Direct electrochemistry and electrocatalysis of horseradish peroxidase based on halloysite nanotubes/chitosan nanocomposite film

The novel halloysite nanotubes/chitosan (HNTs/Chi) composite films were firstly explored to utilize for the immobilization of horseradish peroxidase (HRP) and their bioelectrochemical properties were studied, in which the biopolymer chitosan was used as a binder to increase film adherence on glassy carbon (GC) electrode. UV-vis and FTIR spectroscopy demonstrated that HRP in the composite film could retain its native secondary structure. A pair of well-defined redox peaks of HRP was obtained at the HRP/HNTs/Chi composite film-modified electrode, exhibiting its fast direct electron transfer (DET). Furthermore, the immobilized HRP displayed its good electrocatalytic activity for the reduction of hydrogen peroxide (H₂O₂). The results demonstrate that the HNTs/Chi composite film may improve the enzyme loading with the retention of bioactivity and greatly promote the direct electron transfer, which can be attributed to its unique tubular structure, high specific surface area, and good biocompatibility.