Department of Applied Physics , Osaka University , Suita , Osaka 565-0871 , Japan.
CAS Key Lab of Bio-Medical Diagnostics, Suzhou Institute of Biomedical Engineering and Technology , Chinese Academy of Sciences , 215163 , Suzhou , China.
Anal Chem. 2019 Mar 5;91(5):3254-3262. doi: 10.1021/acs.analchem.8b03276. Epub 2019 Feb 14.
Intracellular pH is one of the key factors for understanding various biological processes in biological cells. Plasmonic gold and silver nanoparticles (NPs) have been extensively studied for surface-enhanced Raman scattering (SERS) applications for pH sensing as a local pH probe in a living cell. However, the SERS performance of NPs depends on material, size, and shape, which can be controlled by chemical synthesis. Here, we synthesized 18 types of gold and silver NPs with different morphologies such as sphere, rod, flower, star, core/shell, hollow, octahedra, core/satellites, and chainlike aggregates, and quantitatively compared their SERS performance for pH sensing. The SERS intensity from the most commonly utilized SERS probe molecule ( para-mercaptobenzoic acid, p-MBA) for pH sensing was measured at the single nanoparticle level under the same measurement parameters such as low laser power (0.5 mW/μm), short integration time (100 ms) at wavelengths of 405, 488, 532, 584, 676, and 785 nm. In our measurement, the Ag chain, Ag core/satellites, Ag@Au core/satellites, and Au core/satellites nanoassemblies showed efficient pH sensing at the single particle level. By using p-MBA-conjugated Au@Ag core/satellites, we performed time-lapse pH measurements during apoptosis of HeLa cells. These experimental results confirmed that the pH measurement using p-MBA-conjugated Au@Ag core/satellites can be applied for long-term measurements of intracellular pH during cellular events.
细胞内 pH 值是理解生物细胞中各种生物过程的关键因素之一。等离子体金和银纳米粒子 (NPs) 已被广泛研究用于表面增强拉曼散射 (SERS) 应用，作为活细胞中的局部 pH 探针。然而，NPs 的 SERS 性能取决于材料、尺寸和形状，可以通过化学合成来控制。在这里，我们合成了 18 种具有不同形态的金和银 NPs，如球体、棒体、花体、星型、核/壳体、空心体、八面体、核/卫星体和链式聚集体，并定量比较了它们用于 pH 传感的 SERS 性能。在相同的测量参数下，如低激光功率 (0.5 mW/μm) 和短积分时间 (100 ms)，在 405、488、532、584、676 和 785 nm 波长下，测量最常用的 SERS 探针分子（对巯基苯甲酸，p-MBA）的单个纳米粒子的 SERS 强度。在我们的测量中，Ag 链、Ag 核/卫星体、Ag@Au 核/卫星体和 Au 核/卫星体纳米组装体在单个粒子水平上表现出有效的 pH 传感。通过使用 p-MBA 共轭的 Au@Ag 核/卫星体，我们在 HeLa 细胞凋亡过程中进行了时间分辨的 pH 测量。这些实验结果证实，使用 p-MBA 共轭的 Au@Ag 核/卫星体进行 pH 测量可应用于细胞事件过程中细胞内 pH 的长期测量。
