Polylysine-modified MXene nanosheets with highly loaded glucose oxidase as cascade nanoreactor for glucose decomposition and electrochemical sensing

Abstract

Two-dimensional (2D) nanoreactors with cascade catalytic activity for glucose oxidation and hydrogen peroxide decomposition are prepared via immobilizing glucose oxidase (GOx) on Ti₃C₂ MXene nanosheets. Amino-rich polypeptide, poly-l-lysine (PLL), is applied to modify the ultra-thin Ti₃C₂ MXene nanosheets with a compatible surface for GOx immobilization. The PLL-modified Ti₃C₂ nanosheets possess a positively charged surface and show an excellent GOx loading capacity as high as 50 wt% of the Ti₃C₂ nanosheets. The physically adsorbed enzymes are then cross-linked with the amine groups in the PLL chains to form a robust GOx-PLL network covered on the MXene nanosheets. The GOx-conjugated Ti₃C₂-PLL (Ti₃C₂-PLL-GOx) nanosheets showed superior enzymatic activities than the activities of GOx immobilized on an inert porous silica substrate, largely because that the Ti₃C₂ nanosheets can catalyze the decomposition of the toxic intermediate H₂O₂ generated from the glucose oxidation. Given the excellent electrical conductivity of Ti₃C₂ MXene, the Ti₃C₂-PLL-GOx nanosheets are further deposited on glassy carbon electrode to construct a high-performance biosensor with a glucose detection limit of 2.6 μM.

Keywords: Cascade reaction; Enzyme immobilization; Glucose biosensor; Glucose oxidase; Ti(3)C(2) nanosheets.