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Colloquium: February 12, 2014

Selim Ünlü*
Ultrasensitive Digital Detection of Nanoparticles:
Viral Diagnostics and Multiplexed Protein and,
Nucleic Acid Assays
Day Time Place
February 12, 2014 Wednesday 15:40 EE01

Host: F. Ömer İlday

ABSTRACT —  We apply basic principles of optical interference to biological sensing demonstrating label-free sensing of protein binding and DNA hybridization in a high-throughput micro-array format, and single pathogen detection with size discrimination capability.

Direct monitoring of primary molecular binding interactions without the need for secondary reactants would markedly simplify and expand applications of high-throughput label-free detection methods. We have developed the Interferometric Reflectance Imaging Sensor (IRIS) for label-free, high throughput, high sensitivity and dynamic detection of molecular binding on a solid surface. IRIS has demonstrated protein-protein binding and DNA-protein binding in real time, label-free, and in a high-throughput format with high sensitivity (~10 pg/mm2) and reproducibility [1,2] as well as label-free measurements of DNA hybridization kinetics [3] and viral detection [4].

Synthetic nanoparticles have made signicant impact across a broad range of technological applications including optical nanoantennas, ultra-sensitive imaging and sensing, and diagnostics and therapeutics. Natural nanoparticles such as viruses and pollutants are involved in global health problems. High-throughput characterization of nanoparticles in terms of their size and shape is crucial for practical applications of synthetic nanoparticles and highly sensitive pathogen identification.

Recently, we have demonstrated IRIA with the ability to detect single nanoscale particles [5]. To detect and size pathogens, IRIS shines light from multi-color LED sources sequentially on nanoparticles bound to the sensor surface, which consists of a silicon dioxide layer on top of a silicon substrate. Interference of light reflected from the sensor surface is modified by the presence of particles producing a distinct signal that reveals the size of the particle. In our approach the dielectric layered structure acts as an optical antenna optimizing the elastic scattering characteristics of nanoparticles for sensitive detection and analysis. We have successfully detected 35 nm and 50 nm radius particles and H1N1 viruses (illustrated in the conceptual picture) with accurate size discrimination [5]. Single nanoparticle detection with IRIS has shown promising results for protein [6] and DNA arrays with attomolar detection sensitivity.

1. Ozkumur E., J. W. Needham, D. A. Bergstein, R. Gonzalez, M. Cabodi, J. M. Gershoni, B. B. Goldberg, and M. S. Ünlü. “Label-free and Dynamic Detection of Biomolecular Interactions for High-throughput Microarray Applications.” Proceedings of the National Academy of Sciences, Vol. 105, No. 23, Pages: 7988-7992, (2008).
2. Özkumur E., A. Yalçın, M. Cretich, C. A. Lopez, D. A. Bergstein, B. B. Goldberg, M. Chiari, and M. S. Ünlü. “Quantification of DNA and Protein Adsorption by Optical Phase Shift.” Biosensors and Bioelectronics, Vol. 25, No. 1, 167-172, (2009).
3. E. Ozkumur, S. Ahn, A. Yalcin, C. Lopez, E. Cevik, R. Irani, C. DeLisi, M. Chiari, and M. S. Ünlü, “Label-free microarray imaging for direct detection of DNA hybridization and single-nucleotide mismatches,” Biosensors and Bioelectronics, Vol. 25, No. 7, 15, pp. 1789-1795, (2010).
4. C. Lopez, G. G. Daaboul, R. S. Vedula, E. Ozkumur, D. A. Bergstein, T. W. Geisbert, H. Fawcett, B. B. Goldberg, J. H. Connor, and M. S. Ünlü, “Label-free multiplexed virus detection using spectral reflectance imaging,” Biosensors and Bioelectronics, doi:10.1016/j.bios.2011.01.019, (2011).
5. G. G. Daaboul, A. Yurt, X. Zhang, G. M. Hwang, B. B. Goldberg, and M. S. Ünlü, “High-Throughput Detection and Sizing of Individual Low-Index Nanoparticles and Viruses for Pathogen Identification,” Nano Letters, Vol. 10, No. 11, pp. 4727-4731 (2010).
6. M. R. Monroe, G. G. Daaboul, A. Tuysuzoglu, C. A. Lopez, F. F. Little, and M. S. Ünlü, “Single Nanoparticle Detection for Multiplexed Protein Diagnostics with Attomolar Sensitivity in Serum and Unprocessed Whole Blood,” Analytical Chemistry, Vol. 85, No. 7, March/April 2013, pp. 3698-3706

*Boston University, Massachusetts, USA

The Physics Colloquia are designed to address a non-specialist, broad audience and introduce topics of contemporary research through lectures by leading experts. We warmly invite all members of the student body, including undergraduates enrolled in any programme.

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