Organic Fluorescent Probes for Monitoring Micro-Environments in Living Cells and Tissues

Abstract

As a vital parameter in living cells and tissues, the micro-environment is crucial for the living organisms. Significantly, organelles require proper micro-environment to achieve normal physiological processes, and the micro-environment in organelles can reflect the state of organelles in living cells. Moreover, some abnormal micro-environments in organelles are closely related to organelle dysfunction and disease development. So, visualizing and monitoring the variation of micro-environments in organelles is helpful for physiologists and pathologists to study the mechanisms of the relative diseases. Recently, a large variety of fluorescent probes was developed to study the micro-environments in living cells and tissues. However, the systematic and comprehensive reviews on the organelle micro-environment in living cells and tissues have rarely been published, which may hinder the research progress in the field of organic fluorescent probes. In this review, we will summarize the organic fluorescent probes for monitoring the microenvironment, such as viscosity, pH values, polarity, and temperature. Further, diverse organelles (mitochondria, lysosome, endoplasmic reticulum, cell membrane) about microenvironments will be displayed. In this process, the fluorescent probes about the “off-on” and ratiometric category (the diverse fluorescence emission) will be discussed. Moreover, the molecular designing, chemical synthesis, fluorescent mechanism, and the bio-applications of these organic fluorescent probes in cells and tissues will also be discussed. Significantly, the merits and defects of current microenvironment-sensitive probes are outlined and discussed, and the development tendency and challenges for this kind of probe are presented. In brief, this review mainly summarizes some typical examples and highlights the progress of organic fluorescent probes for monitoring micro-environments in living cells and tissues in recent research. We anticipate that this review will deepen the understanding of microenvironment in cells and tissues and facilitate the studies and development of physiology and pathology.

Targeting Cysteine Oxidation in Thrombotic Disorders

“…However, it should be noted that the pK a of the thiol group of free cysteine is ~8.3 and can range substantially (from 3.5 to 13 depending on the microenvironment) [29,30]. The pH of the local environment is also not uniform [30]; lysosomes, for example, have much lower pH (pH 4-5) relative to the cytosol (pH 6.8-7.4) and mitochondria (pH~8.0 within mitochondrial matrix) [31]. As the pK a is linked to the pH of the aqueous environment, solvent accessibility (e.g., buried vs. exposed) influences cysteine reactivity.…”

A red-emitting mitochondria targetable fluorescent probe for detecting viscosity in HeLa, zebrafish, and mice

“…It impacts cellular proliferation, differentiation, metabolism, protein–protein interactions, signal transduction, and material transportation. 1–6 Due to the significant variation in intracellular microviscosity across different regions, it is necessary to perform measurements within specific organelles in order to accurately monitor changes in microviscosity. Notably, mitochondria are known for their pivotal role in cellular energy production and metabolism, whose functions could be greatly influenced by viscosity.…”

Visualized Tracking and Multidimensional Assessing of Mitochondria-Associated Pyroptosis in Cancer Cells by a Small-Molecule Fluorescent Probe

“…9,10 Studies suggest that pyroptosis is highly related to mitochondrial dysfunction, which can be reflected by physiological microenvironmental changes (e.g., mitochondrial polarity, viscosity, pH, hypoxia, and mitochondrial reactive oxygen species (ROS)) and morphology changes in mitochondria. 11,12 Meanwhile, mitochondrial DNA (mtDNA) contains the essential genetic information for mitochondria to accomplish their functions, whose damage and abnormal accumulation can also induce pyroptosis of cells. 13,14 Tracking the fluctuations of these physiological parameters can be helpful to monitor mitochondria-associated pyroptosis in real time and deepen our understanding of the pyroptosis pathways.…”

“…As one of the important dynamic organelles, mitochondria play essential roles in cellular activities, including differentiation, information transmission, growth, and regulation . Mitochondrial dysfunction is one of the main causes of numerous diseases, including cardiovascular diseases, neurological syndromes, diabetes, cancers, etc. , Studies suggest that pyroptosis is highly related to mitochondrial dysfunction, which can be reflected by physiological microenvironmental changes (e.g., mitochondrial polarity, viscosity, pH, hypoxia, and mitochondrial reactive oxygen species (ROS)) and morphology changes in mitochondria. , Meanwhile, mitochondrial DNA (mtDNA) contains the essential genetic information for mitochondria to accomplish their functions, whose damage and abnormal accumulation can also induce pyroptosis of cells. , Tracking the fluctuations of these physiological parameters can be helpful to monitor mitochondria-associated pyroptosis in real time and deepen our understanding of the pyroptosis pathways. It should be pointed out that the fluctuations of the mitochondrial microenvironmental parameters, mtDNA level, and morphology during pyroptosis are all dynamic processes.…”