The enhanced photoelectrochemical platform constructed by N-doped ZnO nanopolyhedrons and porphyrin for ultrasensitive detection of brain natriuretic peptide

Highlights: • The N–ZnO NP was prepared by directly calcining the ZIF-8 and adopted to enhance the photocurrent of PPIX. • The PEC platform was constructed by successive deposition of PPIX and N–ZnO NP to largely promote the photoelectron transfer. • A label-free PEC aptasensor was built for ultrasensitive assay of BNP-32 protein. Nowadays, brain natriuretic peptide (BNP-32) is fundamental to early cardiovascular clinical diagnosis, whose accurate assay is of significance by photoelectrochemistry (PEC) for the low background and high precision. Herein, a novel enhanced PEC platform was built by successive deposition of N-doped ZnO nanopolyhedra (N–ZnO NP) and protoporphyrin IX (PPIX). Specifically, the N–ZnO NP with a narrow bandgap of 2.60 eV was synthesized by direct calcination of zeolitic imidazole framework-8 (ZIF-8), and performed as the substrate to enhance the photocurrents of PPIX (as photosensitizer) whose photoelectron transfer pathway and enhanced PEC mechanism were studied in detail. Under such foundation, a label-free PEC aptasensor was developed by deposition of DNA aptamer onto the PEC platform and then ultrasensitive assay of BNP-32 based on a "signal off" model. The biosensor showed a wide linear range (1 pg mL⁻¹- 0.1 μg mL⁻¹) with a limit of detection (LOD) as low as 0.14 pg mL⁻¹. This doping technique of ZnO nanomaterials provides some valuable guidelines for synthesis of advanced PEC probes in bioanalysis.