Control of antibody orientation on graphene using porphyrin linker molecules for high-performance graphene-based immuno-biosensors

Abstract The appropriate orientation of antibodies on the graphene surface is critical for the high performance of graphene biosensors. In this paper, we show that a predominantly vertical orientation of antibodies to the graphene surface can be achieved by functionalizing the surface with tetrakis (4-carboxyphenyl) porphyrin (TCPP). We used this method to detect exosome biomarkers using a graphene field effect transistor (GFET) platform, and achieved a two orders of magnitude improvement in the detection limit of a GFET biosensor compared with that achieved by conventionally used 1-pyrene butanoic acid succinimidyl ester (PBASE). Through experimental analysis and computational simulation, we revealed that the antibody can highly exhibit vertical orientation on TCPP-functionalized graphene, while mixed orientations on PBASE-functionalized graphene. We further validated the high efficiency of TCPP method by detecting pancreatic cancer exosome biomarkers in clinical samples. This biofunctionalization method could enable the ultrasensitive detection of disease biomarkers on a graphene surface.