| 摘要: | 表面電漿式的蛋白質微晶片陣列具有免螢光、免清洗、多工、即時等優點，過去三十年來，表面電漿感測元件已從實驗室走向商品，成為生物醫學檢測的一項利器。目前的表面電漿生醫感測系統多採用克式結構(Kretschmann configuration)，以稜鏡產生高動量入射波，搭配鍍有金屬的載玻片及複雜的光學追蹤系統，才能偵測到微弱的光訊號變化。然而稜鏡不只體積大、價格貴，與載玻片之間也有光耦合不易的問題。
在本研究中，我們以高折射率的氮化鎵磊晶層取代稜鏡，並在表面的金屬層產生表面電漿效應，不但能簡化感測元件的設計，還能增加表面電漿的發光強度。此外，我們採用的氮化銦鎵量子井，可做為表面電漿效應的增益層(gain medium)，具備訊號放大效果，能偵測到更低濃度之檢體，因而提升系統敏感度與解析能力。並可藉由調整氮化銦鎵量子井的磊晶結構，優化量子井與表面電漿偏振子(surface plasmon polaritons)之間的耦合效率，以產生更強之表面電漿共振。
藉由檢測酒精、抗原Protein G與人體抗體IgG三種溶液以驗證系統可行性。量測檢果顯示：酒精溶液其敏感度為8×〖10〗^(-5) (RIU^(-1))，人體抗體IgG溶液檢測極限(Limit of detection)可達1.89nM。
;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. |
