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

Development of point-of-care bioassays for sensitive screening of protein-based cancer biomarkers would improve 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 detection of 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 donor and acceptor, respectively. Competitive binding of EpCAM displaced the cDNA, resulting in reduction of FRET. The paper-based bioassay was able to detect EpCAM in buffer solution as well as 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.This work was sponsored by the Natural Sciences and Engineering Research Council of Canad