Microfluidic separation of capture from detection and its application for determination of COVID-19 antibodies

Abstract Electrochemical sensors offer considerable advantages for development of low-cost point-of-care (POC) diagnostics. A common fabrication approach results in the capture agent being located on the sensing electrode. Although this has the advantage of eliciting a rapid response, it has issues with reduced sensitivity and reproducibility caused by the conflicting requirements between the binding of the capture agent and its measurement. In addition, the configuration results in the sensing element being exposed to the sample matrix and the various labelling and wash solutions. This article describes a microfluidic sensing chip that separates capture from detection while maintaining the sensor in its pristine state prior to measurement. Also described is a method that allows electrochemical oxidation and subsequent reduction of a redox marker to be measured without the complexities of an enzymatic redox process, therefore enabling the optimal fluidic parameters to be determined. Finally, application of the sensor chip for the detection of COVID-19 antibodies in plasma, shows that this approach can readily discriminate between positive patient plasma and controls.