Graphene, because its outstanding electrical and optical properties, has been an attractive material for developing biosensors and bioelectronics. The stability of proteins on graphene, as a function of its secondary structure, has been studied computationally; however, there has been a lack of experimental validity of such simulations results. This study examines the stability of two biosensing enzymes on graphene and in solution: horseradish peroxidase (an all α-helix protein) and glucose oxidase (a protein with both α-helix and β-sheet content). At three different temperatures (4, 20, and 37 °C), glucose oxidase tethered to graphene was found to be more stable than when in solution. In contrast, horseradish peroxidase tethered to graphene showed rapid loss in activity than when in solution. This is the first experimental evidence showing differential stability of proteins on graphene, and we believe this is due to the difference in the secondary structure of the proteins.
Keywords: enzyme stability; glucose oxidase; graphene biofunctionalization; graphene surface chemistry; horseradish peroxidase.