Reaction-based small-molecule fluorescent probes for endoplasmic reticulum- and mitochondria-targeted biosensing and bioimaging

Fluorescent probes have revolutionized modern biological research by making it possible to observe and measure an extensive range of cellular and subcellular processes. Among the subcellular compartments, the endoplasmic reticulum (ER) and mitochondria (MT) remain exciting targets owing to the information they reveal about the cellular processes. Consequently, monitoring pH, polarity, viscosity, metal ions, reactive nitrogen species (RNS), reactive sulfur species (RSS) and reactive oxygen species (ROS) in ER and MT with fluorescent probes is of great importance to understand the cellar and subcellular process. Recent years, redox-sensitive probes and ion probes are designed and synthesized for the detection and quantification of RNS/RSS/ROS (collectively as reactive oxygen/nitrogen/sulfur species, RONSS) and metal ions within ER and MT. These probes provide powerful tools for the researchers to learn more about the complex relationship between cellular redox homeostasis and organelle function, and understand the mechanism of disease processes and pathogenesis for developing potential treatments. In this review, the design principles, synthesis methods, targeting mechanism for ER- and MT-targeted RONSS, and metal-ion-specific fluorescent probes are discussed. The recent progress for the synthesis and applications of ER/MT-targeted probes, and their applications for monitoring cellular and subcellular processes are summarized, and the development trends and application prospects of the probes are analyzed.