Etched CoFe Prussian blue analog nanozymes with superior peroxidase activity for colorimetric biosensing of hydrogen peroxide and dopamine.

Nanozymes represent a compelling alternative to natural enzymes due to their exceptional stability and cost-efficiency in diagnostic and therapeutic applications. In this work, a nanozyme etched CoFe Prussian blue analog (etched PBA) was designed and fabricated by a simple approach involving first synthesizing CoFe PBA and then chemical etching. The fabricated etched PBA acts as a peroxidase mimic catalyst. Compared to the naturally occurring enzyme (horseradish peroxidase), the etched PBA exhibited improved peroxidase-like catalytic efficiency for oxidizing 3,3',5,5'-tetramethylbnmenzidine (TMB). Particularly, the exceptional peroxidase-like activity of the etched PBA is attributed to modifications in its electronic and structural properties, which improved affinity for hydrogen peroxide (H₂O₂) and TMB. Hence, these findings highlight etched PBA as a promising peroxidase mimic, enabling a colorimetric assay for real-time H₂O₂ and dopamine (DA) detection. H₂O₂ was detected via PBA-catalyzed TMB oxidation (bluish-green color), while DA monitoring occurred through ox-TMB reduction. The detection thresholds for H₂O₂ and DA were determined to be 0.083 μM and 0.05 μM, respectively, with broad linear ranges of 0.1 μM - 4.0 mM for H₂O₂ and 0.1-240 μM for DA. In addition, the etched PBA was validated for real sample analysis, showing potential for enzyme catalysis, biosensing, and colorimetric analysis of pharmaceuticals and biomolecules.