SBIR Phase I: Improved Substrates for Single Molecule Detection

This Small Business Innovation Research Phase I project will develop substrates for enhancing the fluorescence signal from nearby analytes. This will be achieved by utilizing two-dimensional arrays of regularly spaced metallic nanoparticles thereby generating propagating modes of surface plasmons. These surface plasmon resonances will be tuned by varying the size, composition, and spacing of the nanoparticle array to match the fluorescence emission of the fluorophore. Alternatively, arrays of high dielectric nanomaterials will be used to generate photonic crystals serving to focus and enhance the allowed frequencies with defects serving as sites for the local trapping of light. These nanoparticle arrays will be assembled using two-dimensional protein crystals as templates as previously reported. Localization of the fluorophore to the surface of the arrays will be beneficial for single molecule detection. This will have broad application in many types of fluorescence-based biosensors where, for example, nucleic acid or antibody probes are attached to a surface. Attaching these probes to a fluorescence-enhancing substrate will improve the sensitivity of these assays. Furthermore, these substrates will allow more robust single molecule detection applications by reducing problems associated with fluorophore bleaching and by concentrating the probe region to smaller volumes. This will benefit basic research in areas such as protein folding, enzyme kinetics, and reaction mechanisms as well as promote the development of biosensors to detect low levels of virus or trace amounts of biological warfare agents.