"This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5)."
Silicon photonics has revealed its potential to revolutionize label-free real-time biosensing. Through chemistries that can selectively functionalize both oxidized silicon and silicon nitride with protein, DNA, antibody, carbohydrate and small molecule ligands, it is possible to achieve both specificity and extraordinary sensitivity in a chip-scale system based on the use of nanophotonic waveguides. Among the most promising biosensing structures to emerge from the silicon photonics community is the silicon ring resonator. The ring resonator consists of a travelling-wave ring that is coupled to a nearby silicon waveguide. Analogous to conventional Surface Plasmon Resonance (SPR), the surface functionalized ring resonator's (SFRR) response is a function of the refractive index above the resonator - permitting it to sensitively and specifically detect cells and biomolecules at or near the surface of the device. Literature reports have demonstrated that these and other resonant devices can be used to detect interactions with proteins, DNA, viruses and bacteria. Preliminary studies indicate that the SFRR possesses sensitivities that exceed that of SPR for identical surface chemistries - with limits of detection low enough to potentially detect individual small-molecule binding events. As such, conjugation methods that have been used for decades within the surface science and biosensing communities can now be leveraged, with silicon photonics, to significantly enhance biosensor capabilities. The objective of this proposal is to develop a new generation of ultrasensitive biosensors based on the combination of novel integrated silicon nanophotonic devices and optimized surface chemistries for the presentation of biomolecular ligands. This proposal will focus on the use of synthetic carbohydrates as model ligands to facilitate the design and fabrication of this biosensing platform. Carbohydrates were selected for this application based on the fact that they are involved in a range of high-affinity and lowaffinity binding events, including interactions with other carbohydrates, proteins, nucleic-acids, cells, bacteria, and viruses. Carbohydrates and glycoconjugates are also implicated in a variety of vital biological processes, and real-time label-free glycan biosensors would be invaluable to biomedical research in host-pathogen interactions and vaccine design.
