Functionalization of Poly-L-Lactic Acid Microneedle Tips using Hydrogel Photopolymerization

Although the diagnostic utility of interstitial fluid (ISF) has been extensively explored, collecting and sensing ISF in the body remains challenging. Microneedle devices offer a promising approach for minimally invasive methods to obtain ISF with a small volume or to sense biomolecules in the ISF within the body. In this study, we developed a microneedle with a small volume hydrogel block at the needle tip. The hydrogel block was formed through a photopolymerization reaction of polyethylene glycol diacrylate (PEGDA) under 365 nm irradiation. The hydrogel block measured 100 mu m in diameter and 100 mu m in length, with a total volume of 0.79 nL. The fabricated microneedle had a high-aspect ratio shape (500 mu m in base diameter, 200 mu m in top diameter, and 2000 mu m in length), reaching the reticular layer containing blood vessels. Therefore, microneedle devices can be utilized to obtain ISF with a small volume and to sense biomolecules within the body.