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In this study, dissolving microneedles (MNs) using polyvinyl alcohol (PVA) and poly (1-vinylpyrrolidone-co-vinyl acetate) (P(VP-co-VA)) as matrix materials were developed for transdermal delivery of rizatriptan benzoate (RB) for acute migraine treatment. In-vitro permeation studies were conducted to assess the feasibility of the as-fabricated dissolving MNs to release RB. Drug skin penetration were tested by Franz diffusion cells, showing an increase of the transdermal flux compared to passive diffusion due to the as-fabricated dissolving MNs having a sufficient mechanical strength to penetrate the skin and form microchannels. The pharmacological study in vivo showed that RB-loaded dissolving MNs significantly alleviated migraine-related response by up-regulating the level of 5-hydroxytryptamine (5-HT) and down-regulating the levels of calcitonin gene-related peptide (CGRP) and substance P (SP). In conclusion, the RB-loaded dissolving MNs have advantages of safety, convenience, and high efficacy over conventional administrations, laying a foundation for the transdermal drug delivery system treatment for acute migraine. [ABSTRACT FROM AUTHOR]

In the past two decades, microneedles (MNs) patches as a promising platform have been extensively investigated for transdermal delivery of drug drugs, cells, and active substances and extraction of bio‐fluids. To realize painless, efficacious, and safe transdermal delivery, these MNs must penetrate the skin to the appropriate depth without breaking or bending. Therefore, effective prediction of mechanical properties such as skin penetration of microneedles is crucial for the material and structural design of MNs. In this article, a numerical simulation of the insertion process of the microneedle into various types of skin modeling is reported using the finite element method. The effective stress failure criterion has been coupled with the element deletion technique to predict the complete insertion process. The numerical results show a good agreement with the reported experimental data for the deformation and failure of the skin and the insertion force. [ABSTRACT FROM AUTHOR]

In recent years, transdermal drug delivery based on microneedles (MNs) technology has received extensive attention, which offers a safer and painless alternative to hypodermic needle injections. They can pierce the stratum corneum and deliver drugs to the epidermis and dermis‐structures of skin, showing prominent properties such as minimally invasiveness, bypassing first‐pass metabolism, and can be self‐administered. A range of materials has been used to fabricate MNs, such as silicon, metal, glass, and polymers. Among them, polymer MNs have gained increasing attention from pharmaceutical and cosmetic companies as one of the promising drug delivery methods. MN products have recently become available on the market, and some of them are under evaluation for efficacy and safety. This paper focuses on the current state of polymer MNs in drug transdermal delivery. The materials and methods for the fabrication of polymer MNs and their drug administration are described. The recent progress of polymer MNs for treatment of cancer, vaccine delivery, blood glucose regulation, androgenetic alopecia, obesity, tissue healing, myocardial infarction, and gout are reviewed. The challenges of MNs technology are summarized and the future development trend of MNs is also prospected. [ABSTRACT FROM AUTHOR]

[Display omitted] • Hollow-adjustable polymer MNs were developed by cyclic freeze-thawing technique. • The obtained MNs had sufficient mechanical strength and drug-loading capacity. • A notable hypoglycemic effect up to 14 h in vivo could be obtained. • The obtained MNs can be used a potential candidate for transdermal delivery of high-dose drugs. Maintaining blood glucose levels within a safe range is critical for diabetic management. In recent decades, microneedles (MNs) have emerged as a potential method for delivering drugs to treat diabetes. However, insufficient drug loading and the complexity of achieving long-acting release have presented challenges that research has not addressed well. In this study, the hollow-adjustable biocompatible polymer MNs with varying cavity volumes were developed by cyclic freeze-thawing technique. The structure of shell-layer of hollow MNs was optimized with a sequential casting approach for regulating drug release kinetics. This design can ensure the sufficient mechanical strength of MNs and help to improve the drug-loading capacity, thereby solving the problem of low drug-loading capacity and short pharmacodynamic action time of traditional polymer MNs. In vivo experiments performed on diabetic rat models revealed the potential of the as-fabricated MNs to effectively pierce into the skin, leading to a notable hypoglycemic effect lasting up to 14 h without inducing the risk of hypoglycemia. These results indicate that the fabricated hollow-adjustable polymer MNs is a potential candidate for transdermal delivery of high-dose drugs. [ABSTRACT FROM AUTHOR]

[Display omitted] • Microneedle transdermal drug delivery has the advantages of minimally invasive, safe and efficient. • The core–shell type microneedle is obtained by a vacuuming and hot melting strategy. • The microneedle system is designed to release drugs quickly and improve the utilization rate of drugs. • The photothermal conversion efficiency of Cu-PDA NPs is increased to 50.40%. • Transdermal delivery of Cu-PDA NPs using MNs exhibited PTT-CDT synergistic therapy against skin melanoma. Multimodal nanoformulations with limited side-effects for tumor theranostics that catalyze a cascade of intracellular reactions show great potentials for tumor treatment with high specificity and efficiency. In this study, Cu-doped polydopamine nanoparticles (Cu-PDA NPs) have been prepared and embedded into microneedles (MNs) for photothermal and chemodynamic synergistic therapy against skin melanoma, by virtue of enhanced drug transdermal delivery owing to the unique core–shell structure of MNs. This multimodal tumor therapeutic strategy accumulates the high photothermal effect of Cu-PDA NPs (~50.40%) to acquire the energy from NIR irradiation and convert it into heat, and good Fenton-like catalytic activity of Cu+ ions to produce toxic free hydroxyl groups (‧OH) by reaction with excessive H 2 O 2 in tumor cells, leading to the generation of a new minimally invasive synergistic therapy. The B16F10 mouse melanoma model demonstrates that the active delivery of Cu-PDA NPs results in greatly inhibit proliferation of tumor and induce mixed necrosis/apoptosis of tumor cells in vivo. This study offers a new avenue for the development of microneedles-based microdevices for skin melanoma by a minimally invasive delivery of multimodal nanoformulation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Polymer microneedles (MNs) have been prepared for transdermal delivery of drugs. • Free Met and Met-loaded BGNs were encapsulated into MNs for a sustained drug release. • MNs with integration of free and loaded Met exhibit a significant hypoglycemic effect. Transdermal delivery provides a suitable and painless self-administration for diabetic patients. In this work, the polymer microneedles (MNs) integrated with mesoporous bioactive glass nanoparticles (BGNs) for transdermal delivery of metformin (Met) have been developed for regulation of blood glucose levels (BGLs) on diabetic rats. The obtained MNs system contains free Met and Met-loaded BGNs (Met/BGNs) for independently controlling the kinetics of anti-diabetic drug during the treatment. Once these MNs are penetrated into the skin, the free Met is firstly released due to the swelling and degradation of matrix material of MNs. And then the loaded Met is slowly seep through the microchannels of BGNs to form a sustained drug release behaviors and a better hypoglycemic effect, suggesting the potential of this new transdermal delivery system as substitutes for multiple daily injections. [ABSTRACT FROM AUTHOR]

In this work, the rapidly separable microneedles (MNs) consisted of needle-tips and supporting bases have been fabricated by a step-by-step coating method. Poly (vinyl alcohol) (PVA) have been used to prepare the needle-tips of MNs in which they are capped on the solvable supporting bases consisted of sodium bicarbonate, poly (vinyl pyrolidone) (PVP), and tartaric acid (TA) (NaHCO 3 /PVP/TA). After insertion into the skin, the needle-tips can be separated rapidly from the patches within 90 s due to the generation of air bubbles in the supporting bases by the reaction between NaHCO 3 and TA after absorption of tissue fluid, leading to the needle-tips remaining in the skin tissue. Metformin, a hypoglycemic drug, encapsulated in the needle-tips of MNs can be released due to swelling and decomposition of PVA by the absorption of tissue fluid. To investigate the pharmacological effect via transdermal delivery route, metformin-loaded MNs are applied on the diabetic SD rats induced by streptozotocin (STZ). They exhibit a longer hypoglycemic effect in vivo than that of subcutaneous injection. These results indicated the as-fabricated rapidly separable MNs present a promising platform for transdermal delivery of drugs against diabetic patients. [Display omitted] • Rapidly separable microneedles (MNs) have been fabricated by a step-by-step coating method. • Metformin has been encapsulated in the needle-tips of MNs. • The as-fabricated MNs exhibit a longer hypoglycemic effect on the diabetic SD rat. • This work provided a remarkable hypoglycemic effect. [ABSTRACT FROM AUTHOR]