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Research on ferroptosis in myocardial ischemia/reperfusion injury (MIRI) using mitochondrial viscosity as a nexus holds great promise for MIRI therapy. However, high‐precision visualisation of mitochondrial viscosity remains a formidable task owing to the debilitating electrostatic interactions caused by damaged mitochondrial membrane potential. Herein, we propose a dual‐locking mitochondria‐targeting strategy that incorporates electrostatic forces and probe‐protein molecular docking. Even in damaged mitochondria, stable and precise visualisation of mitochondrial viscosity in triggered and medicated MIRI was achieved owing to the sustained driving forces (e.g. pi‐cation, pi‐alkyl interactions, etc.) between the developed probe, CBS, and the mitochondrial membrane protein. Moreover, complemented by a western blot, we confirmed that ferrostatin‐1 exerts its therapeutic effect on MIRI by improving the system xc−/GSH/GPX4 antioxidant system, confirming the therapeutic value of ferroptosis in MIRI. This study presents a novel strategy for developing robust mitochondrial probes, thereby advancing MIRI treatment. [ABSTRACT FROM AUTHOR]

Research on ferroptosis in myocardial ischemia/reperfusion injury (MIRI) using mitochondrial viscosity as a nexus holds great promise for MIRI therapy. However, high‐precision visualisation of mitochondrial viscosity remains a formidable task owing to the debilitating electrostatic interactions caused by damaged mitochondrial membrane potential. Herein, we propose a dual‐locking mitochondria‐targeting strategy that incorporates electrostatic forces and probe‐protein molecular docking. Even in damaged mitochondria, stable and precise visualisation of mitochondrial viscosity in triggered and medicated MIRI was achieved owing to the sustained driving forces (e.g. pi‐cation, pi‐alkyl interactions, etc.) between the developed probe, CBS, and the mitochondrial membrane protein. Moreover, complemented by a western blot, we confirmed that ferrostatin‐1 exerts its therapeutic effect on MIRI by improving the system xc−/GSH/GPX4 antioxidant system, confirming the therapeutic value of ferroptosis in MIRI. This study presents a novel strategy for developing robust mitochondrial probes, thereby advancing MIRI treatment. [ABSTRACT FROM AUTHOR]

Ferroptosis is a form of regulatory cell death distinct from caspase-dependent apoptosis and plays an important role in life entities. Since ferroptosis involves a variety of complex regulatory factors, the levels of certain biological species and microenvironments would change during this process. Thus, the investigation of the level fluctuation of key target analytes during ferroptosis is of great significance for disease treatment and drug design. Toward this aim, multiple organic fluorescent probes with simple preparation and non-destructive detection have been developed, and research over the past decade has uncovered a vast array of homeostasis and other physiological characteristics of ferroptosis. However, this significant and cutting-edge topic has not yet been reviewed. In this work, we aim to highlight the latest breakthrough results of fluorescent probes for monitoring various bio-related molecules and microenvironments during ferroptosis at the cellular, tissue and in vivo levels. Accordingly, this tutorial review has been organized according to the target molecules identified by the probes including ionic species, reactive sulfur species, reactive oxygen species, biomacromolecules, microenvironment, and others. In addition to providing new insights into the findings of each fluorescent probe in ferroptosis studies, we also discuss the defects and limitations of the probes developed, and highlight the potential challenges and further prospects in this domain. We anticipate that this review will convey profound implications for designing powerful fluorescent probes to decrypt changes in key molecules and microenvironments during ferroptosis. [ABSTRACT FROM AUTHOR]

The microenvironment (local environment), including viscosity, temperature, polarity, hypoxia, and acidic-basic status (pH), plays indispensable roles in cellular processes. Significantly, organelles require an appropriate microenvironment to perform their specific physiological functions, and disruption of the microenvironmental homeostasis could lead to malfunctions of organelles, resulting in disorder and disease development. Consequently, monitoring the microenvironment within specific organelles is vital to understand organelle-related physiopathology. Over the past few years, many fluorescent probes have been developed to help reveal variations in the microenvironment within specific cellular regions. Given that a comprehensive understanding of the microenvironment in a particular cellular region is of great significance for further exploration of life events, a thorough summary of this topic is urgently required. However, there has not been a comprehensive and critical review published recently on small-molecule fluorescent chemosensors for the cellular microenvironment. With this review, we summarize the recent progress since 2015 towards small-molecule based fluorescent probes for imaging the microenvironment within specific cellular regions, including the mitochondria, lysosomes, lipid drops, endoplasmic reticulum, golgi, nucleus, cytoplasmic matrix and cell membrane. Further classifications at the suborganelle level, according to detection of microenvironmental factors by probes, including polarity, viscosity, temperature, pH and hypoxia, are presented. Notably, in each category, design principles, chemical synthesis, recognition mechanism, fluorescent signals, and bio-imaging applications are summarized and compared. In addition, the limitations of the current microenvironment-sensitive probes are analyzed and the prospects for future developments are outlined. In a nutshell, this review comprehensively summarizes and highlights recent progress towards small molecule based fluorescent probes for sensing and imaging the microenvironment within specific cellular regions since 2015. We anticipate that this summary will facilitate a deeper understanding of the topic and encourage research directed towards the development of probes for the detection of cellular microenvironments. [ABSTRACT FROM AUTHOR]

Exploring the changes in the polarity of intracellular lipid droplets (LDs) during the evolution of cancer is important for cancer detection and treatment. Therefore, we designed and synthesized a new type of polarity-sensitive fluorescent probe, CTPE, which uses coumarin as the polarity-sensitive group and tetraphenylethylene as the electron-donating group to target LDs. Due to its special intramolecular charge transfer mechanism, CTPE emitted a weak green fluorescence in high-polar solvents, and a strong green fluorescence in low-polar solvents, thus exhibiting a drastic change in fluorescence signal as a function of the solvent polarity. In virtue of the probe CTPE, tumorous tissues have been successfully identified from normal ones and the decrease in LDs' polarity could be revealed with the evolution of cancer. Moreover, the changes in the LDs' polarity in drugs-treated tumor were observed at the tissue level, endowing its capacity for anti-cancer drug efficacy evaluation. This work provides a promising imaging tool for LDs tracking in cancer research and clinical diagnosis. [ABSTRACT FROM AUTHOR]

A two-photon fluorescent probe, Mito-V, was designed and prepared for sensing the viscosity changes of mitochondria. The systematic investigations demonstrated that the fluorescence emission at 634 nm increased about 22-fold from methanol to 99% glycerol, indicating high viscosity dependence. Notably, using the probe, the mitochondrial viscosity fluctuations have been successfully monitored not only in living cells but also in zebrafish and living mice. [ABSTRACT FROM AUTHOR]

Elucidating lysosome polarity effect in complicated biosystems was impeded with the deficiency of lacking multi-disease models for researching the relation between lysosomal polarity and diseases. So far, dissecting the abnormal lysosome polarity in the inflamed and obese living mice has not been realized. To overcome this challenge, a robust probe MND-Lys was proposed for monitoring lysosomal polarity with two-photon emission. Using the probe, monitoring the intrinsic polarity variance in embryos and adult zebrafish has been achieved for the first time. Moreover, besides obviously discriminating tumors from normal ones, the probe also enabled tracing polarity changes in inflammatory and obese mice for the first time. The unique tracking and distinguishing polarity in lysosome make the probe a promising agent for fluorescence visualization studies of LD-lysosome related bioprocess and metabolism diseases. [ABSTRACT FROM AUTHOR]

The first dual organelle-targeted fluorescent probe DML-P was engineered for monitoring endogenous SO 2 in the mitochondria and lysosomes simultaneously. • A novel dual mitochondria- and lysosome-targeted fluorescent probe for detecting SO 2 in living system was reported. • The probe was successfully applied for the imaging of endogenous SO 2 in living cells. • The fluorescence imaging of mitochondria- and lysosome- SO 2 in living cells was successfully achieved with probe. SO 2 is recognized as the fourth gas messenger followed by NO, H 2 S and CO, it plays pivotal roles in many cellular activities and apoptosis in mitochondria and lysosomes. However, current molecular tools for of sensing SO 2 in mitochondria and lysosomes respectively, which is not conducive to well defining the functions and relationships between mitochondria- and lysosome-SO 2 in regulation of cellular activities. Thus, it is critical to develop powerful tool to detect mitochondria- and lysosome-SO 2 simultaneously. Herein, we have rationally designed and synthesized a novel fluorescent probe DML-P based on a dual organelle-targeted groups for imaging SO 2 in mitochondria and lysosomes simultaneously for the first time. The novel probe showed well water-solubility, high selectivity and high stability. Furthermore, probe has achieved in tracing endogenous SO 2 with two stimulation methods by one- and two-photon modes. Significantly, the probe has succeeded in tracing endogenous SO 2 in lysosomes and mitochondria concurrently in living cells. We hope this probe could provide a significative tool for studying the system functions and connections of mitochondria-and lysosomes-SO 2. [ABSTRACT FROM AUTHOR]

Highlights • A fluorescent sensor for potential cancer diagnosis has been constructed. • High sensitivity, photo-stability and desirable biocompatibility were performed. • Normal cells and tissues have been obviously discriminated from cancerous ones for the first time. • This probe CBMC will be be potentially applied in tumor diagnosis in the case of treatment. Graphical abstract A new lipid dropt-targeted two-photon fluorescence probe was engineered to detect polarity in cells and tissues toward cancer diagnosis. Abstract Monitoring the polarity of intracellular lipid droplets (LDs) is of great importance toward cancer diagnosis. Herein, we have rationally designed a novel LDs-targeting and polarity-sensitive fluorescent probe CBMC , which contains carbazole as an electron-donating group and malononitrile as an electron-accepting group forming intramolecular charge transfer mechanism. Due to its excellent solvatochromism, the probe emits stronger fluorescence in normal cells but weaker in cancer cells. By means of CBMC, normal tissues with stronger fluorescence have been obviously pointed out from cancerous tissues. For cancer therapy, the probe CBMC could be an ideal candidate to evaluate tumor, because the tumor area would decrease while the normal tissue area would increase with treatment time. Compared with existing probes with turn-off signal to normal cells, such a new probe with turn on type in normal cells could provide more reliable information with advantages of lower background interference, higher signal to noise ratio, and higher sensitivity. This probe CBMC will be a powerful tool to be potentially applied in tumor diagnosis in the case of treatment. [ABSTRACT FROM AUTHOR]

The detection of lipid droplet (LD) viscosity is very important for clinical research. Herein, we described a new two-photon fluorescent probe CBA for sensing the viscosity changes of LDs. Using this powerful probe, monitoring the viscosity variations has been achieved not only in cells but also in zebra fish. [ABSTRACT FROM AUTHOR]

A robust fluorescent probe CTPA has been rationally designed for cancer diagnosis by monitoring lipid drop (LD) polarity and number variation. With the outstanding properties of CTPA, we have shown that the diagnosis of cancer can be achieved not only at the cellular levels but also in organs and living mice for the first time. [ABSTRACT FROM AUTHOR]

Lipid droplets (LDs) are organelles which storage the lipids for all organisms. They are involved in many biological processes. LDs stored neutral lipids consisting of triglycerides, steryl esters, and retinyl esters. Herein, we constructed a novel NIR viscosity probe NLV-1 for monitoring the viscosity changes in biological systems. The probe NLV-1 showed a very strong fluorescence emission at around 719 nm in viscous media, the fluorescence intensity of the probe NLV-1 increased 13.77-fold from methanol to 99% glycerol. Moreover, the probe NLV-1 have been successfully utilized for monitoring the viscosity changes in cellular lipid droplets, and in zebra fishes. More importantly, we utilized the probe for measuring the viscosity variations in living mice. [ABSTRACT FROM AUTHOR]

Quantitative detection of antibiotic residues in animal food stuffs is of great significance. In this work, a highly sensitive electrochemical aptasensor for the sensitive detection of streptomycin antibiotic was fabricated based on a novel signal amplification strategy. Specifically, this aptasensor was constructed utilizing porous carbon nanorods (PCNR) formed by porous carbon nanosphere and multifunctional graphene composite (GR–Fe 3 O 4 –AuNPs) as biosensing substrate. PCNR samples with large specific pore volume and high specific surface area were successfully prepared by hydrothermal and chemical activation treatment for the first time. GR–Fe 3 O 4 –AuNPs was served as labels to achieve a high sensitivity and low limit of detection (LOD). Under the optimized conditions, the proposed aptasensor exhibited a high sensitivity and a wider linearity to streptomycin in the range 0.05–200 ng/mL with a low detection limit of 0.028 ng/mL. The proposed aptasensor displayed an excellent analytical performance with great reproducibility, high selectivity and stability. In addition, the as–prepared aptasensor was successfully utilized for the determination of streptomycin in real samples. [ABSTRACT FROM AUTHOR]

In this paper, a convenient electrochemical aptasensor for sensitive and selective determination of streptomycin antibiotic was constructed. Signal amplification strategy of the aptasensor was achieved by utilizing porous carbon nanorods, gold nanoparticles and copper oxide functionalized multiwalled carbon nanotube composites as biosensing substrates. Porous carbon nanorods were adopted in our strategy as the core conductive material for signal amplification. The multiwalled carbon nanotube–copper oxide–gold nanoparticle nanocomposites combined the advantages of their components, which not only promote electron transfer, but also provide abundant binding sites for the immobilization of biomolecules. The streptomycin aptamer was immobilized on the nanocomposites' surface via the strong bonding interaction between the gold nanoparticles and the thiol group to generate a referenced differential pulse voltammetry signal, Iaptamer. Then, the streptomycin was immobilized on the aptasensor via the specific interaction between the aptamer and streptomycin to generate the attenuated signal, Istreptomycin. Under the optimized conditions, the changes in the signals were linear with the concentration of streptomycin in the range of 0.05–300 ng mL−1 with a low detection limit of 0.036 ng mL−1 when “ΔI = Iaptamer−Istreptomycin was used as the response signal for quantitative determination of streptomycin. In addition, the electrochemical aptasensor was also successfully applied to the determination of streptomycin in milk and honey samples. This highly sensitive electrochemical aptasensor is of great practical importance in food safety and could be widely extended to the detection of other antibiotics by replacing the sequence of the aptamer. [ABSTRACT FROM AUTHOR]

• A de novo concept using mitochondrial polarity as a new biomarker. • High sensitivity, photo-stability and desirable biocompatibility were performed. • Investigating of the pharmacokinetics of the optical agent. • In site imaging of mitochondrial polarity in breast cancer mice. • Evaluating the prospect of the probe in breast cancer diagnosis. Due to the lack of effective target analyte and real-time tools, noninvasive investigating breast cancer still remains a formidable challenge. Herein, we proposed, for the first time , mitochondrial polarity as a potential indicator, and further develop a new optical agent PNN for monitoring mitochondrial polarity variations to explore breast cancer. The solvatochromic quality of the probe PNN was intelligently designed based on canonical pull–push molecular structure tactics, and further effectively integrate targeting module for mitochondrial anchoring. Intriguingly, the fluorescence of probe PNN was specifically activated by polarity and exhibited high sensitivity, low biotoxicity and excellent biocompatibility performances. Capitalizing on these features, such a probe noninvasively achieved reporting abnormal polarity levels at the site of breast cancer with a high signal-to-background ratio, and the decreased mitochondrial polarity in mammary epithelial tissue cancer lesions was revealed. In addition, the pharmacokinetics of PNN was investigated, and the main liver metabolic pathways were confirmed. This study not only proposed mitochondrial polarity as a potential indicator for breast cancer but also provided a noninvasive imaging tool for intravital imaging of mitochondrial polarity, demonstrating its clinical promise for breast cancer disease. [ABSTRACT FROM AUTHOR]

[Display omitted] • A near infrared emission fluorescent sensor for potential AKI diagnosis. • High sensitivity, excellent photo-stability, large stokes shift and desirable biocompatibility. • Revealing the increase of kidney organ and tissue viscosity in AKI mice for the first time. • Exploring the inhibitory effect of early intake of reduced glutathione on AKI for the first time. • This probe MI-F will be a powerful tool to be potentially applied in AKI diagnosis in the case of treatment. Elucidating the viscosity level under the pathology of acute kidney injury (AKI) is of great significance. However, this necessary and interesting work has never been explored. In view of this, a near-infrared (NIR) emission fluorescent probe MI-F was developed to visualize the viscosity level of AKI and evaluate the intervention ability of reduced glutathione on AKI. With MI-F , the increase of viscosity under the pathology of AKI was revealed. It also proved that the early intake of reduced glutathione has a certain inhibitory and preventive effect on the degree of kidney organ damage during AKI process. In addition, no obvious changes in the fluorescence intensity of other organs including the heart, liver, spleen and lung have been found, revealing the early stage of AKI may have less impact on other organs. Therefore, our work will provide pathological guidance for clinical studies of AKI such as diagnosis, prevention and treatment. [ABSTRACT FROM AUTHOR]

Exploring the connection between blood viscosity and liver in it have great significance for the detection and treatment of hyperlipidemic. Therefore, we designed a new near-infrared viscosity sensitive fluorescent probe Vis-LW based on the twisted intramolecular charge transfer mechanism. The probe exhibited a strong dependence on viscosity as well as good anti-interference performance. With the aid of Vis-LW , we successfully detected the viscosity changes in chloroquine induced cells and realized the diagnosis of diseases in hyperlipidemic mice by utilizing blood viscosity as a diagnostic indicator for hyperlipidemia. Not only that, the increased liver viscosity of hyperlipidemic mice was found for the first time, the reduced blood and liver viscosity after treatment with lipid-lowering drug fenofibrate was also tracked. This work provides a new method for the diagnosis of hyperlipidemia and offered a new idea on the research and treatment of hyperlipidemia in the future. [Display omitted] • A near infrared emission fluorescent probe for hyperlipidemia diagnosis. • The advantageous features of the probe Vis-LW include high sensitivity, good selectivity and large stokes shift. • The viscosity changes in liver organs from the hyperlipidemia and normal mice have visualized for the first time. • The change trend of the liver viscosity in the therapeutic effects of fenofibrate was explored. • This probe Vis-LW will be a powerful tool to be potentially applied in hyperlipidemia diagnosis in the case of treatment. [ABSTRACT FROM AUTHOR]

A powerful polar-sensitive fluorescent probe with precise LDs targeting as well as excellent biocompatibility was synthesized for revealing the intrinsic relationship between lipid droplet polarity and muscle injury. [Display omitted] • A new fluorescent probe for potential muscle injury diagnosis. • Accurate lipid droplet targeting and high sensitivity, excellent photo-stability and desirable biocompatibility. • Distinguishing between normal cells and cancer cells and monitoring the polarity of lipid droplets in dysfunctional cells. • Revealing the internal and external relationship between muscle injury and lipid droplet polarity for the first time. Revealing the relationship between lipid droplets (LDs)polarity and disease is indispensable in clinicopathological diagnosis. So far, muscle injury is often ignored as it is not life-threatening as cardiovascular and cerebrovascular diseases, making the exploration of the internal relationship between muscle injury and LDs polarity a gray area. Herein, a fluorescent probe (CCB) with powerful polar-sensitive as well as precise LDs targeting was designed for visualizing the LDs polarity in the pathology of muscle injury. By means of the probe CCB , the identification of cancer cells and the monitoring of LDs polarity changes in dysfunctional cells were successfully realized. Furthermore, the penetration ability of CCB in tissues of mice was tested to verify the applicability of the probe in organisms. Importantly, by CCB , the relationship between muscle damage and LDs polarity was explored, revealing that muscle damage caused a significant decrease in LDs polarity accompanied by a significant increase in fluorescence. Most importantly, it is the first time to reveal the relationship between muscle damage and LDs polarity. Therefore, the probe CCB will be a powerful monitoring platform for diagnosing related diseases caused by abnormal LDs polarity. [ABSTRACT FROM AUTHOR]

We developed a powerful fluorescent probe LW-1 for sensing the polarity changes of LDs. In virtue of the LW-1 , monitoring the polarity variations has been achieved in asthma mice for the first time. [Display omitted] • Detecting changes of LDs polarity during asthma for the first time. • The advantageous features of the probe LW-1 include high sensitivity, good selectivity and large stocks shift. • In virtue of the LW-1 , asthma lung were distinguished from normal lung. • The change trend of the LD polarity in the herapeutic effects of ketotifen fumarate were explored. Exploring the changes in the polarity of lipid droplets (LDs) in the lungs of asthma patients is of great significance for the detection and treatment of asthma. For this reason, we have synthesized a powerful polarity-sensitive fluorescent probe LW-1 targeting LDs, which was constructed with pyrene as the fluorophore and malononitrile as the electron withdrawing group. Due to its special intramolecular charge transfer mechanism, the probe exhibits strong solvatochromic response toward polarity. With the assistance of LW-1 , we not only successfully distinguished cancer cells from normal cells but also detected the changes of LDs polarity under the stimulation of starvation, oleic acid and hydrogen peroxide. Moreover, the polarity changes of LDs in lungs of asthma mice were successfully monitored at organ and tissue levels, and revealed for the first time that lung polarity is reduced in asthmatic conditions. In addition, the therapeutic efficacy of ketotifen fumarate for asthmatic mice has also been successfully tracked by monitoring LDs polarity, confirming the potential of LW-1 medical applications. This work provides a new perspective for asthma research, and will inspire more strategies for clinical diagnosis and the development of new asthma drugs. [ABSTRACT FROM AUTHOR]

Monitoring of the viscosity levels in cells and tissues is of great significance for the preliminary diagnosis related to abnormal viscosity. However, tracking of the viscosity level of tumors in different growth stages at the tissue level has not been reported. Therefore, a new viscosity-sensitive fluorescent probe (TA-I) with large Stokes shift and high viscosity dependence is in this work designed to visualize the viscosity level of tumors at different growth stages. And this probe exhibited a 20-fold fluorescence enhancement in viscous medium. With the aid of TA-I , a rapidly increasing fluorescent signal (16 times) was captured in the cells stimulated by exogenous stimuli, and the probe was also successfully applied to monitor viscosity changes in inflammatory mice. In addition, the viscosity levels in tumor tissues of mice at different growth stages (3 days, 6 days and 10 days) were also visualized in tissue level and revealed that the intratumoral viscosity level is highly dependent on tumor growth period. Importantly, the decreased viscosity of drugs-treated tumor tissue was obtained by the probe. It is worth noting that this is the first time to visualize the viscosity change rule of tumor at different growth stages at the tissue level. Image 1 • A new fluorescent sensor for potential tumor diagnosis. • Large stokes shift, high sensitivity, excellent photo-stability and desirable biocompatibility. • Visualizing at tissues level the viscosity changes of tumors in different growth stages. • Firstly tracking the viscosity changes from drugs-treated tumor mice at tissues level. [ABSTRACT FROM AUTHOR]

Fluorescent labeling technology has been prevailing in the field of biotechnology, but in the more complex pathology, such as diabetes, tracking lipid droplets (LDs) viscosity remains a vacancy. To fill this gap, a new fluorescent probe (ABI-V), was herein synthesized for detecting the viscosity change of LDs in complicated biological systems. This probe displayed a larger stokes shift (195 nm), near-infrared emission and high sensitivity and selectivity to viscosity, exhibiting a 95-fold fluorescence enhancement from methanol to glycerol. In light of its distinguishable optical signals toward viscosity, the blood viscosity of diabetic mice was measured and a stronger fluorescence was obtained in the blood of diabetic mice with 2.5 times higher than normal mice. Importantly, with the assistance of ABI-V , the LDs viscosity changes in diabetic liver injury was successfully monitored at the organ and tissue levels and the results indicate that the viscosity of LDs in the liver increased under diabetic pathological conditions. Moreover, the LDs viscosity in metformin-treated diabetic liver injury was also detected accompanied by decreased fluorescence intensity comparing with the pure diabetic model, suggesting that the proposed probe ABI-V can achieve tracking the efficacy of diabetes treatment by monitoring the viscosity changes. This work provides a rewarding perspective to elucidate the role of LDs viscosity in the pathology of diabetes. Image 1 [ABSTRACT FROM AUTHOR]

The recent strategies in the design and biological applications of the carbazole-based chemosensors have been summarized and highlighted for the first time. • The general significance of developing the small-molecule carbazole derivatives. • Recent advances in the strategies to design the carbazole-based fluorescent probes. • The diverse biological applications of the carbazole-based fluorescent probes. • Challenges of existing probes with the carbazole scaffold in bioimaging. • The prospects of the carbazole-based fluorescent probes for future applications. Carbazole derivatives have been receiving extensive attention owing to the merits of favorable donor ability, good planarity, rich photophysical properties, and excellent biocompatibility. In recent years, carbazole-based small molecular fluorescent probes have developed rapidly and extensively utilized for bioimaging, providing abundant and valuable information for studying important life processes. Although the topic of carbazole-based fluorescent probes for bioimaging is important and frontier, no review focused on this hot subject so far. Thus, in this tutorial review, we firstly summarize and highlight the recent advances in design, photophysical properties, and biological applications of carbazole-based probes. In order to legibly and intuitively grasp the topic, this work was classified into five parts according to the sensing targets detected by carbazole-based probes. Accordingly, we provide an overview of recent advances of carbazole derivatives for bioimaging in the perspective of biological applications of the carbazole chemosensors toward ionic species, reactive sulfur species (RSS), reactive oxygen species (ROS), biomacromolecules, microenvironment and others. Several representative examples for each bio-application have been reviewed, and all these cases demonstrate that carbazole derivatives could act as a robust tool for monitoring biomolecules in living systems. Moreover, with the assistance of fluorescence imaging, some carbazole-based probes can be employed to feedback the subtle concentration changes of biomarkers at the disease sites, greatly facilitating the significant advances in cell biology and medical diagnostic imaging. In addition, we also discuss the unsolved problems and future challenges in the terms of synthesis and biological application of carbazole derivatives. Future attention should be focused on the designing carbazole-based probes involving near-infrared emission and multiple sites to improve detection efficacy and provide more biological information. More importantly, great effort and collaboration from different communities of chemists, physicists and biologists are required to translating laboratory feasibility of carbazole derivatives to clinical practicability. This review herein will promote new progress and improvements of novel carbazole-based probes for further exploring life events. [ABSTRACT FROM AUTHOR]

The recent progress of organic fluorescence probes for simultaneous sensing of nucleic acid and associated cellular components in living organisms have been reviewed for the first time. • The significance of simultaneous imaging nucleic acid and cellular components. • The sensing mechanisms of probes for nucleic acids and cellular components. • The application of these reviewed probes in living systems. • The outlook of probes for sensing nucleic acids and associated cellular components. Nucleic acid, including deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), acts a vital role in the gene expression process and it is the prime source for storing, duplicating and transferring the genetic information in all eukaryotic cells. Some associated cellular components may lead to changes in location, number and morphology of nucleic acid, which are closely related to several diseases. Thus, it is of highly significant to simultaneously sense nucleic acid and associated cellular components with organic fluorescent chemsensors. However, this interesting and frontier topic has not been reviewed so far. Therefore, it is important to summarize the recent advances in organic fluorescent probes for simultaneous sensing of nucleic acid and related cellular components in living systems. Thus, in this review, we focus on the recent progress in the design strategies, sensing mechanisms, and the applications of organic fluorescence probes for simultaneous sensing of nucleic acid and associated cellular components in living organisms. This critical review may promote the development of more robust fluorescent probes for simultaneous imaging nucleic acid and associated cellular components in the future. [ABSTRACT FROM AUTHOR]

The detection of viscosity is of great significance for medical research. Herein, we have developed a two-photon fluorescent probe CB-V for monitoring micro-viscosity changes. The fluorescence emission intensity of CB-V increased 9.6-fold from methanol to glycerol exhibiting an excellent fluorescence response. With excellent properties of CB-V , monitoring the viscosity variations has been achieved not only in living cells but also in zebra fish and mice. A two-photon fluorescent probe CB-V with near infrared emission has been developed to measure the viscosity changes in living cells, zebra fish and mice. Unlabelled Image • A fluorescent probe for detecting viscosity has been constructed. • The probe CB-V exhibit two-photon excitation, near infrared emission, high selectivity, and excellent biocompatibility. • The probe CB-V successfully achieved viscosity detection not only in cells but also in zebra fish and in inflamed mice. [ABSTRACT FROM AUTHOR]

As a ubiquitous degradation process in cells, autophagy plays important roles in various biological activities. However, the abnormality of autophagy is closely related to many diseases, such as aging, neurological disorder, and cancer. Thus, monitoring the process of autophagy in living cells has high significance in biological studies and diagnosis of related diseases. In order to real-time and in situ monitor the process of autophagy, various organic fluorescent probes have been explored in recent years owing to the advantages such as handy staining processes, flexible molecular design strategies, and near-nondestructive detection. However, this interesting and frontier topic has not been reviewed so far. In this tutorial review, we will focus on the latest breakthrough results of organic fluorescent probes in monitoring autophagy of living cells, especially the probe design strategies based on the several microenvironment changes of the autophagy process, and the responding mechanisms and bio-imaging applications in the autophagy process. In addition, we will discuss the shortcomings and limitations of the probes developed, such as susceptible to interference, unable to monitor the whole process, and lack of clinical applications. Finally, we will highlight some challenges and further opportunities in this field. This tutorial review may promote the development of more robust fluorescent probes to further reveal the mechanisms of autophagy, which is the basis of degradation and recycling of cell components. [ABSTRACT FROM AUTHOR]

Reactive carbonyl species (RCS) are involved not only in diverse physiological pathways but also in various pathological processes, including Alzheimer's disease, diabetes, cardiovascular disease, and other malignant diseases. Therefore, it is essential to develop a simple and sensitive technology which can be employed to selectively monitor RCS in living biological samples, such as living cells, tissues, and animals. The subtle changes in the concentration of RCS in organisms can be detected by this technique. In this review, the design strategies of the typical examples of RCS fluorescent probes are highlighted and discussed. These advanced RCS probes may set the foundation for biomedical research on dynamic real-time monitoring of RCS in living systems. [ABSTRACT FROM AUTHOR]

Exploring the changes in intracellular viscosity in response to inflammatory stress is of great significance for the detection and treatment of various diseases. For this purpose, we synthesized a viscosity-sensitive fluorescent probe VisP, which was constructed with carbazole as the fluorophore and indole salt as the rotor. The probe VisP emitted weak red fluorescence in low viscosity media, and strong red fluorescence in highly viscous solvents, exhibiting a drastic viscosity dependence and linear correlation (R2 = 0.996). The spectral tests and cell imaging experiments jointly confirmed the satisfactory photostability of the VisP. In addition, the MTT test results showed that the probe has low cytotoxicity, further supporting the application prospect of the probe in biological systems. By using the probe VisP, changes in the viscosity in nystatin and monensin-induced cells were tracked in situ, revealing the phenomenon of increased physiological viscosity in response to inflammatory stress. Moreover, the fluctuation of viscosity in dexamethasone sodium phosphate treated inflamed cells has also been sensed. This work not only provides an important tool for inflammation research, but also provides a new perspective for the study of viscosity-related diseases. [ABSTRACT FROM AUTHOR]

Fluorine (F) is a highly reactive and non-biodegradable pollutant widely present in the environment, which has seriously threatened ecosystems and human health. To date, no fluorescent probes have been reported to visually observe the accumulation of excess fluoride ions in living plants and animals, which severely limits the study of the toxic effects of fluoride ions in biological chains. In this work, we designed and synthesized a new deep-red emission fluorescent probe NRF for detecting the accumulation of F− in living animals and plants. Exploiting F-induced cleavage of the silicon-oxygen bond, the probe NRF exhibited remarkable fluorescence changes from weak to strong. In addition, this probe displayed some significant advantages in detecting F−, including excellent selectivity, good photostability, and low biological toxicity. Furthermore, its favorable properties for detecting F− were successfully demonstrated in HeLa cells and zebrafish. Notably, utilizing the robust probe NRF , visualization of F− accumulation in acute F− toxicity model and the roots of Arabidopsis thaliana tissues had been achieved. This study shows that NRF can be used as an effective tool to detect excess F− in living cells, animals and plants, and provides a method for elucidating the toxicity mechanism of fluoride in physiological and pathological processes. [Display omitted] • We have developed a new deep-red emission fluorescent probe (NRF) for the detection of F− in living organisms. • The probe NRF was successfully applied to high-contrast imaging of F− in HeLa cells and zebrafish. • The unique probe NRF was used effectively to visualize F− in a mouse model of acute F− toxicity. • The accumulation of F− in the roots of Arabidopsis thaliana can be effectively observed using the novel probe NRF. [ABSTRACT FROM AUTHOR]

[Display omitted] • A systematic summary of the Si O Si bridged materials for bioimaging has been presented for the first time. • This review describes our recent works for the design and synthesis of fluorescent probes to detect various species. • It is urgent to develop general strategies to achieve concise regulation of fluorescence properties with desired structures. Fluorescence imaging is one of the most powerful methods for the spatial and temporal visualization of bio-species in living systems. Various fluorescent materials have obtained intense and continuous attention, including small-molecule organic fluorophores, luminescent transition metal complex, emissive polymers, and fluorescent proteins. Organosilicon materials, bearing Si O Si bonds, are important sorts of functional platforms exhibiting great applications in various fields such as catalysis, energy, and bioscience, due to their unique electronic, optical, and biocompatibility properties. Fluorescent materials based on Si O Si bridged materials have presented new potential for imaging biological processes in living systems. Therefore, an in-depth understanding of the roles that Si O Si bonds play is instructive for further designing of organosilicon fluorescent materials. This review highlights the recent trends in the development of fluorescent organosilicon compounds as powerful tools for bioimaging within diverse living systems and summarizes the roles of Si O Si bonds acted in bioimaging. Besides, we put outlooks forward for the field of fluorescent organosilicon materials and their prospective functions as materials for bioimaging. [ABSTRACT FROM AUTHOR]

The recent developments of organic fluorescence probes for detecting mitochondrial membrane potential (MMP) have been reviewed for the first time. • The significance of designing organic fluorescent probes for the detection of MMP. • The design concept and recognition mechanisms of the fluorescent probes for the detection of MMP. • The advantages and limitations of the fluorescent probes in the application to detect MMP. • The perspectives of the organic fluorescent probes for sensing MMP. Mitochondrial membrane potential (MMP), as a key indicator of mitochondrial function, can reflect the cellular health status. The dysfunction of MMP, even the subtle unusual changes, can greatly affect the intracellular bioactivities, causing various diseases, such as keratitis, diabetes, Alzheimer's disease and even cancer. Thus, detecting the variation of MMP has great significance for biological research and medical diagnosis. Due to the advantages of real-time and in-situ monitoring, a variety of organic fluorescent probes have been developed in recent years for the detection of MMP. However, this interesting and frontier topic has not been reviewed so far. In this review, we will focus on several kinds of recent organic fluorescent probes that have provided insights into MMP detection, including design concepts, responding mechanisms and applications of the representative examples. In addition, there are still some shortcomings and limitations of existing fluorescent probes on MMP detection, such as susceptible to interference, unquantifiable detection, and lack of clinical application. This critical review may promote the development of more robust MMP fluorescent probes, providing more powerful tools for researching basic biology to improve cancer diagnoses and treatments in clinics in the future. [ABSTRACT FROM AUTHOR]