A near-infrared fluorescent probe for monitoring abnormal mitochondrial viscosity in cancer and fatty-liver mice model

Triphenylphosphine-bonded coumaranone dyes realize dual color imaging of mitochondria and nucleoli

Probing intracellular organelles with fluorescent dyes offers opportunities to understand the structures and functions of these cellular compartments, which is attracting increasing interests. Normally, the design principle varies for different organelle targets as they possess distinct structural and functional profiles against each other. Therefore, developing a probe with dual intracellular targets is of great challenge. In this work, a new sort of donor-π-bridge-acceptor (D-π-A) type coumaranone dyes (CMO-1/2/3/4) have been prepared. Four fluorescent probes (TPP@CMO-1/2/3/4) were then synthesized by linking these coumaranone dyes with an amphiphilic cation triphenylphosphonium (TPP). Interestingly, both TPP@CMO-1 and TPP@CMO-2 exhibited dual color emission upon targeting to two different organelles, respectively. The green emission is well localized in mitochondria, while, the red emission realizes nucleoli imaging. RNA is the target of TPP@CMOs, which was confirmed by spectroscopic analysis and computational calculation. More importantly, the number and morphology changes of nucleoli under drug stress have been successfully evaluated using TPP@CMO-1.

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.

Rational design of mitochondria-targeted fluorescent biosensors for in vivo elucidation of the interaction between breast cancer metastasis and mitochondrial autophagy

Breast cancer lung metastases (BCLM) are a major cause of high mortality in patients. The shortage of therapeutic targets and rapid drug screening tools for BCLM is a major challenge at present. Mitochondrial autophagy, which involves the degradation of proteins associated with cancer cell aggressiveness, represents a possible therapeutic approach for the treatment of BCLM. Herein, four fluorescent biosensors with different alkyl chains were designed and synthesized to monitor mitochondrial autophagy. Among them, PMV-12 demonstrated the highest sensitivity to viscosity variance, the least impact on polarity, and the longest imaging time. The introduction of the C12-chain made PMV-12 anchored in the mitochondrial membrane without being disturbed by changes of the mitochondrial membrane potential (MMP), thereby achieving the long-term monitor in situ for mitochondrial autophagy. Mitochondria stained with PMV-12 induced swelling and viscosity increase after treating with apigenin, which indicated that apigenin is a potential mitochondrial autophagy inducer. Apigenin was subsequently verified to inhibit cancer cell invasion by 92%. Furthermore, PMV-12 could monitor the process of BCLM in vivo and evaluate the therapeutic effects of apigenin. This work provides a fluorescent tool for elucidating the role of mitochondrial autophagy in the BCLM process and for anti-metastatic drug development.

Mechanistic analysis of viscosity-sensitive fluorescent probes for applications in diabetes detection

Diabetes is one of the most detrimental diseases affecting the human life because it can initiate several other afflictions such as liver damage, kidney malfunctioning, and cardiac inflammation. The primary method for diabetes diagnosis involves the analysis of blood samples to quantify the level of glucose, while secondary diagnostic methods involve the qualitative analysis of obesity, fatigue, etc. However, all these symptoms start showing up only when the patient has been suffering from diabetes for a certain period of time. In order to avoid such delay in diagnosis, the development of specific fluorescent probes has attracted considerable attention. Prominent biomarkers for diabetes include abundance of certain analytes in blood serum, e.g., glucose, methylglyoxal, albumin, and reactive oxygen species; high intracellular viscosity; alteration of enzyme functionality, etc. Among these, high viscosity can greatly affect the fluorescence properties of various chromophores owing to the environment sensitivity of fluorescence spectra. In this review article, we have illustrated the application of some prominent fluorophores such as coumarin, BODIPY, xanthene, and rhodamine in the development of viscosity-dependent fluorescent probes. Detailed mechanistic aspects determining the influence of viscosity on the fluorescent properties of the probes have also been elaborated. Fluorescence mechanisms that are directly affected by the high-viscosity heterogeneous microenvironment are based on intramolecular rotations like twisted intramolecular charge transfer (TICT), aggregation-induced emission (AIE), and through-bond energy transfer (TBET). In this regard, this review article will be highly useful for researchers working in the field of diabetes treatment and fluorescent probes. It also provides a platform for the planning of futuristic clinical translation of fluorescent probes for the early-stage diagnosis and therapy of diabetes.

A turn-on fluorescent probe for detecting and bioimaging of HOCl in inflammatory and liver disease models

Hypochlorous acid (HOCl) is a common reactive oxygen species (ROS) associated with the development of liver, tumor, inflammatory, and other diseases. In this work, the turn-on fluorescent probe named (WZ-HOCl) with a naphthalimide structure was designed and synthesized to detect endogenous HOCl in disease models. WZ-HOCl can achieve a fast response to HOCl with good linearity in the range of 0-45 μM (LOD = 147 nM). The application of WZ-HOCl in bioimaging was investigated by constructing a series of cellular disease models, and the results showed that WZ-HOCl could sensitively detect endogenous HOCl in inflammatory and liver disease models. It can also be used to differentiate between hepatocytes and hepatoma cells. WZ-HOCl will provide new methods and ideas for fluorescent probes in detecting drug-induced liver injury, alcoholic and non-alcoholic steatohepatitis, and some inflammation-related diseases.

Activatable fluorescent probes for early diagnosis and evaluation of liver injury

With the increase in people's living standards, the number of patients suffering from liver injury keeps on increasing. Traditional diagnostic methods can no longer meet the needs of early and accurate diagnosis due to their limitations in application. However, fluorescent probes based on different fluorophores and nanomaterials have been gradually lighting up medical research due to their unique properties, such as high specificity and non-invasiveness. In addition, accurate identification of the different types of liver injury biomarkers can significantly improve the level of early diagnosis. Therefore, this review reviews the fluorescent probes used in the detection of biomarkers of liver injury over recent years and briefly summarizes the corresponding biomarkers of different types of liver injury. Impressively, this review also lists the structures and the response mechanisms of the different probes, and concludes with an outlook, suggesting directions in which improvements can be made. Finally, we hope that this review will contribute to the further development of fluorescent probes for the early diagnosis and assessment of liver injury.

Strategic design of an NIR probe for viscosity imaging in inflammatory and non-alcoholic steatohepatitis mice

Two novel near-infrared (NIR) fluorescent probes Cy-Vis1 and Cy-Vis2 with large Stokes shifts (>100 nm) were constructed using a "symmetry collapse" strategy. Notably, Cy-Vis2 was significantly more sensitive to viscosity than Cy-Vis1 through an enhanced intramolecular interaction strategy. The fluorescence intensities of Cy-Vis1 and Cy-Vis2 exhibited increases, by 7.6- and 19.9-fold, respectively, across the viscosity range from 0.8 cp to 359.9 cp. Cy-Vis2 was successfully used to visualize viscosity abnormalities in lipopolysaccharide (LPS)-induced inflammatory and NASH model mice.

Customized fluorescent probe for peering into the expression of butyrylcholinesterase in thyroid cancer

BACKGROUND

Thyroid cancer has been increasingly prevalent in recent years. The main diagnostic methods for thyroid are B-ultrasound scan, serum detection and puncture detection. However, these methods are invasive and complex. It is a pressing need to develop non-invasive or minimally invasive methods for thyroid cancer diagnosis. Fluorescence method as a non-invasive detection method has attracted much attention. Butyrylcholinesterase (BChE) is a common enzyme in the human body, and many diseases affect its reduction. We found that BChE is also a marker for thyroid cancer. Therefore, it is of certain clinical value to explore the expression of BChE in thyroid cancer cells through a customized fluorescent probe to provide valuable experimental data and clues for studying the expression of thyroid cancer marker to reflect thyroid status.

RESULTS

In this study, we customized a fluorescent probe named Kang-BChE, which is easy to synthesize with a high yield. The experimental results show that the probe Kang-BChE can detect BChE in the linear range of 0-900 U L-1 (R2 = 0.9963), and the detection limit is as low as 3.93 U L-1 (λex/em = 550/689 nm). In addition, Kang-BChE probes have low cytotoxicity, good specificity, and can completely eliminate interference from acetylcholinesterase (AChE). Kang-BChE showed excellent stability in the detection of complex biological samples in serum recovery experiments (95.64-103.12 %). This study was the first time using Kang-BChE to study the low expression of BChE in thyroid cancer cells (Tpc-1 cells). In addition, we observed that H2O2 concentration in Tpc-1 cells was positively correlated with BChE activity.

SIGNIFICANCE

Kang-BChE is expected to be an important tool for monitoring the change of BChE content in complex biological environments due to its excellent performance. Kang-BChE can also be used to explore the influence of molecules in more organisms on the change of BChE content due to its excellent anti-interference ability. We expect that Kang-BChE can play a significant role in the clinical diagnosis and treatment of thyroid cancer.

A dual-function fluorescence 'turn-on' probe that allows Zn (II) bioimaging and quantification of water in the organic solvent

Herein, a Eugenol-derived fluorescence 'turn-on' probe FLHE was synthesized by condensing 2-((3-(trifluoromethyl)phenyl)amino)benzohydrazide with 5-allyl-2-hydroxy-3-methoxybenzaldehyde. FLHE demonstrated very low fluorescence in the studied organic solvents of varying polarities. However, upon titration with Zn2+ in HEPES buffer (pH = 7.4, 50% ACN, v/v), FLHE showed 40-fold higher fluorescence signals indicating the formation of the FLHE-Zn2+ complex. The fluorescence turn-on phenomenon upon FLHE-Zn2+ complex formation results from a chelation-enhanced fluorescence (CHEF) effect. The FLHE-Zn2+ complexation demonstrated a stokes shift of 156 nm (λex = 350 nm, λem = 506 nm) and an about 33-fold increase in the quantum yield (FLHE, Φ = 0.007; FLHE-Zn2+ complex, Φ = 0.23). The binding constant (Ka) determined by the Benesi-Hildebrand plot for interaction between FLHE and Zn2+ was 5.33 × 103 M-1. FLHE demonstrated a LOD of 31.8 nM for detecting Zn2+ in the environmental samples without interference from other cations and anions. FLHE-based paper strip (FLHE-PS) assay was developed to quantify the Zn2+ ions in water and the water content of organic solvent. FLHE-PS allows the detection of Zn2+ in aqueous solutions with a LOD of 63.2 nM and quantifying water in acetonitrile with a LOD of 0.14%. These results indicate that the FLHE has high applicability for detecting Zn2+ in living cells and environmental samples and detecting the presence of water in the organic solvents.

Development of a novel near-infrared molecule rotator for early diagnosis and visualization of viscosity changes in acute liver injury models

Acute liver injury leading to acute liver failure can be a life-threatening condition. Therefore, timely and accurate early diagnosis of the onset of acute liver injury in vivo is critical. Viscosity is one of the key parameters that can accurately reflect the levels of relevant active analytes at the cellular level. Herein, a novel near-infrared molecule rotator, DJM, was designed and synthesized. This probe exhibited a highly sensitive (461-fold from PBS solution to 95% glycerol solution) and selective response to viscosity with a maximum emission wavelength of 760 nm and a Stokes shift of 240 nm. Furthermore, DJM has exhibited a remarkable capacity to discern viscosity changes induced by nystatin in viable cells with sensitivity and selectivity and further applied in the zebrafish and mouse model of acute liver injury. Additionally, DJM may potentially offer direction for the timely observation and visualization of viscosity in more relevant disease models in the future.