FRET on lateral flow test strip to enhance sensitivity for detecting cancer biomarker

Fluorescence resonance energy transfer (FRET) between fluorescein isothiocyanate (FITC) and gold nano-particles (Au NPs) is introduced in the lateral flow strip to detect cancer biomarker CEA with the color and fluorescence dual-readout. Anti-CEA monoclonal antibody coated Au NPs were on the conjugate pad and FITC labelled antibody (FITC-Ab) for CEA was coated on the test line. All the reagents were general in the lateral flow strip or commercially available and no new materials or technique were involved, which make our proposal a more universal method and easier to operate. With the addition of CEA on the sample pad, anti-CEA monoclonal antibody coated Au NPs-CEA-FITC-Ab complex formed on the test line, leading to a megascopic red line and simultaneous quenched fluorescence of FITC via FRET. The visual limit of detection (LOD) through distinguishing red color change was 10 ng/mL and the LOD by differentiating fluorescence intensity was 0.1 ng/mL, which was two orders of magnitude lower than that without considering fluorescence in the strip. And the linear range changed from 10-80 ng/mL to 5-80 ng/mL with the analysis of fluorescence change. Meanwhile, the feasibility of our method applied in real clinical samples was also confirmed.