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^-10molcm^-2, thus exhibiting a surface-controlled reversible redox reaction, with a fast heterogeneous electron transfer rate of 5.48s^-1. The immobilized CAT shows a couple of reversible and well-defined cyclic voltammetry peaks with a formal potential (E⁰) of -0.471V (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 (392mAcm^-2M^-1) and a lower Michaelis-Menten constant (0.224mM). It provided high-catalytic activity towards H₂O₂ in a shorter time (5s), with a detection limit of 8nM. 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.