Smartphone-Based Free-to-total Prostate Specific Antigen Ratio Detection System Using a Colorimetric Reaction Integrated with Proximity-Induced Bio-Barcode and Crispr/Cas12a Assay

The free-to-total prostate specific antigen (f/t-PSA) ratio is of great significance in the accurate diagnosis of prostate cancer. Herein, we report a smartphone-based detection system using a colorimetric reaction integrated with proximity-induced bio-barcode and the CRISPR/Cas12a assay for f/t-PSA ratio detection within an hour. DNA/antibody recognition probes were designed to bind f-PSA or t-PSA and induce the release of the DNA bio-barcode. The CRISPR/Cas12a system was activated by the DNA bio-barcode to release Ag+ from the C-Ag+-C structure of the hairpin DNA. The released Ag+ was used to affect the TMB-H2O2-based colorimetric reaction catalyzed by Pt NPs, as the peroxidase-like activity of the Pt NPs could be efficiently inhibited by Ag+. A smartphone with a self-developed app was used as an image reader and analyzer to analyze the colorimetric reaction and provide the results. A limit of detection of 0.06 and 0.04 ng/mL was achieved for t-PSA and f-PSA, respectively. In addition, a concentration of 10 ng/mL could be distinguished by the naked eye. The smartphone-based method showed a linear response between 0.1–100 ng/mL of t-PSA or f-PSA. In tests with clinical samples, the smartphone-based method successfully diagnosed prostate cancer patients from benign prostatic hyperplasia patients and healthy cases with sensitivity and specificity of 100%, thus showing application prospects for on-site, rapid, and accurate diagnosis of prostate cancer.