Preparation of a novel hyaluronic acid-based separable hydrogel microneedle with niacinamide to treat pigment deposition using solvent-free solid-state crosslinking method

With the increase in age and prolonged exposure to ultraviolet radiation, especially on the face, pigment deposition often has a negative impact on individuals physically and emotionally. In order to address this issue, a solvent-free solid-state crosslinked hyaluronic acid (HA)-based separable hydrogel microneedle (SHMN) was developed by combining the advantages of hydrogel microneedle and soluble microneedle. This microneedle could separate the needle tip from the backing within five minutes and had the advantage of slow drug release. Hydrogel microneedle tips were prepared by solid-state crosslinking method of HA and poly (methyl vinyl ether)-maleic acid (GAN) for the first time. This crosslinking method without the need for dialysis or the addition of organic solvents, making it a safer, more reliable, and significantly time-saving process compared to previous methods. The soluble material polyvinylpyrrolidone (PVP) was selected as the root and backing of the microneedle. When the microneedle penetrated the skin and contacted with interstitial fluid, the bottom of the microneedle dissolved, and the tip of hydrogel loaded with drugs was separated from the shaft. In addition, the microneedle patch has high drug loading and excellent mechanical properties, which can meet the effective treatment of skin pigmentation.