Designing a unique feedback mechanism for hydrogel-forming microneedle array patches: a concept study

Hydrogel-forming microarray patches combined with powder-based reservoir for labetalol hydrochloride transdermal delivery

Hypertension is the most common pregnancy disorder and can lead to life-threatening conditions for both mother and fetus. However, managing this condition with oral and intravenous labetalol can be challenging, highlighting the need for alternative delivery methods. This study presents, for the first time, the development of novel powder-based reservoirs incorporated with hydrogel-forming microarray patches (MAPs) to facilitate the transdermal delivery of labetalol hydrochloride (HCl). A holder, created from poly(propylene) using a 3D printer, was designed to house labetalol HCl powder, which was then combined with hydrogel-forming MAPs. This novel system improved the insertion profile of MAPs into Parafilm® layers and excised full-thickness neonatal porcine skin, achieving up to 85 % of needle height penetration without compromising needle integrity (only 8 % height reduction after applying 32 N of force). The current holder design was able to load 50 mg of labetalol HCl and allowed for single or multiple injections of deionised water to dissolve the powder and facilitate permeation through dermatomed neonatal porcine skin in in vitro studies using a Franz cell setup. The results showed that this powder-based reservoir design delivered labetalol HCl more effectively over 24 h compared to directly compressed tablets. Additionally, poly(vinyl alcohol)/poly(vinyl pyrrolidone)/citric acid-based hydrogel-forming MAPs delivered more labetalol HCl than Gantrez® S-97/poly(ethylene glycol)-based MAPs (9 mg vs. 5 mg) in 24 h. This novel system holds promise for improving the delivery of compounds in a simple manner, though further design modifications for one-step application are needed.

Design of a Novel Delivery Efficiency Feedback System for Biphasic Dissolving Microarray Patches Based on Poly(Lactic Acid) and Moisture-Indicating Silica

Dissolving microarray patches (DMAPs) represent an innovative approach to minimally invasive transdermal drug delivery, demonstrating efficacy in delivering both small and large therapeutic molecules. However, concerns raised in end-user surveys have hindered their commercialization efforts. One prevalent issue highlighted in these surveys is the lack of clear indicators for successful patch insertion and removal time. To address this challenge, a color-change-based feedback system is devised, which confirms the insertion and dissolution of DMAPs, aiming to mitigate the aforementioned problems. The approach combines hydrophilic needles containing model drugs (fluorescein sodium and fluorescein isothiocyanate (FITC)-dextran) with a hydrophobic poly(lactic acid) baseplate infused with moisture-sensitive silica gel particles. The successful insertion and subsequent complete dissolution of the needle shaft are indicated by the progressive color change of crystal violet encapsulated in the silica. Notably, distinct color alterations on the baseplate, observed 30 min and 1 h after insertion for FITC-dextran and fluorescein sodium DMAPs respectively, signal the full dissolution of the needles, confirming the complete cargo delivery and enabling timely patch removal. This innovative feedback system offers a practical solution for addressing end-user concerns and may significantly contribute to the successful commercialization of DMAPs by providing a visualized drug delivery method.

Swellable Microneedles in Drug Delivery and Diagnostics

This manuscript explores the transformative potential of swellable microneedles (MNs) in drug delivery and diagnostics, addressing critical needs in medical treatment and monitoring. Innovations in hydrogel-integrated MN arrays facilitate controlled drug release, thereby expanding treatment options for chronic diseases and conditions that require precise dosage control. The review covers challenges, such as scalability, patient compliance, and manufacturing processes, as well as achievements in advanced manufacturing, biocompatibility, and versatile applications. Nonetheless, limitations in physiological responsiveness and long-term stability remain, necessitating further research in material innovation and integration with digital technologies. Future directions focus on expanding biomedical applications, material advancements, and regulatory considerations for widespread clinical adoption.

mRNA nanodelivery systems: targeting strategies and administration routes

With the great success of coronavirus disease (COVID-19) messenger ribonucleic acid (mRNA) vaccines, mRNA therapeutics have gained significant momentum for the prevention and treatment of various refractory diseases. To function efficiently in vivo and overcome clinical limitations, mRNA demands safe and stable vectors and a reasonable administration route, bypassing multiple biological barriers and achieving organ-specific targeted delivery of mRNA. Nanoparticle (NP)-based delivery systems representing leading vector approaches ensure the successful intracellular delivery of mRNA to the target organ. In this review, chemical modifications of mRNA and various types of advanced mRNA NPs, including lipid NPs and polymers are summarized. The importance of passive targeting, especially endogenous targeting, and active targeting in mRNA nano-delivery is emphasized, and different cellular endocytic mechanisms are discussed. Most importantly, based on the above content and the physiological structure characteristics of various organs in vivo, the design strategies of mRNA NPs targeting different organs and cells are classified and discussed. Furthermore, the influence of administration routes on targeting design is highlighted. Finally, an outlook on the remaining challenges and future development toward mRNA targeted therapies and precision medicine is provided.