Ghosh Sandip, Lai Jui-Yang
Department of Biomedical Engineering, Chang Gung University, Taoyuan, 33302, Taiwan.
Department of Biomedical Engineering, Chang Gung University, Taoyuan, 33302, Taiwan; Department of Ophthalmology, Chang Gung Memorial Hospital, Linkou, Taoyuan, 33305, Taiwan; Department of Materials Engineering, Ming Chi University of Technology, New Taipei City, 24301, Taiwan; Research Center for Chinese Herbal Medicine, College of Human Ecology, Chang Gung University of Science and Technology, Taoyuan, 33303, Taiwan.
Environ Res. 2023 Nov 15;237(Pt 2):117089. doi: 10.1016/j.envres.2023.117089. Epub 2023 Sep 6.
In the biological system, the intracellular pH (pH) plays an important role in regulating diverse physiological activities, including enzymatic action, ion transport, cell proliferation, metabolism, and programmed cell death. The monitoring of pH inside living cells is also crucial for studying cellular events such as phagocytosis, endocytosis, and receptor-ligand internalization. Furthermore, some organelles, viz., endosomes and lysosomes, have intracompartmental pH, which is critical for maintaining the stability of protein structure and function. The dysfunction and abnormal pH regulation can result in terminal diseases such as cancer, Alzheimer, and so forth. Therefore, the accuracy of intracellular pH measurement is always the top priority and demands cutting-edge research and analysis. Such techniques, such as Raman spectroscopy and fluorescence imaging, preferably use nanotechnology due to their remarkable advantages, such as a non-invasive approach and providing accuracy, repeatability, and reproducibility. In the past decades, there have been numerous attempts to design and construct non-invasive organic and inorganic materials-based nanoprobes for pH sensing. For Raman-based techniques, metal nanostructures such as Au/Ag/Cu nanoparticles are utilized to enhance the signal intensity. As for the fluorescence-based studies, the organic-based small molecules, such as dyes, show higher sensitivity toward pH. However, they possess several drawbacks, including high photobleaching rate, and autofluorescence background signals. To this end, there are alternative nanomaterials proposed, including semiconductor quantum dots (QDs), carbon QDs, upconversion nanoparticles, and so forth. Moreover, the fluorescence technique allows for ratiometric measurement of pH, which as a result, offers a reliable calibration curve. This timely review will critically examine the current progression in the existing nanoprobes. In addition, based on our knowledge and available research findings, we provide a brief future outlook that may advance the state-of-the-art methodologies for pH sensing.
在生物系统中，细胞内pH值在调节多种生理活动中发挥着重要作用，包括酶促作用、离子转运、细胞增殖、新陈代谢和程序性细胞死亡。监测活细胞内的pH值对于研究细胞吞噬、内吞作用和受体-配体内化等细胞事件也至关重要。此外，一些细胞器，即内体和溶酶体，具有隔室内pH值，这对于维持蛋白质结构和功能的稳定性至关重要。功能障碍和pH调节异常会导致诸如癌症、阿尔茨海默病等终末期疾病。因此，细胞内pH测量的准确性一直是首要任务，需要前沿的研究和分析。诸如拉曼光谱和荧光成像等技术，由于其显著的优势，如非侵入性方法以及提供准确性、可重复性和再现性，最好使用纳米技术。在过去几十年中，人们进行了大量尝试，设计和构建基于非侵入性有机和无机材料的纳米探针用于pH传感。对于基于拉曼的技术，利用金/银/铜纳米颗粒等金属纳米结构来增强信号强度。至于基于荧光的研究，基于有机的小分子，如染料，对pH显示出更高的灵敏度。然而，它们存在几个缺点，包括高光漂白率和自发荧光背景信号。为此，提出了替代纳米材料，包括半导体量子点（QDs）、碳量子点、上转换纳米颗粒等。此外，荧光技术允许对pH进行比率测量，从而提供可靠的校准曲线。这篇及时的综述将批判性地审视现有纳米探针的当前进展。此外，基于我们的知识和现有研究结果，我们提供了一个简要的未来展望，这可能会推动pH传感的最新方法。
