A novel photoelectrochemical aptasensor based on nitrogen vacancies g-C3N5/TiO2 heterostructure and endonuclease assisted recycling amplification for ultrasensitive analysis of 17β-estradiol

Herein, we developed nitrogen vacancies g-C3N5/TiO2 heterostructure modified electrode for sensitive photoelectrochemical (PEC) sensing of 17β-estradiol (E2) based on target-triggered Endonuclease assisted recycling and horseradish peroxidase (HRP)-induced biocatalytic precipitation (BCP) cascade signal amplification strategies. The nitrogen vacancies g-C3N5 (NV-g-C3N5) was produced with thermal polycondensation method and employed as a photoactive material. Since the synergy effect between the TiO2 and NV-g-C3N5 can reduce the photo-induced electron-hole recombination and expedite the spatial charge separation, NV-g-C3N5/TiO2 heterostructure showed higher PEC activity. HRP-labeled Assistant DNA (HRP-AD) hybridized with Substrate DNA (SD) on the electrode in the absence of E2, and precipitation generated by HRP catalyzed could quench the photocurrent of the electrode. In the presence of E2, the target triggered Endonuclease assisted recycling reaction and achieved the conversion of the E2 to a massive output of template DNA (tDNA). Owing to tDNA strong affinity to the SD, HRP-AD was released from the electrode, gradually terminating the BCP reaction and restoring the photocurrent. The PEC aptasensor for E2 detection exhibited a broad linear range from 0.01 pM to 100 pM, with a detection limit of 0.0087 pM, and could be used to detect E2 in bioanalysis of environmental samples.