Serum and Saliva CEA Determinations via Fluorescent Nanoparticles

Objectives: Carcinoembryonic antigen (CEA) is an oncofetal glycoprotein normally present in utero, with elevated adult levels correlated to a number of cancers including lung, breast, and colorectal. Extension of effective quantitative detection range for CEA in saliva and serum versus ELISA is accomplished with the integration of semiconductor nanoparticles quantum dots (QDs) as a next-generation transduction element as opposed to traditional molecular dyes. Because of reduced optical requirements, these fluorophores may play a critical role in developing point-of-care diagnostic and monitoring devices for biomarkers such as CEA.

Methods: Whole unstimulated saliva and serum samples were collected from control (N=20) and cervical cancer (N=20) volunteers and prepared for analysis via centrifugation and dilution in normal saline. Fluorescence signal arose from QD labeled detecting antibody after antigen immobilization on agarose beads via sandwich-type assay. Data acquired in the nano-bio-chip sensor system was converted to effective concentration via a dose response curve created with recombinant antigen and similarly with commercially available ELISA reagents vended both from ALPCO and BioQuant.

Results: Limit of detection (LOD) for CEA was reduced to 0.02 ng/mL in the nano-bio-sensor, nearly two orders of magnitude lower than that of ELISA systems. The QD fluorophores give nearly 30x amplification of signal versus Alexa 488. Samples from diseased individuals showed consistently elevated CEA levels compared to their healthy counterparts in both saliva and serum. Strong correlation was observed between the two analytical techniques.

Conclusion: Serum and saliva samples were investigated with nano-bio-chip and CEA values found to be in agreement with commercially available ELISA kits. The new platform in tandem with next generation fluorophores promises to be a robust tool for analysis of complex fluids over range of concentrations.

NIH/NIDCR (#U01DE017793).