Sensitive detection of hydrogen peroxide in foodstuff using an organic-inorganic hybrid multilayer-functionalized graphene biosensing platform

We report on a new electrochemical biosensing strategy for the sensitive detection of hydrogen peroxide (H2O2) in foodstuff samples. It is based on a gold electrode modified with layer of graphene patterned with a multilayer made from an organic-inorganic hybrid nanomaterial. Initially, a layer of thionine (Th) was assembled on the surface of the graphene nanosheets, and these were then cast on the surface of the electrode for the alternate assembly of gold nanoparticles and horseradish peroxidase. The large surface-to-volume ratio and high conductivity of the nanosheets provides a benign microenvironment for the construction of the biosensor. The use of such a multilayer not only shortens the electron transfer pathway of the active center of the enzyme due to the presence of gold nanoparticles, but also enhances the electrocatalytic efficiency of the biosensor toward the reduction of H2O2. The electrochemical characteristics of the biosensor were studied by cyclic voltammetry and chronoamperometry. The number of layers, the operating potential, and the pH of the supporting electrolyte were optimized. Linear response is obtained for the range from 0.5 mu M to 1.8 mM of H2O2, the detection limit is 10 nM (at S/N = 3), and 95% of the steady-state current is reached within 2 s. The method was applied to sense H2O2 in spiked sterilized milk and correlated excellently with the permanganate titration method.