Dual-Channel Interdigitated Aptamer-Based Sensors for Rapid Small-Molecule Detection in Biofluids

Timely and decentralized quantification of small-molecule biomarkers is essential for point-of-care (POC) diagnostics, but their reliable detection in biofluids remains challenging. Here, we introduce an engineered electrochemical aptamer sensing platform that employs a dual-channel signal conversion strategy to overcome these limitations. By integrating spatially separated interdigitated working electrodes with selective self-assembled monolayer (SAM) removal, the system enables target-induced release and recapture of methylene blue-labeled complementary DNA (MB-cDNA) probes across two electrodes. This configuration minimizes background interference and enhances mass transport, facilitating robust dual-channel signal transduction. The platform enables rapid (≤ 30 min), low-volume (30 µL) detection of prototypical small molecules, dopamine and cortisol, in diverse biofluids, including artificial cerebrospinal fluid (aCSF), human serum, and saliva. Notably, the signal conversion mechanism remained effective across different targets and sample types, requiring only minimal adaptation of the recognition sequence. Together, these features establish a versatile electrochemical sensing architecture with broad potential for rapid, quantitative small-molecule analysis in complex biological media.