High-speed spinning-disk interferometry on the BioCD for human diagnostic applications

The BioCD is an optical biosensor that uses highspeed spinning-disk interferometry for direct detection of antigen binding in multiplexed immunoassay protein arrays. The high-frequency sampling suppresses the noise floor and enables a metrology-limited height resolution of 1 picometer for measuring surface-bound protein. In assay protocols there is a direct trade-off between multiplex degree and limit of detection. In this paper, we demonstrate quantitative assays and the scaling properties of direct detection on the BioCD in assays of clinical relevance for human diagnostics, including haptoglobin assays and prostate-specific antigen assays in human patient sera.