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

Abstract 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-Fe3O4@polypyrrole (h-Fe3O4@ppy) was synthesized by chemical oxidation polymerization. The results showed that the h-Fe3O4@ppy had stronger peroxidase activity than Fe3O4 nanoparticles (Fe3O4 NPs) and h-ppy NPs, and was indicated by Michaelis-Menten constant (Km) and maximum initial velocity (Vmax). Therefore, we used h-Fe3O4@ppy catalyzing H2O2 to oxidize the chromogenic substrate TMB, and built Hydrogen peroxide (H2O2) and Glutathione (GSH) colorimetric biosensors with the help of signal intrinsic exponential amplification and easy operation. The controllable catalysis was realized by h-Fe3O4@ppy which was prone to separation. The method of removing h-Fe3O4@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 H2O2 and GSH were 0.2–100 μM and 0.5–80 μM, respectively. The detection limits of H2O2 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.