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

Abstract 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 2 O 2 . The generated polymer‐molecule of polydopamine served as efficient signal reporter for simultaneously amplifying signal and switching photocurrent polarity, which not only improved the sensitivity but also enhanced the reliability. This biosensing platform is capable of sensitively quantifying PTP1B with ultralow detection limit (0.04 fM), wide linear range (0.1 f m –0.1 µ m ), and good applicability in complex biological samples. This work pioneers the utilization of nanozyme‐based cascade catalytic polymerization strategy for improving sensitivity and reliability in biosensing technologies.