Shanghai Key Laboratory of Contemporary Optics System, School of Optical Electrical and Computer Engineering, University of Shanghai for Science and Technology, Shanghai, 200093, China.
Anal Bioanal Chem. 2021 Jun;413(15):4091-4101. doi: 10.1007/s00216-021-03365-w. Epub 2021 May 20.
Exosomes have attracted significant attention as cancer diagnostic targets and therapeutic agents due to their unique biogenesis and structure. To clarify the biological activities of exosomes, it is important to obtain a picture of their intracellular distribution and how they evolve over time. In this work, a new kind of intracellular exosome imaging and concurrent pH sensing method is demonstrated by using the surface-enhanced Raman scattering (SERS) technique. Specifically, 4-mercaptobenzoic acid (4MBA)-tagged silver nanoparticles are attached onto the outer surfaces of exosomes, in which silver nanoparticles are employed as SERS generators. Raman agents 4MBA are susceptible to a specific intracellular stimulus, that is, undergo a protonation or deprotonation in response to intracellular pH variation, which correspondingly exhibit different vibrational spectra features. By using the SERS spectroscopy, tracking of the intracellular distribution of exosomes and the concurrent quantitative sensing of environmental pH were achieved, which demonstrated that, as time prolonged, exosomes first attached with the tumor cell surfaces, and then entered into the cells and accumulated in lysosomes. Such SERS-active hybridized exosomes, that are sensitive to discrete variations in intracellular pH, have proved their capability for the investigation of interactions between exosomes and cells. The spectral diversity and flexible surface modification of these hybridized exosomes are also highly expected in developing multifunctional exosome-based nanoplatforms, which offers great potential to promote the exosome-based therapeutics forward into an advanced stage.
外泌体由于其独特的生物发生和结构，引起了人们对其作为癌症诊断靶点和治疗剂的极大关注。为了阐明外泌体的生物学活性，了解其细胞内分布以及随时间演变的情况非常重要。在这项工作中，通过使用表面增强拉曼散射（SERS）技术，展示了一种新型的细胞内外泌体成像和同时 pH 传感方法。具体来说，将 4-巯基苯甲酸（4MBA）标记的银纳米粒子附着在外泌体的外表面上，其中银纳米粒子用作 SERS 发生器。拉曼试剂 4MBA 易受特定细胞内刺激的影响，即对细胞内 pH 变化作出质子化或去质子化反应，相应地表现出不同的振动光谱特征。通过 SERS 光谱学，实现了对外泌体细胞内分布的跟踪和环境 pH 的同时定量传感，结果表明，随着时间的延长，外泌体首先与肿瘤细胞表面结合，然后进入细胞并在溶酶体中积累。这种对细胞内 pH 离散变化敏感的 SERS 活性杂交外泌体，已经证明了它们在研究外泌体与细胞之间相互作用方面的能力。这些杂交外泌体的光谱多样性和灵活的表面修饰也有望在开发多功能基于外泌体的纳米平台方面发挥重要作用，这为推进基于外泌体的治疗进入高级阶段提供了巨大潜力。
