A H2O2 electrochemical biosensor based on biocompatible PNIPAM-g-P (NIPAM-co-St) nanoparticles and multi-walled carbon nanotubes modified glass carbon electrode

The poly(N-isopropylacrylamide)-g-poly(N-isopropylacrylamide-co-styrene) (PNIPAM-g-P (NIPAM-co-St), we denote as PNNS in the later content) nanoparticles were obtained by an emulsifier-free emulsion polymerization method. Hemoglobin (Hb), as a model enzyme, was immobilized on the film, which was mixed by multi-walled carbon nanotubes (MWCNTs) and PNNS nanoparticles to construct a novel H2O2 biosensor. The PNNS/MWCNTs films were examined by scanning electron microscopy (SEM) and Fourier transform infrared spectrophotometer (FTIR). The performances of the PNNS/MWCNTs/GCE were characterized with cyclic voltammetry (CV), electrochemical impedance spectra (EIS) and typical amperometric response (i-t) measurements. The immobilized Hb maintains its bioactivities and displays an excellent electrochemical behavior with a formal potential of −349 mV. The biosensor exhibited a good electrocatalytic activity to the reduction of hydrogen peroxide (H2O2). The linear response range of the H2O2 biosensor was from 1.0 × 10−7 to 5.9 × 10−4 M with a low detection limit of 2.9 × 10−8 M. The apparent Michaelis–Menten constant ( K app M ) of Hb on the PNNS/MWCNTs film was estimated to be 0.19 mM, showing its high affinity to H2O2 and good bioactivity of the Hb/PNNS/MWCNTs film toward H2O2 reduction. Good stability and repeatability were assessed for the biosensor.