| dc.description.abstract |
Comparing with conventional biosensing techniques, surface plasmon resonance (SPR) biosensors allow label-free, wash-free, multi-analyte and real-time measurement, which can significantly expedite the assay process. However, most of current SPRi devices attain the SPR effect through the Kretschmann configuration, i.e. a complex involving a prism coupler, a glass slide, the refractive-index-matching oil, and intricate optical tracking components. In specific, a prism coupled with an Au-coated glass is usually required to attain the SPR effect through total internal reflection. The prism-glass complex is expensive, and often encounters the difficulty in optical coupling between the two components.
In this project, we built a nitride-based SPR proteome microarrays. The SPR structure comprises a single GaN/InGaN/GaN quantum well coated with a thin Ag layer. Biomolecular interactions are detected by the SPR effect induced at the GaN/Ag interface, where a minute change in refractive index can lead to measurable variation of the emission intensity from the quantum well. The InGaN quantum wells are of many inherent properties that are matchlessly suitable for SPRi biosensing, including the waveguide-like behaviour, the chemical and physical inertness, the TM-(or p-) polarized wave, and most importantly: the gain effect. These favorable properties not only simplify the sensing architecture by eliminating all the aforementioned apparatuses (prism, glass slide, index-matching oil, optical tracking components, etc.), but also pave a new route to push sensing performances via the prolonged propagation lengths of SP polaritons. More importantly, we show that the multi-mode characteristic of the quantum wells lead to an exponentially improved sensitivity/resolution upon the increase of surface refractive index, unlike the linear response exhibited by current SPR biosensors. Using human IgG, we demonstrate the detection limit of 1.89 nM with the nitride-based SPR biosensor. | en_US |