Development of an Amperometric Cholesterol Biosensor Based on Graphene-Pt Nanoparticle Hybrid Material

We describe the development of a highly sensitive amperometric biosensor based on the hybrid material derived from nanoscale Pt particles (nPt) and graphene for the sensing of H2O2 and cholesterol. The biosensing platform was developed using the hybrid material and enzymes cholesterol oxidase and cholesterol esterase. Chemically synthesized graphene has been decorated with nanosized Pt particles. The electron microscopic measurements show that the Pt nanoparticles on graphene have an average size of 12 nm and are randomly distributed throughout the surface. The Pt nanoparticle based hybrid material modified electrode efficiently catalyzes the electrochemical oxidation of H2O2 at the potential of 0.4 V, which is > 100 mV less positive with respect to the bulk Pt electrode. The sensing platform is highly sensitive and shows linear response toward H2O2 up to 12 mM with a detection limit of 0.5 nM [SIN (signal-to-noise ratio) = 3] in the absence of any redox mediator or enzyme. The combination of electronically highly conductive graphene and catalytically active Pt nanoparticle favors the facilitated electron transfer for the oxidation of H2O2. The cholesterol biosensor was developed by immobilizing cholesterol oxidase and cholesterol esterase on the surface of graphene-nanoparticle hybrid material. The bienzyme integrated nanostructured platform is very sensitive, selective toward cholesterol, and it has a fast response time. The sensitivity and limit of detection of the electrode toward cholesterol ester are 2.07 +/- 0.1 mu A/mu M/cm(2) and 0.2 mu M, respectively. The apparent Michaelis-Menten constant (K-m(app)) was calculated to be 5 mM. The sensor does not suffer from the interference due to other common electroactive species and is highly stable. The analytical performance of the hybrid material was further evaluated using screen-printed electrodes with 50 mu L of electrolyte.