Enzyme-integrated cholesterol biosensing scaffold based on in situ synthesized reduced graphene oxide and dendritic Pd nanostructure

Abstract

A new approach for the one-pot synthesis of reduced graphene oxide–dendritic Pd nanoparticle (rGO–nPd) hybrid material and the development of biosensing scaffold for the amperometric sensing of H₂O₂ and total cholesterol in human serum are described. In situ reduction of both graphene oxide (GO) and PdCl₄^2- in acidic solution was achieved with Zn to obtain rGO–nPd hybrid material. The oxygen containing functionalities of GO were reduced by the liberated atomic hydrogen in 20 min. The formal potential of Zn/Zn²⁺ and PdCl₄^2-/Pd couples favor the facile reduction of PdCl₄^2-. The in situ produced Pd nanoparticles behave like hydrogen sponge and increase the local concentration of atomic hydrogen. Biosensing platforms for H₂O₂ and cholesterol in human serum and butter sample were developed using the hybrid material. Amperometric sensing of H₂O₂ at 0.2 nM level without any redox mediator or enzymes in neutral pH is demonstrated. The cholesterol biosensing platform was developed by integrating cholesterol oxidase and cholesterol esterase with the hybrid material. The biosensor is highly sensitive (5.12±0.05 μA/μM cm²) and stable with a fast response time of 4 s; it could detect cholesterol ester as low as 0.05 μM (S/N=3). The biosensor is successfully used for the analysis of total cholesterol in human serum and butter.