Plasmonic Nanodiamond – Microneedle Bioinspired System for Ultrarapid Sampling and Quantum Sensing of Melanoma‐Related MiRNA

Abstract MicroRNA (miRNA) in interstitial fluid (ISF) is a promising biomarker for early disease diagnosis, but its quantification is challenging due to low sampling efficiency and weak signals. Here, inspired by the osmotic pressure‐driven feeding mechanism of sea anemones, a novel is designed that plasmonic nanodiamonds – microneedles (PND‐MNs) bioinspired system for ultrarapid sampling and quantum sensing of melanoma‐related miRNA. Specifically, high‐osmotic hydrogel microneedles, prepared by immersing in LiCl solution, exhibit a substantial swelling ratio for rapid ISF enrichment, extracting 0.92 ± 0.14 mg within 5 min. Concurrently, by coating fluorescent nanodiamonds (FNDs) with hollow composite metal Au‐Ag NPs, precise modulation of the fluorescence intensity of nitrogen vacancy color centers (NV‐center) in FNDs has been achieved. This innovative quantum sensing technology significantly enhances the fluorescence signal in the PND‐MNs bioinspired system, amplifying it by a factor of 16, reducing the detection limit of miRNA to an unprecedented 0.68 f m (to the knowledge, no method based on fluorescent microneedles for detecting biomarkers has surpassed this level). Furthermore, the PND‐MNs bioinspired system, employing backpropagation neural network (BPNN), achieves high accuracy in recognizing miRNA concentrations (R 2 = 0.9986). By combining rapid sampling, signal enhancement, and machine learning, it holds promise for detecting ISF biomarkers, offering significant clinical applications.