Resonant Cavity Imaging Biosensor (RCIB)
The Resonant Cavity Imaging Biosensor (RCIB) detects binding between target biomolecules from a sample and probe biomolecules fixed to a microarray surface with the potential for tens of thousands of simultaneous parallel observation sites. Such ability yields information about the affinity of the biomolecules under test for the molecules on the capturing surface. Information about the affinity between molecules of interest such as particular proteins or DNA strands, yields great benefit to a number of applications in biological research, medical diagnostics, and biohazard detection. Current high-throughput microarray technology requires that the target molecules be labeled with a fluorescent dye. At best, this preparation step adds an acceptably small amount of time and money, but at its worse, can be prohibitively difficult depending on the nature of the application.
RCIB operates label-free without the need to add fluorescent labels or otherwise modify the target molecules in any way. An optical IR beam couples resonantly through a cavity constructed from Bragg mirrors that contains the microarray surface; the wavelength of the IR beam is swept using a tunable IR laser source; and an IR camera monitors cavity transmittance at each pixel, creating a highly parallel signature of transmittance versus wavelength for the microarray surface. This novel technique is enabled by high quality silicon substrates with buried Bragg reflectors previously developed within our group for improved photodetectors. The technique additionally relies on the use of commercial telecommunications hardware that has become readily available in recent years. In an alternative approach for microarray detection, the reflection from the substrate is measured with the varying wavelength. When binding occurs on the surface of the wafer, reflectivity vs. wavelength curve shifts, from which the height information can be extracted. This alternative approach is less sensitive than RCIB, but it draws attention with its simplicity. RCIB improves on existing label-free methods by offering dramatically improved throughput necessary to meet the needs of the microarray user community.