A simple strategy for the immobilization of catalase on multi-walled carbon nanotube/poly (l-lysine) biocomposite for the detection of H2O2 and iodate

Herein, we report a novel third-generation H2O2 and IO3− biosensor, which was fabricated by loading catalase (CAT) onto l-lysine/multiwalled carbon nanotube (PLL/f-MWCNT) film modified glassy carbon electrode (GCE). The UV–visible (UV–vis) and Fourier-transform infrared (FTIR) spectra show that the catalase encapsulated in the PLL/f-MWCNT film can effectively retain its bioactivity. The immobilized CAT retained its bioactivity with a high protein loading of 4.072×10−10 mol cm−2, thus exhibiting a surface-controlled reversible redox reaction, with a fast heterogeneous electron transfer rate of 5.48 s−1. The immobilized CAT shows a couple of reversible and well-defined cyclic voltammetry peaks with a formal potential (E0) of −0.471 V (vs. Ag/AgCl) in a pH 6.5 phosphate buffer solution (PBS). Moreover, the modified film exhibited high electrocatalytic activity for the reduction of hydrogen peroxide (H2O2). It exhibited a wide linear response to H2O2 in the concentration range of 1×10−6–3.6×10−3, with higher sensitivity (392 mA cm−2 M−1) and a lower Michaelis–Menten constant (0.224 mM). It provided high-catalytic activity towards H2O2 in a shorter time (5 s), with a detection limit of 8 nM. These results indicate great improvement in the electrochemical and electrocatalytic properties of the CAT/PLL/f-MWCNT biosensor, offering a new idea for the design of third-generation electrochemical biosensors.