Functionalized laser-induced graphene enabled ultrasensitive electroimmunoassay for rapid hepatitis B virus detection

Hepatitis B virus (HBV) infection remains a major global health challenge, necessitating the development of rapid, sensitive, and cost-effective diagnostics for disease and public health management. Herein, a high-performance electrochemical immunosensor for the ultratrace detection of hepatitis B surface antigen (HBsAg) is presented, leveraging laser-induced graphene (LIG) to address critical limitations of conventional diagnostics. A facile CO₂ laser process fabricates a porous, three-electrode graphene sensor on polyimide, which is subsequently functionalized via electrochemical oxidation to introduce carboxylic groups for covalent antibody immobilization. The assay operates on the steric-hindrance principle, where immunocomplex formation impedes redox probe diffusion, quantifiable via square wave voltammetry. The platform demonstrates exceptional analytical performance: a wide linear range (1 × 10^-4 to 1 × 10¹ ng mL^-1), an ultra-low detection limit of 0.04 pg mL^-1 in buffer, and robust functionality in human serum with detection limit of 0.18 pg mL^-1. It also exhibits outstanding selectivity against viral interferents and strong storage stability over 30 days. Combining laboratory-level sensitivity with point-of-care practicality, this biosensor offers a promising tool for early HBV screening, particularly in resource-limited settings.