Recent advances in the design of intracellular pH sensing nanoprobes based on organic and inorganic materials

Sandip Ghosh; Jui-Yang Lai

doi:10.1016/j.envres.2023.117089

Recent advances in the design of intracellular pH sensing nanoprobes based on organic and inorganic materials

Environ Res. 2023 Nov 15;237(Pt 2):117089. doi: 10.1016/j.envres.2023.117089. Epub 2023 Sep 6.

Authors

Sandip Ghosh¹, Jui-Yang Lai²

Affiliations

¹ Department of Biomedical Engineering, Chang Gung University, Taoyuan, 33302, Taiwan.
² 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. Electronic address: jylai@mail.cgu.edu.tw.

PMID: 37683789
DOI: 10.1016/j.envres.2023.117089

Abstract

In the biological system, the intracellular pH (pH_i) 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_i 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_i, 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_i sensing.

Keywords: Intracellular pH sensing; Non-invasive biosensors; pH nanoprobes.

Publication types

Review