Ultrasensitive, Real-Time Molecular Sensing in Unprocessed Whole Blood Using Surface-Enhanced Raman Scattering...

Rapid, real-time, and ultrasensitive molecular sensing in unprocessed whole blood remains a major challenge due to biofouling, narrow dynamic ranges, and the need for rapid equilibration. We report a biomimetic surface-enhanced Raman scattering (SERS) platform that integrates structure-switching aptamers with a self-assembling, lubricin (proteoglycan 4; PRG4)-derived glycocalyx mimicking structure that enables ultrasensitive, real-time detection directly within unprocessed whole bovine blood. This architecture achieves femtomolar detection in buffer and sub-nanomolar quantification in whole blood, expanding the dynamic range by six orders of magnitude compared to electrochemical aptamer sensors, while preserving the fast response required for continuous monitoring. In this biomimetic sensor platform, the glycocalyx-like lubricin layer performs multiple functions. (i) It prevents surface biofouling and associated signal losses, instabilities, and interferences. (ii) Lubricin enhances sensor selectivity through size-dependent molecular transport, and (iii) it facilitates amplification via molecular crowding within the lubricin layer, which acts as a signal amplifying mechanism via its effect on aptamer structure-switching dynamics and aptamer-analyte interactions. These findings establish biomimetic-SERS as a generalizable strategy for amplification-free, real-time molecular sensing in complex biofluids, with broad implications for therapeutic drug monitoring and point-of-care diagnostics.