In Situ Cascade Catalytic Polymerization of Dopamine Based on Pt NPs/CoSAs@NC Nanoenzyme for Constructing Highly Sensitive Photocurrent‐Polarity‐Switching PEC Biosensing Platform

Nanozymes open up new avenues for amplifying signals in photoelectrochemical (PEC) biosensing, which are yet limited by the generated small-molecule signal reporters. Herein, a multifunctional nanoenzyme of Pt NPs/CoSAs@NC consisting of Co single atoms on N-doped porous carbon decorated with Pt nanoparticles is successfully synthesized for cascade catalytic polymerization of dopamine for constructing a highly sensitive photocurrent-polarity-switching PEC biosensing platform. Taking protein tyrosine phosphatase 1B (PTP1B) as a target model, Pt NPs/CoSAs@NC nanoenzymes are linked to magnetic microspheres via phosphorylated peptides. Upon dephosphorylation of PTP1B, Pt NPs/CoSAs@NC nanoenzymes with multiple enzyme-like activities, including peroxidase (POD)-like, catalase (CAT)-like, and oxidase (OXD)-like activities, are released and collected to induce the in situ cascade catalytic polymerization of dopamine on ZnCdS photoelectrode in the presence of H