Advances in microneedle-based transdermal fluorescent sensors

Microneedles (MNs) are minimally invasive tools capable of accessing interstitial fluid beneath the skin. Their integration with fluorescent probes has enabled the development of versatile platforms for transdermal biomarker detection with high sensitivity and spatial resolution. This feature article classifies MN-based transdermal fluorescent sensors into three types: porous, dissolving, and hydrogel types, and discusses three representative sensing strategies: probe-loaded, probe-fixed, and probe-released. In particular, recent progress in detecting nucleic acids, metal ions, proteins, and metabolites using these systems is thoroughly reviewed. These fluorescent sensors exhibit excellent analytical performance and visual signal output, which hold great potential for multiplexed detection and responsive biosensing. Finally, we address existing challenges in this rapidly developing field, including signal stability, fabrication scalability, and continuous monitoring, and provide perspectives on future directions for next-generation diagnostics and biomedical application.