A fully integrated distance readout ELISA-Chip for point-of-care testing with sample-in-answer-out capability

Enzyme-linked immunosorbent assay (ELISA) is a popular laboratory technique for detection of disease-specific protein biomarkers with high specificity and sensitivity. However, ELISA requires labor-intensive and time-consuming procedures with skilled operators and spectroscopic instrumentation. Simplification of the procedures and miniaturization of the devices are crucial for ELISA-based point-of-care (POC) testing in resource-limited settings. Here, we present a fully integrated, instrument-free, low-cost and portable POC platform which integrates the process of ELISA and the distance readout into a single microfluidic chip. Based on manipulation using a permanent magnet, the process is initiated by moving magnetic beads with capture antibody through different aqueous phases containing ELISA reagents to form bead/antibody/antigen/antibody sandwich structure, and finally converts the molecular recognition signal into a highly sensitive distance readout for visual quantitative bioanalysis. Without additional equipment and complicated operations, our integrated ELISA-Chip with distance readout allows ultrasensitive quantitation of disease biomarkers within 2 h. The ELISA-Chip method also showed high specificity, good precision and great accuracy. Furthermore, the ELISA-Chip system is highly applicable as a sandwich-based platform for the detection of a variety of protein biomarkers. With the advantages of visual analysis, easy operation, high sensitivity, and low cost, the integrated sample-in-answer-out ELISA-Chip with distance readout shows great potential for quantitative POCT in resource-limited settings.