Dissolving and Swelling Hydrogel-Based Microneedles: An Overview of Their Materials, Fabrication, Characterization Methods, and Challenges

Abstract

Polymeric hydrogels are a complex class of materials with one common feature—the ability to form three-dimensional networks capable of imbibing large amounts of water or biological fluids without being dissolved, acting as self-sustained containers for various purposes, including pharmaceutical and biomedical applications. Transdermal pharmaceutical microneedles are a pain-free drug delivery system that continues on the path to widespread adoption—regulatory guidelines are on the horizon, and investments in the field continue to grow annually. Recently, hydrogels have generated interest in the field of transdermal microneedles due to their tunable properties, allowing them to be exploited as delivery systems and extraction tools. As hydrogel microneedles are a new emerging technology, their fabrication faces various challenges that must be resolved for them to redeem themselves as a viable pharmaceutical option. This article discusses hydrogel microneedles from a material perspective, regardless of their mechanism of action. It cites the recent advances in their formulation, presents relevant fabrication and characterization methods, and discusses manufacturing and regulatory challenges facing these emerging technologies before their approval.

Hydrogel Microneedles with Programmed Mesophase Transitions for Controlled Drug Delivery

“…A tension/compression tester consisting of a motorized vertical test stand equipped with a digital force gauge (PCE-VTS 50-DFG N 500) was employed (PCE Instruments UK Ltd., Manchester, U.K.). In this test, the MN samples were glued to the moving probe of the machine and were pressed against fixed chicken skin at a rate of 1 mm/min, until the desired normal force of 20 N was achieved (on average 200 mN/needle), followed by 30 s waiting dwell time under the loaded state, followed by withdrawing the upper holder that holds the MN samples in the opposite normal direction. ,,, Continuous force and displacement measurements were recorded to identify the point of needle insertion. The curves of force versus displacement were generated for each test, and the average insertion force was determined from 5 independent measurements.…”

“…In this test, the MN samples were glued to the moving probe of the machine and were pressed against fixed chicken skin at a rate of 1 mm/min, until the desired normal force of 20 N was achieved (on average 200 mN/needle), followed by 30 s waiting dwell time under the loaded state, followed by withdrawing the upper holder that holds the MN samples in the opposite normal direction. 11 , 14 , 35 , 36 Continuous force and displacement measurements were recorded to identify the point of needle insertion. The curves of force versus displacement were generated for each test, and the average insertion force was determined from 5 independent measurements.…”

Research Progress of Extracellular Vesicles-Loaded Microneedle Technology

“…Materials used to prepare MNs include silicon [ 73 ], metal [ 6 ], ceramics [ 74 ], silica glass [ 2 ], silk proteins [ 75 ], polymers [ 76 ], etc., which have been summarized in detail in many reviews [ 3 , 27 , 77 ]. Polymer MNs have received more attention in recent years, and here, we focus on new advances in the preparation of MNs from this material.…”

Advances in electrochemical sensors for real-time glucose monitoring

“…9b) for in situ analysis of interstitial fluid, particularly focusing on glucose and lactate monitoring. The MNs, made from methacrylated hyaluronic acid (MeHA), known for its exceptional swelling capacity and mechanical robustness, 119 were selected for their effectiveness in extracting ISF. The sensitivity of the sensor against glucose and lactate was evaluated using benchtop and in vivo assessment methods.…”