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 antiinterference capability toward reductive substances in samples, so it is highly desirable to develop highperformance photocathodic materials for PEC analysis. Herein, a Zr-based metal-organic framework (ZrMOF), 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 sandwichedtype 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-101NH2(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 peroxidasemimetic Fe-MOF.