Disposable and sensitive electrochemical magneto-immunosensor for point-of-care HCV diagnostics: Targeting HCVcAg, the active viremia biomarker, in patient samples.

Early detection of hepatitis C virus (HCV) infection is crucial for eliminating this silent killer, especially in resource-limited settings. HCV core antigen (HCVcAg) represents a promising alternative to the current "gold standard" HCV RNA assays as an active viremia biomarker. Herein, a highly sensitive electrochemical magneto-immunosensor for the HCVcAg was developed. The biosensing strategy involved capturing HCVcAg using antibody-coated magnetic beads, followed by a sandwich immunoassay before electrochemical detection on disposable screen-printed electrodes. To achieve signal amplification and consequent enhanced sensitivity, the antigen-antibody reaction was detected with a biotinylated polyclonal antibody subsequently labelled with a streptavidin poly horseradish peroxidase conjugate followed by amperometric detection via a hydroquinone/hydrogen peroxide system. The developed biosensor exhibited a cathodic current variation directly proportional to the HCVcAg concentration over a wide range (0.1-500 ng/mL), with a detection limit of 10 pg/mL. Moreover, it successfully discriminated healthy control human plasma samples from HCVcAg-spiked samples, showed no interference from endogenous plasma constituents or cross-reactivity with other viruses tested, and possessed excellent percentage recoveries of HCVcAg (≥92.83%), demonstrating high specificity. The proposed bioplatform remained stable for at least ten days and showed excellent clinical performance in detecting HCVcAg across a cohort of thirty-six plasma and serum samples from active hepatitis C cases, and healthy individuals, with results matching those previously obtained using clinically validated qPCR and serological testing. In summary, this biosensor provides a simple, rapid and economic alternative to other available techniques such as ELISA and qPCR for early diagnosis of HCV infection.