Sensitivity enhanced SPR immunosensor based on graphene oxide and SPA co-modified photonic crystal fiber

A sensitivity enhanced surface plasmon resonance (SPR) immunosensor based on Graphene oxide (GO) composite and staphylococcal protein A (SPA) co-modified photonic crystal fiber (PCF) is developed for human IgG detection. The PCF spliced between two section of multimode fibers (MMFs) is sputtered with gold film, which was then modified with graphene oxide and SPA for further immunosensing. Graphene oxide with abundant functional groups has a large surface area for more biomolecules immobilization and can enhance the interaction between Au film and external medium, leading to the sensitivity increased greatly. SPA can specifically bind the Fc region of the antibodies and has a high degree of orientation for capturing antibodies. Experimental results indicated that the refractive index (RI) sensitivity of graphene oxide modified Au-PCF SPR sensor reaches 4649.8 nm/RIU, which is about 1888 nm/RIU higher than that without graphene oxide film and the human IgG detection limit reaches as low as 10 ng/mL. Such a sensitivity enhanced immunosensor based on graphene oxide and SPA co-modified PCF shows a great promise in biosensing.