Microneedle-iontophoresis combinations for enhanced transdermal drug delivery

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.

Microneedle-Mediated Treatment of Obesity

Obesity has become a major public health threat, as it can cause various complications such as diabetes, cardiovascular disease, sleep apnea, cancer, and osteoarthritis. The primary anti-obesity therapies include dietary control, physical exercise, surgical interventions, and drug therapy; however, these treatments often have poor therapeutic efficacy, significant side effects, and unavoidable weight rebound. As a revolutionized transdermal drug delivery system, microneedles (MNs) have been increasingly used to deliver anti-obesity therapeutics to subcutaneous adipose tissue or targeted absorption sites, significantly enhancing anti-obese effects. Nevertheless, there is still a lack of a review to comprehensively summarize the latest progress of MN-mediated treatment of obesity. This review provides an overview of the application of MN technology in obesity, focusing on the delivery of various therapeutics to promote the browning of white adipose tissue (WAT), suppress adipogenesis, and improve metabolic function. In addition, this review presents detailed examples of the integration of MN technology with iontophoresis (INT) or photothermal therapy (PTT) to promote drug penetration into deeper dermis and exert synergistic anti-obese effects. Furthermore, the challenges and prospects of MN technology used for obesity treatment are also discussed, which helps to guide the design and optimization of MNs. Overall, this review provides insight into the development and clinical translation of MN technology for the treatment of obesity.

Tailoring Design of Microneedles for Drug Delivery and Biosensing

Microneedles (MNs) are emerging as versatile tools for both therapeutic drug delivery and diagnostic monitoring. Unlike hypodermic needles, MNs achieve these applications with minimal or no pain and customizable designs, making them suitable for personalized medicine. Understanding the key design parameters and the challenges during contact with biofluids is crucial to optimizing their use across applications. This review summarizes the current fabrication techniques and design considerations tailored to meet the distinct requirements for drug delivery and biosensing applications. We further underscore the current state of theranostic MNs that integrate drug delivery and biosensing and propose future directions for advancing MNs toward clinical use.

Current Status of Microneedle Array Technology for Therapeutic Delivery: From Bench to Clinic

In recent years, microneedle (MN) patches have emerged as an alternative technology for transdermal delivery of various drugs, therapeutics proteins, and vaccines. Therefore, there is an urgent need to understand the status of MN-based therapeutics. The article aims to illustrate the current status of microneedle array technology for therapeutic delivery through a comprehensive review. However, the PubMed search was performed to understand the MN's therapeutics delivery status. At the same time, the search shows the number no of publications on MN is increasing (63). The search was performed with the keywords "Coated microneedle," "Hollow microneedle," "Dissolvable microneedle," and "Hydrogel microneedle," which also shows increasing trend. Similarly, the article highlighted the application of different microneedle arrays for treating different diseases. The article also illustrated the current status of different phases of MN-based therapeutics clinical trials. It discusses the delivery of different therapeutic molecules, such as drug molecule delivery, using microneedle array technology. The approach mainly discusses the delivery of different therapeutic molecules. The leading pharmaceutical companies that produce the microneedle array for therapeutic purposes have also been discussed. Finally, we discussed the limitations and future prospects of this technology.

Transcutaneous Delivery of Dexamethasone Sodium Phosphate Via Microneedle-Assisted Iontophoretic Enhancement - A Potential Therapeutic Option for Inflammatory Disorders

AIM

This study aimed to fabricate dexamethasone sodium phosphate loaded microneedle arrays (MNA) and investigate their efficiency in combination with iontophoresis for the treatment of hind paw oedema in rats.

METHODS

Drug loaded polyvinyl alcohol, polyvinyl pyrrolidone and D-sorbitol-based MNA11 were fabricated by vacuum micromolding. Physicochemical, morphological, thermal, in-silico, in-vitro insertion ability (on parafilm) and drug release studies were performed. Ex-vivo permeation, in-vivo insertion and anti-inflammatory studies were performed in combination with iontophoresis.

RESULTS

MNA11 displayed sharp-tipped projections and acceptable physicochemical features. Differential scanning calorimetry results indicated that drug loaded MNA11 were amorphous solids. Drug interacted with PVP and PVA predominately via hydrogen bonding. Parafilm displayed conspicuously engraved complementary structure of MNA11. Within 60 min, 91.50 ± 3.1% drug released from MNA11. A significantly higher i.e., 95.06 ± 2.5% permeation of drug was observed rapidly (within 60 min) from MNA11-iontophoresis combination than MNA11 i.e., 84.07 ± 3.5% within 240 min. Rat skin treated using MNA11 and MNA11-iontophoresis showed disruptions / microchannels in the epidermis without any damage to underlying anatomical structures. MNA11-iontophoresis combination led to significant reduction (83.02 ± 3.9%) in paw oedema as compared to MNA11 alone (72.55 ± 4.1%).

CONCLUSION

MNA11-iontophoresis combination can act as a promising candidate to deliver drugs transcutaneously for treating inflammatory diseases.

Protein-based microneedles for biomedical applications: A systematic review

Microneedles are minimally-invasive devices with the unique capability of bypassing physiological barriers. Hence, they are widely used for different applications from drug/vaccine delivery to diagnosis and cosmetic fields. Recently, natural biopolymers (particularly carbohydrates and proteins) have garnered attention as safe and biocompatible materials with tailorable features for microneedle construction. Several review articles have dealt with carbohydrate-based microneedles. This review aims to highlight the less-noticed role of proteins through a systematic search strategy based on the PRISMA guideline from international databases of PubMed, Science Direct, Scopus, and Google Scholar. Original English articles with the keyword "microneedle(s)" in their titles along with at least one of the keywords "biopolymers, silk, gelatin, collagen, zein, keratin, fish-scale, mussel, and suckerin" were collected and those in which the proteins undertook a structural role were screened. Then, we focused on the structures and applications of protein-based microneedles. Also, the unique features of some protein biopolymers that make them ideal for microneedle construction (e.g., excellent mechanical strength, self-adhesion, and self-assembly), as well as the challenges associated with them were reviewed. Altogether, the proteins identified so far seem not only promising for the fabrication of "better" microneedles in the future but also inspiring for designing biomimetic structural biopolymers with ideal characteristics.

Intradermal Delivery of Naked mRNA Vaccines via Iontophoresis

Messenger RNA (mRNA) vaccines against infectious diseases and for anticancer immunotherapy have garnered considerable attention. Currently, mRNA vaccines encapsulated in lipid nanoparticles are administrated via intramuscular injection using a needle. However, such administration is associated with pain, needle phobia, and lack of patient compliance. Furthermore, side effects such as fever and anaphylaxis associated with the lipid nanoparticle components are also serious problems. Therefore, noninvasive, painless administration of mRNA vaccines that do not contain other problematic components is highly desirable. Antigen-presenting cells reside in the epidermis and dermis, making the skin an attractive vaccination site. Iontophoresis (ItP) uses weak electric current applied to the skin surface and offers a noninvasive permeation technology that enables intradermal delivery of hydrophilic and ionic substances. ItP-mediated intradermal delivery of biological macromolecules has also been studied. Herein, we review the literature on the use of ItP technology for intradermal delivery of naked mRNA vaccines which is expected to overcome the challenges associated with mRNA vaccination. In addition to the physical mechanism, we discuss novel biological mechanisms of iontophoresis, particularly ItP-mediated opening of the skin barriers and the intracellular uptake pathway, and how the combined mechanisms can allow for effective intradermal delivery of mRNA vaccines.

Improved Transdermal Delivery of Rabies Vaccine using Iontophoresis Coupled Microneedle Approach

AIM

This study was aimed to develop rabies vaccine incorporated microneedle (MN) patches and evaluate the immunogenicity of prepared formulations in combination with iontophoresis.

METHODS

Patches comprising of polyvinyl pyrrolidone, hyaluronic acid and polyethylene glycol 400 were engineered by vacuum micromolding technique. Physical evaluation of patches included determination of folding endurance, % swelling and morphological features. In vitro release study was performed in skin simulant agarose gel using model drug (methylene blue) loaded patches. In vitro insertion ability was assessed using stratum corneum simulant parafilm. In vivo insertion study was performed in rats. Immunogenicity was evaluated in dogs by determining immunoglobulin G (IgG) and rabies virus neutralizing antibodies (RVNA) titer.

RESULTS

Patches displayed uniformly distributed microprojections with pointed tips and smooth surface,  ~ 70% swelling, remained intact for  ~ 200 foldings and successfully penetrated the parafilm. The area covered by model drug across agarose gel was almost double following treatment with MN-iontophoresis combination (MNdi) compared to MN alone (MNdo). Histological examination of rat skin treated with vaccine laden MN (MNvo) and MN-iontophoresis combination (MNvi) confirmed the formation of grooves in epidermis without any damage to the deep vasculature. A ~ 73% and  ~ 206% increase (compared to untreated counterpart) was observed in the IgG titer of MNvo and MNvi treated dogs, respectively. The RVNA titer was increased by  ~ 1.2 and  ~ 2.2 times (compared to threshold value) after MNvo and MNvi treatment, respectively.

CONCLUSION

MN-iontophoresis combination provided relatively potent immunogenic response over the conventional intramuscular injection, hence, can be used for administering vaccines transcutaneously.

Bibliometric and visualized analysis of ocular drug delivery from 2001 to 2020

OBJECTIVE

To perform a bibliometric analysis in the field of ocular drug delivery research to characterize the current international trends and to present visual representations of the past and emerging trends on ocular drug delivery research over the past decade.

METHOD

In this cross-sectional study, a bibliometric analysis of data retrieved and extracted from the Web of Science Core Collection (WoSCC) database was performed to analyze evolution and theme trends on ocular drug delivery research from January 1, 2001, to December 31, 2020. A total of 4334 articles on ocular drug delivery were evaluated for specific characteristics, such as publication year, journals, authors, institutions, countries/regions, references, and keywords. Co-authorship analysis, co-occurrence analysis, co-citation analysis, and network visualization were constructed by VOSviewer. Some important subtopics identified by bibliometric characterization were further discussed and reviewed.

RESULTS

From 2001 to 2020, the annual global publications increased by 746.15%, from 52 to 440. International Journal of Pharmaceutics published the most manuscripts (250 publications) and produced the highest citations (9509 citations), followed by Investigative Ophthalmology & Visual Science (202 publications) and Journal of Ocular Pharmacology and Therapeutics (136 publications). The United States (1289 publications, 31,512 citations), the University of Florida (82 publications, 2986 citations), and Chauhan, Anuj (52 publications, 2354 citations) were the most productive and impactful institution, country, and author respectively. The co-occurrence cluster analysis of the top 100 keywords form five clusters: (1) micro/nano ocular drug delivery systems; (2) the treatment of inflammation and posterior diseases; (3) macroscopic ocular drug delivery systems/devices; (4) the characteristics of drug delivery systems; (5) and the ocular drug delivery for glaucoma treatment. Diabetic macular edema, anti-VEGF, ranibizumab, bevacizumab, micelles and latanoprost, were the latest high-frequency keywords, indicating the emerging frontiers of ocular drug delivery. Further discussions into the subtopics were provided to assist researchers to determine the range of research topics and plan research direction.

CONCLUSIONS

Over the last two decades there has been a progressive increase in the number of publications and citations on research related to ocular drug delivery across many countries, institutions, and authors. The present study sheds light on current trends, global collaboration patterns, basic knowledge, research hotspots, and emerging frontiers of ocular drug delivery. Novel solutions for ocular drug delivery and the treatment of inflammation and posterior diseases were the major themes over the last 20 years.

Neoteric direct physical approaches in tdds: a boon for permeation enhancement

Abstract:

Human skin has been tremendously explored for decades as a potential route for the delivery of various substances. It has shown great applications to deliver drugs to systemic circulation as well as has provided adequate advantages to treat local manifestations over the skin. However, the rigid stratum corneum layer has served as the biggest barrier in transdermal drug delivery; various methods have been designed to overcome the stratum corneum layer and make the molecule pass through this. These methods were then broadly classified into chemical and physical approaches. The below study is an overall review of the physical approaches being used in transdermal drug delivery for overcoming the stratum corneum layer. Physical approaches also include direct and indirect methods; we will be physically considering the direct approaches herein.

Microneedle system: a modulated approach for penetration enhancement

The microneedles show advantages over transdermal drug delivery systems on account of better skin permeation bypassing the stratum corneum. To increase the flux of permeation, penetration enhancement techniques like physical and chemical methods are combined with a trans-epidermal delivery system across the skin causing minimal pain. These techniques include iontophoresis, sonophoresis, and electroporation for physical enhancement of drug delivery via topical route by either disrupting the structure of the stratum corneum or by creating pores/micro-channels within the skin. The use of chemical penetrants such as ethanol, lipids, surfactants, and terpenes improves the release kinetics by mechanisms like fluidization of lipids, denaturation of proteins, etc. A combination of microneedles and these techniques show a significant increase in the permeability of drugs across the skin by 5-10 times compared to microneedles alone. This review article focuses on various advanced strategies like the use of drug-polymer complexes, application of ultrasound frequency or tolerable electric current, formation of nano-formulations, etc. with microneedle delivery for transportation of high payload of actives, macromolecules, antibodies, gene, proteins, and peptides. In the near future, microneedle systems will offer potential targeted drug delivery, self-sealable administration across the skin, and minimally invasive vaccine transportation in cancer, diabetes, Alzheimer's, and cardiovascular diseases.HighlightsPhysical penetration enhancement techniques: iontophoresis, electroporation, and sonophoresis.Chemical penetration enhancers: polymers, lipids, surfactants.Strategies to use microneedle system with penetration enhancement techniques.The significant difference in the penetration ability of high payload actives.

Wearable patch delivery system for artificial pancreas health diagnostic-therapeutic application: A review

The advanced stimuli-responsive approaches for on-demand drug delivery systems have received tremendous attention as they have great potential to be integrated with sensing and multi-functional electronics on a flexible and stretchable single platform (all-in-one concept) in order to develop skin-integration with close-loop sensation for personalized diagnostic and therapeutic application. The wearable patch pumps have evolved from reservoir-based to matrix patch and drug-in-adhesive (single-layer or multi-layer) type. In this review, we presented the basic requirements of an artificial pancreas, surveyed the design and technologies used in commercial patch pumps available on the market and provided general information about the latest wearable patch pump. We summarized the various advanced delivery strategies with their mechanisms that have been developed to date and representative examples. Mechanical, electrical, light, thermal, acoustic and glucose-responsive approaches on patch form have been successfully utilized in the controllable transdermal drug delivery manner. We highlighted key challenges associated with wearable transdermal delivery systems, their research direction and future development trends.

An Overview of Drug Delivery Systems

This is an overview of the current drug delivery systems (DDSs) starting with various routes of drug administration. Various drug formulations are then described as well as devices used for drug delivery and targeted drug delivery. There has been a considerable increase in the number of new biotechnology-based therapeutics. Most of these are proteins and peptides, and their delivery present special challenges. Cell and gene therapies are sophisticated methods of delivery of therapeutics. Nanoparticles are important for refining drug delivery. In addition to being vehicles for drug delivery, nanoparticles can be used as pharmaceuticals as well as diagnostics. Most of the advances in targeted drug delivery have occurred in therapy of cancer. Drug delivery to the brain across the blood-brain barrier presents many challenges. Refinements in drug delivery will facilitate the development of personalized medicine. The ideal DDS is defined. Commercial aspects, challenges, and future of DDSs are discussed.

Topical and Transdermal Drug Delivery: From Simple Potions to Smart Technologies

This overview on skin delivery considers the evolution of the principles of percutaneous ab-sorption and skin products from ancient times to today. Over the ages, it has been recognised that products may be applied to the skin for either local or systemic effects. As our understanding of the anatomy and physiology of the skin has improved, this has facilitated the development of technologies to effectively and quantitatively deliver solutes across this barrier to specific target sites in the skin and beyond. We focus on these technologies and their role in skin delivery today and in the future.

Topical and cutaneous delivery using nanosystems

The goal of topical and cutaneous delivery is to deliver therapeutic and other substances to a desired target site in the skin at appropriate doses to achieve a safe and efficacious outcome. Normally, however, when the stratum corneum is intact and the skin barrier is uncompromised, this is limited to molecules that are relatively lipophilic, small and uncharged, thereby excluding many potentially useful therapeutic peptides, proteins, vaccines, gene fragments or drug-carrying particles. In this review we will describe how nanosystems are being increasingly exploited for topical and cutaneous delivery, particularly for these previously difficult substances. This is also being driven by the development of novel technologies, which include minimally invasive delivery systems and more precise fabrication techniques. While there is a vast array of nanosystems under development and many undergoing advanced clinical trials, relatively few have achieved full translation to clinical practice. This slow uptake may be due, in part, to the need for a rigorous demonstration of safety in these new nanotechnologies. Some of the safety aspects associated with nanosystems will be considered in this review.

Delivery of large molecular protein using flat and short microneedles prepared using focused ion beam (FIB) as a skin ablation tool

Many studies have been reported in the literature on the effects of various geometries and lengths of microneedles (MNs) on transdermal drug delivery using a variety of drug molecules. In particular, sharp-tipped MNs have been used to disrupt the top layer of the skin, namely, stratum corneum (SC). It has also been shown that short- and flat-tipped MNs can pierce the SC and they have the potential to increase drug permeability. However, there is little work that explores MNs as a skin ablative tool with a view to increasing skin permeability. To address this point, well-defined small patterns (size of individual pattern 10–20 μm) on the tip of flat MN (tip radius of individual MN ∼250 μm) were created and their effects evaluated on the permeability of bovine serum albumin (BSA), which is chosen as a model drug of high molecular weight. The patterns on the tip of flat MN act as rough surfaces (e.g. like sand paper) which when applied on the surface of the skin ablate the SC layer. Focused ion beam (FIB) has been used as the fabrication technique for the MNs. The permeability data are then compared with the other data for flat- and sharp-tipped MN. The permeability data from passive diffusion experiments are used as the reference case. The exact number of MNs or patterns in the flat and patterned MN patches is not considered as important as they have not been designed to pierce the skin. However, this is an important consideration in the case of sharp MNs as they pierce and create cavities in the skin. It is found that the delivery of BSA with the fabricated flat and patterned MNs gave similar but somewhat lower drug permeation profile in comparison to the sharp MNs. Passive diffusion showed no permeation, as would be expected due to the large size of the chosen molecule.

Biodegradable and conductive chitosan–graphene quantum dot nanocomposite microneedles for delivery of both small and large molecular weight therapeutics

Chitosan–graphene quantum dot nanocomposites are used in microneedle arrays for transdermal delivery of small and large molecular weight drugs.

The role of microneedles for drug and vaccine delivery

INTRODUCTION

Transdermal drug delivery offers a number of advantages for the patient, not only due to its non-invasive and convenient nature, but also due to factors such as avoidance of first-pass metabolism and prevention of gastrointestinal degradation. It has been demonstrated that microneedles (MNs) can increase the number of compounds amenable to transdermal delivery by penetrating the skin's protective barrier, the stratum corneum, and creating a pathway for drug permeation to the dermal tissue below.

AREAS COVERED

MNs have been extensively investigated for drug and vaccine delivery. The different types of MN arrays and their delivery capabilities are discussed in terms of drugs, including biopharmaceutics and vaccines. Patient usage and effects on the skin are also considered.

EXPERT OPINION

MN research and development is now at the stage where commercialisation is a viable possibility. There are a number of long-term safety questions relating to patient usage which will need to be addressed moving forward. Regulatory guidance is awaited to direct the scale-up of the manufacturing process alongside provision of clearer patient instruction for safe and effective use of MN devices.