A flexible hydrogel microneedle patch-mediated electrochemical sensor for rapid and minimally invasive fentanyl...

Rapid sampling and monitoring of fentanyl and its analogues is of great significance for drug control and enforcement. Conventional fentanyl detection techniques require sophisticated pre-treatment and bulky instruments, limiting their applications in wearable fentanyl monitoring. Microneedle-based electrochemical sensors provide rapid and facile detection of small molecules and drugs in skin interstitial fluid with high sensitivity, decent selectivity, and low detection limits. However, they suffered from insufficient geometries, mechanical flexibility, and device integrity, affecting applications for wearable minimally invasive fentanyl detection. Herein, a methacrylated hyaluronic acid/polyvinyl alcohol (MeHA/PVA) composite hydrogel microneedle patch was prepared by templated molding, exhibiting good mechanical strength exceeding 0.1 N/needle and decent swelling property of 400%. Such a MeHA/PVA microneedle patch could be intimately integrated with the screen-printed electrochemical fentanyl sensor, which has a linear range of 10 - 100 μM, a good sensitivity of 0.3 μA μM^-1, a low detection limit of 4.4 μM, and excellent selectivity. More importantly, due to strong interfacial adhesion, the integrated microneedle-mediated electrochemical sensor exhibited good mechanical flexibility, which effectively extracted fentanyl from a phantom skin model while simultaneously detecting its concentration. This demonstrated the great potential of the proposed device for wearable and minimally invasive detection of fentanyl and its analogues.