| Summary: | An “on-off-on” type photoelectrochemical (PEC) aptamer sensor for prostate-specific antigen (PSA) detection is constructed based on nanocomposite materials obtained from CdS functionalized titanium dioxide (CdS/TiO2 NPs). Firstly, due to high photocurrent signal of the CdS/TiO2 NPs, it can achieve the initial signal “on” state to improve the stability of the sensing platform. Then, AuNPs, as the energy acceptor of CdS, are used to label PSA aptamers to obtain signal “off” state through energy resonance transfer (RET). Finally, in the process of detecting PSA, part of the AuNPs-modified aptamer detaches from the electrode surface, causing the sensor signal to “on” state again. This stepped energy level structure formed by the coupling of CdS and TiO2 NPs can broaden the light absorption range, enhance electron-hole separation, and lay a good foundation for the signal “on-off-on” strategy. The method on RET to realize signal quenching and opening significantly improves the sensitivity of the PEC sensor. Based on this innovative “on-off-on” design, this PEC aptamer sensor has high sensitivity to PSA, and its linear detection range (LDR) is 0.0005–50 ng mL−1. The limit of detection (LOD) is 0.00017 ng mL−1. This constructed PEC sensor also has good detection performances in actual human serum sample detection. And this study based on RET can also provide a new strategy for the detection of other biomarkers.
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