SALSA School of Analytical Sciences Adlershof, Humboldt-Universität zu Berlin, Albert-Einstein-Str. 5-9, 12489 Berlin, Germany and Department of Chemistry, Humboldt-Universität zu Berlin, Brook-Taylor-Str. 2, 12489 Berlin, Germany.
Department of Chemistry, Humboldt-Universität zu Berlin, Brook-Taylor-Str. 2, 12489 Berlin, Germany.
Nanoscale. 2017 Jun 14;9(23):8024-8032. doi: 10.1039/c7nr02762a.
Hyper Raman scattering, that is, spontaneous, two-photon excited Raman scattering, of organic molecules becomes strong when it occurs as surface-enhanced hyper Raman scattering (SEHRS), in the proximity of plasmonic nanostructures. Its advantages over one-photon excited surface-enhanced Raman scattering (SERS) include complementary vibrational information resulting from different selection rules, probing of very small focal volumes, and beneficial excitation with long wavelengths. Here, imaging of macrophage cells by SEHRS is demonstrated, using SEHRS labels consisting of silver nanoparticles and two different molecules, 2-naphthalenethiol and para-mercaptobenzoic acid, that are excited off-resonance. The vibrational signatures of the molecules are discriminated using hyperspectral analysis and provide information about the subcellular localization of the SEHRS probes. The SEHRS based hyperspectral imaging approach presented here uses principal component analysis (PCA) to localize the reporter molecules inside the cells and is augmented by hierarchical cluster analysis (HCA). The high sensitivity of SEHRS spectra with respect to small environmental changes can be utilized for mapping of physiological parameters in the endosomal system of the cells. This is illustrated by discussing the spatial distribution of endosomes of varying pH inside the cytosol.
超拉曼散射，即自发的双光子激发拉曼散射，当它发生在等离子体纳米结构附近的表面增强超拉曼散射（SEHRS）中时会变得很强。与单光子激发表面增强拉曼散射（SERS）相比，它具有互补的振动信息，这是由于不同的选择规则，探测非常小的焦点体积，以及有益的长波长激发。在这里，使用由银纳米粒子和两种不同分子（2-萘硫醇和对巯基苯甲酸）组成的 SEHRS 标记物，通过 SEHRS 对巨噬细胞进行了成像，这些分子在离共振激发。通过高光谱分析对分子的振动特征进行了区分，并提供了有关 SEHRS 探针亚细胞定位的信息。这里提出的基于 SEHRS 的高光谱成像方法使用主成分分析（PCA）来定位细胞内的报告分子，并通过层次聚类分析（HCA）进行增强。SEHRS 光谱对小环境变化的高灵敏度可用于绘制细胞内内体系统中的生理参数。通过讨论细胞质中不同 pH 值的内体的空间分布来说明这一点。
