Graphene oxide and dextran capped gold nanoparticles based surface plasmon resonance sensor for sensitive detection of concanavalin A

Carbohydrate-protein interactions mediate the important physiological and pathophysiological processes in living organism. Their study has attracted great attention due to its importance in understanding these biological processes and in fabricating biosensors for diagnostics and drug development. Here, by using concanavalin A (ConA) as a model protein, a novel surface plasmon resonance (SPR) sensor was developed for sensitive detection ConA. In this sensing platform, dextran (Dex) capped gold nanoparticles (Dex-Au NPs) were initially synthesized in one-pot and utilized as amplification reagent. After deposition of graphene oxide (GO) on the SPR gold film, phenoxy-derivatized dextran (DexP) was assembled onto the GO-modified gold chip surface through π-π interaction. The resultant GO/DexP sensing interface could specifically capture ConA which could further react with Dex-Au NPs through the specific interaction between ConA and Dex, forming a sandwich configuration. The morphologies and the electrochemistry of the formed sensing surface were investigated by using scanning electron microscopy and electrochemical techniques including electrochemical impedance spectroscopy and cyclic voltammogram. Owing to the high surface area of GO and the excellent amplification of Dex-Au NPs, the developed sandwich SPR sensor successfully fulfilled the sensitive detection of ConA in the range of 1.0-20.0 μg mL−1 with a detection limit of 0.39 μg mL−1. Compared to the direct assay format, the prepared sandwich SPR sensor led to an improvement of 28.7-fold in the sensitivity. The results demonstrated that the proposed method might provide a new direction in designing high-performance SPR biosensors for sensitive and selective detection of a wide spectrum of biomolecules.