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Proceedings Paper

Phase-contrast BioCD: high-speed immunoassays at sub-picogram detection levels
Author(s): Ming Zhao; Leilei Peng; W. Cho; F. Regnier; D. D. Nolte
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Paper Abstract

We previously introduced the biological compact disk (BioCD) as a sensitive detection platform to detect patterned biomolecules immobilized on the surface of a spinning disk. Spinning-disk interferometry allows high speed detection (10 microseconds per spot) of optical path length changes down to sub-nanometer scales with high repeatability. The key to performing stable interferometry on a mechanically spinning disk is self-referencing: locking the phase of the signal and reference beams to quadrature (μ/2 phase difference) independent of mechanical vibrations or relative motion. Two quadrature classes of BioCD have been reported previously: the micro-diffraction class (MD-Class) and the adaptive optical class (AO-Class) {Peng, 2004 #565; Varma, 2004 #440}. In this paper, we introduce a third class of BioCD, the Phase-Contrast-Class (PC-Class) BioCD. Protein is immobilized using photolithography on a disk in a 1024 spoke pattern. The edge of the printed protein pattern diffracts a focused laser beam that is detected in the Fourier plane with a split detector. The signal from the split detector is differenced, which plays a role in the electronic domain similar to that of a phase plate in optical phase contrast imaging. The PC-Class BioCD is simple in both theory and implementation, requiring no microstructure fabrication and no complex detection. Its potential in high speed label-free biosensing is demonstrated by a two-analyte immunoassay that shows good rejection of nonspecific binding and low antibody cross-reactivity. Immunoassays were performed against IgG immunoglobulins with detection of bound analyte on pictogram level. To show the potential of scaling up to hundreds or thousands of analytes per disk, an experiment was also performed with small drops of protein solution.

Paper Details

Date Published: 28 February 2006
PDF: 12 pages
Proc. SPIE 6095, Nanobiophotonics and Biomedical Applications III, 60950L (28 February 2006); doi: 10.1117/12.646827
Show Author Affiliations
Ming Zhao, Purdue Univ. (United States)
Leilei Peng, Purdue Univ. (United States)
W. Cho, Purdue Univ. (United States)
F. Regnier, Purdue Univ. (United States)
D. D. Nolte, Purdue Univ. (United States)

Published in SPIE Proceedings Vol. 6095:
Nanobiophotonics and Biomedical Applications III
Alexander N. Cartwright; Dan V. Nicolau, Editor(s)

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