A sensitive immunosensing platform based on the high cathodic photoelectrochemical activity of Zr-MOF and dual-signal amplification of peroxidase-mimetic Fe-MOF

Cathodic photoelectrochemical (PEC) analysis has received special concerns because of its outstanding anti-interference capability toward reductive substances in samples, so it is highly desirable to develop high-performance photocathodic materials for PEC analysis. Herein, a Zr-based metal–organic framework (Zr-MOF), MOF-525, is explored as a photoactive material in aqueous solution for the first time, which shows a narrow band-gap of 1.82 eV, excellent visible-light absorption, and high cathodic PEC activity. A sandwiched-type PEC immunosensor for detecting prostate-specific antigen (PSA) is fabricated by using MIL-101-NH2(Fe) label and MOF-525 photoactive material. MIL-101-NH2(Fe) as a typical Fe-MOF can serve as a peroxidase mimic to catalyze the production of precipitates on the photoelectrode. Both the produced precipitates and the MIL-101-NH2(Fe) labels can quench the photocathodic current, enabling “signal-off” immunosensing of PSA. The detection limit is 3 fg mL−1, and the linear range is between 10 fg mL−1 and 100 ng mL−1 for detecting PSA. The present study not only develops a high-performance Zr-MOF photoactive material for cathodic PEC analysis but also constructs a sensitive PEC immunosensing platform based on the dual-signal amplification of peroxidase-mimetic Fe-MOF.