Molecular-Sieving Label-Free Surface-Enhanced Raman\nSpectroscopy for Sensitive Detection of Trace Small-Molecule Biomarkers\nin Clinical Samples

Small-molecule\nbiomarkers are ubiquitous in biological fluids with\npathological implications, but major challenges persist in their quantitative\nanalysis directly in complex clinical samples. Herein, a molecular-sieving\nlabel-free surface-enhanced Raman spectroscopy (SERS) biosensor is\nreported for selective quantitative analysis of trace small-molecule\ntrimetazidine (TMZ) in clinical samples. Our biosensor is fabricated\nby decorating a superhydrophobic monolayer of microporous metal–organic\nframeworks (MOF) shell-coated Au nanostar nanoparticles on a silicon\nsubstrate. The design strategy principally combines the hydrophobic\nsurface-enabled physical confinement and preconcentration, MOF-assisted\nmolecular enrichment and sieving of small molecules, and sensitive\nSERS detection. Our biosensor utilizes such a “molecular confinement-and-sieving”\nstrategy to achieve a five orders-of-magnitude dynamic detection range\nand a limit of detection of ≈0.5 nM for TMZ detection in either\nurine or whole blood. We further demonstrate the applicability of\nour biosensing platform for longitudinal label-free SERS detection\nof the TMZ level directly in clinical samples in a mouse model.