The in-line-quadrature bioCD

Ming Zhao; Xuefeng Wang; David Nolte

doi:10.1117/12.701212

10 February 2007 The in-line-quadrature bioCD

Ming Zhao, Xuefeng Wang, David Nolte

Proceedings Volume 6447, Nanoscale Imaging, Spectroscopy, Sensing, and Actuation for Biomedical Applications IV; 64470B (2007) https://doi.org/10.1117/12.701212
Event: SPIE BiOS, 2007, San Jose, California, United States

Abstract

The biological compact disc (BioCD) is a sensitive detection platform that detects immobilized biomolecules on the surface of a spinning disc by quadrature laser interferometry. Spinning-disc interferometry (SDI) has the advantage of operating faraway from the 1/f system noise which has a 40 dB per octave slope, thus reducing the detection noise floor by more than 50 dB compared to static interferometric detection techniques. Three quadrature classes of BioCD have been previously reported: micro-diffraction, adaptive optical and phase contrast. In this paper, we introduce a new class of BioCD, the in-line quadrature class, which has achieved a new level of simplicity and sensitivity. A silicon wafer coated by a layer of SiO₂ is used as a substrate for immobilized biomolecules. The thickness of the SiO₂ layer is chosen so that light reflected from the SiO₂ surface on top and the silicon surface below is approximately in phase quadrature. Protein molecules scatter the incident light, adding a phase shift linearly proportional to the mass density of the immobilized protein, which is converted to a far-field intensity shift by quadrature interference. Patterning of protein is achieved by spot printing with a jet printer, which produces protein spots 0.1 mm in diameter. We demonstrate the sensitivity of the in-line quadrature BioCD by an equilibrium dose response experiment on a disc printed with 25,000 proteins spots with a detection limit of 1 ng/mL when divided into 32 virtual wells and treated as 32 separate assays. This current performance is not a fundamental limit, and improvements in disc uniformity will enable scaling up to large numbers of individual assays per disc.

Citation Download Citation

Ming Zhao, Xuefeng Wang, and David Nolte "The in-line-quadrature bioCD", Proc. SPIE 6447, Nanoscale Imaging, Spectroscopy, Sensing, and Actuation for Biomedical Applications IV, 64470B (10 February 2007); https://doi.org/10.1117/12.701212

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