Hydroxyethyl methacrylate hydrogel microneedles with high mechanical strength and skin penetration by template method

This study employed the template method to fabricate microneedle (MN) arrays from hydroxyethyl methacrylate (HEMA) hydrogel: a high-drug-load pyramid-shaped microneedle array (MN-A) and a low-pain volcano-shaped microneedle array (MN-B). In addition, a pen-tip-shaped microneedle array (MN-C) was developed on the basis of the characteristics of the aforementioned two types of arrays. The results indicated that HEMA hydrogel, when photopolymerized under a fixed ultraviolet A (365 nm) intensity of 25 mW/cm² for 15 min, achieved optimal polymerization, with its elongation, moisture content, oxygen permeability, and maximum load-bearing capacity being 80%, 55.1%, 22.8 barrer, and 96.5 gf/cm², respectively. In addition, when the three microneedle arrays were fabricated from HEMA hydrogel under the aforementioned optimal process parameters, they exhibited penetration diameters of less than 500 μm and penetration depths of 300–600 μm in pig ear piercing experiments. Among the three microneedle arrays, the MN-A array exhibited the highest drug load and effective penetration depth, whereas the MN-B array exhibited the smallest wound area, thereby effectively reducing tingling sensation. The MN-C array, which was an improvement over the MN-A and MN-B arrays, not only exhibited the highest penetration stress (3.9 mN) but also retained the high drug load and low tingling sensation characteristics of the other two arrays. These findings suggest that microneedles produced from HEMA hydrogel by using the template method not only possess excellent mechanical stability and skin penetration capabilities but also have high potential for use in applications related to dermatology and cosmetology.