A sensitive colorimetric sensor based on one-pot preparation of h-Fe3O4@ppy with high peroxidase-like activity for determination of glutathione and H2O2.

• A novel magnetic ternary nanocomposite hemin-Fe 3 O 4 @polypyrrole with stronger peroxidase-like activity was synthesized. • The residual catalytic effect can be removed and the real-time regulation of the catalytic reaction can be realized. • Its excellent stability and reusable characteristics can increase the practicality of this colorimetric sensors. • The analysis of actual samples showed that GSH/GSSG was more significant in clinical diagnosis. At present, artificial mimic enzyme has become a powerful substitute for natural enzyme. In particular, the biosensors based on nano-enzymes have been the focus of current research. Herein, a novel magnetic ternary nanocomposite hemin-Fe 3 O 4 @polypyrrole (h-Fe 3 O 4 @ppy) was synthesized by chemical oxidation polymerization. The results showed that the h-Fe 3 O 4 @ppy had stronger peroxidase activity than Fe 3 O 4 nanoparticles (Fe 3 O 4 NPs) and h-ppy NPs, and was indicated by Michaelis-Menten constant (K m) and maximum initial velocity (V max). Therefore, we used h-Fe 3 O 4 @ppy catalyzing H 2 O 2 to oxidize the chromogenic substrate TMB, and built Hydrogen peroxide (H 2 O 2) and Glutathione (GSH) colorimetric biosensors with the help of signal intrinsic exponential amplification and easy operation. The controllable catalysis was realized by h-Fe 3 O 4 @ppy which was prone to separation. The method of removing h-Fe 3 O 4 @ppy by magnetic separation effectively eliminated the effect of residual catalysis when terminating the reaction. The sensor was then applied to the determination of GSH in biological samples from acute coronary syndrome patients. The linear ranges of H 2 O 2 and GSH were 0.2–100 μM and 0.5–80 μM, respectively. The detection limits of H 2 O 2 and GSH are 0.18 μM and 0.15 μM, respectively. This research not only proposes a new type of nanoenzyme, but also shows the multiple advantages of magnetic nano-enzymes for the construction of biosensors. [ABSTRACT FROM AUTHOR]