Series of Mitochondria/Lysosomes Self-Targetable Near-Infrared Hemicyanine Dyes for Viscosity Detection

Abstract

Six mitochondria/lysosomes self-targetable and viscosity-sensitive dyes (1a–1f) were developed via simple structure modification on cyanine-derived dyes. They all showed remarkable OFF–ON fluorescent response to viscosity in the near-infrared region (652–690 nm) and exhibited good linear relationship with solution viscosity. The transient absorption spectra were used to evaluate the excited-state lifetime of dye 1a in different viscosity environments. Furthermore, cellular imaging assays indicated that different derivatives (1a–1f) with the same chromophore core exhibited different organelle-targeting abilities. Among them, dyes 1a–1c could sense lysosomal viscosity fluctuations while dyes 1d–1f could be applied in mitochondrial viscosity detections.

Small Molecular Fluorescent Probes for Imaging of Viscosity in Living Biosystems

“…Ge et al. synthesized a series of hemicyanine‐based fluorescent probes 22 a – 22 f for determination of viscosity in mitochondria or lysosomes [49] . All these probes displayed excellent viscosity‐dependence and a good linear relationship with the viscosity index.…”

Real-Time Monitoring Mitochondrial Viscosity during Mitophagy Using a Mitochondria-Immobilized Near-Infrared Aggregation-Induced Emission Probe

“…, viscosity, pH, and polarity) between the mitochondria and autophagosomes, the detection of the mitochondrial microenvironment changes may be an efficient and practical method for real-time monitoring of the mitophagy process. − In particular, as a key indicator of microenvironments, mitochondrial viscosity is closely related to the mitochondrial respiratory state function by changing its own network organization, and the changes can regulate metabolite diffusion and further reflect the disease state of the body . Although many small molecular fluorescent probes have been developed for monitoring mitochondrial viscosity, − the reliable viscosity-sensitive probes that allow for tracking mitochondrial viscosity during mitophagy are rather scarce. , Yang and co-workers exploited a carbazole derivative as mitochondria-anchored molecular rotor (BMVC), revealing an increased viscosity in the mitochondria during mitophagy . However, similar to traditional mitochondria trackers without immobilization function, BMVC was a typical membrane potential-dependent probe that readily leaked out from mitochondria when the membrane potential was decreased or vanished, easily resulting in unstable localization and unreliable signal.…”

A Fluorogenic Far Red-Emitting Molecular Viscometer for Ascertaining Lysosomal Stress in Live Cells and Caenorhabditis elegans

“…To assess the temporal changes of lysosomal viscosity in human GBM cells (U87-MG) using JIND-Mor , we have used Dexa as the stimulation reagent. Dexa acts as a lysosomal membrane stabilizer and an inhibitor of lysosomal enzymatic release, which causes an increase in the lysosomal viscosity ( Yang et al, 2020 ). Therefore, the dynamic fluorescence change of the lysosomal compartment of U87-MG cells was measured after treating with JIND-Mor for 15 min and then stimulated with 50 µM of Dexa ( Figure 5A ).…”