Device-assisted transdermal drug delivery

Innovative approaches in bioadhesive design: A comprehensive review of crosslinking methods and mechanical performance

In biomedical applications, bioadhesives have become a game-changer, offering novel approaches to tissue engineering, surgical adhesion, and wound healing. This comprehensive review paper provides a thorough analysis of bioadhesives and their categorization according to application site and crosslinking process, bonding efficacy, and mechanical characteristics. The use of bioadhesives to stop bleeding and seal leaks is also covered in the review. The article delves into the various crosslinking techniques used in bioadhesives, including chemical, physical, and hybrid approaches. It emphasizes on how these mechanisms control the adhesive's elasticity, durability, and structural integrity. In addition, the review looks at the mechanical strength of bioadhesives, taking important characteristics like shear strength, toughness, elasticity, and tensile strength into account. It is highlighted how important bioadhesives are to the life sciences because they drive innovation and interdisciplinary cooperation, address present healthcare issues, and create new avenues for therapeutic development. The paper also explores some vital characteristics of bioadhesives that, when strategically combined with one another, improve their efficacy and usefulness in a variety of surgical and medical applications. The analysis concludes by examining nature-inspired adhesives, including those based on geckos, mussels, and tannic acid, and their unique bonding mechanisms and potential for use in advanced biomedical applications.

Breathable and imperceptible on-skin electronic tattoos with a hybrid of silk and cellulose and highly conductive electrodes for monitoring skin hydration

Skin, the largest organ protecting the body, acts as a pathway connecting the inside and outside of the body, allowing us to examine health conditions. Therefore, on-skin electronics are attractive for monitoring biosignals in daily life for point-on-care healthcare. However, integrating highly conductive electrodes while maintaining all the properties suitable for on-skin devices, such as flexibility, imperceptibility, breathability, and biocompatibility, is still challenging. Here, we present breathable and imperceptible electronic tattoos (E-tattoos), on which highly conductive gold (Au) electrodes are integrated. The E-tattoo, which a hybrid of two nanostructured biomaterials, ultrathin silk film and cellulose nanofiber mat, possesses all favorable properties for on-skin electronics. Due to the inherent strong adhesion of silk to Au, patterned Au electrodes, with a high conductivity (2.84 × 107 S/m) comparable to that of pure Au (4.01 × 107 S/m), can be integrated on the E-tattoo. High water-vapor transmission and low leakage current through E-tattoos provide skin-compatibility (nonirritating response). With these advantages, the E-tattoo is applied to monitor skin hydration. On-skin impedance measurements reveal dependency on skin hydration, and impedances measured with E-tattoos show better signal stability than those measured for Au nanomesh patches. This study presents a new on-skin electronic platform for monitoring skin conditions.

Dissolving microneedles fabricated from 3D-printed master molds for application in veterinary medicine

Microneedle (MN) technology is gaining popularity as it offers many benefits and advantages over the conventional drug delivery methods. The transdermal drug delivery system (TDDS) with MNs offers painless, precise, and easy-to-use solutions that can be obtained using cost-effective technologies such as 3D printing. Numerous examples of microneedle applications have been reported for human use, especially given the context of the recent pandemic and the development of vaccination technologies. However, there is limited exploration of microneedles in veterinary medicine. In the following work, we presented a proposal for the efficient production of quickly dissolving microneedle patches from PVP (polyvinylpyrrolidone) and PVA (polyvinyl alcohol) polymers based on a model microneedle array printed using DLP (Digital Light Processing) technology. We have developed a repeatable process in which the obtained microneedles can easily penetrate the outer layers of skin and quickly deliver the model drug. Such a versatile platform can be used, among others, in the treatment of animal gingival diseases, which affect a significant amount of the cat and dog population. An important advantage of the presented solution is the possibility of implementing the whole technological process in a veterinary office in a short time and the possibility of easy adjusting the size of the patches to a specific animal.

Bioinspired Suction-Driven Strategies with Nanoscale Skin-Controllable Adhesive Architectures for Efficient Liquid Formulated Transdermal Patches

For highly efficient and precise drug release, transdermal drug delivery systems (TDDS) have recently evolved through the combination of intelligent material-based structures with various active components. These strategies are an effort to overcome the significant difficulties in delivering large molecule drugs and nanomaterials due to the physical barrier of the skin, especially the stratum corneum, in traditional TDDS. Interestingly, multiscale suction-driven architectures (SDAs) inspired by bioinspired suction adhesion mechanisms have provided innovative solutions to these challenges. These architectures employ negative pressure to enhance nanoscale skin-controllable skin adhesion, temporarily bypass the skin barrier, and facilitate deep penetration of therapeutic agents, thereby, achieving the goals of increasing drug delivery efficiency and maximizing user convenience as a minimal invasive, needle-free platform. This review provides a comprehensive overview of suction-driven transdermal patches and emphasizes their integration with multifunctional materials to achieve stable adhesion and controlled drug release. Next, we present cost-effective and user-friendly suction-driven drug delivery patch devices through optimization of cupping structures without the incorporation of additional devices. Furthermore, we present cost-effective and user-friendly transdermal drug delivery patch devices that optimize multiscale cupping architectures without the need for additional devices. Potential of bioinspired SDAs in localized and systemic drug delivery through challenging and complex skin, as well as future perspectives, are discussed, along with innovative directions for more efficient and patient-centric transdermal drug delivery solutions.

Biodegradable Microneedle Patch Confers Crocin with Outstanding Effects in the Treatment of Myocardial Infarction

Crocin (CRO), the main active component of Crocus sativus (saffron), exhibits significant therapeutic potential for the treatment of myocardial infarction (MI). However, its clinical application is hindered by poor oral administration due to the intestinal barrier. To overcome this limitation, a CRO-incorporated biodegradable microneedle (CRO-DMN) patch was developed to transdermally deliver CRO into the bloodstream, enhancing its therapeutic effect against MI. The microneedle patch, fabricated from sodium hyaluronate (HA), demonstrated excellent mechanical strength, effectively penetrating the stratum corneum and facilitating CRO infiltration to a depth exceeding 300 μm successfully. Studies revealed that CRO was fully released within 30 min postapplication, and the skin self-healed within 90 min after patch removal. Importantly, administration of CRO-DMNs to MI mice resulted in significant improvements in cardiac function and reductions in infarct size compared with CRO treatment alone. Additionally, CRO-DMNs also provided superior protective effects on the myocardium and mitochondria and significantly increased angiogenesis in the infarction border area. In conclusion, CRO-DMNs represent a promising transdermal drug delivery system that effectively improves the therapeutic efficacy of CRO in the treatment of MI.

Harnessing the Power of Antimicrobial Peptides: From Mechanisms to Delivery Optimization for Topical Infections

Antimicrobial peptides (AMPs) have emerged as promising agents for treating topical infections due to their enhanced biocompatibility and resistance to systemic degradation. AMPs possess host immunomodulatory effects and disintegrate bacterial cell membranes, a mechanism less prone to microbial resistance compared to conventional antibiotics, making AMPs potential candidates for antimicrobial delivery. The review discusses the challenges posed by antimicrobial resistance (AMR) and explores the mechanisms by which bacteria develop resistance to AMPs. The authors provide a detailed analysis of the mechanisms of action of AMPs, their limitations, and strategies to improve their efficacy. Conventional AMP delivery systems, including polymeric, synthetic, and lipid-based nanoparticles and cubosomes, face challenges of microbial resistance mechanisms via efflux pump systems, bacterial cell membrane modifications, and protease enzyme release. This review explores strategies to optimize these delivery systems. Furthermore, market statistics and the growing interest in peptide antibiotics have been explored in this review. The authors provide future research directions, such as exploring gene-targeting approaches to combat emerging bacterial resistance against AMPs, and emphasize considering the conformational stability of peptides, the skin microbiome's nature at the infection site, and proteolytic stability for developing efficient AMP delivery systems for topical infections.

Self-Oxygenating PROTAC Microneedle for Spatiotemporally-Confined Protein Degradation and Enhanced Glioblastoma Therapy

Glioblastoma (GBM) is the most aggressive subtype of primary brain tumors, which marginally respond to standard chemotherapy due to the blood-brain barrier (BBB) and the low tumor specificity of the therapeutics. Herein, a double-layered microneedle (MN) patch is rationally engineered by integrating acid and light dual-activatable PROteolysis TArgeting Chimera (PROTAC) nanoparticles and self-oxygenating BSA-MnO2 (BM) nanoparticles for GBM treatment. The MN is administrated at the tumor site to locally deliver the PROTAC prodrug and BM nanoparticles. The PROTAC nanoparticles are rapidly released from the outer layer of the MN and specifically activated in the acidic intracellular environment of tumor cells. Subsequently, near-infrared light activates the photosensitizer to produce singlet oxygen (1O2) through photodynamic therapy (PDT), thereby triggering spatiotemporally-tunable degradation of bromodomain and extraterminal protein 4 (BRD4). The BM nanoparticles, in the inner layer of the MN, serve as an oxygen supply station, and counteracts tumor hypoxia by converting hydrogen peroxide (H2O2) into oxygen (O2), thus promoting PDT and PROTAC activation. This PROTAC prodrug-integrated MN significantly inhibits tumor growth in both subcutaneous and orthotopic GBM tumor models. This study describes the first spatiotemporally-tunable protein degradation strategy for highly efficient GBM therapy, potentially advancing precise therapy of other kinds of refractory brain tumors.

Research progress and strategy of FGF21 for skin wound healing

Fibroblast Growth Factor 21 (FGF21), a pivotal member of the fibroblast growth factor family, exhibits multifaceted biological functions, including the modulation of pro-inflammatory cytokines and metabolic regulation. Recent research has revealed that in impaired skin tissues, FGF21 and its receptors are upregulated and play a significant role in accelerating the wound healing process. However, the clinical application of FGF21 is severely limited by its short in vivo half-life: this factor is often degraded by enzymes before it can exert its therapeutic effects. To address this limitation, the transdermal drug delivery system (TDDS) has emerged as an innovative approach that enables sustained drug release, significantly prolonging the therapeutic duration. Leveraging genetic recombination technology, research teams have ingeniously fused FGF21 with cell-penetrating peptides (CPPs) to construct recombinant FGF21 complexes. These novel conjugates can efficiently penetrate the epidermal barrier and achieve sustained and stable pharmacological activity through TDDS. This review systematically analyzes the potential signaling pathways by which FGF21 accelerates skin wound repair, summarizes the latest advancements in TDDS technology, explores the therapeutic potential of FGF21, and evaluates the efficacy of CPP fusion tags. The manuscript not only proposes an innovative paradigm for the application of FGF21 in skin injury treatment but also provides new insights into its use in transdermal delivery, marking a significant step toward overcoming existing clinical therapeutic challenges. From a clinical medical perspective, this innovative delivery system holds promise for addressing the bioavailability issues of traditional FGF21 therapies, offering new strategies for the clinical treatment of metabolism-related diseases and wound healing. With further research, this technology holds vast potential for clinical applications in hard-to-heal wounds such as diabetic foot ulcers and burns.

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.

Metal-organic framework microneedles for precision transdermal drug delivery: design strategy and therapeutic potential

Metal-organic frameworks (MOFs) are porous materials renowned for their high porosity, large specific surface area, biocompatibility, and biodegradability. Hydrogel microneedles (MNs) is an emerging technology that minimally disrupts the skin or mucosal membranes, bypassing gastrointestinal absorption and the rapid metabolism typical of oral drug delivery. Over the past few decades, both MOFs and MNs have found applications across a range of fields. However, MOFs alone cannot penetrate the skin or mucosal barrier to deliver drugs effectively, and MNs have limited direct loading capacity. When combined, MOFs enhance the loading efficiency of therapeutic agents in hydrogel MNs and optimize their release kinetics. Additionally, the incorporation of MOFs improves the mechanical properties of hydrogel MNs, increasing their permeability to the skin. In turn, hydrogel MNs enable MOFs-whether therapeutically active or drug-loaded-to bypass the skin or mucosal barrier and deliver active compounds directly to the target site for localized treatment. This review discusses the structural features and preparation methods of MOFs and MOF-based MNs, explores their synergistic potential, and highlights strategies for integrating MOFs with MNs to enhance transdermal drug delivery in applications such as wound healing, scar management, acne treatment, and tumor suppression. Finally, we examine the challenges and future potential of MOF-based MNs and offer insights into their role in advancing transdermal therapies.

Transdermal Delivery of Valproate-Choline Ionic Liquid Induces Hair Regrowth

Alopecia treatment research has been increasingly focused on innovative materials systems and drug delivery methods. Valproic acid (VPA) has been shown to promote hair regrowth by upregulating the Wnt/β-catenin signaling pathway, a key regulator of hair papilla cell proliferation. However, topical administration of VPA typically requires organic solvents or complex transdermal devices to enhance skin penetration. Biocompatible ionic liquids have gained attention as customizable solvents for transdermal drug delivery (TDD). In this study, we introduce a novel choline-based valproic acid ionic liquid (VPA-IL) for the treatment of hair loss. Our findings demonstrate that VPA-IL significantly enhances the transdermal penetration of VPA by disrupting the lipid bilayer structure of stratum corneum (SC), due to strong hydrogen bonding between the methyl hydrogen of the choline and the carboxyl group of phospholipid molecules. In vivo pharmacodynamic assessments revealed that topical application of VPA-IL effectively promotes hair regrowth by activating the Wnt/β-catenin pathway and upregulating proliferating cell nuclear antigen (PCNA), K14, loricrin, and several hair follicle (HF) stem cell markers without causing skin irritation or systemic toxicity. This work offers a safe and promising new therapeutic option for alopecia.

Mathematical modelling of hollow microneedle-mediated transdermal drug delivery

Hollow microneedles represent a promising approach for overcoming the protective barrier of the stratum corneum, facilitating direct drug infusion into viable skin tissue and thereby enhancing the efficacy of transdermal delivery. However, delivery outcomes across different skin layers and into the systemic circulation can vary substantially due to the diverse properties of drug delivery systems, clinical settings, and environmental factors. The optimal strategies for enhancing the efficiency of hollow microneedle-mediated transdermal drug delivery remain to be elucidated. This study employs mathematical modelling and a reconstructed skin model with realistic anatomical structures to investigate drug transport and accumulation across different skin layers and into the bloodstream under different delivery conditions. The modelling results reveal the crucial role of interstitial fluid flow in determining drug transport in this transdermal delivery. Delivery outcomes of each skin layer and blood exhibit distinct responses to changes in delivery conditions. Specifically, increasing the vascular permeability or nanocarrier diffusivity raises drug concentration in the blood or reticular dermis, respectively, while leading to reductions in other skin layers. The use of microneedles with narrower infusion channels can only enhance drug availability in the viable epidermis. Optimisation requires a tailored approach to several parameters depending on the target skin layer, including drug release rate, infusion rate, infusion duration, and microneedle length. Environmental factors that promote trans-epidermal water loss can increase drug concentration in the viable epidermis but have a limited impact on deeper skin tissues. The findings support the selection or customisation of hollow microneedles and nanocarriers to address specific therapeutic needs, such as targeting specific skin layers or systemic circulation, while minimising the risk of side effects from high drug concentrations in normal tissues. This study provides guidance for optimising transdermal drug delivery systems.

Thumb-sized 3D-Printed cymbal microneedle array (CyMA) for enhanced transdermal drug delivery

Transdermal drug delivery presents a compelling alternative to both needle injection and oral ingestion of medication, as it enhances patient adherence and convenience through its non-invasive and painless administration method. The use of microneedles penetrates the barrier of the stratum corneum, facilitating the sustained delivery of drugs across the skin. However, their efficacy has been limited by the slow diffusion of molecules and often requires external triggers. Herein, a lightweight and minimized 3D-printed microneedle array is introduced, employing a cymbal-type ultrasound transducer, as the external engine for deeper and faster transdermal drug delivery. A theoretical finite element model was developed and the optimization design was conducted for structural parameters. The optimized assembled prototype was fabricated using high-precision 3D printing and weighs only 20 g. In vivo experiments using a diabetic mouse model demonstrate that local insulin delivery with CyMA achieves systemic effects comparable to intraperitoneal administration. Such compact and effective microneedle delivery technology offers considerable promise therapeutic applications on the skin and intraoral use.

Design and development of a soluble PDA-Emodin-PVP-MN patch and its anti-obesity effect in rats

Emodin has been proven to have weight-reducing and lipid-lowering effects. In order to make emodin play a better anti-obesity role, we designed and developed an emodin loaded dissolving microneedle patch, in which emodin existed in the form of emodin-polyvinylpyrrolidone co-precipitate (Emodin-PVP). Meanwhile, polydopamine (PDA) was added to the microneedle patch (PDA-Emodin-PVP-MN) for photothermal-enhanced chemotherapy of obesity. The average weight of the patch was 0.1 ± 0.05 g and the drug loading was 0.37 ± 0.031 mg. After 5 min of NIR irradiation (808 nm, 0.6 W/cm2), the rat abdominal temperature could reach 48 ℃, and the cumulative release of emodin reached 96.25%. The diffusion coefficient of emodin in the in vitro agar diffusion experiment was 249.27 mm2 h-1. No obvious toxicity was observed in hemolysis test, CCK-8 assay and microscopic histopathological analysis. The patch significantly reduced the percent of body weight ( P < 0.01), lipid-body ratio ( P < 0.001), serum FFAs ( P < 0.01) and the cell volume of peritesticular adipose tissue in the high-fat diet induced obese rats, indicating the patch had good anti-obesity effect. The mechanism of action may be related to the up-regulation of HSL and LPL protein levels in rat peritesticular adipose tissue.

Microneedle-Assisted Delivery of Curcumin: Evaluating the Effects of Needle Length and Formulation

Dermal drug delivery presents a significant challenge for poorly soluble active compounds like curcumin, which often struggle to penetrate the skin barrier effectively. In this study, the dermal penetration efficacy of curcumin nanocrystals and bulk suspensions when applied to skin using microneedles of varying lengths-0.25 mm, 0.5 mm, and 1.0 mm-was investigated in an ex vivo porcine ear model. The findings revealed that all formulations, in conjunction with microneedle application, facilitated transepidermal penetration; however, the combination of microneedles and curcumin nanocrystals demonstrated the highest efficacy. Notably, the 1.0 mm microneedle length provided optimal penetration, significantly enhancing curcumin delivery compared with bulk suspensions alone. Additionally, even the use of 0.25 mm microneedles resulted in a high level of efficiency, indicating that shorter microneedles can still effectively facilitate drug delivery. Overall, this study underscores the potential of microneedle technology in improving the transepidermal absorption of poorly soluble actives like curcumin, suggesting that the integration of nanocrystals with microneedles could enhance the therapeutic effects of topical curcumin applications.

A wearable iontophoresis enables dual-responsive transdermal delivery for atopic dermatitis treatment

Atopic dermatitis is a chronic, inflammation skin disease that remains a major public health challenge. The current drug-loading hydrogel dressings offer numerous benefits with enhanced loading capacity and a moist-rich environment. However, their development is still limited by the accessibility of a suitable driven source outside the clinical environment for precise control over transdermal delivery kinetics. Here, we prepare a sulfonated poly(3,4-ethylenedioxythiophene) (PEDOT) polyelectrolyte hydrogel drug reservoir that responds to different stimuli-both endogenous cue (body temperature) and exogenous cue (electrical stimulation), for wearable on-demand transdermal delivery with enhanced efficacy. Functioned as both the drug reservoir and cathode in a Zn battery-powered iontophoresis patch, this dual-responsive hydrogel achieves high drug release efficiency (68.4 %) at 37 °C. Evaluation in hairless mouse skin demonstrates the efficacy of this technology by facilitating transdermal transport of 12.2 μg cm-2 dexamethasone phosphate when discharged with a 103 Ω external resistor for 3 h. The Zn battery-driven iontophoresis results in an effective treatment of atopic dermatitis, displaying reductions in epidermal thickness, mast cell infiltration inhibition, and a decrease in IgE levels. This work provides a new treatment modality for chronic epidermal diseases that require precise drug delivery in a non-invasive way.

Vialess heterogeneous skin patch for multimodal monitoring and stimulation

System-level wearable electronics require to be flexible to ensure conformal contact with the skin, but they also need to integrate rigid and bulky functional components to achieve system-level functionality. As one of integration methods, folding integration offers simplified processing and enhanced functionality through rigid-soft region separation, but so far, it has mainly been applied to modality of electrical sensing and stimulation. This paper introduces a vialess heterogeneous skin patch with multi modalities that separates the soft region and strain-robust region through folded structure. Our system includes electrical and optical modalities for hemodynamic and cardiovascular monitoring, and a force-electrically driven micropump for drug delivery. Each modality is demonstrated through on-demand drug delivery, flexible waveguide-based PPG monitoring, and ECG and body movement monitoring. Wireless data transmission and real-time measurement validate the feedback operation for multi-modalities. This engineered closed-loop platform offers the possibility for broad applications, including cardiovascular monitoring and chronic disease management.

Hydrogel-Based Network Metamaterials with Biological Tissue-like Poisson's Ratio Behavior and Stress Response

Soft network metamaterials are widely used in fields such as flexible electronics, tissue engineering, and biomedicine due to their superior properties including low density, high stretchability, and high breathability. However, the prediction and customization of the nonlinear mechanical behavior of soft network metamaterials remain a challenging problem. In this study, a family of hydrogel-based network metamaterials with biological tissue-like mechanical properties are developed based on a machine learning-driven optimization design method. Numerical and experimental results explain the relationship between the mechanical properties of the designed metamaterials and their microstructural features and stretching ratios. The results indicate that the hydrogel-based network metamaterials exhibit J-shaped stress-deformation (σ-λ) behavior similar to biological tissues. This phenomenon arises from the transition of the deformation mode of metamaterials from bending-dominated to stretching-dominated as the stretching ratio increases. Based on the proposed design scheme, the Poisson's ratio of metamaterials can be adjusted within a remarkably wide range of -1.06 to 1.34. Furthermore, through optimizing the design parameters of the metamaterial, the customization of network metamaterials with biological tissue-like zero Poisson's ratio behavior and stress response is achieved. The potential applications of hydrogel-based network metamaterials are demonstrated through artificial skin and LED integrated device. This research offers novel insights into predicting, designing, and fabricating the mechanical behavior of soft network metamaterials.

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.

Transdermal Drug Delivery Systems: Different Generations and Dermatokinetic Assessment of Drug Concentration in Skin

Transdermal drug delivery systems (TDDS) are a highly appealing and innovative method of administering drugs through the skin, as it enables the drugs to achieve systemic effects. A TDDS offers patient convenience, avoids first-pass hepatic metabolism, enables local targeting, and reduces the toxic effect of drug. This review details several generations of TDDS and the advancements made in their development to address the constraints associated with skin delivery systems. Transdermal delivery methods of the first generation have been consistently growing in their clinical application for administering small, lipophilic, low-dose drugs. Second-generation TDDS, utilizing chemical enhancers and iontophoresis, have led to the development of clinical products. Third-generation delivery systems employ microneedles, thermal ablation, and electroporation to specifically target the stratum corneum, which is the skin's barrier layer. Dermatokinetics is the study of the movement of drugs and formulations applied to the skin over a period of time. It provides important information regarding the rate and extent to which drugs penetrate skin layers. Several dermatokinetic techniques, including tape stripping, microdialysis, and laser scanning microscopy, have been used to study the intricate barrier properties and clearance mechanisms of the skin. This understanding is essential for developing and improving effective TDDS.

Use of Optical Coherence Tomography to Assess Properties of Cutaneous Defects Following Radiofrequency Microneedling and Laser Treatment

OBJECTIVES

To characterize the properties of cutaneous defects created by energy-based devices using optical coherence tomography.

MATERIALS AND METHODS

Radiofrequency (RF) microneedling and non-ablative fractional laser (NAFL) treatment were performed in vivo with various parameters. Following treatment, optical coherence tomography (OCT) was used to image and measure cutaneous defects at multiple time points over a 24 h period.

RESULTS

Channel-like cutaneous defects were visible with OCT following bipolar RF microneedling and NAFL treatment. Using a double pulse technique with RF microneedling yielded a greater number of defects visible with OCT, as well as defects that were deeper and more durable over time. Following treatment with 1927 nm thulium fiber laser, the average diameter of the defects was greater when the energy level was 20 mJ as compared to 10 mJ (0.33 mm vs. 0.27 mm, p < 0.01).

CONCLUSIONS

Cutaneous defects were observed following both RF microneedling and NAFL treatment. Properties of the cutaneous defects varied based on device, treatment setting, and technique, which may be useful in guiding further study of device-assisted drug delivery.

A wearable non-enzymatic sensor for continuous monitoring of glucose in human sweat

To enhance personalized diabetes management, there is a critical need for non-invasive wearable electrochemical sensors made from flexible materials to enable continuous monitoring of sweat glucose levels. The main challenge lies in developing glucose sensors with superior electrochemical characteristics and high adaptability. Herein, we present a wearable sensor for non-enzymatic electrochemical glucose analysis. The sensor was synthesized using hydrothermal and one-pot preparation methods, incorporating gold nanoparticles (AuNPs) functionalized onto aminated multi-walled carbon nanotubes (AMWCNTs) as an efficient catalyst, and crosslinked with carboxylated styrene butadiene rubber (XSBR) and PEDOT:PSS. The sensors were then integrated onto screen-printed electrodes (SPEs) to create flexible glucose sensors (XSBR-PEDOT:PSS-AMWCNTs/AuNPs/SPE). Operating under neutral conditions, the sensor exhibits a linear range of 50 μmol/L to 600 μmol/L, with a limit of detection limit of 3.2 μmol/L (S/N = 3), enabling the detection of minute glucose concentrations. The flexible glucose sensor maintains functionality after 500 repetitions of bending at a 180° angle, without significant degradation in performance. Furthermore, the sensor exhibits exceptional stability, repeatability, and resistance to interference. Importantly, we successfully monitored changes in sweat glucose levels by applying screen-printed electrodes to human skin, with results consistent with normal physiological blood glucose fluctuations. This study details the fabrication of a wearable sensor characterized by ease of manufacture, remarkable flexibility, high sensitivity, and adaptability for non-invasive blood glucose monitoring through non-enzymatic electrochemical analysis. Thus, this streamlined fabrication process presents a novel approach for non-invasive, real-time blood glucose level monitoring.

Ambient Moisture-Driven Self-Powered Iontophoresis Patch for Enhanced Transdermal Drug Delivery

Iontophoretic transdermal drug delivery (TDD) devices are known to enhance the transdermal transport of drugs. However, conventional transdermal iontophoretic devices require external power sources, wired connections, or mechanical parts, which reduce the comfort level for patients during extended use. In this work, a self-powered, wearable transdermal iontophoretic patch (TIP) is proposed by harvesting ambient humidity for energy generation, enabling controlled TDD. This patch primarily uses moist-electric generators (MEGs) as its power source, thus obviating the need for complex power management modules and mechanical components. A single MEG unit can produce an open-circuit voltage of 0.80 V and a short-circuit current of 11.65 µA under the condition of 80% relative humidity. Amplification of the electrical output is feasible by connecting multiple generator units in series and parallel, facilitating the powering of certain commercial electronic devices. Subsequently, the MEG array is integrated with the TDD circuit to create the wearable TIP. After 20 min of application, the depth of drug penetration through the skin is observed to increase threefold. The effective promotion effect of TIP on the transdermal delivery of ionized drugs is corroborated by simulations and experiments. This wearable TIP offers a simple, noninvasive solution for TDD.

From lab to wearables: Innovations in multifunctional hydrogel chemistry for next-generation bioelectronic devices

Functional hydrogels have emerged as foundational materials in diagnostics, therapy, and wearable devices, owing to their high stretchability, flexibility, sensing, and outstanding biocompatibility. Their significance stems from their resemblance to biological tissue and their exceptional versatility in electrical, mechanical, and biofunctional engineering, positioning themselves as a bridge between living organisms and electronic systems, paving the way for the development of highly compatible, efficient, and stable interfaces. These multifaceted capability revolutionizes the essence of hydrogel-based wearable devices, distinguishing them from conventional biomedical devices in real-world practical applications. In this comprehensive review, we first discuss the fundamental chemistry of hydrogels, elucidating their distinct properties and functionalities. Subsequently, we examine the applications of these bioelectronics within the human body, unveiling their transformative potential in diagnostics, therapy, and human-machine interfaces (HMI) in real wearable bioelectronics. This exploration serves as a scientific compass for researchers navigating the interdisciplinary landscape of chemistry, materials science, and bioelectronics.

Hyaluronidase overcomes the extracellular matrix barrier to enhance local drug delivery

The stratum corneum of the skin presents the initial barrier to transdermal penetration. The dense structure of the extracellular matrix (ECM) further impedes local drug dispersion. Hyaluronidase (HAase) is a key component for the degradation of glycosidic bonding sites in hyaluronic acid (HA) within the ECM to overcome this barrier and enhance drug dispersion. HAase activity is optimal at 37-45 °C and in the pH range 4.5-5.5. Numerous FDA-approved formulations are available for the clinical treatment of extravasation and other diseases. HAase combined with various new nanoformulations can markedly improve intradermal dispersion. By degrading HA to create tiny channels that reduce the ECM density, these small nanoformulations then use these channels to deliver drugs to deeper layers of the skin. This deep penetration may increase local drug concentration or facilitate penetration into the blood or lymphatic circulation. Based on the generalization of 114 studies from 2010 to 2024, this article summarizes the most recent strategies to overcome the HAase-based ECM barrier for local drug delivery, discusses opportunities and challenges in clinical applications, and provides references for the future development of HAase. In the future, HAase-assisted topical administration is necessary to achieve systemic effects and to standardize HAase application protocols.

Progress and Challenges of Topical Delivery Technologies Meditated Drug Therapy for Osteoarthritis

Osteoarthritis (OA) is a degenerative disease commonly seen in middle-aged and elderly people. Multiple cytokines are involved in the local tissue damage in OA. Currently, non-pharmacologic and surgical interventions are the main conventional approaches for the treatment of OA. In terms of pharmaceutical drug therapy, NSAIDs and acetaminophen are mainly used to treat OA. However, it is prone to various adverse reactions such as digestive tract ulcer, thromboembolism, prosthesis loosening, nerve injury and so on. With the in-depth study of OA, more and more novel topical drug delivery strategies and vehicles have been developed, which can make up for the shortcomings of traditional dosage forms, improve the bioavailability of drugs, and significantly reduce drug side effects. This review summarizes the immunopathogenesis, treatment guidelines, and progress and challenges of topical delivery technologies of OA, with some perspectives on the future pharmacological treatment of OA proposed.

Integrating microneedles and sensing strategies for diagnostic and monitoring applications: The state of the art

Microneedles (MNs) offer minimally-invasive access to interstitial fluid (ISF) - a potent alternative to blood in terms of monitoring physiological analytes. This property is particularly advantageous for the painless detection and monitoring of drugs and biomolecules. However, the complexity of the skin environment, coupled with the inherent nature of the analytes being detected and the inherent physical properties of MNs, pose challenges when conducting physiological monitoring using this fluid. In this review, we discuss different sensing mechanisms and highlight advancements in monitoring different targets, with a particular focus on drug monitoring. We further list the current challenges facing the field and conclude by discussing aspects of MN design which serve to enhance their performance when monitoring different classes of analytes.

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.

Polyelectrolytes for Environmental, Agricultural, and Medical Applications

In recent decades, polyelectrolytes (PELs) have attracted significant interest owing to a surge in research dedicated to the development of new technologies and applications at the biological level. Polyelectrolytes are macromolecules of which a substantial portion of the constituent units contains ionizable or ionic groups. These macromolecules demonstrate varied behaviors across different pH ranges, ionic strengths, and concentrations, making them fascinating subjects within the scientific community. The aim of this review is to present a comprehensive survey of the progress in the application studies of polyelectrolytes and their derivatives in various fields that are vital for the advancement, conservation, and technological progress of the planet, including agriculture, environmental science, and medicine. Through this bibliographic review, we seek to highlight the significance of these materials and their extensive range of applications in modern times.

Potent drug delivery enhancement of betulinic acid and NVX-207 into equine skin in vitro - a comparison between a novel oxygen flow-assisted transdermal application device and microemulsion gels

BACKGROUND

Gray horses are predisposed to equine malignant melanoma (EMM) with advancing age. Depending on the tumor's location and size, they can cause severe problems (e.g., defaecation, urination, feeding). A feasible therapy for EMM has not yet been established and surgical excision can be difficult depending on the location of the melanoma. Thus, an effective and safe therapy is needed. Naturally occurring betulinic acid (BA), a pentacyclic triterpene and its synthetic derivate, NVX-207 (3-acetyl-betulinic acid-2-amino-3-hydroxy-2-hydroxymethyl-propanoate) are known for their cytotoxic properties against melanomas and other tumors and have already shown good safety and tolerability in vivo. In this study, BA and NVX-207 were tested for their permeation potential into equine skin in vitro in Franz-type diffusion cell (FDC) experiments after incubation of 5 min, 30 min and 24 h, aiming to use these formulations for prospective in vivo studies as a treatment for early melanoma stages. Potent permeation was defined as reaching or exceeding the half maximal inhibitory concentrations (IC50) of BA or NVX-207 for equine melanoma cells in equine skin samples. The active ingredients were either dissolved in a microemulsion (ME) or in a microemulsion gel (MEG). All of the formulations were transdermally applied but the oil-in-water microemulsion was administered with a novel oxygen flow-assisted (OFA) applicator (DERMADROP TDA).

RESULTS

All tested formulations exceeded the IC50 values for equine melanoma cells for BA and NVX-207 in equine skin samples, independently of the incubation time NVX-207 applied with the OFA applicator showed a significant time-dependent accumulation and depot-effect in the skin after 30 min and 24 h (P < 0.05).

CONCLUSIONS

All tested substances showed promising results. Additionally, OFA administration showed a significant accumulation of NVX-207 after 30 min and 24 h of incubation. Further in vivo trials with OFA application are recommended.

A reconfigurable integrated smart device for real-time monitoring and synergistic treatment of rheumatoid arthritis

Rheumatoid arthritis (RA) is a global autoimmune disease that requires long-term management. Ambulatory monitoring and treatment of RA favors remission and rehabilitation. Here, we developed a wearable reconfigurable integrated smart device (ISD) for real-time inflammatory monitoring and synergistic therapy of RA. The device establishes an electrical-coupling and substance delivery interfaces with the skin through template-free conductive polymer microneedles that exhibit high capacitance, low impedance, and appropriate mechanical properties. The reconfigurable electronics drive the microneedle-skin interfaces to monitor tissue impedance and on-demand drug delivery. Studies in vitro demonstrated the anti-inflammatory effect of electrical stimulation on macrophages and revealed the molecular mechanism. In a rodent model, impedance sensing was validated to hint inflammation condition and facilitate diagnosis through machine learning model. The outcome of subsequent synergistic therapy showed notable relief of symptoms, elimination of synovial inflammation, and avoidance of bone destruction.

Kinetic assessment of iontophoretic delivery efficiency of niosomal tetracycline hydrochloride incorporated in electroconductive gel

The purpose of this study was to conduct the kinetic assessment of iontophoretic delivery of niosomal tetracycline-HCl formulated in an electroconductive gel. Tween-80 and Span-80 were used to obtain tetracycline-HCl niosomes with an average diameter of 101.9 ± 3.3 nm, a polydispersity index of 0.247 ± 0.004, a zeta potential of - 34.1 mV, and an entrapment efficiency of 70.08 ± 0.16%. Four different gel preparations, two of which contained niosomal tetracycline-HCl, were transdermally delivered using Franz diffusion cells under the trigger effect of iontophoresis, applied at 0.2, 0.5, and 1 mA/cm2 current density. The control group was the passive diffusion results of the preparation made using a tetracycline-HCl-based drug marketed in Turkey. The control group was compared with the groups that contained (a) tetracycline-HCl in an electroconductive gel, (b) the niosomal tetracycline-HCl formulation in water, and (c) the niosomal tetracycline-HCl formulation in the electroconductive gel. The group with the niosomal formulation in the electroconductive gel displayed the highest increase in iontophoretic transdermal delivery relative to the control group, displaying a 2-, 2.1-, and 2.2-fold increase, respectively, by current density. The experimental results of transdermal delivery using the synergistic effect of niosomal formulation in electroconductive gel and the trigger effect of iontophoresis appeared to divert slightly from zero-order kinetics, demonstrating a statistically significant increase in the rate of controlled transdermal drug delivery. Considering that about 20% of the formulation is transdermally delivered in the first half-hour, the iontophoretic transdermal delivery of niosomal tetracycline-HCl can be efficiently used in local iontophoretic therapy.

Latest advances in glucose-responsive microneedle-based systems for transdermal insulin delivery

The development of a self-regulated minimally invasive system for insulin delivery can be considered as the holy grail in the field of diabetes mellitus. A delivery system capable of releasing insulin in response to blood glucose levels would significantly improve the quality of life of diabetic patients, eliminating the need for frequent finger-prick tests and providing better glycaemic control with lower risk of hypoglycaemia. In this context, the latest advances in glucose-responsive microneedle-based transdermal insulin delivery are here compiled with a thorough analysis of the delivery mechanisms and challenges lying ahead in their clinical translation. Two main groups of microneedle-based systems have been developed so far: glucose oxidase-containing and phenylboronic acid-containing systems. Both strategies in combination have also been tested and two other novel strategies are under development, namely electronic closed-loop and glucose transporter-based systems. Results from preclinical studies conducted using these different types of glucose-triggered release systems are comprehensively discussed. Altogether, this analysis from both a mechanistic and translational perspective will provide rationale and/or guidance for future trends in the research hotspot of glucose-responsive microneedle-based insulin delivery systems.

Advancements in transdermal drug delivery: A comprehensive review of physical penetration enhancement techniques

Transdermal drug administration has grown in popularity in the pharmaceutical research community due to its potential to improve drug bioavailability, compliance among patients, and therapeutic effectiveness. To overcome the substantial barrier posed by the stratum corneum (SC) and promote drug absorption within the skin, various physical penetration augmentation approaches have been devised. This review article delves into popular physical penetration augmentation techniques, which include sonophoresis, iontophoresis, magnetophoresis, thermophoresis, needle-free injection, and microneedles (MNs) Sonophoresis is a technique that uses low-frequency ultrasonic waves to break the skin's barrier characteristics, therefore improving drug transport and distribution. In contrast, iontophoresis uses an applied electric current to push charged molecules of drugs inside the skin, effectively enhancing medication absorption. Magnetophoresis uses magnetic fields to drive drug carriers into the dermis, a technology that has shown promise in aiding targeted medication delivery. Thermophoresis is the regulated heating of the skin in order to improve drug absorption, particularly with thermally sensitive drug carriers. Needle-free injection technologies, such as jet injectors (JIs) and microprojection arrays, offer another option by producing temporary small pore sizes in the skin, facilitating painless and effective drug delivery. MNs are a painless, minimally invasive method, easy to self-administration, as well as high drug bioavailability. This study focuses on the underlying processes, current breakthroughs, and limitations connected with all of these approaches, with an emphasis on their applicability in diverse therapeutic areas. Finally, a thorough knowledge of these physical enhancement approaches and their incorporation into pharmaceutical research has the potential to revolutionize drug delivery, providing more efficient and secure treatment choices for a wide range of health-related diseases.

Smart Physical-Based Transdermal Drug Delivery System:Towards Intelligence and Controlled Release

Transdermal drug delivery systems based on physical principles have provided a stable, efficient, and safe strategy for disease therapy. However, the intelligent device with real-time control and precise drug release is required to enhance treatment efficacy and improve patient compliance. This review summarizes the recent developments, application scenarios, and drug release characteristics of smart transdermal drug delivery systems fabricated with physical principle. Special attention is paid to the progress of intelligent design and concepts in of physical-based transdermal drug delivery technologies for real-time monitoring and precise drug release. In addition, facing with the needs of clinical treatment and personalized medicine, the recent progress and trend of physical enhancement are further highlighted for transdermal drug delivery systems in combination with pharmaceutical dosage forms to achieve better transdermal effects and facilitate the development of smart medical devices. Finally, the next generation and future application scenarios of smart physical-based transdermal drug delivery systems are discussed, a particular focus in vaccine delivery and tumor treatment.

Transdermal Drug Delivery Systems: A Focused Review of the Physical Methods of Permeation Enhancement

The skin is the body's largest organ and serves as a site of administration for various medications. Transdermal drug delivery systems have several advantages over traditional delivery systems. It has both local and systemic therapeutic properties. Controlled plasma drug levels, reduced dosing frequency, and avoidance of hepatic first-pass metabolism are just a few of these systems' advantages. To achieve maximum efficacy, it is critical to understand the kinetics, physiochemical properties of the drug moiety, and drug transport route. This manuscript focused on the principles of various physical means to facilitate transdermal drug delivery. Some examples are iontophoresis, electrophoresis, photomechanical waves, ultrasound, needleless injections, and microneedles. Mechanical, chemical, magnetic, and electrical energy are all used in physical methods. A major advantage of physical methods is their capability to abbreviate pain, which can be used for effective disease management. Further investigation should be carried out at the clinical level to understand these methods for effective drug delivery.

Advancements in Skin-Mediated Drug Delivery: Mechanisms, Techniques, and Applications

Skin-mediated drug delivery methods currently are receiving significant attention as a promising approach for the enhanced delivery of drugs through the skin. Skin-mediated drug delivery offers the potential to overcome the limitations of traditional drug delivery methods, including oral administration and intravenous injection. The challenges associated with drug permeation through layers of skin, which act as a major barrier, are explored, and strategies to overcome these limitations are discussed in detail. This review categorizes skin-mediated drug delivery methods based on the means of increasing drug permeation, and it provides a comprehensive overview of the mechanisms and techniques associated with these methods. In addition, recent advancements in the application of skin-mediated drug delivery are presented. The review also outlines the limitations of ongoing research and suggests future perspectives of studies regarding the skin-mediated delivery of drugs.

Recent Advances in Bioelectronics for Localized Drug Delivery

The last decade has witnessed remarkable advancements in bioelectronics, ushering in a new era of wearable and implantable devices for drug delivery. By utilizing miniaturized system design and/or flexible materials, bioelectronics illustrates ideal integration with target organs and tissues, making them ideal platforms for localized drug delivery. Furthermore, the development of electrically assisted drug delivery systems has enhanced the efficiency and safety of therapeutic administration, particularly for the macromolecules that encounter additional challenges in penetrating biological barriers. In this review, a concise overview of recent progress in bioelectronic devices for in vivo localized drug delivery, with highlights on the latest trends in device design, working principles, and their corresponding functionalities, is provided. The reported systems based on their targeted delivery locations as wearable systems, ingestible systems, and implantable systems are categorized. Each category is introduced in detail by highlighting the special requirements for devices and the corresponding solutions. The remaining challenges in this field and future directions are also discussed.

Anti-obesity and metabolic benefits of metformin: Comparison of different delivery routes

Obesity is a severe public health problem. Healthy lifestyle interventions are commonly recommended for fighting obesity. But they are hard to follow and have low efficacy. Pharmacotherapy and surgery are of high efficacy but are beset with side effects. Browning subcutaneous white adipose tissue (WAT) is a practical and efficient approach for combating obesity. Metformin, a commonly used FDA-approved antidiabetic drug, is potent to induce browning of WAT through phosphorylation and activation of AMP-activated protein kinase. However, oral administration of metformin has low oral bioavailability, fast renal clearance, and low target specificity that limit metformin's application in browning WAT. Local and transdermal delivery of metformin directly to subcutaneous WAT using injection or microneedle (MN) in combination with iontophoresis (INT) may solve these problems. In this paper, we administered metformin to C57BL/6J obese mice using the following three routes: transdermal delivery (MN and INT), local injection into inguinal WAT (IgWAT, a type of subcutaneous WAT in mice), and oral gavage. The anti-obesity and metabolic effects of metformin via these delivery routes were determined and compared. As compared to local IgWAT injection and oral gavage delivery, transdermal delivery of metformin using MN and INT resulted in 9% lower body weight and 7% decrease in body fat% accompanied by improved energy metabolism and decreased inflammation through browning IgWAT in obese C57BL/6J mice. Transdermal delivery of metformin using MN and INT is an effective approach in browning subcutaneous WAT for combating obesity and improving metabolic health.

Smart Responsive Microneedles for Controlled Drug Delivery

As an emerging technology, microneedles offer advantages such as painless administration, good biocompatibility, and ease of self-administration, so as to effectively treat various diseases, such as diabetes, wound repair, tumor treatment and so on. How to regulate the release behavior of loaded drugs in polymer microneedles is the core element of transdermal drug delivery. As an emerging on-demand drug-delivery technology, intelligent responsive microneedles can achieve local accurate release of drugs according to external stimuli or internal physiological environment changes. This review focuses on the research efforts in smart responsive polymer microneedles at home and abroad in recent years. It summarizes the response mechanisms based on various stimuli and their respective application scenarios. Utilizing innovative, responsive microneedle systems offers a convenient and precise targeted drug delivery method, holding significant research implications in transdermal drug administration. Safety and efficacy will remain the key areas of continuous efforts for research scholars in the future.

Evolution of Transdermal Drug Delivery Devices and Novel Microneedle Technologies: A Historical Perspective and Review

The history of transdermal drug delivery is as old as humankind. Transdermal drug delivery has undergone three generations of development; the third generation has involved the use of medical devices and instruments. This review provides a historical perspective on the primary approaches employed in the three generations of transdermal drug delivery. In addition, we explore some of the recently developed transdermal techniques that are deemed promising in the field of drug delivery. We discuss how advances in these techniques have led to the development of devices for the delivery of a therapeutically effective amount of drug across human skin and highlight the limitations of the first- and second-generation drug delivery tools. As such, a review of the performance of these techniques and the toxicity of the devices used in transdermal drug delivery are considered. In the last section of the review, a discussion of the fabrication and operation of different types of microneedles is presented. The applications of microneedles in the sensing and delivery of various therapeutic agents are described in detail. Furthermore, an overview of the efficacy of microneedles as emerging tools for the controlled release of drugs is presented.

Applications and recent advances in transdermal drug delivery systems for the treatment of rheumatoid arthritis

Rheumatoid arthritis is a chronic, systemic autoimmune disease predominantly based on joint lesions with an extremely high disability and deformity rate. Several drugs have been used for the treatment of rheumatoid arthritis, but their use is limited by suboptimal bioavailability, serious adverse effects, and nonnegligible first-pass effects. In contrast, transdermal drug delivery systems (TDDSs) can avoid these drawbacks and improve patient compliance, making them a promising option for the treatment of rheumatoid arthritis (RA). Of course, TDDSs also face unique challenges, as the physiological barrier of the skin makes drug delivery somewhat limited. To overcome this barrier and maximize drug delivery efficiency, TDDSs have evolved in terms of the principle of transdermal facilitation and transdermal facilitation technology, and different generations of TDDSs have been derived, which have significantly improved transdermal efficiency and even achieved individualized controlled drug delivery. In this review, we summarize the different generations of transdermal drug delivery systems, the corresponding transdermal strategies, and their applications in the treatment of RA.

Strategies to develop polymeric microneedles for controlled drug release

The remarkable appeal of microneedle controlled-release systems has captivated both the academic community and pharmaceutical industry due to their great potential for achieving spatiotemporally controlled release, coupled with their the minimally invasive nature and ease of application. Over the years, scientists have dedicated their efforts to advancing microneedle systems by manipulating the physicochemical properties of matrix materials, refining microneedle designs, and interfacing with external devices to provide tailored drug release profiles in a spatiotemporally controllable manner. Expanding upon our understanding of drug release mechanisms from polymeric microneedles, which include diffusion, swelling, degradation, triggering, and targeting, there is a growing focus on manipulating the location and rate of drug release through innovative microneedle designs. This burgeoning field of microneedle-based drug delivery systems offers further prospects for precise control over drug release. The design strategies of polymeric microneedle systems for temporally controlled and locally targeted release, as well as the delivery mechanisms by which drugs can be released from a microneedle system are critically reviewed in this work. Furthermore, this review also puts forward some perspectives on the potential and challenges involved in translating these microneedle-based delivery systems into the next generation therapies.

Development of a Microfluidic Formatted Ultrasound-Controlled Monodisperse Lipid Vesicles' Hydrogel Dressing Combined with Ultrasound for Transdermal Drug Delivery System

Transdermal drug delivery system (TDDS) has attracted much attention in the pharmaceutical technology area. However, the current methods are difficult to ensure penetration efficiency, controllability, and safety in the dermis, so its widespread clinical use has been limited. This work proposes an ultrasound-controlled monodisperse lipid vesicles (U-CMLVs) hydrogel dressing, which combines with ultrasound to form TDDS. Using microfluidic technology, prepare size controllable U-CMLVs with high drug encapsulation efficiency and quantitative encapsulation of ultrasonic response materials, and even uniform mix them with hydrogel to prepare the required thickness of dressings. The high encapsulation efficiency can ensure sufficient dosage of the drugs and further realize the control of ultrasonic response through quantitative encapsulation of ultrasound-responsive materials. Using high frequency (5 MHz, 0.4 W cm-2 ) and low frequency (60 kHz, 1 W cm-2 ) ultrasound to control the movement and rupture of U-CMLVs, the contents not only penetrate the stratum corneum into the epidermis but also break through the bottleneck of penetration efficiency, and deep into the dermis. These findings provide the groundwork for deep, controllable, efficient, and safe drug delivery through TDDS and lay a foundation for further expanding its application.

Biodegradable Microneedles Array with Dual-Release Behavior and Parameter Optimization by Finite Element Analysis

Microneedles (MNs) are particularly attractive for transdermal administration because of the improved safety, patient compliance and convenience. Dissolving MNs could provide rapid transdermal delivery, but with relatively low mechanical strength and almost no sustainability. On the other hand, hydrogel MNs are complicated to fabricate and have risk concerns. Herein, we developed a biodegradable MNs array composed of biocompatible silk fibroin and poly(vinyl alcohol) to overcome these limitations. Finite element analysis was employed for parameter optimization. The MNs array fabricated by the optimal parameters and material displayed sufficient mechanical strength to disrupt stratum corneum and formed microchannels for transdermal delivery. Dual-release profile was observed in the MNs array, with rapid release in the beginning, and prolonged release afterward. This release behavior fits Weibull release model and is favorable for topical application. The initial immediate release can quickly deliver active compounds to reach the therapeutic effective concentration and facilitate skin penetration, and the sustained release may supply the skin with active compounds over a prolonged period. This biodegradable MNs array is easy to fabricate, mechanically robust, could eliminate safety concerns, and provide the sustainability and advantage for large-scale production.

Dendrimer-conjugated isotretinoin for controlled transdermal drug delivery

BACKGROUND

In the present study, we aimed to develop a novel isotretinoin delivery model for treating skin diseases, revealing its potential advantages in drug delivery and targeted therapy. Using a self-assembly strategy, we grafted a dendrimer, based on a well-defined branched structure for nanomedical devices, with a well-defined nanoarchitecture, yielding spherical, highly homogeneous molecules with multiple surface functionalities. Accordingly, a self-assembled dendrimer-conjugated system was developed to achieve the transdermal delivery of isotretinoin (13cRA-D).

RESULTS

Herein, 13cRA-D showed remarkable controlled release, characterized by slow release in normal tissues but accelerated release in tissues with low pH, such as sites of inflammation. These release characteristics could abrogate the nonteratogenic side effects of isotretinoin and allow efficient skin permeation. Moreover, 13cRA-D exhibited high therapeutic efficacy in acne models. Based on in vitro and in vivo experimental results, 13cRA-D afforded better skin penetration than isotretinoin and allowed lesion targeting. Additionally, 13cRA-D induced minimal skin irritation.

CONCLUSION

Our findings suggest that 13cRA-D is a safe and effective isotretinoin formulation for treating patients with skin disorders.