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No single biomarker can accurately predict disease. An ideal biodetection technology should be capable of the quantitative, reproducible, and sensitive detection of a limited suite of such molecules. To this end, we have developed a multiplex biomarker assay for protective antigen and lethal factor of the Bacillus anthracis lethal toxin using semiconductor quantum dots as the fluorescence reporters on our waveguide-based biosensor platform. The platform is extendable to a wide array of biomarkers, facilitating rapid, quantitative, sensitive, and multiplex detection, better than achievable by conventional immunoassay. Our assay allows for the sensitive (limit of detection 1 pM each), specific (minimal nonspecific binding), and rapid (15 min) detection of these biomarkers in complex biological samples (e.g., serum). To address the issue of reproducibility in measurement and to increase our sample throughput, we have incorporated multichannel waveguides capable of simultaneous multiplex detection of biomarkers in three samples in quadruplicate. In this paper, we present the design, fabrication, and development of multichannel waveguides for the simultaneous detection of lethal factor and protective antigen in serum. Evaluation of the multichannel waveguide shows an excellent concordance with single-channel data and effective, simultaneous, and reproducible measurement of lethal toxins in three samples. 10.1021/ac901497g

The article discusses the synthesis and properties of the viral neuraminidase (NA) resistant S-sialosides, which are used for the detection of intact influenza viruses. A new stable strategy for the production of stable glycoconjugates is also presented.

The sensor team at the Los Alamos National Laboratory has developed a waveguide-based optical biosensor for the detection of biomarkers associated with disease. We have previously demonstrated the application of this technology to the sensitive detection of carcinoembryonic antigen in serum and nipple aspirate fluid from breast cancer patients. In this publication, we report improvements to this technology that will facilitate transition to a point-of-care diagnostic system and/or robust research tool. The first improvement involved replacing phospholipid bilayers used for waveguide functionalization with self-assembled monolayers. These thin films are stable, specific, and robust silane-based surfaces that reduce nonspecific binding and enhance the signal to background ratio. Second, we have explored four different fluorescent labeling paradigms to determine the optimal procedure for use in the assay. Labeling the detector antibody with an organic dye (AlexaFluor 647) in the hinge region allows for unusual signal enhancement with repeat excitation (at 635 nm) in our assay format, thereby facilitating a better signal resolution at lower concentrations of the antigen. We have also labeled the detector antibody with photostable quantum dots through either the amine groups of lysine (Fc, NH) or using a histidine tag in the hinge region of the antibody (Hinge, H). Both labeling strategies allow for acceptable signal resolution, but quantum dots show much greater resistance to photobleaching than organic dyes.