Direct electrochemistry and biosensing of horseradish peroxidase immobilized onto chitosan wrapped multiwalled carbon nanotubes

Horseradish peroxidase（HRP） was immobilized onto chitosan wrapped multiwalled carbon nanotubes（MWCNTs） for the construction of a bioelectrochemical platform for direct electrochemistry and biosensing purposes.The direct electron transfer between HRP and the electrode surface was observed with a formal potential of about -0.354 V（vs.SCE） in phosphate buffer solution and the calculated heterogeneous electron transfer rate constant is about 4.24±1.02 s^-1.Experimental results confirmed that the immobilized HRP retains its catalytic activity toward the reduction of nitrite.Such an HRP-MWCNTs-chitosan based biosensor exhibited a rapid response time of less than 11 s and a good linear range from 1.0×10^-4 to 1.4×10^-3 mol L^-1 with a detection limit of 7×10^-4 mol L^-1 for the nitric oxide detection.Both the unique electrical properties of MWCNTs and the biocompatibility of chitosan enable us to construct an excellent biosensing platform for improving electrocatalysis of HRP,especially for the detection of trace of nitric oxide.