Functional graphene-gold nanoparticle hybrid system for enhanced electrochemical biosensing of free cholesterol

Realizing the unavailability of fast and reliable diagnostic techniques, especially for cholesterol measurement, the present work reports the development of cost effective bioelectrodes based on a reduced graphene oxide-functionalized gold nanoparticle (∼25 nm) hybrid system (RGO-Fn Au NPs). The electrodes fabricated by the electrophoretic deposition technique attest a synergistically enhanced electrochemical sensing ability of 193.4 μA mM^-1 cm^-2 for free cholesterol detection, which is much higher than that of the traditional RGO system. The electrochemical impedance studies (EIS) show low charge transfer resistance, R_CT, for the hybrid system which is 57% and 60% lower than those of RGO and Au NPs respectively. Also higher loading capacity and enhanced kinetics have been realized for the hybrid system, owing to lower K_m value (0.005 mM) and enhanced rate constant (3.8 × 10^-4 cm s^-1) in comparison with RGO and Au NPs. Moreover, the RGO-Fn Au NP platform promises a wider range of cholesterol detection (0.65-12.93 mM), while simultaneously being capable of detecting as low as 0.34 mM of free cholesterol. Apart from better sensitivity, loading capacity, kinetics and detection range, the system also has appreciable selectivity and stability. This supports its potential to be brought on field in the near future for cost effective and reliable detection from the complex system of human serum.