Planar optical waveguide-based biosensor for the quantitative detection of tumor markers

There is an immediate need for rapid and sensitive early diagnostics for breast cancer. In this manuscript we demonstrate, for the first time, the application of a waveguide-based biosensor developed at the Los Alamos National Laboratory for the sensitive (<0.5 pM), specific (low non-specific binding), rapid (15 min) and quantitative detection of carcinoembryonic antigen (CEA), a breast cancer biomarker. Our assay format involves the detection of the antigen in a fluorescence-based sandwich immunoassay within the evanescent field of single mode planar optical waveguides. The assay was tested with a small cohort of serum and nipple aspirate fluid samples from patients with abnormal mammograms. Seven of the 15 serum samples tested had CEA concentrations above the assumed normal threshold concentration in serum (∼39 pM). Only one aspirate sample presented with significantly high CEA concentrations, and this concentration correlated with the disease status of the patient. These results simply demonstrate the applicability of our biosensor for the detection of biomarkers in complex samples. We envision translating this assay to a multi-channel format for the simultaneous detection of several biomarkers. Such a platform, in addition to current imaging strategies, will allow for the more reliable early detection of breast cancer.