- We describe herein a newly developed optical microbiosensor for the diagnosis of hepatitis C virus (HCV) by using a novel photoimmobilization methodology based on a photoactivable electrogenerated polymer film deposited upon surface-conductive fiber optics, which are then used to link a biological receptor to the fiber tip through light mediation. This fiber-optic electroconductive surface modification is done by the deposition of a thin layer of indium tin oxide on the silica surface of the fiber optics. Monomers are then electropolymerized onto the conductive metal oxide surface; thereafter, the fibers are immersed in a solution containing HCV-E2 envelope protein antigen and illuminated with UV light (wavelength approximately 345 nm). As a result of the photochemical reaction, a thin layer of the antigen becomes covalently bound to the benzophenone-modified surface. The photochemically modified fiber optics were tested as immunosensors for the detection of anti-E2 protein antibody analyte that was measured through chemiluminescence reaction. The biosensor was tested for sensitivity, specificity, and overall practicality. Our results suggest that the detection of anti-E2 antibodies with this microbiosensor may enhance significantly HCV serological standard testing especially among patients during dialysis, which were diagnosed as HCV negative, by standard immunological tests, but were known to carry the virus. If transformed into an easy to use procedure, this assay might be used in the future as an important clinical tool for HCV screening in blood banks.