A novel Co-SnO2/Rhodamine B composite as photoactive material with excellent photoelectrochemical performance for ultrasensitive detection of prostate cancer biomarker.

Herein, a novel Co-SnO2/Rhodamine B sensitization structure with high photoelectric conversion efficiency was synthesized to construct photoelectrochemical (PEC) biosensor for ultrasensitive detection of miRNA-141 related to prostate cancer. Notably, compared to the low photoelectric performance of pristine SnO2, Co-SnO2 exhibits high photocurrent response, since Co doping into the SnO2 lattice not only narrowed the energy band gap but also introduced more defects and oxygen vacancies to facilitate the separation of photogenerated carriers and enhance the photocurrent signal. Furthermore, sensitizer Rhodamine B effectively matched the energy bandwidth of Co-SnO2 to boost photo-generated electron transfer, resulting in a further enhancement of the photocurrent signal. In addition, with the aid of the RCA-HCR cascade amplification strategy, the target miRNA-141 could be converted into DNA nanoprisms for immobilizing a large amount of MnPP molecules to catalyze the conversion of 4-CN into 4-CD, achieving significant signal amplification. Consequently, the fabricated PEC biosensor exhibited a broad linear detection range from 1 fM to 10 nM with a low detection limit of 0.33 fM, and was successfully applied for the detection of cancer cell lysates. This work demonstrates an analytical proof-of-concept for enhancing the photocurrent signal and sensitivity of PEC sensing platforms, and validates its feasibility for miRNA-141 determination in cell lysates and spiked serum samples.