Integrated Colorimetric CRISPR/Cas12a Detection of Double-Stranded DNA on Microfluidic Paper-Based Analytical Devices

Early detection of high-risk human papillomavirus (HPV), particularly HPV16 E7, is critical for cervical cancer prevention. Here, we report a novel, portable, and instrument-free biosensing platform that integrates recombinase polymerase amplification (RPA) with CRISPR/Cas12a-mediated detection on a microfluidic paper-based analytical device (μPAD) for colorimetric, visual readout of double-stranded DNA (dsDNA). The μPAD features seven functional zones, including lyophilized RPA and CRISPR reagents, and immobilized streptavidin and anti-FAM antibodies for signal generation. Upon target recognition, Cas12a's trans-cleavage activity releases biotinylated-FAM-labeled reporters that form a sandwich complex with gold nanoparticle (AuNP)-conjugated anti-FAM antibodies, producing a visible red signal at the test zone. The gray value of the colorimetric signal correlates linearly with target concentration, enabling the quantitative detection of HPV16 E7 dsDNA down to 100 pM within 60 min. The assay demonstrated high accuracy and reproducibility in spiked samples. By combining isothermal amplification, CRISPR specificity, and paper-based microfluidics, this platform offers a rapid, low-cost, and user-friendly solution for point-of-care HPV screening in resource-limited settings. This work advances the integration of CRISPR diagnostics with μPAD, paving the way for scalable point-of-care molecular diagnostics beyond HPV.