Yu Xinke, Hayden Eric Y, Wang Pu, Xia Ming, Liang Owen, Bai Yu, Teplow David B, Xie Ya-Hong
Department of Materials Science and Engineering, University of California, Los Angeles California, 90095, United States.
Department of Neurology, David Geffen School of Medicine at UCLA, University of California, Los Angeles, California, 90095, United States.
J Raman Spectrosc. 2020 Mar;51(3):432-441. doi: 10.1002/jrs.5785. Epub 2019 Dec 17.
Surface enhanced Raman spectroscopy (SERS) holds great promise in biosensing because of its single-molecule, label-free sensitivity. We describe here the use of a graphene-gold hybrid plasmonic platform that enables quantitative SERS measurement. Quantification is enabled by normalizing analyte peak intensities to that of the graphene G peak. We show that two complementary quantification modes are intrinsic features of the platform, and that through their combined use, the platform enables accurate determination of analyte concentration over a concentration range spanning seven orders of magnitude. We demonstrate, using a biologically relevant test analyte, the amyloid β-protein (Aβ), a seminal pathologic agent of Alzheimer's disease (AD), that linear relationships exist between (a) peak intensity and concentration at a single plasmonic hot spot smaller than 100 nm, and (b) frequency of hot spots with observable protein signals, i.e. the co-location of an Aβ protein and a hot spot. We demonstrate the detection of Aβ at a concentration as low as 10 M after a single 20 μl aliquot of the analyte onto the hybrid platform. This detection sensitivity can be improved further through multiple applications of analyte to the platform and by rastering the laser beam with smaller step sizes.
表面增强拉曼光谱（SERS）因其单分子、无标记的灵敏度在生物传感领域具有巨大潜力。我们在此描述了一种石墨烯-金混合等离子体平台的应用，该平台能够进行定量SERS测量。通过将分析物峰强度与石墨烯G峰强度进行归一化来实现定量。我们表明，两种互补的定量模式是该平台的固有特性，并且通过联合使用，该平台能够在跨越七个数量级的浓度范围内准确测定分析物浓度。我们使用一种与生物学相关的测试分析物——淀粉样β蛋白（Aβ）（阿尔茨海默病（AD）的一种重要病理因子）进行了演示，结果表明：（a）在小于100 nm的单个等离子体热点处，峰强度与浓度之间存在线性关系；（b）具有可观察到蛋白质信号的热点频率，即Aβ蛋白与热点的共定位之间存在线性关系。我们展示了在将20 μl单份分析物滴加到混合平台上后，能够检测到低至10 M浓度的Aβ。通过多次将分析物应用于该平台以及以更小的步长扫描激光束，这种检测灵敏度可以进一步提高。
