Microneedles for drug and vaccine delivery

Devices to overcome the buccal mucosal barrier to administer therapeutic peptides

Peptide therapeutics are important in healthcare owing to their high target specificity, therapeutic efficacy, and relatively low side effect profile. Injections of these agents have improved thetreatment of chronic diseases including autoimmune, metabolic disorders, and cancer. However, their administration via injections can prove a barrier to patient acceptability of treatments. While oral delivery of these molecules is preferable, oral peptide formulations are associated with limited bioavailability due to degradation in the intestine and low epithelial permeability. Buccal administration of peptides is a potential alternative to injections and oral formulations. Similar to the oral route, the buccal route can promote better patient adherence to dosing regimens, along with the added advantages of not requiring restriction on food or drink consumption before and after administration, as well as avoidance of the liver first-pass metabolism. However, like oral, effective buccal absorption of peptides is still challenging due to the high epithelial permeability barrier. We present a multidisciplinary approach to understanding the buccal physiological barrier to macromolecule permeation and discuss how engineered devices may overcome it. Selected examples of buccal devices can facilitate fast and efficient macromolecule absorption through multiple mechanisms including physical disruption of epithelia, convection-based mass transfer, and a combination of physicochemical strategies. Importantly, minimally invasive devices can be self-applied and are associated with the maintenance of the barrier after exposure. We analysed the critical attributes that are required forthe clinical translation of buccal peptide administration devices. These include performance-driven device development, manufacturing features, patient acceptability, and commercial viability.

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.

Development and comparative analysis of clobetasol-loaded microneedle patches versus clobetasol propionate ointment in experimental induced-psoriasis model

The utilization of dissolvable microneedles (MNs) is a promising and cutting-edge approach to drug delivery for the treatment of psoriasis, an autoimmune skin disorder characterized by the appearance of red, scaly patches on the skin. This study presents the development of a dissolving MN patch made of polyvinylpyrrolidone for the purpose of delivering Clobetasol 17-Propionate through the skin. The MN patches were evaluated for their physical characteristics, including morphology, solubility, strength, and ability to penetrate the skin. This evaluation was conducted on both unloaded and drug-loaded MN patches to determine their suitability for future applications. The manufacturing of 484 pyramidal-shaped tips, each measuring roughly 400 µm in height, was demonstrated by microscopy photographs. Compression tests revealed that the MN patch could endure a force greater than 1 N/needle while displacing around 300 µm, confirming the needle's ability to penetrate the stratum corneum. Following H&E staining, the penetration depth in mice skin was determined to be around 200 µm. The MN tips exhibited rapid drug release within a 10-minute timeframe, while the MN patch dissolved in the mice skin in roughly 20 min. An animal model was utilized to examine the effects of the produced patches on the treatment of psoriasis. Psoriasis was artificially induced in three groups of mice using imiquimod cream, applied for eight consecutive days to evaluate the inhibitory effect of clobetasol on exacerbating the disease. This assessment was accomplished using two methods: applying clobetasol ointment and using CP-loaded MNs. This innovative drug delivery system demonstrated encouraging results in terms of quick and effective administration, highlighting the potential of dissolvable MNs for psoriasis treatment.

Advancements in vaccine delivery: harnessing 3D printing for microneedle patch technology

The development of 3D-printed microneedle (MN) technology is a significant step in vaccine delivery, providing a painless, effective, and adaptable substitute for conventional injection-based techniques. Direct transdermal vaccination distribution without the need for needles is made possible by microneedle patches, which employ a variety of tiny needles that dissolve when they penetrate the skin. By using 3D printing to precisely customise microneedles' size, shape, and density to meet particular vaccine requirements, administration control can be improved and vaccine efficiency may even be increased. Furthermore, rapid prototyping made possible by 3D printing speeds up the development process, enabling quicker testing and improvement of vaccines. Additionally, this scalable technology can greatly increase vaccine accessibility, particularly in environments with limited resources. Research indicates that by directly interacting with the skin's immune-rich layers, microneedle patches enhance antigen delivery and elicit a strong immune response. Because MN technology offers a useful, self-administrable vaccination approach with little waste, it has significant potential for use in public health applications, notably during pandemics. This study emphasises how 3D-printed microneedle patches have the potential to revolutionise vaccination procedures and increase vaccine accessibility globally.

Recent advances in microneedles for enhanced functional angiogenesis and vascular drug delivery

Many therapeutic applications use the transdermal method to avoid the severe restrictions associated with oral medication delivery. Given the limitations of traditional drug delivery via skin, transdermal microneedle (MN) arrays have been reported to be versatile and very efficient devices due to their outstanding characteristics such as painless penetration, affordability, excellent medicinal efficacy, and relative safety. MNs have recently received increased attention for their ability to cure vascular illnesses such as hypertension and thrombosis, as well as promote wound healing via the angiogenesis impact. The integrant of method manufacturing and biodegradable material allows for the modification of MN form and drug release pattern, hence increasing the flexibility of such drug delivery. In this review, we focused on recent improvements in MN-mediated transdermal administration of protein and peptide medicines for improved functional angiogenesis and vascular therapy. We also provide an overview of the present applications of MNs-mediated transdermal protein and peptide administration, particularly in the realm of vascular system disease therapy. Finally, the current state of clinical translation and a forecast for future progress are provided.

Additional Use of Hyaluronic Acid-Based Dissolving Microneedle Patches to Treat Psoriatic Plaques: A Randomized Controlled Trial

BACKGROUND

Despite advances in systemic targeted therapies, topical agents remain the primary treatment for localized psoriasis. However, their therapeutic effects are often delayed and unsatisfactory. The dissolving microneedle (DMN) patch, a novel transdermal drug delivery system, enhances the absorption of topical agents through micro-channels.

OBJECTIVE

To evaluate the efficacy of DMN patches in enhancing drug delivery and improving clinical outcomes in psoriatic plaques.

METHODS

A prospective, randomized, split-body study was conducted to verify the efficacy of additional use of DMN patches after topical agent application in psoriasis treatment. Patients with mild psoriasis were enrolled and 6 paired lesions per patient were randomized into 3 groups: ointment-only, ointment-with-no needle patch, and ointment-with-DMN patch. Lesions were treated with a topical agent (betamethasone and calcipotriol) once daily for 2 weeks. Modified psoriasis area and severity index (mPASI) scores were measured weekly. In vitro and ex vivo experiments were performed to confirm micro-channel formation, microneedle dissolution, and drug penetration enhancement.

RESULTS

A total of 132 paired lesions from 22 patients were analyzed. The ointment-with-DMN patch group showed significantly improved mPASI scores (80.4%±20.5%; 5.42→1.06) compared to the ointment-with-no needle patch (64.6%±33.0%; 4.94→1.68) (p<0.05) and ointment-only groups (55.5%±31.4%; 5.00→2.15) (p<0.001). In vitro studies demonstrated 2.1-fold enhanced drug delivery with DMN patches, while ex vivo histological analysis confirmed micro-channel formation. No adverse events, including infection or psoriasis exacerbation, were observed.

CONCLUSION

The DMN patch is an effective adjunctive tool that enhances transdermal drug delivery and improves therapeutic outcomes in psoriatic plaques, particularly those refractory to topical agents.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02955576.

Microneedle arrays coated with Middle East respiratory syndrome coronavirus DNA vaccine via electrospray deposition

Microneedle arrays have been shown to be a minimally invasive method of transdermal drug delivery. However, methods to coat these arrays often require a reservoir of the active ingredient, leading to unused and wasted material. Electrospray deposition is a targeted coating method that offers a competitive alternative for coating microneedles. By architecting the charge landscape of the setup, this technology can achieve coating deposition efficiencies nearing 100%, with little to no material wasted during the coating process. A Middle East respiratory syndrome coronavirus DNA vaccine was used as the model material to assess deposition efficiency as well as the efficacy of fragile biological materials subjected to electrospray deposition. Trehalose and polystyrene-block-polyacrylic acid were used as excipients to encourage coating dispersion. These coatings were inserted into Sprague Dawley rats where the antigen was subsequently detected and located using immunohistochemistry. Both coatings, with and without excipients, showed that protein expression is achieved after the vaccine is subjected to electrospray, however, the presence of excipients qualitatively leads to a more disperse diffusion profile. Further, this work demonstrates the capability of electrospray deposition as a highly efficient method to coat microneedles for transdermal drug delivery.

Identification of potential vaccines for use with microarray patches in low- and middle-income countries: An assessment from the Vaccine Innovation Prioritisation Strategy Alliance

INTRODUCTION

Microarray patches (MAPs) have the potential to increase equitable vaccine coverage in low- and middle-income countries (LMICs). However, MAP developers and vaccine manufacturers have identified a barrier to development of MAPs for global health applications: the need for guidance on which vaccine MAPs would be of value to LMIC immunization programs. To address this gap, the Vaccine Innovation Prioritisation Strategy (VIPS) Alliance conducted a prioritization process to identify high-priority vaccines that could be delivered via MAPs in LMICs.

METHODS

We first compiled a reference list of vaccine targets through desk research, then filtered these targets based on route of administration, market distribution, existing interest from a global/regional health organization, whether the vaccine would address a specific global health priority or stakeholder agenda, development status, and potential MAP use cases. To further down-select the list, we consulted an external advisory group and evaluated the potential regulatory pathway, programmatic impact, and financial sustainability to define two priority levels.

RESULTS

From a reference list of 91 vaccine targets, we identified 21 with applicability to LMICs, which were further down-selected to a VIPS priority list of 11 vaccine targets grouped by priority level. Priority group 1 included vaccines against hepatitis B virus, measles-rubella/measles-mumps-rubella viruses, human papillomavirus, rabies virus, yellow fever, influenza virus (seasonal and pandemic), and SARS-CoV-2. Priority group 2 included vaccines against Group B streptococcus, Neisseria meningitidis A,C,W,Y,(X), Salmonella Typhi, and Streptococcus pneumoniae.

CONCLUSIONS

These vaccine MAP priorities will inform the investment decisions of MAP developers, vaccine manufacturers, donors, and global health partners to better respond to country needs when designing their MAP portfolios. By providing a holistic assessment of the potential drivers for and key risks of developing specific vaccine MAPs, our findings have the potential to promote MAP development activities for vaccines that are priorities for LMICs.

Graphene-Based Polymeric Microneedles for Biomedical Applications: A Comprehensive Review

Transdermal drug delivery presents a promising noninvasive approach, bypassing first-pass metabolism and gastrointestinal degradation. However, the stratum corneum (SC) barrier limits drug absorption, necessitating the development of effective delivery systems. Microneedles, particularly polymer-based ones, offer a solution by penetrating the SC while avoiding critical nerves and capillaries. These microneedles are biodegradable, nontoxic, and easily manufacturable, making them a highly attractive platform for transdermal drug delivery. However, their clinical application remains limited due to suboptimal therapeutic efficacy and slow drug release rates. Recent advancements have introduced the incorporation of nanodrugs, such as nanoparticles and encapsulated drugs, into microneedles to enhance drug delivery efficiency. Among the materials explored, graphene and its derivatives, including graphene oxide (GO) and reduced graphene oxide (rGO), have garnered significant attention. Their exceptional mechanical strength, electrical conductivity, and antibacterial properties not only improve the mechanical performance of microneedles but also enhance drug release rates and biocompatibility. This review synthesizes the current state of microneedle technologies, focusing on the materials, fabrication techniques, and performance challenges. It particularly examines the potential of graphene-based microneedles, comparing them to traditional polymer-based microneedles in terms of drug release efficiency and stability. The review highlights key challenges, such as scalability, biocompatibility, and fabrication complexity, and suggests future research directions to address these issues. The incorporation of graphene quantum dots (GQDs) is identified as a promising avenue for improving drug release profiles, stability, and real-time tracking of drug diffusion. Finally, the review outlines emerging applications, including smart drug delivery systems, biosensing, and real-time monitoring, urging further exploration to unlock the full potential of graphene-enhanced microneedles in clinical settings.

Responsive Microneedles for Diagnostic and Therapeutic Applications of Ocular Diseases

Traditional ophthalmic formulations are characterized by low bioavailability, short intraocular retention time, strong irritation, and failure to achieve the expected therapeutic effect due to the special physiological structure of the eye and the existence of many barriers. Microneedle drug delivery is a novel transdermal drug delivery modality. Responsive microneedles are defined as controllably releasing the drug payloads in response to physiological stimuli, including pH levels, temperature, enzymes, and reactive oxygen species (ROS), as well as external stimuli such as magnetic fields and light. In addition to inheriting the advantages of traditional microneedles, which include enhanced targeting and permeability, non-invasiveness, and painless application, the integration with stimulus-responsive materials enables responsive microneedles to achieve a personalized precision drug delivery process, which further increases the accuracy and efficiency of ocular treatments, making on-demand drug delivery possible. This article systematically reviews the classification, mechanisms, and characteristics of responsive microneedles and provides a detailed introduction to their diagnostic and therapeutic applications as well as real-time monitoring potential in ocular diseases, aiming to offer insights for the precision treatment of ocular diseases in the future.

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.

Applications and prospects of biomaterials in diabetes management

Diabetes is a widespread metabolic disorder that presents considerable challenges in its management. Recent advancements in biomaterial research have shed light on innovative approaches for the treatment of diabetes. This review examines the role of biomaterials in diabetes diagnosis and treatment, as well as their application in managing diabetic wounds. By evaluating recent research developments alongside future obstacles, the review highlights the promising potential of biomaterials in diabetes care, underscoring their importance in enhancing patient outcomes and refining treatment methodologies.

Engineering exosomes and exosome-like nanovesicles for improving tissue targeting and retention

Exosomes are natural nano-size particles secreted by human cells, containing numerous bioactive cargos. Serving as crucial mediators of intercellular communication, exosomes are involved in many physiological and pathological processes, such as inflammation, tissue injury, cardiovascular diseases, tumorigenesis and tumor development. Exosomes have exhibited promising results in the diagnosis and treatment of cancer, cardiovascular diseases and others. They are a rapidly growing class of drug delivery vehicles with many advantages over conventional synthetic carriers. Exosomes used in therapeutic applications encounter several challenges, such as the lack of tissue targeting capabilities and short residence time. In this review, we discuss recent advances in exosome engineering to improve tissue targeting and describe the current types of engineered exosome-like nanovesicles, and summarize their preclinical applications in the treatment of diseases. Further, we also highlight the latest engineering strategies developed to extend exosomes retention time in vivo and exosome-like nanovesicles.

Novel antimicrobial strategies for diabetic foot infections: addressing challenges and resistance

AIMS

This review examines the challenges posed by Diabetic Foot Infections (DFIs), focusing on the impact of neuropathy, peripheral arterial disease, immunopathy, and the polymicrobial nature of these infections. The aim is to explore the factors contributing to antimicrobial resistance and assess the potential of novel antimicrobial treatments and drug delivery systems in improving patient outcomes.

METHOD

A comprehensive analysis of existing literature on DFIs was conducted, highlighting the multifactorial pathogenesis and polymicrobial composition of these infections. The review delves into the rise of antimicrobial resistance due to the overuse of antimicrobials, biofilm formation, and microbial genetic adaptability. Additionally, it considers glycemic control, patient adherence, and recurrence rates as contributing factors to treatment failure. Emerging therapies, including new antimicrobial classes and innovative drug delivery systems, were evaluated for their potential efficacy.

RESULTS

DFIs present unique treatment challenges, with high rates of antimicrobial resistance and poor response to standard therapies. Biofilm formation and the genetic adaptability of pathogens worsen resistance, complicating treatment. Current antimicrobial therapies are further hindered by poor glycemic control and patient adherence, leading to recurrent infections. Novel antimicrobial classes and innovative delivery systems show promise in addressing these challenges by offering more targeted, effective treatments. These new approaches aim to reduce resistance and improve treatment outcomes.

CONCLUSION

DFIs remain a clinical challenge due to their multifactorial nature and antimicrobial resistance. The development of novel antimicrobials and drug delivery systems is crucial to improving patient outcomes and combating resistance. Future research should focus on enhancing treatment efficacy, reducing resistance, and addressing patient adherence to reduce the burden of DFIs.

Microneedle-mediated intradermal delivery of Bacille Calmette-Guérin (BCG) vaccines for single-dose tuberculosis vaccination

Tuberculosis (TB) remains a highly lethal infectious disease. The primary preventive measure is Bacille Calmette-Guérin (BCG), a live attenuated vaccine. However, the current intradermal vaccination method with 10-dose vials faces challenges such as inadequate infant injection, inaccurate dispensing, and unstable storage. Researchers have explored microneedle (MN) technology to address these concerns as a intradermal vaccine delivery approach. MN array patches offer painless administration, convenience, improved immunogenicity, and vaccine stability. This study aimed to develop a coated MN system using a micro-dispensing technique at a low temperature (4 °C) and specific excipients for precise dosing and vaccine viability enhancement. Long-term storage stability revealed enhanced storage stability of the BCG-coated MN (BCG-MN) vaccine, maintaining a survival rate of over 60 % for 8 weeks at -20 °C. In vivo vaccination tests using BCG-MN vaccines on guinea pigs exhibited no adverse reactions. Moreover, the BCG-MN vaccine demonstrated superior immune response compared to injections, suggesting that this BCG vaccine-coated MN platform has the potential as a single-dose TB vaccination technology, offering precise dosing control and enhanced immune effectiveness with high storage stability.

Transdermal delivery of PeptiCRAd cancer vaccine using microneedle patches

Microneedles (MNs) are a prospective system in cancer immunotherapy to overcome barriers regarding proper antigen delivery and presentation. This study aims at identifying the potential of MNs for the delivery of Peptide-coated Conditionally Replicating Adenoviruses (PeptiCRAd), whereby peptides enhance the immunogenic properties of adenoviruses presenting tumor associated antigens. The combination of PeptiCRAd with MNs containing polyvinylpyrrolidone and sucrose was tested for the preservation of structure, induction of immune response, and tumor eradication. The findings indicated that MN-delivered PeptiCRAd was effective in peptide presentation in vivo, leading to complete tumor rejection when mice were pre-vaccinated. A rise in the cDC1 population in the lymph nodes of the MN treated mice led to an increase in the effector memory T cells in the body. Thus, the results of this study demonstrate that the combination of MN technology with PeptiCRAd may provide a safer, more tolerable, and efficient approach to cancer immunotherapy, potentially translatable to other therapeutic applications.

Cancer vaccines: current status and future directions

Cancer continues to be a major global health burden, with high morbidity and mortality. Building on the success of immune checkpoint inhibitors and adoptive cellular therapy, cancer vaccines have garnered significant interest, but their clinical success remains modest. Benefiting from advancements in technology, many meticulously designed cancer vaccines have shown promise, warranting further investigations to reach their full potential. Cancer vaccines hold unique benefits, particularly for patients resistant to other therapies, and they offer the ability to initiate broad and durable T cell responses. In this review, we highlight the antigen selection for cancer vaccines, introduce the immune responses induced by vaccines, and propose strategies to enhance vaccine immunogenicity. Furthermore, we summarize key features and notable clinical advances of various vaccine platforms. Lastly, we delve into the mechanisms of tumor resistance and explore the potential benefits of combining cancer vaccines with standard treatments and other immunomodulatory approaches to improve vaccine efficacy.

A wearable antifouling electrochemical sensor integrated with an antimicrobial microneedle array for uric acid detection in interstitial fluid

Wearable microneedle array (MNA) based electrochemical sensors have gained increasing attention for their capability to analyze biomarkers in the interstitial fluid (ISF), enabling noninvasive, continuous monitoring of health parameters. However, challenges such as nonspecific adsorption of biomolecules on the sensor surfaces and the risk of infection at the microneedle penetration sites hinder their practical application. Herein, a wearable dual-layer microneedle patch was prepared to overcome these issues by integrating an antimicrobial microneedle layer with an antifouling sensing layer. The microneedle layer was prepared from polyvinyl alcohol, carboxylated nanocellulose, quaternary ammonium chitosan and carbon nanotubes, and it possessed antimicrobial and mechanical properties necessary for skin penetration, ISF collection and effective transmission to the sensing layer. The sensing layer was prepared from bacterial cellulose, epoxy propyl dimethyl dodecyl ammonium chloride, carbon nanotubes and gold nanoparticles, and it was capable of preventing biofouling and sensing uric acid (UA) in ISF. The wearable MNA based sensor exhibited a linear range of 0.5 μM - 2.5 μM and 9.6 μM - 2.15 mM for UA detection, with a limit of detection of 0.17 μM. Moreover, it was capable of accurately monitoring UA levels in ISF of mice without significant biofouling, as verified by the ELISA method. This innovative wearable sensor based on the MNA effectively balances the antifouling and antimicrobial functions, offering a reliable strategy for the assay of ISF, and making it a promising tool for personalized and decentralized health monitoring.

Beyond the Needle: Innovative Microneedle-Based Transdermal Vaccination

Vaccination represents a critical preventive strategy in the current global healthcare system, serving as an indispensable intervention against diverse pathogenic threats. Although conventional immunization relies predominantly on hypodermic needle-based administration, this method carries substantial limitations, including needle-associated fear, bloodborne pathogen transmission risks, occupational injuries among healthcare workers, waste management issues, and dependence on trained medical personnel. Microneedle technology has emerged as an innovative vaccine delivery system, offering convenient, effective, and minimally invasive administration. These microscale needle devices facilitate targeted antigen delivery to epidermal and dermal tissues, where abundant populations of antigen-presenting cells, specifically Langerhans and dermal dendritic cells, provide robust immunological responses. Multiple research groups have extensively investigated microneedle-based vaccination strategies. This transdermal delivery technique offers several advantages, notably circumventing cold-chain requirements and enabling self-administration. Numerous preclinical investigations and clinical trials have demonstrated the safety profile, immunogenicity, and patient acceptance of microneedle-mediated vaccine delivery across diverse immunization applications. This comprehensive review examines the fundamental aspects of microneedle-based immunization, including vaccination principles, transcutaneous immunization strategies, and microneedle-based transdermal delivery-including classifications, advantages, and barriers. Furthermore, this review addresses critical technical considerations, such as treatment efficacy, application methodologies, wear duration, dimensional optimization, manufacturing processes, regulatory frameworks, and sustainability considerations, followed by an analysis of the future perspective of this technology.

Microneedle-Based Approaches for Skin Disease Treatment

The use of microneedles (MNs) has been established as an effective transdermal drug delivery strategy that has been extensively deployed for treating various diseases, including skin diseases. MNs can surpass the constraints of conventional drug delivery methods by their superior safety and efficacy through precise targeting, while simultaneously enabling painless delivery. Currently, MNs are increasingly used as carriers for drug delivery, with the loading of insoluble drugs to improve their treatment efficiency or combining with bioactive substances for the construction of an efficient drug delivery system to maximize the effects of bioactive substances. The methods used for preparation MNs are diverse, enabling them to meet the requirements of most applications. The emergence of MNs has addressed the shortcomings associated with insoluble drugs, expanded the applications of bioactive substances, and improved their use in clinical practice. This review summarizes current information on the application of MNs in a variety of skin diseases, such as psoriasis, vitiligo, alopecia, hypertrophic scarring, atopic dermatitis, melanoma, acne, and skin infections. The current clinical applications and future opportunities for MNs in the treatment of skin diseases are also discussed. Despite substantial progress in the clinical application of MNs as delivery vectors, issues such as low drug loading and poor mechanical strength during MNs preparation remain the main challenges. Therefore, clinical implementation of MNs-based therapies remains limited, highlighting key opportunities for future research.

Multifunctional Microneedle Patches Loaded With Engineered Nitric Oxide-Releasing Nanocarriers for Targeted and Synergistic Chronic Wound Therapy

Chronic wounds impose significant physical and mental burdens on patients. Nano-based formulations offer a promising strategy for chronic wound healing due to their non-invasive nature and enhanced biofilms penetration, but they often lack targeting capability or fail to achieve long-term and synergistic effects. In this work, a multifunctional microneedle (MN) patch loaded with engineered nitric oxide (NO)-releasing nanocarriers are presented that encapsulate an antibacterial agent and are immobilized with Concanavalin A (Con A) and NO molecules for targeted and synergistic treatment of chronic wounds. With the assistance of MNs, the nanoparticles (NPs) can directly cross bacterial biofilms and be efficiently delivered to wound tissues, where they target harmful bacteria through the specific recognition between Con A and polysaccharides on bacterial surfaces, followed by the release of the encapsulated antimicrobial agent, thereby achieving effective antibacterial effect. Moreover, the NPs generate NO in a sustained manner as they dissociate in the wound tissue, which exerts potent anti-inflammatory action and benefits tissue regeneration, further promoting chronic wounds closure. Consequently, this work provides a novel MN patch loaded with engineered NPs designed for accelerating chronic wound healing through targeted and synergistic therapy.

Microneedles at the Forefront of Next Generation Theranostics

Theranostics, combining therapeutic and diagnostic functions, marks a revolutionary advancement in modern medicine, with microneedle technology at its forefront. This review explores the substantial developments and multifaceted applications of microneedles, which have evolved from basic transdermal drug delivery devices to sophisticated diagnostic and therapeutic platforms. Microneedles enhance access to biomarkers via interstitial fluid, enabling real-time monitoring of physiological conditions, such as glucose and hormone levels, thus facilitating continuous health tracking. The evolution of microneedle design from solid to dissolvable forms broadens their utility from mere drug delivery to complex sensing and therapeutic applications, including insulin delivery for diabetes management, vaccination, and gene therapy. This paper delves into the integration of microneedles with wearable technologies, highlighting their role in closed-loop systems that combine real-time monitoring with dynamic, precise therapeutic delivery. By addressing gaps in the literature regarding their integrated diagnostic and treatment capabilities, this review underscores the pivotal role of microneedles in personalizing medicine. It concludes with a visionary perspective on the future trajectory of microneedle technology, emphasizing its potential to revolutionize therapeutic strategies through enhanced efficacy, safety, and patient compliance.

Electrostatic Force-Enabled Microneedle Patches that Exploit Photoredox Catalysis for Transdermal Phototherapy

Microneedle patches for topical administration of photodynamic therapy (PDT) sensitizers are attractive owing to their safety, selectivity, and noninvasiveness. However, low-efficiency photosensitizer delivery coupled with the limitations of the hypoxic tumor microenvironment remains challenging. To overcome these issues, we developed an effective microneedle patch based on intermolecular electrostatic interactions within a photosensitizer matrix containing a zinc-containing porphyrin analogue, ZnBP (w). This design improved the mechanical strength of the microneedle patch and enhanced the photosensitizer loading efficiency in aqueous environments. A key feature of the system is efficient electron transfer between ZnBP (w) and NADH upon photoirradiation. Electrostatic interactions between ZnBP (w) and NADH were hypothesized to support initial binding and subsequent photoinduced electron transfer, disrupting NADH/NAD+ homeostasis and inducing tumor cell death. The developed microneedle patch demonstrated an antiangiogenesis effect in a vascular malformation model and an antitumor effect in a melanoma mouse model after transdermal administration. This study highlights the benefits of electrostatic interactions in designing microneedle PDT patches and their clinical potential, particularly in reducing systemic phototoxicity.

Using Oscillation to Improve the Insertion Depth and Consistency of Hollow Microneedles for Transdermal Insulin Delivery with Mechanistic Insights

Microneedles (MNs) offer the potential for discrete and painless transdermal drug delivery, yet poor insertion and dosing consistency have hindered their clinical translation. Specifically, hollow MNs are appropriate for the administration of liquid modalities, including insulin, which could prove to be beneficial for patients with type 1 diabetes mellitus. This work aimed to design and manufacture a hollow MN with an improved insertion and delivery profile suitable for insulin administration. Ex vivo insertion studies demonstrated that oscillation of MNs upon insertion into skin produced a favorable insertion profile, with reduced variation, compared to static MN insertion. Histological staining showed that this could be due to the repeated motion of the oscillating MN disrupting elastic fibers in the dermis. Additionally, permeation studies demonstrated that increased quantities of insulin were able to permeate the skin when oscillation was employed compared to static MN insertion. This study has shown that oscillation is a valuable tool in improving the transdermal delivery of insulin via a single hollow MN in vitro. Moving forward, in vivo studies should be completed to gain a fuller understanding of the benefits of the oscillation of MNs on transdermal drug delivery.

Multi-Layered Microneedles Loaded with Microspheres

Delivery of therapies into skin is attractive for medical indications including vaccination and treatment of dermatoses but is highly constrained by the stratum corneum barrier. Microneedle (MN) patches have emerged as a promising technology to enable non-invasive, intuitive, and low-cost skin delivery. When combined with biodegradable polymer formulations, MN patches can further enable controlled-release drug delivery without injection. Herein, we sought to expand on the capability of MN patches to deliver therapies into skin by providing improved spatiotemporal control. Polylactic-co-glycolic acid (PLGA) microspheres were used to encapsulate model dye and then loaded into MN patches through a layer-by-layer fabrication method that created multiple layers of different composition within each MN. MN patches were loaded with up to 5 μg/MN of PLGA microspheres. Mechanical testing demonstrated that mechanical strength of MNs decreased with increasing number of microsphere layers. Microsphere-loaded MN patches inserted into porcine skin ex vivo and murine skin in vivo fully dissolved within 15 min, administering drug-loaded microspheres for controlled release lasting over 45 days. These data support the feasibility of multi-layered, microsphere-loaded MN patches designed for spatially targeted and sustained delivery of therapies into skin.

Microneedle patch with pure drug tips for delivery of liraglutide: pharmacokinetics in rats and minipigs

Transdermal delivery of peptide drugs is almost impossible with conventional penetration enhancers because of epidermal barrier function. Microneedle (MN) patches can bypass the epidermal barrier and have been developed for trans- and intradermal delivery of peptide drugs and vaccines. However, dissolving MN patches are limited by low drug loading capacities due to their small size and admixture of drug and water-soluble excipients. Furthermore, few in vivo pharmacokinetic studies, especially in large animals such as pigs, have been performed to assess post-application systemic drug exposure. Here, we developed a dissolving MN patch with pure liraglutide at the needle tips. The MN patch could load up to 2.21 ± 0.14 mg of liraglutide in a patch size of 0.9 cm2, which was nearly two orders of magnitude higher than that obtained with conventional MN patches of the same size. Raman imaging confirmed that liraglutide was localized at the MN tips. The MN had sufficient mechanical strength to penetrate the epidermis and could deliver up to 0.93 ± 0.04 mg of liraglutide into skin with a dosing variability of less than 6.8%. The MN patch delivery enabled faster absorption of liraglutide than that provided by subcutaneous (S.C.) injection, and achieved relative bioavailability of 69.8% and 46.3% compared to S.C. injection in rats and minipigs, respectively. The MN patch also exhibited similar patterns of anti-hyperglycemic effect in diabetic rats and individual variability in pharmacokinetic parameters as S.C. injection. The liraglutide MN application was well tolerated; no skin irritation was observed in minipigs except for mild erythema occurring within 4 h after once daily administration for 7 days at the same site. Our preclinical study suggests that MN patch with pure drug needle tips might offer a safe and effective alternative to S.C. injection for administration of liraglutide.

3D printing of drug delivery systems enhanced with micro/nano-technology

Drug delivery systems (DDSs) are increasingly important in ensuring drug safety and enhancing therapeutic efficacy. Micro/nano-technology has been utilized to develop DDSs for achieving high stability, bioavailability, and drug efficiency, as well as targeted delivery; meanwhile, 3D printing technology has made it possible to tailor DDSs with diverse components and intricate structures. This review presents the latest research progress integrating 3D printing technology and micro/nano-technology for developing novel DDSs. The technological fundamentals of 3D printing technology supporting the development of DDSs are presented, mainly from the perspective of different 3D printing mechanisms. Distinct types of DDSs leveraging 3D printing and micro/nano-technology are analyzed deeply, featuring micro/nanoscale materials and structures to enrich functionalities and improve effectiveness. Finally, we will discuss the future directions of 3D-printed DDSs integrated with micro/nano-technology, focusing on technological innovation and clinical application. This review will support interdisciplinary research efforts to advance drug delivery technology.

Design, fabrication, and evaluation of antimicrobial sponge microneedles for the transdermal delivery of insulin

Transdermal drug delivery systems hold promise, but their effectiveness is often constrained by the skin's barrier. Microneedles (MNs) improve drug permeability by creating micro-channels in the skin, yet they continue to face challenges such as infection risks and safety concerns. To overcome these challenges, a novel antimicrobial sponge MNs (ASMNs@PVP-INS) modified with polyvinylpyrrolidone (PVP) for insulin (INS) delivery was designed. Mechanical testing demonstrated that these MNs possess excellent mechanical strength, capable of withstanding at least 0.11 N per needle without rupture. In vitro drug penetration tests revealed that the MNs consistently released over 75 % of INS within a 6 h. In an animal model, ASMNs@PVP-INS reduced initial blood glucose levels from 22.4 to 5.72 mmol/L, effectively maintaining glucose control for more than 6 h without inducing hypoglycemia. Additionally, agar diffusion assays indicated that INS loading did not compromise the antimicrobial properties of antimicrobial sponge MNs (ASMNs). Skin irritation tests showed that ASMNs@PVP-INS exhibited mild irritation (PII < 0.6), with skin damage fully recovering within 8 h. Safety assessments indicated no significant toxicity to mice, with biochemical markers remaining within normal ranges, thereby confirming their good biocompatibility. In conclusion, ASMNs@PVP-INS hold promise as a novel drug delivery vehicle.

Formulation, Characterization, and in vivo Immunogenicity of Heat-Stabilized Dissolvable Microneedles Containing a Novel VLP Vaccine

Since its introduction, vaccination has heavily improved health outcomes. However, implementing vaccination efforts can be challenging, particularly in low and middle-income countries with warmer climates. Microneedle technology has been developed for its simple and relatively painless applications of vaccines. However, no microneedle vaccine has yet been approved by the FDA. A few hurdles must be overcome, including the need to evaluate the safety and biocompatibility of the polymer used to fabricate these microneedles. Additionally, it is important to demonstrate reliable immune responses comparable to or better than those achieved through traditional administration routes. Scalability in manufacturing and the ability to maintain vaccine potency during storage and transportation are also critical factors. In this study, we developed vaccine-loaded dissolvable microneedles that showed preclinical immunogenicity after storage in extreme conditions. We developed our microneedles using the conventional micromolding technique with polyacrylic acid (PAA) polymer, incorporating a novel virus-like particle (VLP) vaccine targeting arboviruses. We performed characterization studies on these microneedles to assess needle sharpness, skin insertion force, and VLP integrity. We also investigated the thermostability of the vaccine after storing the microneedles at elevated temperatures for approximately 140 days. Finally, we evaluated the immunogenicity of this vaccine in mice, comparing transdermal (microneedle) with intramuscular (hypodermic needle) administration. We successfully fabricated and characterized VLP-loaded microneedles that could penetrate the skin and maintain vaccine integrity even after exposure to extreme storage conditions. These microneedles also elicited robust and long-lasting antibody responses similar to those achieved with intramuscular administration.

Whole-Cell Vaccine Preparation Through Prussian Blue Nanoparticles-Elicited Immunogenic Cell Death and Loading in Gel Microneedles Patches

Tumor whole-cell vaccines are designed to introduce a wide range of tumor-associated antigens into the body to counteract the immunosuppression caused by tumors. In cases of lymphoma of which the specific antigen is not yet determined, the tumor whole-cell vaccine offers distinct advantages. However, there is still a lack of research on an effective preparation method for the lymphoma whole-cell vaccine. To solve this challenge, we prepared a whole-cell vaccine derived from non-Hodgkin B-cell lymphoma (A20) via the photothermal effect mediated by Prussian blue nanoparticles (PBNPs). The immune activation effect of this vaccine against lymphoma was verified at the cellular level. The PBNPs-treated A20 cells underwent immunogenic cell death (ICD), causing the loss of their ability to form tumors while retaining their ability to trigger an immune response. A20 cells that experienced ICD were further ultrasonically crushed to prepare the A20 whole-cell vaccine with exposed antigens and enhanced immunogenicity. The A20 whole-cell vaccine was able to activate the dendritic cells (DCs) to present antigens to T cells and trigger specific immune responses against lymphoma. Whole-cell vaccines are primarily administered through direct injection, a method that often results in low delivery efficiency and poor patient compliance. Comparatively, the microneedle patch system provides intradermal delivery, offering enhanced lymphatic absorption and improved patient adherence due to its minimally invasive approach. Thus, we developed a porous microneedle patch system for whole-cell vaccine delivery using Gelatin Methacryloyl (GelMA) hydrogel and n-arm-poly(lactic-co-glycolic acid) (n-arm-PLGA). This whole-cell vaccine combined with porous gel microneedle patch delivery system has the potential to become a simple immunotherapy method with controllable production and represents a promising new direction for the treatment of lymphoma.

A systematic review of microneedles technology in drug delivery through a bibliometric and patent overview

The transdermal drug delivery (TDD) route has gathered considerable attention for its potential to improve therapeutic efficacy while minimizing systemic side effects. Among transdermal technologies, microneedle (MN) devices have proven to be a promising approach that combines the advantages of traditional needle injections and non-invasive topical applications. This review provides a comprehensive analysis of progress in transdermal drug delivery systems (TDDS) via MN from 2000 to 2023, integrating bibliometric analysis and patent landscape to present a multi-faceted perspective on the evolution of this technology. The study identifies key trends, challenges, and opportunities in the research, implementation, and commercialization of MN tools through a systematic examination of scientific literature and an extensive investigation of global patent databases. The study of bibliometric trends reveals the leading experts, organizations, companies, and countries contributing to this field, collaboration networks, and the thematic evolution of research topics. The patent analysis offers insights into innovative trajectories, key players, and geographical distribution of intellectual property. This review resumes the latest advancements in MN devices and provides a strategic outlook that can guide future research directions, promote partnerships, and inform stakeholders involved in the development of TDDS.

Smart drug delivery and responsive microneedles for wound healing

Wound healing is an ongoing concern for the medical community. The limitations of traditional dressings are being addressed by materials and manufacturing technology. Microneedles (MNs) are a novel type of drug delivery system that has been widely used in cancer therapy, dermatological treatment, and insulin and vaccine delivery. MNs locally penetrate necrotic tissue, eschar, biofilm and epidermis into deep tissues, avoiding the possibility of drug dilution and degradation and greatly improving administration efficiency with less pain. MNs represent a new direction for wound treatment and transdermal delivery. In this study, we summarise the skin wound healing process and the mechanical stimulation of MNs in the context of the wound healing process. We also introduce the structural design and manufacture of MNs. Subsequently, MNs are categorised according to the loaded drugs, where the design of the MNs according to the traumatic biological/biochemical microenvironment (pH, glucose, and bacteria) and the physical microenvironment (temperature, light, and ultrasound) is emphasised. Finally, the advantages of MNs are compared with traditional drug delivery systems and their prospects are discussed.

Evolution of microneedle applicators for vaccination: the role of the latch applicator in optimizing dissolving microneedle-based immunization

INTRODUCTION

Dissolving microneedles (DMN) offer advantages in vaccine delivery, such as enhanced immunogenicity and simplified administration, by targeting immune-rich layers of the skin. However, these benefits require precise and consistent delivery, which poses practical challenges. To address this, specialized applicators are essential for ensuring the accurate deployment of DMNs, making this technology a viable alternative to traditional methods, particularly in low- and middle-income countries (LMICs), where healthcare infrastructure is limited.

AREAS COVERED

In this review, we examine the advancements in DMN-based vaccination and applicator design, focusing on their joint effort. These innovations have improved the precision and efficiency of DMN vaccine delivery. Complex and costly early-stage applicators have evolved into simpler and more cost-effective designs. We highlight these developments in this review, with the latch applicator as a key example of a feature that enhances vaccine delivery.

EXPERT OPINION

Although applicator development has advanced DMN-based vaccination toward practical use, challenges remain. Key areas for further optimization include user friendliness, cost, packaging volume, and wear time. Once optimized, DMN vaccination may become a highly effective and accessible tool for global immunization, supporting efforts to achieve worldwide vaccine equality.

Development and optimization of the Glabridin-loaded dissolving microneedle for enhanced treatment of keloid

Glabridin (Gla) has been reported to have significant effects in scar treatment, and however, the water insolubility of Gla leads to its poor transdermal absorption ability, which affects its bioactivities. Therefore, we attempted to prepare the Gla dissolving microneedles (Gla-MN) to improve the absorbtion of Gla. After investigation of the 3 factors including the needle tip matrix concentration, the prescription concentration of backing material, and the dissolution method of Gla, we finally determined the process parameters of 10% hyaluronic acid (HA) as the needle tip and 5% polyvinyl alcohol (PVA) as the backing, according to which the Gla-MN was prepared with the good characteristics of high hardness, complete appearance and good in vitro dissolution ability. We then loaded Gla onto the microneedles and measured that the average drug loading of Gla-MN was 2.26 ± 0.11 μg/mg and the cumulative transdermal release of Gla-MN was up to 76.9% after 24 h. In addition, Gla-MN had good skin penetration properties, with Gla-MN penetrating at least 4 to 5 layers of parafilm. And the skin basically could return to normal after 4 h of piercing. Importantly, our results showed that Gla-MN had higher transdermal delivery and therapeutic effects against keloid than that of Gla at the same dosage.

A Self-Assembled Transdermal Nanomedicines Incorporating Pendant Disulfides for Non-Invasive, Synergistic Treatment of Melanoma

Transdermal drug delivery system (TDDS) offers lower systemic toxicity and good patient compliance, making it a promising treatment option for skin-related cancers. However, physiological barriers in the skin frequently impede the therapeutic efficiency of TDDS. To address this, a unique self-assembled TDDS that incorporates disulfide pendant groups (termed Sup-TDDS) is presented. It is formulated with dithiolane-containing lipoic acid (LA), photosensitizers Ce6, and chemotherapeutic agents trametinib. Pendant disulfide moieties on Sup-TDDS facilitate thiol-disulfide exchange reactions with exofacial thiols on cell surfaces, thus enhancing stratum corneum penetration. In contrast to intravenous injection, topical administration of Sup-TDDS can penetrate deeper into the skin (> 500 µm) and promote drug accumulation in subcutaneous tumors. In a B16F10-bearing mouse model, Sup-TDDS treatment demonstrates significant anti-tumor effects in primary and recurrent melanoma, benefiting from the synergistic effects of Ce6 and trametinib. These results underscore that Sup-TDDS's transdermal properties allow non-invasive melanoma therapy, implying the potential of nanodrugs containing pendant disulfides for transdermal treatment of skin illnesses.

Self-Assembly of Microstructured Protein Coatings with Programmable Functionality for Fluorescent Biosensors

Proteins, as genetically programmable functional macromolecules, hold immense potential as biocompatible self-assembling building blocks, owing to their versatility in building coating materials and programming their functionality genetically. In this study, we demonstrate a modular self-assembly of protein coatings that are genetically programmable for a biosensor application. We designed and produced recombinant fusion protein building blocks to form microstructured coatings on diverse substrates, such as glass or polymers, through thermally triggered liquid-liquid phase separation and an orthogonal high-affinity coiled-coil interaction. We incorporated fluorescence proteins into coatings and controlled the protein density to enable fluorescence imaging and quantification in a low-resource setting. Then, we created a coating for a calcium biosensor using a genetically engineered calcium indicator protein. This protein coating served as the foundation for our smartphone-based fluorescent biosensor, which successfully measured free calcium concentrations in the millimolar range at which extracellular calcium homeostasis is maintained. Using this fluorescent biosensor, we were able to detect abnormal physiological conditions, such as mild or moderate hypercalcemia. We envision that this modular and genetically programmable functional protein coating platform could be extended to the development of highly accessible, low-cost fluorescent biosensors for a variety of targets.

Reconnoitring signaling pathways and exploiting innovative approaches tailoring multifaceted therapies for skin cancer

Nowadays, skin cancer is widespread just like a varied malignant cancer which can cause serious health issues. Skin cancer, which encompasses malignant melanoma, basal cell carcinoma, and squamous cell carcinoma, is a prevalent form of cancer among humans. Due to its broad prevalence, financial burden, mortality rates, and cosmetic effects, it is a major public health issue. Skin cancer treatment involves surgery, chemotherapy, and radiation. Recently, personalized treatment in the fields of targeted therapies and precision medicine has been shown to diagnose early detection of every individual tumor by knowing their genetic and molecular characteristics. To target the molecular pathways responsible for tumor growth and reduce the damage to healthy tissue, new targeted therapies have emerged for melanoma, basal cell carcinoma, and squamous cell carcinoma. B-raf serine/threonine kinase (BRAF) and mitogen-activated protein kinase (MEK) inhibitors, immune checkpoint inhibitors, and precision medications have strong response rates to improve patient survival. Targeted therapeutics like nanocarriers have shown promising results by reducing skin irritation and protecting encapsulated therapeutics. These formulations have been shown to improve the transdermal permeability of anticancer drugs. The consideration of employing physical techniques to enhance the permeation of nanocarriers warrants attention to augment the dermal permeation of anticancer agents and facilitate targeted drug delivery within neoplastic cells. Targeted therapies face obstacles like resistance mechanisms and treatment strategy monitoring. Taken together, this review delves into the basic mechanisms of skin cancer, current treatment methods, drug resistance processes, and nano-based targeted techniques for cancer treatment. It will also delineate the challenges and perspectives in pre-clinical and clinical contexts.

Review of Microneedle Technology for Targeted Therapeutics in Vitiligo: Design Principles, Application Prospects

Vitiligo is a chronic autoimmune disorder characterized by depigmented patches of the skin. The treatment of vitiligo remains challenging, partly owing to the lack of efficient drug delivery system. Microneedles (MNs), an ideal transdermal drug delivery system, have emerged as promising drug delivery platform for vitiligo. Recently, the emergence of novel MNs with increased biocompatibility, including hydrogel and hollow MNs, further enhance the translational value of MNs in the treatment of vitiligo. However, up-to-date review of these advancements remains lacking. This review aims to summarize the most recent studies of MN-based drug delivery systems for vitiligo, highlighting the translational potential of MNs as a therapeutic platform for the treatment of vitiligo in the near future.

Amyloid-β-targeting immunotherapies for Alzheimer's disease

Recent advances in clinical passive immunotherapy have provided compelling evidence that eliminating amyloid-β (Aβ) slows cognitive decline in Alzheimer's disease (AD). However, the modest benefits and side effects observed in clinical trials indicate that current immunotherapy therapy is not a panacea, highlighting the need for a deeper understanding of AD mechanisms and the significance of early intervention through optimized immunotherapy or immunoprevention. This review focuses on the centrality of Aβ pathology in AD and summarizes recent clinical progress in passive and active immunotherapies targeting Aβ, discussing their lessons and failures to inform future anti-Aβ biotherapeutics design. Various delivery strategies to optimize Aβ-targeting immunotherapies are outlined, highlighting their benefits and drawbacks in overcoming challenges such as poor stability and limited tissue accessibility of anti-Aβ biotherapeutics. Additionally, the perspectives and challenges of immunotherapy and immunoprevention targeting Aβ are concluded in the end, aiming to guide the development of next-generation anti-Aβ immunotherapeutic agents towards improved efficacy and safety.

Novel long-acting treatment for schizophrenia based on paliperidone dissolving and implantable microarray patches

Schizophrenia is a severe mental disorder that affects millions of people worldwide. Several atypical antipsychotic medications, including paliperidone (PPD), has been developed and proven effective in treating it. To date, four PPD extended-release products have been launched commercially, providing up to six months of therapeutic effect with a single administration. However, the need for hospital injections by professional healthcare workers not only lead to poor patients' adherence, but also put additional pressure on the healthcare system. Therefore, three PPD microarray patch (PPD MAP) systems based on dissolving microneedle technology and implantable microneedle technology were developed in this work. The two dissolving microarray patch systems contained either PPD crude drug (PPD DMAP-CD) or PPD nanocrystal (PPD DMAP-NC) and the implantable MAP contained PPD crude drug (PPD IMAP). All three types of PPD MAPs showed excellent mechanical and insertion properties as they achieved over 256 µm insertion depth in skin model. In vitro release study showed that PPD released from IMAP in a much more sustained manner (up to 14 days) than PPD did from DMAPs (7 days), with only 20 % initial burst release from IMAP compared with 43-71 % from DMAPs. The MAP dissolution study showed that both DMAPs can be immediately dissolved within less than 3 min once inserted into the skin, indicating a faster action potential compared with IMAP. Ex vivo delivery study showed that 1.68 ± 0.23 mg, 1.39 ± 0.07 mg, and 1.18 ± 0.12 mg were delivered from DMAP-CD, DMAP-NC and IMAP, respectively, demonstrating that over 50 % and up to 70 % of PPD in the MAPs can be delivered into the skin. The IMAP offers most sustained release of PPD whereas DMAP-NC exhibits fastest PPD release (11.19 % vs 20.01 % into Franz cell receiver compartment over 24 h). This work presents a promising alternative for the sustained delivery of antipsychotic drugs, allowing for patient self-administration and extended release concurrently. Patients may potentially use both DMAP and IMAP to achieve a sustained release of PPD while also avoid having an initial therapeutic lag.

Microneedles: A minimally invasive delivery system for ocular treatment

This review article delves into the extensive use of microneedles in ocular therapy, emphasizing their efficacy in delivering drug substances to the posterior region of the eye. The conventional methods of drug delivery, while widely employed, are marred by inherent drawbacks such as neovascularization, abrasion, and infiltration. To address these limitations, the review explores various approaches to microneedle fabrication, shedding light on the diverse materials employed in the process. Furthermore, the article meticulously examines the delivered drug substances using distinct microneedle approaches and their applications in ocular therapy. By critically evaluating the drawbacks associated with conventional ophthalmic drug delivery, the review seeks to pave the way for a paradigm shift. It advocates for a novel approach centered around minimally invasive microneedles, presenting them as a promising solution to overcome the limitations of current drug delivery methods. The comprehensive discussion within this article not only offers insights into the fabrication techniques and materials used for microneedles but also provides a nuanced understanding of the applications and advantages associated with this innovative approach. As the exploration of microneedle technology continues to evolve, this review serves as a valuable resource for researchers, clinicians, and pharmaceutical professionals seeking to enhance ocular therapy by embracing the potential of minimally invasive microneedles.

Comparative study of permeation effects between vibrating microneedle and low-frequency sonophoresis systems

Microneedle transdermal administration and low-frequency ultrasound represent two important physical penetration-promoting methods for enhancing drug penetration. This article aims to investigate and compare the effects of drug penetration enhancement through transdermal administration using vibrating microneedles versus low-frequency sonophoresis. In Vitro permeation studies were conducted using Valia-Chien double chamber diffusion cells to evaluate the transdermal delivery of tetramethylpyrazine hydrochloride (TMPH). The TMPH concentration in the receiving compartment was determined using high-performance liquid chromatography (HPLC). Several combinations of microneedles and ultrasound settings were investigated, including different needle heights, vibration frequencies, exposure times, and assorted distances of ultrasound horn and skin. The results revealed the vibrating microneedle system as the most efficacious treatment to increase the TMPH permeability into the rat skin. The combination of a larger needle, higher frequency, and a 3-min exposure led to a 41.92-fold increase in cumulative permeability compared to the control group. The ultrasound treatment exhibited a moderate enhancement effect on TMPH skin penetration. Using a horn-to-skin distance of 3 mm and a 3-min exposure resulted in a 4.34-fold increase in TMPH cumulative permeation compared to the control group. It could be concluded that while both the vibrating microneedle and the low-frequency ultrasound systems act as penetration enhancers for promoting the TMPH permeation through the skin, the vibrating microneedle system notably demonstrates a more effective penetration-promoting effect.

Characterisation of skin penetration pathways using stimulated Raman scattering microscopy

Understanding the mechanisms governing the penetration of substances into the skin is crucial for the development of safe and effective topical drug delivery systems and skincare products. This study examined the partitioning of model permeants into human skin, by assessing six substances with diverse logP values. We employed stimulated Raman scattering (SRS) microscopy, an ambient, label-free optical imaging technique known for its ability to provide chemical distribution with subcellular resolution. Our investigation assessed partitioning into the two primary pathways through which substances traverse the skin: the intercellular lipid matrix and the intracellular route via corneocyte cells. We observed that the partitioning behaviour was strongly influenced by the lipophilicity of the molecule, with lipophilic compounds showing greater affinity for intercellular matrix with increased lipophilicity. Conversely, hydrophilic molecules demonstrated a preference for corneocyte cells, with their affinity increasing with increased hydrophilicity. The findings contribute to our understanding of the mechanisms underlying topical delivery and offer important implications and new methods beneficial for the development of safe and effective topical products. In addition, the methods presented could be valuable to reveal changes in drug partitioning or to assess targeting approaches in diseased skin models.

3D-Printed Latticed Microneedle Array Patches for Tunable and Versatile Intradermal Delivery

Using high-resolution 3D printing, a novel class of microneedle array patches (MAPs) is introduced, called latticed MAPs (L-MAPs). Unlike most MAPs which are composed of either solid structures or hollow needles, L-MAPs incorporate tapered struts that form hollow cells capable of trapping liquid droplets. The lattice structures can also be coated with traditional viscous coating formulations, enabling both liquid- and solid-state cargo delivery, on a single patch. Here, a library of 43 L-MAP designs is generated and in-silico modeling is used to down-select optimal geometries for further characterization. Compared to traditionally molded and solid-coated MAPs, L-MAPs can load more cargo with fewer needles per patch, enhancing cargo loading and drug delivery capabilities. Further, L-MAP cargo release kinetics into the skin can be tuned based on formulation and needle geometry. In this work, the utility of L-MAPs as a platform is demonstrated for the delivery of small molecules, mRNA lipid nanoparticles, and solid-state ovalbumin protein. In addition, the production of programmable L-MAPs is demonstrated with tunable cargo release profiles, enabled by combining needle geometries on a single patch.

Development of 3D printed microneedles of varied needle geometries and lengths, designed to improve the dermal delivery of topically applied psoriasis treatments

The aim of this study was to investigate the impact of using microneedle patches in addition to topical therapy for the treatment of psoriasis. Using continuous liquid interface production (CLIP) 3D printing we manufactured round microneedle array patches (MAPs) with a diameter of 14 mm. Needle geometries were varied from square pyramidal, conical, and obelisk, with varied needle lengths of 400 µm, 600 µm, 800 µm, or 1000 µm. MAPs were characterized for force to fracture, skin penetration, skin damage, as well as their ability to deliver a novel oleogel-based corticosteroid (betamethasone dipropionate (BDP) formulation into ex-vivo porcine skin. We found that the obelisk shaped MAPs are more durable compared to the conical and square pyramidal-shaped MAPs. When the obelisk shaped MAPs were used in combination with the oleogel-based BDP formulation, the amount of BDP penetrating the skin was significantly increased with greater needle lengths.

Revolutionizing Eye Care: Exploring the Potential of Microneedle Drug Delivery

Microneedle technology revolutionizes ocular drug delivery by addressing challenges in treating ocular diseases. This review explores its potential impact, recent advancements, and clinical uses. This minimally invasive technique offers precise control of drug delivery to the eye, with various microneedle types showing the potential to penetrate barriers in the cornea and sclera, ensuring effective drug delivery. Recent advancements have improved safety and efficacy, offering sustained and controlled drug delivery for conditions like age-related macular degeneration and glaucoma. While promising, challenges such as regulatory barriers and long-term biocompatibility persist. Overcoming these through interdisciplinary research is crucial. Ultimately, microneedle drug delivery presents a revolutionary method with the potential to significantly enhance ocular disease treatment, marking a new era in eye care.

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

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

Modeling of Dissolving Microneedle-Based Transdermal Drug Delivery: Effects of Dynamics of Polymers in Solution

Dissolving microneedle (DMN)-assisted transdermal drug delivery (TDD) has received attention from the scientific community in recent years due to its ability to control the rate of drug delivery through its design, the choice of polymers, and its composition. The dissolution of the polymer depends strongly on the polymer-solvent interaction and polymer physics. Here, we developed a mathematical model based on the physicochemical parameters of DMNs and polymer physics to determine the drug release profiles. An annular gap width is defined when the MN is inserted in the skin, accumulating interstitial fluid (ISF) from the surrounding skin and acting as a boundary layer between the skin and the MN. Poly(vinylpyrrolidone) (PVP) is used as a model dissolving polymer, and ceftriaxone is used as a representative drug. The model agrees well with the literature data for ex vivo permeation studies, along with the percent height reduction of the MN. Based on the suggested mathematical model, when loading 0.39 mg of ceftriaxone, the prediction indicates that approximately 93% of the drug will be cleared from the bloodstream within 24 h. The proposed modeling strategy can be utilized to optimize drug transport behavior using DMNs.

Atorvastatin-Loaded Dissolving Microarray Patches for Long-Acting Microdepot Delivery: Comparison of Nanoparticle and Microparticle Drug Formulations

The increasing popularity of prolonged-release dosage forms, owing to their ability to provide continuous drug release after administration, has significantly improved patient compliance and overall quality of life. However, achieving prolonged release beyond 24 h frequently requires the use of invasive methods, including injections or implants, which may prove challenging for people suffering from needle phobia. This study introduces atorvastatin (ATR) microparticles (MPs) or nanocrystal (NCs) dissolving microarray patches (D-MAPs) as a noninvasive alternative for intradermal drug delivery over a two-week period for the management of hyperlipidemia. The MP-loaded D-MAPs exhibited an average drug loading of 5.15 ± 0.4 mg of ATR per patch, surpassing the 2.4 ± 0.11 mg/patch observed with NC-loaded D-MAPs. Skin deposition studies demonstrated the superior performance of MP D-MAPs, which delivered 2.0 ± 0.33 mg of ATR per 0.75 cm2 patch within 24 h, representing 38.76% of the initial amount of drug loaded. In contrast, NC D-MAPs delivered approximately 0.89 ± 0.12 mg of ATR per 0.75 cm2 patch at 24 h, equivalent to 38.42 ± 5.13% of the initial ATR loaded. Due to their favorable results, MP D-MAPs were chosen for an in vivo study using Sprague-Dawley rats. The findings demonstrated the capacity of D-MAPs to deliver and attain therapeutically relevant ATR concentrations (>20 ng/mL) for 14 days after a single 24-h application. This study is the first to successfully demonstrate the long-acting transdermal delivery of ATR using MP-loaded D-MAPs after a 24-h single-dose application. The innovative D-MAP system, particularly when loaded with MP, arises as a promising, minimally invasive, long-acting substitute for ATR delivery. This technology has the potential to improve patient compliance and therapeutic outcomes while also significantly advancing the field of transdermal drug delivery.

Panoramic review on polymeric microneedle arrays for clinical applications

Transdermal drug delivery (TDD) has significantly advanced medical practice in recent years due to its ability to prevent the degradation of substances in the gastrointestinal tract and avoid hepatic metabolism. Among different available approaches, microneedle arrays (MNAs) technology represents a fascinating delivery tool for enhancing TDD by penetrating the stratum corneum painless and minimally invasive for delivering antibacterial, antifungal, and antiviral medications. Polymeric MNAs are extensively utilized among many available materials due to their biodegradability, biocompatibility, and low toxicity. Therefore, this review provides a comprehensive discussion of polymeric MNAs, starting with understanding stratum corneum and developing MNA technology. Furthermore, the engineering concepts, fundamental considerations, challenges, and future perspectives of polymeric MNAs in clinical applications are properly outlined, offering a comprehensive and unique overview of polymeric MNAs and their potential for a broad spectrum of clinical applications.