高灵敏倏逝波光纤SERS探针及其微流控生物检测应用

Currently when SERS spectroscopy is used in the microfluidic biological detection, a major difficulty is the relative low sensitivity, which is caused by the small Raman scattering cross-section and low photothermal damage threshold of biomolecules. In this project, we propose a novel way by combining the microfluidic technique with evanescent-wave fiber SERS probe. By utilizing the large light-matter interaction area, the photothermal damage effect can be avoid effectively. At the same time, the nanoparticle capture characteristic of fiber evanescent-wave is beneficial to construct fiber SERS probes with "light field adaptive" distribution, which improves the sensitivity of SERS for biomolecules. Here, we will focus on the transmission loss properties caused by the metal nanoparticles in the evanescent-wave fiber SERS probes, and investigate the influence of the nanoparticles distribution on the probe performances and reveals its intrinsic mechanism. We will develop the laser-evanescent-wave-induced trapping method, and realize the controllable fabrications of fiber SERS probe using fiber evanescent wave technique, which realizes the "light field adaptive" distribution of nanoparticles. Finally, we will build the microfluidic & fiber-SERS-probe composite chip, and develop a portable microfluidic SERS spectrometer prototype to achieve high sensitivity and field detection of dopamine. This project will provide a new idea for the design and construction of the highly sensitive evanescent-wave fiber SERS probe, and it is helpful to promote the practical applications of microfluidic SERS spectroscopy.

针对当前SERS光谱用于微流控生物检测时因生物分子较小的拉曼散射截面和较低的光热损伤阈值导致检测灵敏度低的问题，本项目提出将倏逝波光纤SERS探针与微流控技术相结合，利用光纤倏逝波特性极大增大SERS相互作用面积，避免生物分子的光热损伤；同时，光纤倏逝波可俘获纳米颗粒形成“光场自适应”分布的光纤SERS探针，提高生物检测灵敏度。我们将重点研究倏逝波光纤SERS探针中贵金属纳米颗粒引起的波导传输损耗特性，探明纳米颗粒分布对探针性能的影响规律及内在机制；发展激光诱导倏逝波俘获法，实现“光场自适应”分布光纤SERS探针的可控重复制备；构建微流控-光纤SERS探针组合芯片，研制便携式微流控SERS光谱检测样机，实现多巴胺高灵敏、现场检测。本项目的顺利开展将为高灵敏倏逝波光纤SERS探针的设计及构筑提供新思路，并利于促进微流控SERS光谱技术的实用化进程，具有重要研究意义。

本项目针对生物分子较小的拉曼散射截面和较低的光热损伤阈值导致的SERS光谱检测灵敏度低的问题，将光纤SERS探针与微流控芯片相结合，系统开展了微流控-SERS光谱生物检测技术的理论和实验研究。理论上，研究了基于光纤倏逝波的SERS激发与收集特性，揭示了光纤倏逝波能够显著增大SERS相互作用面积，提高光谱检测灵敏度和重复性；同时，倏逝波相互作用可有效避免生物分子的光热损伤，提高SERS光谱检测的可靠性。实验上，发展了激光诱导蒸发自组装法、激光诱导的滑移辅助界面自组装法等两种光纤SERS探针制备方法，详细阐明了两种方法中激光诱导下贵金属纳米颗粒在光纤表面自组装的机理；并通过优化激光诱导实验条件，实现多种类型的平端面、锥形及D型光纤SERS探针的可控、重复制备；制备出的光纤SERS探针展现出优良的液相检测灵敏度和重复性（对R6G、CV等常规拉曼分子的液相原位检测灵敏度优于10^-9 M，光谱重复性RSD小于10%）。进一步地，我们利用超快激光直写法制备玻璃基微流控芯片，通过将高性能光纤SERS探针与微流控芯片相结合，研制出“一字型”和“T型”两种微流控-光纤SERS探针组合芯片，揭示了组合芯片中光纤探针引入方式、液体流速等对光谱检测的影响；研制出一台785nm便携式微流控SERS光谱检测样机，与微流控-光纤SERS探针组合芯片联用，实现微流控通道中多巴胺、细胞外泌体、盐酸奥达特罗等多种生物或药物分子的高灵敏、液相原位检测（对多巴胺和盐酸奥达特罗的检测灵敏度分别优于10^-6 M和0.01 mg/ml）；该微流控SERS检测方式有效避免了光谱检测过程中生物分子的损伤或氧化，且通过简单更换光纤SERS探针即可实现微流控-SERS芯片的重复使用，较大降低检测成本。本项目为高灵敏倏逝波光纤SERS探针的设计及构筑提供新思路，也为生物分子的高灵敏、高可靠性微流控SERS光谱检测提供一种简单、低成本的实现方案，进而促进微流控SERS光谱技术在生物医药领域的实用化进程。