Universal, sensitive, and visual sandwich-type biosensor based on nanogold-catalyzed reduction and its application for detecting C-reactive protein in serum by a portable colorimeter

Abstract

We proposed a low-cost, high sensitive and universal point-of-care testing method of different dimension biomarkers based on the target-mediated catalytic reduction suppression of double-sequence aptamers-modified gold nanoparticles (dsApts@AuNPs) and NaBH₄ on the organic dyes (T-AAND). Herein, carcinoembryonic antigen, alpha-fetoprotein, C-reactive protein (CRP), thrombin, lipopolysaccharide, Staphylococcus aureus, and Escherichia coli were chosen as model biomarkers and all successfully detected, with limit of detections of 6.5 pg/mL, 12.7 pg/mL, 79.7 pg/mL, 34.2 fM, 459 fM, 718 CFU/mL, and 830 CFU/mL, respectively. Remarkably, the assay is completed in a single EP tube within 40 minutes, with on-site quantification performed using a $70 portable colorimeter and the cost of reagents for each test is $0.75. The CRP levels of 31 patients and 11 healthy volunteers achieved with the latex-enhanced immunoturbidimetry were high consistency with those of the spectrophotometry (r = 0.9964) and the colorimeter (r = 0.9619), demonstrating the accuracy of the new method. In conclusion, the T-AAND integrated a colorimeter is a superior approach for detecting biomarkers, especially in resource-limited settings.