Programming Accessibility of DNA Monolayers for Degradation-Free Whole-Blood Biosensors

Biosensors for direct detection of circulating biomarkers are of great importance for clinical diagnosis. Nevertheless, preservation of biomolecular probes in the recognition layer of biosensors remains a high challenge in such complex matrices (e.g., whole blood). Here we report the development of a nuclease-resistant DNA monolayer for degradation-free biosensing in whole blood. The accessibility of surface-confined DNA monolayers was programmed by engineering the lateral distances of DNA probes. In particular, we found that nucleases were effectively repelled from the biosensor surface by tuning the DNA density to 25.5 × 10¹² molecules/cm², equivalent to an interstrand lateral distance of ∼2 nm. As a proof-of-concept, we fabricated an electrochemical DNA aptamer sensor for detecting a small-molecule drug doxorubicin (Dox) that exhibited excellent stability and accuracy when deployed for monitoring Dox levels in whole blood. We thus expect the accessibility-programmable DNA biosensors to hold great potential for on-site biomarker analysis and drug monitoring.