Structure Remodeling\nStrategy for Open-Cage NiFe@Fe-bis-PBA\nwith Enhanced Peroxidase-like Activity To Monitor Tumor Markers

The inherent metal elements and structures\nof Prussian blue analogue\n(PBA) nanozymes have restricted their enzyme-mimicking activity. Therefore,\nthe rational regulation of PBA nanozymes to improve their catalytic\nactivity is highly desirable for biosensing applications. Herein,\nwe propose a structure remodeling strategy to construct an open-cage\nFe PBA-anchored NiFePBA (NiFe@Fe bis-PBA) nanozyme with significantly\nenhanced enzyme-mimicking activity. The formation process and mechanism\nfor this bis-PBA nanozyme were studied in detail. Specifically, a\ncubic NiFePBA precursor was first synthesized and modified with polyvinylpyrrolidone\n(PVP). With the aid of hydrochloric acid, the added potassium ferricyanide\nwas reduced by PVP and re-coordinated on the surface of NiFePBA to\nform the NiFe@Fe bis-PBA nanozyme with a special open-cage core–shell\nstructure. The resultant NiFe@Fe bis-PBA nanozyme was further exploited\nto immobilize secondary antibodies, serving as a novel signal probe\nfor developing highly sensitive electrochemical immunosensors for\nmonitoring tumor markers. The constructed electrochemical immunosensor\npossesses a very wide linear range of 0.005–100 ng/mL and a\nlow detection limit of 0.89 pg/mL for alpha-fetoprotein with high\nspecificity and acceptable reproducibility and stability. This work\noffers a general and promising strategy for remodeling PBA nanozymes\nwith a very favorable structure and metal element distribution, which\nenhances their enzyme-mimicking properties for applications in different\nfields.