Engineering DNA circuit powered by entropy integrated into robust and elegant photoelectrochemical and photothermal dual-mode biosensing.

Dual-signal mode sensors that can self-validate detection results have attracted considerable interest; however, creating those with superior overall performance still presents significant challenges. Herein, we develop a unique photoelectrochemical (PEC) and photothermal (PT) dual-mode biosensor targeting microRNA-221 (miRNA-221), built on an innovative entropy-driven DNA circuit (EDC). The zinc oxide nanorods (ZnO NRs) serve as PEC beacons, while copper sulfide nanoparticles (CuS NPs) function as photocurrent inhibitors and PT beacons, both biofunctionalized with DNAs before being assembled through partial base pairing. When target miRNA-221 is present, the EDC activates and releases output DNAs that open partially hybridized strands anchored to ZnO NRs via competitive assembly. This process liberates CuS-DNA1 and restores the suppressed photocurrent. The results demonstrate linear relationships between photocurrent/temperature increment and the logarithm of target concentration across ranges of 1.0 fmol L^-1-50.0 pmol L^-1 (limit of detection (LOD): 0.35 fmol L^-1) and 5.0×10² fmol L^-1-5.0 nmol L^-1 (LOD: 1.22×10² fmol L^-1), respectively. Compared to conventional EDCs, our optimally designed EDC not only doubles the output DNA yield but also significantly enhances sensor sensitivity. Additionally, the target-triggered EDC amplification strategy effectively minimizes reversibility in each reaction step, preserves base sequence integrity, boosts efficiency, and demonstrates strong thermal stability and selectivity, thereby increasing the specificity of the dual-mode biosensor. Furthermore, ZnO NR photoelectric beacons fabricated via electrodeposition greatly improve the stability and controllability of the photoelectrode while avoiding lengthy modification processes. Overall, this thoughtfully engineered dual-mode biosensor offers numerous advantages, including a wide linear range, excellent stability, high reproducibility, and user-friendly operation. Specifically, this signal-on type dual-signal output biosensor enables self-confirmation of detection results, significantly enhancing both accuracy and reliability.