A portable and low-cost microfluidic POCT device for detecting N protein

Point-of-care testing (POCT) is attractive for disease diagnosis, offering low cost, high efficiency, and accessibility. Microfluidic chip technology for POCT, though promising, has limitations, since its sensitivity depends on enzymes with poor environmental tolerance and it requires complex instruments. To address this, we present a novel portable microfluidic POCT device (PMPD). It replaces enzymatic reactions with a metal cascade protocol, combining metal stability and immunochemical sensitivity. The PMPD features a microfluidic analytic colorimetric chip for enzyme-free biomarker detection and a hand-held photoelectric colorimetric system for quantification. Testing the PMPD with SARS-CoV-2 N proteins showed a low limit of detection (LOD) (<0.04 ng/mL), a linear range of 0.1–14 ng/mL, and a 27-min detection time. In simulated clinical samples, the LOD was <0.05 ng/ml. The device can be adapted for other biomarkers by changing affinity molecules. Overall, the PMPD has great potential in disease screening for its cost-effectiveness, high sensitivity, and portability.