Duplex Electrochemical Microfluidic Sensor for COVID‐19 Antibody Detection: Natural versus Vaccine‐Induced Humoral Response

Abstract The rapid transmission and resilience of coronavirus disease 2019 (COVID‐19) have led to urgent demands in monitoring humoral response for effective vaccine development, thus a multiplex co‐detection platform to discriminate infection‐induced from vaccine‐induced antibodies is needed. Here a duplex electrochemical immunosensor for co‐detection of anti‐nucleocapsid IgG (N‐IgG) and anti‐spike IgG (S‐IgG) is developed by using a two‐working electrode system, via an indirect immunoassay, with antibody quantification obtained by differential pulse voltammetry. The screen‐printed electrodes (SPEs) are modified by carbon black and electrodeposited gold nanoflowers for maximized surface areas, enabling the construction of an immunological chain for S‐IgG and N‐IgG electrochemical detection with enhanced performance. Using an optimized immunoassay protocol, a wide linear range between 30–750 and 20–1000 ng mL⁻¹, and a limit of detection of 28 and 15 ng mL⁻¹ are achieved to detect N‐IgG and S‐IgG simultaneously in serum samples. This duplex immunosensor is then integrated in a microfluidic device to obtain significantly reduced detection time (≤ 7 min) while maintaining its analytical performance. The duplex microfluidic immunosensor can be easily expanded into multiplex format to achieve high throughput screening for the sero‐surveillance of COVID‐19 and other infectious diseases.