The authors describe a voltammetric immunoassay for the hepatitis C virus core antigen. It is based on the use of vanadium oxide nanobelts that were used to modify a glassy carbon electrode (GCE). The nanobelts have a large specific surface area that can be heavily loaded with antibody against the hepatitis C virus core antigen. Following blocking with BSA and by using riboflavin as an electrochemical probe, the immuno GCE (best operated at a working voltage of −0.45 V vs. Ag/AgCl) has a linear response that covers the 10 fg·mL−1 to 100 ng·mL−1 core antigen concentration range and a limit of detection as low as 1.3 fg mL−1. Compared to the other redox probes, riboflavin is superior because it is oxidized in the negative potential range, where the number of interfering species for riboflavin is small. The method was successfully applied to the determination of hepatitis C virus core antigen in spiked serum. In our perception, the use of a V2O5 nanobelt film as a support for bioreceptors has a wide scope in that in that it may be extended to immunoassays for various other diagnostically significant analytes.
