Ultrasensitive Photoelectrochemical Biosensing Platform for Detecting N-Terminal Pro-brain Natriuretic Peptide Based on SnO2/SnS2/mpg-C3N4 Amplified by PbS/SiO2.

A sandwich-type photoelectrochemical (PEC) immunosensor for detecting N-terminal pro-brain natriuretic peptide (NT-proBNP) was constructed on the basis of SnO2/SnS2/mpg-C3N4 nanocomposites and PbS/SiO2, with the former as a photoactive matrix and the latter as an efficient quencher. SnO2/SnS2/mpg-C3N4 was synthesized via in situ growth of SnO2 and SnS2 on mesoporous graphene like C3N4 nanocomposites (mpg-C3N4). Specifically, SnO2/SnS2/mpg-C3N4 exhibited intense PEC signal responses, which are tens of times stronger than its each single component. Because of its superior performance, SnO2/SnS2/mpg-C3N4 was applied as a photoactive matrix and signal indicator for fabricating PEC immunosensor. Interestingly, the excellent PEC signals from SnO2/SnS2/mpg-C3N4 could be reduced severely with the addition of PbS/SiO2. Hence, the secondary antibody bioconjugates (PbS/SiO2-Ab2) were prepared as an efficient quencher. The mechanism of the quench reaction was further discussed in detail. On the basis of the interaction between the matrix and the quencher, the NT-proBNP immunosensor was fabricated and a wide linear range of 0.1 pg·mL-1 to 50 ng·mL-1 was obtained with a low detection limit of 0.05 pg·mL-1. Additionally, the PEC immunosensor manifested good stability, reproducibility, and selectivity, which could underlie robust platforms for detecting multitudinous biomarkers or other targets of interest.