Four-channel Optical Detection on Protein-Patterned BioCD

摘要

We have developed a four-channel detection method on a protein-patterned BioCD that simultaneously measures fluorescence, Rayleigh scattering and/or diffraction, and two interferometric channels in orthogonal quadratures: one that measures differential phase and the other that measures direct phase. The latter two channels constitute label-free interferometric protein detection, while fluorescence and Mie scattering detection provide complementary tools. The BioCD is constructed as dielectric coated disks. Protein molecules patterned on dielectric films change the Fresnel reflection coefficient of the films. The change is exhibited in two ways: the reflection coefficient and the phase are both modulated. These are detected simultaneously by a split detector and designated as "amplitude" signal and "phase contrast" (PC) signal. We are able to scan and image patterned proteins across an entire coated disk with high speed in four channels. A single-analyte immunoassay shows strong correlation between the fluorescence channel and the interferometry channel with a detection limit of 10 ng/ml in a complex protein background (rat lysate) concentration of 7 mg/ml.