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Optical Interference for Nanoscale Biological Imaging and Detection

Photonics Seminar SeriesPresents
“Optical Interference for Nanoscale Biological Imaging and Detectionâ€Â
Professor M. Selim ÜnlüDepartment of Electrical and Computer EngineeringBoston University
We have utilized basic principles of optical interference and resonance in biological applicationsdemonstrating nanometer scale measurement capability in fluorescence microscopy and label-freesensing of protein binding and viruses in a high-throughput micro-array format.
We have developed a technique â€" spectral self-interference fluorescent microscopy (SSFM) â€" thattransforms the variation in emission intensity for different path lengths used in fluorescenceinterferometry to a variation in the intensity for different wavelengths in emission, encoding the high-resolution information in the emission spectrum. Using SSFM, we have estimated the shape of coiledsingle-stranded DNA, the average tilt of double-stranded DNA of different lengths, and the amount ofhybridization. The determination of DNA conformations on surfaces and hybridization behavior provideinformation required to move DNA interfacial applications forward and thus impact emerging clinical andbiotechnological fields. Recently, we have also applied SSFM to study the conformational changes ofpolymers and DNA-protein complexes. [1]
Direct monitoring of primary molecular binding interactions without the need for secondary reactantswould markedly simplify and expand applications of high-throughput label-free detection methods. We developed a simple interferometric technique â€" Spectral Reflectance Imaging Biosensor (SRIB) â€" that monitors the optical phase difference resulting from accumulated biomolecular mass. Dynamic measurements were made at ~10pg/mm2 sensitivity. We have also demonstrated simultaneous detection of antigens and antibodies in solution using corresponding probes on the SRIBsurface as well as label-free measurements of DNA hybridization kinetics. [2] [1] P. S. Spuhler, J. Knezevic, A. Yalcin, Q. Bao, E. Pringsheim, P. Dröge, U. Rant, and M. S. Ãœnlü, "Platform for in situ real-time measurement of protein-induced conformational changes of DNA ," Proceedings of the National Academy of Science, January 2010.
[2] I. E. Ozkumur J.W. Needham, D. A. Bergstein, R. Gonzalez, M. Cabodi, J. M. Gershoni, B. B.Goldberg, and M. S. Ãœnlü, “ “Label-free and dynamic detection of biomolecular interactions for high-throughput microarray applications,â€Â PNAS, Vol. 105, pp. 7988â€"7992(2008)

Location: Hughes Aircraft Electrical Engineering Center (EEB) - 248

Audiences: Everyone Is Invited

Contact: Petra Pearce Sapir