Fluorescence quenching-based signal amplification on immunochromatography test strips for dual-mode sensing of two biomarkers of breast cancer.

Recently, immunochromatography test strips (ICTS) have been fully developed for point-of-care testing (POCT). However, the intrinsic limitations including non-quantitative detection of colloidal gold ICTS and low sensitivity of fluorescence ICTS (FICTS) significantly restrict their further application in clinical diagnosis. Taking advantages of rapid colorimetric qualitative detection and fluorescence quantitation, we designed a kind of sensitive and dual-mode magnetic FICTS (mFICTS) based on PLGA@Fe3O4 super-paramagnetic nanosphere (SPMN) probes quenching multiplex fluorescer on the test line through sandwich immunoreactions. Owing to the large number of Fe3O4 nanoparticles (about 47) encapsulated in one SPMN, about 2680 Cy5 molecules were quenched by one SPMN on the test line such that to significantly improve the analytical sensitivity as well as the detection of whole blood samples via magnetic separation. Moreover, the aggregation of black SPMN on the test line enabled a quick naked-eye screening in 3 min. For high accuracy breast cancer diagnosis, combined determination of carcinoembryonic antigen (CEA) and carbohydrate antigen (CA153) was performed on one mFICTS with the limits of detection of about 0.06 ng mL-1 and 0.09 U mL-1, respectively. Then, more than 50 clinical serum samples were investigated for high-resolution screening by mFICTS, and the results were coincident with those obtained by electrochemiluminescence immunoassay (ECLIA). Thus, the designed mFICTS is suitable for point-of-care diagnostics.