A FRET immunosensor for sensitive detection of CA 15-3 tumor marker in human serum sample and breast cancer cells using antibody functionalized luminescent carbon-dots and AuNPs-dendrimeraptamer as donor-acceptor pair

We proposed a FRET immunosensing for detection of CA15-3 tumor marker by highly biospecific interactions between CA 15-3 antigen and the corresponding antibody and aptamer. In this sandwich type immunoassay, CA15-3 antibody-functionalized carbon dots and AuNPs labeled PAMAM-Dendrimer/aptamer were used as donor/acceptor, respectively. When CA 15-3 Ag was added to homogenous immunoassay, the strong complex interaction between CA15-3 Ab-CA15-3 Ag- aptamer caused in more coming closer carbon dot and AuNPs and more decreasing fluorescence signal. The decreased fluorescence intensity was linear at three ranges including in concentration range 1.1 mu UmL(-1) to 16 mu U mL(-1) with regression of R-2 = 0.9879, at the concentration range 16 mu U mL(-1) to 0.163 mU mL(-1) with regression of R-2 = 0.9944 and at the concentration range 0.163 mU mL(-1) to 5.0 mU mL(-1) with regression of R-2 = 0.9805. The detection limit of the FRET immunoassay was 0.9 mu U mL(-1). This assay revealed good sensitivity and specificity with MDA-MB-231 breast cancer cells concentrations from 1000 to 40000 cells/mL with correlation coefficient of 0.9955 and detection limit of 300 cells/mL (3 cells in 10 mu L of injected sample). In addition, this FRET immunosensing is applicable in diluted human serum. The recovery values were in the range of 95.86-96.97% for CA 15-3 Ag in spiked serum sample with RSD lower than 7.3%. The proposed immunoassay could be a valid model for establishing other immunoassays for detection of different cancer tumor markers with relevant antigens and antibodies.