Photonic crystals: A platform for label-free and enhanced fluorescence biomolecular and cellular assays
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1133-AA04-01
Photonic crystals: A platform for label-free and enhanced fluorescence biomolecular and cellular assays Brian T. Cunningham1, Leo Chan1, Patrick C. Mathias2, Nikhil Ganesh3, Sherine George2, Erich Lidstone2, James Heeres4, and Paul J. Hergenrother4 1 3
Department of Electrical and Computer Engineering, 2Department of Bioengineering, Department of Material Science and Engineering, 4Department of Chemistry
University of Illinois at Urbana-Champaign, Urbana, IL 61801 ABSTRACT Photonic crystal surfaces represent a class of resonant optical structures that are capable of supporting high intensity electromagnetic standing waves with near-field and far-field properties that can be exploited for high sensitivity detection of biomolecules and cells. While modulation of the resonant wavelength of a photonic crystal by the dielectric permittivity of adsorbed biomaterials enables label-free detection, the resonance can also be tuned to coincide with the excitation wavelength of common fluorescent tags including organic molecules and semiconductor quantum dots. Photonic crystals are also capable of efficiently channeling fluorescent emission into a preferred direction for enhanced extraction efficiency. Photonic crystals can be designed to support multiple resonant modes that can perform label free detection, enhanced fluorescence excitation, and enhanced fluorescence extraction simultaneously on the same device. Because photonic crystal surfaces may be inexpensively produced over large surface areas by nanoreplica molding processes, they can be incorporated into disposable labware for applications such as pharmaceutical high throughput screening. In this talk, the optical properties of surface photonic crystals will be reviewed and several applications will be described, including results from screening a 200,000-member chemical compound library for inhibitors of protein-DNA interactions, gene expression microarrays, and high sensitivity of protein biomarkers. INTRODUCTION Today, most assays used in drug discovery research use some sort of label to help visualize or quantify protein, DNA, small molecules, or cells. Organic fluorescent dye molecules, radioligands, and secondary reporters comprise the most common classes of tags. In contrast with labeled methods, label-free detection involves the use of a transducer that is capable of directly measuring some physical property of a chemical compound, DNA molecule, peptide, protein, or cell. For example, all biochemical molecules and cells have finite dielectric permittivity, mass, and height (i.e. the ability of charges to interact with the electric field of light waves propagating through them) that can be used to indicate their presence or absence using an appropriate sensor. The sensor functions as a transducer that can convert one of these physical properties into a quantifiable signal that can be gathered by an appropriate instrument. Label-free detection removes experimental uncertainty induced by the effect of the label on
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