Nanoemulsion: Factory for Food and Drug Delivery

BACKGROUND

A nanoemulsion is a colloidal system of small droplets dispersed in another liquid. It has attracted considerable attention due to its unique properties and various applications. Throughout this review, we provide an overview of nanoemulsions and how they can be applied to various applications such as drug delivery, food applications, and pesticide formulations.

OBJECTIVE

This updated review aims to comprehensively overview nanoemulsions and their applications as a versatile platform for drug delivery, food applications, and pesticide formulations.

METHODS

Research relevant scientific literature across various databases, including PubMed, Scopus, and Web of Science. Suitable keywords for this purpose include "nanoemulsion," "drug delivery," and "food applications." Ensure the search criteria include recent publications to ensure current knowledge is included.

RESULTS

Several benefits have been demonstrated in the delivery of drugs using nanoemulsions, including improved solubility, increased bioavailability, and controlled delivery. Nanoemulsions have improved some bioactive compounds in food applications, including vitamins and antioxidants. At the same time, pesticide formulations based on nanoemulsions have also improved solubility, shelf life, and effectiveness.

CONCLUSION

The versatility of nanoemulsions makes them ideal for drug delivery, food, and pesticide formulation applications. These products are highly soluble, bioavailable, and targeted, providing significant advantages. More research and development are required to implement nanoemulsion-based products on a commercial scale.

Transdermal Patches for Pain Relief in Orthodontic Procedures: A Narrative Review

Pain relief is an integral component of any orthodontic procedure given its high association with patient compliance and treatment adherence. A transdermal drug delivery system (TDDS) is a non-invasive method of drug delivery through the skin surface that can spread the medication throughout the dermis at a predetermined rate to produce a local or systemic effect. It might be used in place of hypodermic injections and the oral medication route. A transdermal analgesic, often known as a pain reliever patch, is an adhesive patch that contains medication to treat mild-to-severe pain. Many opioids and non-steroidal anti-inflammatory drugs are currently available as patches. TDDS offers many benefits over the conventional medication delivery method. The non-invasive transdermal route or therapy has features such as excellent bioavailability, stable medication plasma concentration, and no first-pass metabolism effect. This review aims to explore the available evidence on the use of transdermal patches for pain relief in orthodontic procedures and possibly suggest recommendations based on the findings.

A Comprehensive Review on Potential Chemical and Herbal Permeation Enhancers Used in Transdermal Drug Delivery Systems

Using skin patches to deliver drugs is dependable and doesn't have the same issues as permeation enhancers, which help drugs get through the skin but struggle because of the skin's natural barrier. Strategies are required to increase topical bioavailability to enhance drug absorption. Natural compounds offer a promising solution by temporarily reducing skin barrier resistance and improving drug absorption. Natural substances allow a wider variety of medications to be distributed through the stratum corneum, offering a dependable approach to enhancing transdermal drug delivery. Natural substances have distinct advantages as permeability enhancers. They are pharmacologically effective and safe, inactive, non-allergenic, and non-irritating. These characteristics ensure their suitability for use without causing adverse effects. Natural compounds are readily available and well tolerated by the body. Studies investigating the structure-activity relationship of natural chemicals have demonstrated significant enhancer effects. By understanding the connection between chemical composition and enhancer activity, researchers can identify effective natural compounds for improving drug penetration. In conclusion, current research focuses on utilizing natural compounds as permeability enhancers in transdermal therapy systems. These substances offer safety, non-toxicity, pharmacological inactivity, and non-irritation. Through structure-activity relationship investigations, promising advancements have been made in enhancing drug delivery. Using natural compounds holds enormous potential for improving the penetration of trans-dermally delivered medications.

Quantification of skin penetration of caffeine and propylene glycol applied topically in a mixture by tailored multivariate curve resolution-alternating least squares of depth-resolved Raman spectra

The quantitative determination of topically applied substances in the skin is severely limited and represents a challenging task. The porcine skin ex vivo was topically treated with a gel containing caffeine (CF) and propylene glycol (PG), and depth-resolved Raman spectra were recorded with two confocal Raman microscopes. We applied a novel tailored multivariate curve resolution-alternating least squares method to the selected spectral regions (512-604 and 778-1148 cm-1 ) of gel-treated skin and quantitatively determined the concentrations of CF and PG in the stratum corneum (SC). The highest concentration of CF (181 mg/cm3 ) was found at the surface, while PG (384 mg/cm3 ) was found at 10% SC depth, indicating the formation of a reservoir at the superficial SC. The concentrations of CF and PG decreased monotonically and reached the detection limit at ≈60% and ≈80% SC depth, respectively, indicating that neither permeate the SC.

Niosomal Delivery of Celecoxib and Metformin for Targeted Breast Cancer Treatment

Breast cancer continues to be a prominent worldwide health concern and requires continued investigation into innovative therapeutic approaches. Here, we report the first investigation into the therapeutic efficacy of combining Metformin (MET) and Celecoxib (CXB), both in free and niosomal form, for the treatment of breast cancer. Our investigation encompassed the characterization of these niosomal drug carriers, their stability assessment, and their effect on breast cancer cell models. The thin-film hydration technique was employed to prepare niosomes with spherical, uniform-size distributions and high encapsulation efficiencies. The niosomes were characterized by TEM, particle size analyzer, and ATR-FTIR. The niosomes with an average size of 110.6 ± 0.6 and 96.7 ± 0.7, respectively, for MET and CXB were stable when stored at 4 °C for three months with minimal drug leakage, minor changes in encapsulation efficiency and size, and unchanged physicochemical parameters. Evaluation in two-dimensional (2D) and three-dimensional (3D) viability assays demonstrated an increased cytotoxicity of encapsulated drugs when compared to their free-drug counterparts. Additionally, the combination of Metformin Niosomal Particles (MET NPs) and Celecoxib Niosomal Particles (CXB NPs) led to decreased cell viability in both 2D and 3D models compared to each drug administered individually. When comparing the effect of the niosomal versus the free combination of the drugs on cell migration, we found that both interventions effectively prevented cell migration. However, the efficacy of the niosomes' combination was not superior to that of the free drug combination (p < 0.05). In conclusion, the results of this study provide valuable insights into the potential application of combining MET and CXB nanoparticle delivery systems to breast cancer treatment. Exploring the in vivo application of this drug delivery system could open new avenues for more effective and targeted therapeutic approaches for breast cancer patients.

Optical Methods for Non-Invasive Determination of Skin Penetration: Current Trends, Advances, Possibilities, Prospects, and Translation into In Vivo Human Studies

Information on the penetration depth, pathways, metabolization, storage of vehicles, active pharmaceutical ingredients (APIs), and functional cosmetic ingredients (FCIs) of topically applied formulations or contaminants (substances) in skin is of great importance for understanding their interaction with skin targets, treatment efficacy, and risk assessment-a challenging task in dermatology, cosmetology, and pharmacy. Non-invasive methods for the qualitative and quantitative visualization of substances in skin in vivo are favored and limited to optical imaging and spectroscopic methods such as fluorescence/reflectance confocal laser scanning microscopy (CLSM); two-photon tomography (2PT) combined with autofluorescence (2PT-AF), fluorescence lifetime imaging (2PT-FLIM), second-harmonic generation (SHG), coherent anti-Stokes Raman scattering (CARS), and reflectance confocal microscopy (2PT-RCM); three-photon tomography (3PT); confocal Raman micro-spectroscopy (CRM); surface-enhanced Raman scattering (SERS) micro-spectroscopy; stimulated Raman scattering (SRS) microscopy; and optical coherence tomography (OCT). This review summarizes the state of the art in the use of the CLSM, 2PT, 3PT, CRM, SERS, SRS, and OCT optical methods to study skin penetration in vivo non-invasively (302 references). The advantages, limitations, possibilities, and prospects of the reviewed optical methods are comprehensively discussed. The ex vivo studies discussed are potentially translatable into in vivo measurements. The requirements for the optical properties of substances to determine their penetration into skin by certain methods are highlighted.

Polysaccharide hydrogel platforms as suitable carriers of liposomes and extracellular vesicles for dermal applications

Lipid-based nanocarriers have been extensively investigated for their application in drug delivery. Particularly, liposomes are now clinically established for treating various diseases such as fungal infections. In contrast, extracellular vesicles (EVs) - small cell-derived nanoparticles involved in cellular communication - have just recently sparked interest as drug carriers but their development is still at the preclinical level. To drive this development further, the methods and technologies exploited in the context of liposome research should be applied in the domain of EVs to facilitate and accelerate their clinical translation. One of the crucial steps for EV-based therapeutics is designing them as proper dosage forms for specific applications. This review offers a comprehensive overview of state-of-the-art polysaccharide-based hydrogel platforms designed for artificial and natural vesicles with application in drug delivery to the skin. We discuss their various physicochemical and biological properties and try to create a sound basis for the optimization of EV-embedded hydrogels as versatile therapeutic avenues.

A Promising Approach to Treat Psoriasis: Inhibiting Cytochrome P450 3A4 Metabolism to Enhance Desoximetasone Therapy

(1) Background: Human keratinocytes and murine skin express various cytochrome P450 enzymes. These include cytochrome P450 3A4, which may participate in the metabolism of cytochrome P450 3A4 substrate drugs. Desoximetasone, a topical corticosteroid and cytochrome P450 3A4 substrate, is used to treat skin conditions such as skin allergies, atopic dermatitis, and psoriasis. In this study, we aimed to investigate the anti-psoriatic effect of a low dose of desoximetasone by inhibiting cytochrome P450 3A4 metabolism in the epidermis. (2) Methods: Psoriasis-like skin was induced in BALB/c mice via the topical administration of imiquimod. The mice were then topically treated with 0.01-0.05% desoximetasone loaded into a cytochrome P450 3A4 enzyme inhibitor excipient base emollient microemulsion, 0.25% commercial desoximetasone ointment, or 0.5 mg/gm clobetasol ointment. (3) Results: The topical application of 0.05% desoximetasone loaded into a cytochrome P450 3A4 enzyme inhibitor excipient base emollient formulation restored the imiquimod-induced skin barrier disruption and resulted in fewer severe clinical and pathological features compared with the treatments with 0.25% commercial desoximetasone ointment and 0.5 mg/gm clobetasol ointment. (4) Conclusions: The cytochrome P450 3A4 enzyme inhibitor excipient base emollient formulation improved and prolonged the therapeutic effect of cytochrome P450 3A4 substrate drugs and may be a promising approach for psoriasis treatment.

Development and Comparative Evaluation of Ciprofloxacin Nanoemulsion-Loaded Bigels Prepared Using Different Ratios of Oleogel to Hydrogels

Nanoemulsions and bigels are biphasic delivery systems that can be used for topical applications. The aim of this study was to incorporate an oil-in-water ciprofloxacin hydrochloride nanoemulsion (CIP.HCl NE) into two types of bigels, Type I (oleogel (OL)-in-hydrogel (WH)) and Type II (WH-in-OL) to enhance drug penetration into skin and treat topical bacterial infections. Bigels were prepared at various ratios of OL and WH (1:1, 1:2, and 1:4). Initially, CIP.HCl NE was prepared and characterized in terms of droplet size, zeta potential, polydispersity index, morphology, and thermodynamic and chemical stability. Then CIP.HCl NE was dispersed into the OL or WH phase of the bigel. The primary physical stability studies showed that Type I bigels were physically stable, showing no phase separation. Whereas Type II bigels were physically unstable, hence excluded from the study. Type I bigels were subjected to microstructural, rheological, in vitro release, antimicrobial, and stability studies. The microscopic images showed a highly structured bigel network with nanoemulsion droplets dispersed within the bigel network. Additionally, bigels exhibited pseudoplastic flow and viscoelastic properties. A complete drug release was achieved after 4-5 h. The in vitro and ex vivo antimicrobial studies revealed that bigels exhibited antimicrobial activity against different bacterial strains. Moreover, stability studies showed that the rheological properties and physical and chemical stability varied based on the bigel composition over three months. Therefore, the physicochemical and rheological properties, drug release rate, and antimicrobial activity of Type I bigels could be modified by altering the OL to WH ratio and the phase in which the nanoemulsion dispersed in.

Preparation and Evaluation of Auxiliary Permeable Microneedle Patch Composed of Polyvinyl Alcohol and Eudragit NM30D Aqueous Dispersion

Poor transdermal permeability limits the possibility of most drug delivery through the skin. Auxiliary permeable microneedles (AP-MNs) with a three-dimensional network structure can effectively break the skin stratum corneum barrier and assist in the transdermal delivery of active ingredients. Herein, we propose a simple method for preparing AP-MNs using polyvinyl alcohol and Eudragit NM30D for the first time. To optimize the formulation of microneedles, the characteristics of swelling properties, skin insertion, solution viscosity, and needle integrity were systematically examined. Additionally, the morphology, mechanical strength, formation mechanism, skin permeability, swelling performance, biocompatibility, and in vitro transdermal drug delivery of AP-MNs were evaluated. The results indicated that the microneedles exhibited excellent mechanical-strength and hydrogel-forming properties after swelling. Further, it proved that a continuous and unblockable network channel was created based on physical entanglement and encapsulation of two materials. The 24 h cumulative permeation of acidic and alkaline model drugs, azelaic acid and matrine, were 51.73 ± 2.61% and 54.02 ± 2.85%, respectively, significantly enhancing the transdermal permeability of the two drugs. In summary, the novel auxiliary permeable microneedles prepared through a simple blending route of two materials was a promising and valuable way to improve drug permeation efficiency.

From Plants to Wound Dressing and Transdermal Delivery of Bioactive Compounds

Transdermal delivery devices and wound dressing materials are constantly improved and upgraded with the aim of enhancing their beneficial effects, biocompatibility, biodegradability, and cost effectiveness. Therefore, researchers in the field have shown an increasing interest in using natural compounds as constituents for such systems. Plants, as an important source of so-called "natural products" with an enormous variety and structural diversity that still exceeds the capacity of present-day sciences to define or even discover them, have been part of medicine since ancient times. However, their benefits are just at the beginning of being fully exploited in modern dermal and transdermal delivery systems. Thus, plant-based primary compounds, with or without biological activity, contained in gums and mucilages, traditionally used as gelling and texturing agents in the food industry, are now being explored as valuable and cost-effective natural components in the biomedical field. Their biodegradability, biocompatibility, and non-toxicity compensate for local availability and compositional variations. Also, secondary metabolites, classified based on their chemical structure, are being intensively investigated for their wide pharmacological and toxicological effects. Their impact on medicine is highlighted in detail through the most recent reported studies. Innovative isolation and purification techniques, new drug delivery devices and systems, and advanced evaluation procedures are presented.