p-Aminostyryl thiazole orange derivatives for monitoring mitochondrial viscosity in live cells

Detecting viscosity changes in the limb ischemia-reperfusion in mice with a near-infrared fluorescence probe

BACKGROUND

Limb ischemia-reperfusion is a common phenomenon in clinical surgery, which disrupts the balanced physiological response process and ultimately leads to changes in intracellular viscosity. Intracellular viscosity is an important microenvironmental parameter that affects the normal function of organisms, and its level is closely related to many diseases. In addition, oxidative stress in the lower limbs can impair body function, and changes in pressure can lead to changes in the viscosity of limb tissues. Therefore, it is necessary to develop effective tools to detect changes in intracellular viscosity and visualize the progression of hind limb ischemia-reperfusion injury.

RESULTS

In order to solve this problem, a near infrared viscometry sensitive fluorescence probe (PH-XQ) with long emission wavelength and stable luminescence performance was designed and synthesized by using oxanthracene derivatives and malononitrile. The fluorescence probe (PH-XQ) has excellent selectivity, high sensitivity, low toxicity, high biocompatibility and excellent detection performance. The fluorescence intensity of the PH-XQ probe at 667 nm is highly sensitive to the change of viscosity. With the increase of viscosity, the fluorescence intensity of probe PH-XQ was significantly enhanced, and the fluorescence enhancement ratio was about 14-fold. In addition, PH-XQ can detect not only changes in viscosity between normal cells and drug-induced inflammatory cells, but also changes in the viscosity of the hind limbs of normal mice and mice after ischemia reperfusion.

SIGNIFICANCE

In particular, we are the first to successfully detect changes in handlimb viscosity after ischemia-reperfusion in mice using a probe. This study clearly elucidates changes in viscosity during ischemia-reperfusion of mouse limbs, providing favorable support for the relationship between viscosity and related diseases, and further providing a potential tool for the diagnosis of viscosity-related diseases.

Hemicyanine-based sensor for mitochondrial viscosity imaging in BV2 cells

Mitochondrial viscosity is a critical factor affecting numerous physiological processes, including phagocytosis. Abnormal viscosity in mitochondria is related to some pathological activities and diseases. Evaluating and detecting the changes in mitochondrial viscosity in vivo is crucial. Thus, a mitochondria-targeted red-emitting fluorescent probe (VP) was prepared, and can be used to detect viscosity with high selectivity and sensitivity. The synthesis of probe VP was as simple as two steps and the cost was low. In addition, the fluorescence intensity (log I615) exhibited an excellent relationship with viscosity (log η) in the range of 0.5 - 2.5 (R2 = 0.9985) in water/glycerol mixture. It is noteworthy that the probe VP displayed the highest signal-to-noise ratio (about 50-fold) for viscosity in water and glycerol system. The probe VP can visualize the mitochondrial viscosity change in living cells. More importantly, phagocytic test for BV2 cells further demonstrated that phagocytosis decreased with increased viscosity. Furthermore, VP was successfully used for monitoring the mitophagy process induced by starvation, and mitochondrial viscosity exhibited enhancement during mitophagy. The probe was a potential tool for studying viscosity and phagocytosis.

Two quinoline-based two-photon fluorescent probes for imaging of viscosity in subcellular organelles of living HeLa cells

Two viscosity-sensitive two-photon fluorescent probes (QL and QLS) were designed and synthesized, which can be localized in lysosome and mitochondria in living HeLa cells, respectively. As the increases of viscosity from 2.55 to 1150 cP, the fluorescence quantum yield (Φ) of QL and QLS was increased by 28-fold and 37-fold, respectively. At the same time, its effective two-photon absorption cross section (Φδ_TPA) was enhanced by 15-fold and 16-fold, respectively. Fluorescence lifetime imaging (FLIM) of living HeLa cells stained with QL and QLS, revealed that lysosomal viscosity ranged from 100.76 to 254.74 cP and mitochondrial viscosity ranged from 92.21 to 286.79 cP. This type of fluorescent probe is helpful in the design and application of materials for monitoring diseases associated with abnormal viscosity.

A dual-response fluorescent probe for N2H4 and viscosity in living cells and zebrafish to evaluate liver injury

Hydrazide drugs can cause severe drug-induced liver injury owing to the enzymatic release of N₂H₄ in the liver. Also, changes in cellular viscosity are associated with liver damage. Thus, simultaneous monitoring of changes in N₂H₄ levels and viscosity can be used to evaluate the side effects of hydrazide drugs. Herein, we firstly reported a near-infrared fluorescent probe (FNN), which contains 1,8-naphthalimide as the fluorophore and a chalcone moiety as the responsive receptor, for sensitively detecting intracellular viscosity and N₂H₄. FNN showed a fast 'turn-on' fluorescence response to N₂H₄ with excellent selectivity. Additionally, FNN could selectively track viscosity without interference from polarity, pH, and other active species. Furthermore, imaging experiments suggested that FNN could be successfully applied in living cells and zebrafish larvae and embryos, which is of great importance for effectively assessing the degree of liver injury.