Jiaxin Hong's research while affiliated with Central China Normal University and other places

LDs (Lipid droplets) are key organelles for lipid metabolism and storage, which are closely related to ferroptosis and fatty liver. Due to its small size and highly dynamic nature, developing high-fidelity fluorescent probes for imaging of LDs is crucial for observing the dynamic physiological processes of LDs and investigating LDs-associated diseases. Herein, we synthesized three dicyanoisophorone-based fluorescent probes (DCIMe, DCIJ, and DCIQ) with different electron-donating groups and studied their imaging performance for LDs. The results show that DCIQ is highly polarity sensitive and can perform high-fidelity imaging for LDs, with significantly better performance than DCIMe, DCIJ, and commercial LD probe BODIPY 493/503. Based on this, DCIQ was successfully applied to real-time observe the interplays between LDs and other organelles (mitochondria, lysosomes, and endoplasmic reticulum), and to image the dynamics of LDs with fast scanning mode (0.44 s/frame) and the generation of oleic acid-induced LDs with high-fidelity. Finally, DCIQ was used to study the changes of LDs in the ferroptosis process and nonalcoholic fatty liver disease tissues. Overall, this study provided a powerful tool for high-fidelity imaging of LDs in cells and tissues.

With the widespread use of drugs, drug-induced acute kidney injury (AKI) has become an increasingly serious health concern worldwide. Currently, early diagnosis of drug-induced AKI remains challenging because of the lack of effective biomarkers and noninvasive imaging tools. SO2 plays important physiological roles in living systems and is an important antioxidant for maintaining redox homeostasis. However, the relationship between SO2 (in water as SO32-/HSO3-) and drug-induced AKI remains largely unknown. Herein, we report the highly sensitive near-infrared fluorescence probe DSMN, which for the first time reveals the relationship between SO2 and drug-induced AKI. The probe responds to SO32-/HSO3- selectively and rapidly (within seconds) and shows a significant turn-on fluorescence at 710 nm with a large Stokes shift (125 nm). With these properties, the probe was successfully applied to detect SO2 in living cells and mice. Importantly, the probe can selectively target the kidneys, allowing for the detection of changes in the SO2 concentration in the kidneys. Based on this, DSMN was successfully used to detect cisplatin-induced AKI and revealed an increase in the SO2 levels. The results indicate that SO2 is a new biomarker for AKI and that DSMN is a powerful tool for studying and diagnosing drug-induced AKI.

Mitophagy is a vital cellular process playing vital roles in regulating cellular metabolism and mitochondrial quality control. Mitochondrial viscosity is a key microenvironmental index, closely associated with mitochondrial status. To monitor mitophagy and mitochondrial viscosity, three molecular rotors (Mito-1, Mito-2, and Mito-3) were developed. All probes contain a cationic quinolinium unit and a C12 chain so that they can tightly bind mitochondria and are not affected by the mitochondrial membrane potential. Optical studies showed that all probes are sensitive to viscosity changes with an off-on fluorescence response, and Mito-3 shows the best fluorescence enhancement. Bioimaging studies showed that all these probes can not only tightly locate and visualize mitochondria with near-infrared fluorescence but also effectively monitor the mitochondrial viscosity changes in cells. Moreover, Mito-3 was successfully applied to visualize the mitophagy process induced by starvation, and mitochondrial viscosity was found to show an increase during mitophagy. We expect Mito-3 to become a useful imaging tool for studying mitochondrial viscosity and mitophagy.

Complex intracellular life processes are usually completed through the cooperation of multiple organelles. Real-time tracking of the interplays between multiple organelles with a single fluorescent probe (SFP) is very helpful to deepen our understanding of complex biological processes. So far, SFP for simultaneously differentiating and visualizing of more than two different organelles has not been reported. Herein, we report an SFP (named ICM) that can be used for simultaneously differentiating and visualizing three important organelles: mitochondria, lysosomes, and lipid droplets (LDs). The probe can simultaneously light up mitochondria/lysosomes (∼700 nm) and LDs (∼480 nm) at significantly different emission wavelengths with high fidelity, and mitochondria and lysosomes can be effectively distinguished by their different shapes and fluorescence intensities. With this smart probe, real-time and simultaneous tracking of the interplays of these three organelles was successfully achieved for the first time.

Lysosome is one of the most crucial organelles in living systems. Lysosomal viscosity is an important microenvironment parameter in lysosomes, which is closely related to the occurrence and development of many diseases, including cancer. To monitor the highly dynamic lysosomes and the lysosomal viscosity changes, we developed a versatile high-performance fluorescent probe DCMP in this work. DCMP shows stronger fluorescence under acidic conditions or in solutions with higher viscosity, especially with high sensitivity to the change of viscosity. More importantly, DCMP can use a low dose (100 nM) and can target lysosomes and image lysosomes with high signal-to-noise ratio and high fidelity. It can also track the lysosomal motility and viscosity changes in real-time, and effectively monitor the interaction between lysosomes and damaged organelles. We also found that DCMP can be successfully used to selectively and sensitively light up cancer cells and cancer tissues. All the results show that this new probe has great potential not only in lysosomal high-fidelity imaging, but also in cancer detection.

Cancer is a health threat worldwide, and it is urgent to develop more sensitive cancer detection methods. Herein, a polarity-sensitive cell membrane probe (named COP) was developed for detecting cancer cells and tumors sensitively and selectively at the cell membrane level. The probe shows a strong polarity-dependent fluorescence and excellent cell membrane targeting ability to visualize cell membrane with red fluorescence with a non-washing process. Notably, COP can selectively light up the tumor cell membranes, which reveals that cancer cell membranes have lower polarity than normal cell membranes. The giant unilamellar vesicle model and cell imaging studies proved this. Moreover, COP can effectively and selectively light up tumors. Overall, this work demonstrates that the polarity of the tumor cell membrane is quite different to normal cell membranes, and based on this, sensitive membrane probes can be developed to selectively visualize cancer cells and tumors, which opens up a new way for tumor diagnosis at the cellular level.

Peroxynitrite and lysosomes are important biologically reactive oxygen species and subcellular organelles, respectively. The level of peroxynitrite and the value change of pH in lysosomes have a significant impact on living cells. Thus, the detection of peroxynitrite and lysosomal pH in live cells is very important. Herein, a novel probe (ONOO-LysopH) was developed, which not only can detect peroxynitrite in lysosomes, but also can be used to track the lysosomal pH changes. ONOO-LysopH is based on a new rhodamine derivate with near-infrared (NIR) emission and large Stokes shift. ONOO-LysopH is sensitive to acid and shows an instantaneous and reversible response of NIR emission around 686 nm with a pKa value of 5.41. ONOO-LysopH also exhibits a quick, sensitive, and selective response to peroxynitrite at physiological pH with a largely enhanced NIR fluorescence signal at 678 nm. The application of ONOO-LysopH to track lysosomal pH changes and image both endogenous and exogenous peroxynitrite in live cells was demonstrated. Thus, this work provided a potential multifunctional probe for peroxynitrite detection and lysosomal pH change tracking in live systems.

With a hybrid coumarin-dicyanoisophorone as report unit and dimethylthiocarbamate as response site, a novel reaction-based fluorescence probe (CDCI-HClO) was synthesized herein for rapid detection of hypochlorous acid (HOCl). CDCI-HClO can respond to HOCl quickly (almost in seconds), selectively, and sensitively, and give an obviously enhanced signal of near-infrared fluorescence at 700 nm. The detection limit of CDCI-HClO for HOCl is about 4 nM. Moreover, with the merit of a large Stokes shift (190 nm), CDCI-HClO was successfully applied to the imaging of HOCl in live cell, zebrafish, and living mice. All results demonstrated that CDCI-HClO is a valuable new NIR fluorescence imaging tool to detect hypochlorous acid in living systems.

Lysosomes are important subcellular organelles with acidic pH. The change of lysosomal pH can affect the normal function and activity of cells. To conveniently detect and visualize lysosomal pH changes, we designed herein a novel fluorescent probe NIR-Rh-LysopH. The probe is based on a Rhodamine 101 derivative, which was modified to include a fused tetrahydroquinoxaline ring to obtain near-infrared fluorescence and a methylcarbitol moiety to locate the lysosome. Based on the proton-induced spirolactam ring-opening mechanism, NIR-Rh-LysopH showed rapid, selective, sensitive, and reversible near-infrared fluorescence responses around 686 nm (Stokes shift 88 nm) with a pKa value of 5.70. From pH 7.4 to 4.0, about 285 folds of fluorescence enhancement was observed. Cell experiments showed that NIR-Rh-LysopH has low cytotoxicity and excellent lysosome-targeting ability. Moreover, NIR-Rh-LysopH was applied successfully to track lysosomal pH changes induced by drugs (such as chloroquine and dexamethasone), heatstroke, and redox stress. Thus, NIR-Rh-LysopH is very promising for conveniently tracking lysosomal pH changes and studying the related life processes.