Detection of a cancer biomarker protein on modified cellulose paper by fluorescence using aptamer-linked quantum dots

The development of point-of-care bioassays for sensitive screening of protein-based cancer biomarkers would improve the opportunity for early stage diagnosis. A strategy for a fluorescence resonance energy transfer (FRET)-based bioassay has been investigated that makes use of modified cellulose paper for the detection of an epithelial cell adhesion molecule (EpCAM), which is a transmembrane glycoprotein that is overexpressed in several tumors of epithelial origin. The paper matrix was a substrate for immobilized aptamer-linked quantum dots (QDs-Apt) and Cy3 labeled complementary DNA (cDNA), which served as a donor and an acceptor, respectively. Competitive binding of EpCAM displaced the cDNA, resulting in the reduction of FRET. The paper-based bioassay was able to detect EpCAM in buffer solution as well as in 10% bovine serum solution using a reaction time of no more than 60 minutes. The dynamic range was 1-100 nM in buffer with a precision better than 4%, and the limit of detection was 250 pM in buffer and 600 pM in 10% serum.