Affinity immobilization of aptamers on graphene oxide for biosensor applications

The preparation of biorecognition layers on the surface of a sensing platform is a very crucial step for the development of sensitive and selective biosensor. The incredibly large specific surface area, the abundant surface functionalities and the high water solubility indicate graphene oxide (GO) sheets as ideal substrate for such application. The immobilization of aptamers as the recognition element on GO allows the formation of a nanocomplex, usable as biosensing platform in an aptasensors. In this work, we investigate the immobilization of the biotin-thrombin-aptamer on GO, exploiting the high affinity of avidin for biotin. Avidin was directly immobilized on GO without any chemical functionalization, following a simple incubation procedure, performed in PBS. The ability of Avidin-GO substrate to bind biotinylated aptamers could lead an oriented immobilization of the recognition element (i.e. aptamer), avoiding unwanted interaction between aptamer and GO and keeping intact the exposed binding sites for the thrombin assay. The immobilization was observed directly using atomic force microscopy (AFM) and the modification of the GO functional groups was verified by UV-vis and Fourier transform infrared (FT-IR) spectroscopy.