Structural regulation of covalent organic framework boost high-performance self-powered electrochemical sensor based on zinc-air battery

Self-powered electrochemical sensor (SPES) has received widespread attention in sensing owing to its low cost, portability, and no need for external power supply. Herein, a new photoassisted zinc-air battery-based SPES (PZAB-SPES) was designed to detect microRNA-21 (miRNA-21) by incorporating covalent organic framework (COF) film with outstanding properties and strand displacement amplification. To achieve high output signal of PZAB-SPES, three kinds of COF films were synthesized and the relationship between their structure and output signal was explored. Through theoretical calculation and structural analysis, it was noticed that using optimal COF film as the photocathode material, PZAB-SPES had a high open-circuit potential up to 1.46 V, which was 2–3 folds higher than that of most photocatalytic fuel cells. In the presence of miRNA-21, signal amplification strategy was used to enhance the output signal of PZAB-SPES, enabling the PZAB-SPES to realize sensitive detection of miRNA-21 with a low detection limit of 2.49 fM. In addition, the proposed PZAB-SPES was successfully used for the detection of miRNA-21 in human serum, suggesting its great application potential in cancer early screening.