Efficient Two-Photon Fluorescent Probe for Glutathione S-Transferase Detection and Imaging in Drug-Induced Liver Injury Sample

A Double-Stranded Aptamer for Highly Sensitive Fluorescent Detection of Glutathione S-Transferases

Aptamer-based biosensors have been widely constructed and applied to detect diverse targets. Glutathione S-transferase (GST), a pivotal phase II metabolic enzyme, plays a critical role in biotransformation in vivo, and aberrant GST expression is associated with various health risks. Herein, aptamers targeting GST were systematically selected from a randomized single-stranded DNA (ssDNA) library of 79 nucleotides (nt) using a biotinylated GST-immobilized streptavidin agarose (SA) bead SELEX technology. Following rigorous screening across eight rounds, four aptamers with strikingly similar secondary structures emerged. Among these, Seq3 exhibited the highest affinity towards GST and was selected for further optimization. A semi-rational post-SELEX truncation strategy was then employed based on base composition analysis, secondary structure analysis and affinity assessment. This strategy enabled the systematic removal of redundant nucleotides in Seq3 without compromising its affinity, ultimately yielding a truncated aptamer, Seq3-3, which retains its specificity with a compact 39nt length. Building upon Seq3-3, a double-stranded fluorescent aptamer probe was ingeniously designed for the in vitro detection of GST. The detection mechanism hinges on the competitive displacement of the complementary chain from the probe, mediated by the target protein, leading to the separation of the antisense oligonucleotide from the double-stranded complex. This process triggers the restoration of the fluorescence signal, enabling sensitive detection, and the probe exhibits excellent response within a linear range of GST activity ranging from 0 to 1500 U/L. The results show that not only an efficient strategy for screening robust and practicable aptamers but also an ultrahighly sensitive detection platform for GST was established.

Fabrication of superior laccase-mimicking enzyme with catalytic oxidative and photothermal properties for anti-bacterial and dual-mode glutathione S-transferase monitoring

A novel laccase mimic enzyme Cu-Mn with excellent photothermal properties was firstly prepared via a combination of hydrothermal and in situ synthesis. Cu-Mn nanozymes could catalyze the typical laccase substrate 2,4-dichlorophenol (2,4-DP) to generate the red quinone imine. Further, loading the MnO2 nanosheets with photothermal properties, Cu-Mn nanozymes possessed not only excellent laccase catalytic activity, but also high photothermal conversion efficiency. The presence of glutathione S-transferase (GST) recovered the glutathione (GSH)-induced weakness of the laccase activity and photothermal properties of Cu-Mn. Hence, a GST enzyme-regulated dual-mode sensing strategy was established based on Cu-Mn nanozymes. The detection limits of GST monitoring based on colorimetric and photothermal methods were 0.092 and 0.087 U/L with response times of 20 min and 8 min, respectively. Furthermore, the proposed method enabled the measuring of GST levels in human serum and was successfully employed in the primary evaluation of hepatitis patients. Another attraction, the impressive photothermal behavior also endowed the Cu-Mn nanozymes with promising antimicrobial properties, which exhibited significant antimicrobial effects against Escherichia coli (E.coli) and Staphylococcus aureus (S.aureus). Unsurprisingly, multifunctional Cu-Mn nanozymes certainly explore new paths in biochemical analysis and antimicrobial applications.

Hepatoprotective Effect of Ethanolic Pomegranate Peel Extract Against Levofloxacin via Suppression of Oxidative Stress, Proinflammation, and Apoptosis in Male Rats

One of the fluoroquinolone antibiotics, levofloxacin (LEV), is used to treat a variety of illnesses leading to oxidative stress and cellular damage. Peel from Punica granatum is a waste product abundant in phytochemicals with various biological activities. This study aimed to evaluate P. granatum peel extract's (PGPE) potential to mitigate oxidative stress, inflammation, apoptosis, and liver damage caused by LEV. There were four groups of rats: control, PGPE, LEV, and PGPE + LEV, respectively, and they were orally administered their daily treatments for 2 weeks. Results revealed that PGPE has a large number of phytochemical components with high antioxidant activity. PGPE intake alone enhanced the antioxidant status and decreased oxidative stress. On the other hand, pretreatment of the LEV group with PGPE restored oxidative stress, antioxidant enzymes, glutathione content, liver function biomarkers, and hematological parameters. Also, normalization of gene expressions (cyclooxygenase-2, transforming growth factor-beta1, caspase-3, heme oxygenase-1, B cell lymphoma-2, interleukin [IL]-10, and IL-1) and improvement in liver architecture, and immunohistochemical alpha-smooth muscle actin, were seen in comparison to the LEV group. Conclusively, PGPE exhibits strong anti-inflammatory, antiapoptotic, and antioxidant properties that shield rat liver from the damaging effects of LEV and offer a fresh viewpoint on the application of fruit waste products.

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.

A Switch-On Affinity-Based Iridium(III) Conjugate Probe for Imaging Mitochondrial Glutathione S-Transferase in Breast Cancer Cells

Glutathione S-transferase is heterogeneously expressed in breast cancer cells and is therefore emerging as a potential diagnostic biomarker for studying the heterogeneity of breast cancers. However, available fluorescent probes for GSTs depend heavily on GSTs-catalyzed glutathione (GSH) nucleophilic substitution reactions, making them susceptible to interference by the high concentration of nucleophilic species in the cellular environment. Moreover, the functions of subcellular GSTs are generally overlooked due to the lack of suitable luminescence probes. Herein, we report a highly selective affinity-based luminescence probe 1 for GST in breast cancer cells through tethering a GST inhibitor, ethacrynic acid, to an iridium(III) complex. Compared to activity-based probes which require the use of GSH, this probe could image GST-pi in the mitochondria by directly adducting to GST-pi (or potentially GST-pi/GS) in living cells. Probe 1 possesses desirable photophysical properties including a lifetime of 911 ns, a Stokes shift of 343 nm, and high photostability. The "turn on" luminescence mode of the probe enables highly selective detection of the GST with a limit of detection of 1.01 μM, while its long emission lifetime allows sensitive detection in organic dye-spiked autofluorescence samples by a time-resolved mode. The probe was further applied to specifically and quantitatively visualize MDA-MB-231 cells via specific binding to mitochondrial GST, and could differentiate breast cell lines based on their expression levels of GST. To the best of our knowledge, this probe is the first affinity-based iridium(III) imaging probe for the subcellular GST. Our work provides a valuable tool for unmasking the diverse roles of a subcellular GST in living systems, as well as for studying the heterogeneity of breast cancers.

Ameliorative effect of mussel-derived ACE inhibitory peptides on spontaneous hypertension rats

PURPOSE

The purpose of this study was to prepare the novel mussel-derived ACE inhibitory peptides (MEPs) by enzymatic hydrolysis of Mytilus edulis and investigate their antihypertensive effects in vivo.

METHODS

After assessing the stability of MEPs in vitro, we investigated the effect of MEPs on hypertension using spontaneously hypertensive rats (SHRs). Subsequently, MEPs were purified and identified by ultrafiltration, gel filtration chromatography and liquid chromatography-tandem mass spectrometry (LC-MS/MS).

RESULTS

Our study demonstrated that MEPs could keep stable ACE inhibitory activity after treatment with heat, acid, alkali, metal ions and simulated gastrointestinal digestive fluid. Additionally, the animal experiments showed that both short-term and long-term treatment with MEPs resulted in a significant reduction in systolic and diastolic blood pressure in SHRs. Mechanistically, the results suggested that MEPs could reduce vascular remodeling, regulate renin-angiotensin system (RAS), and inhibit kidney and myocardial fibrosis. Finally, we isolated and identified five peptides from MEPs, with the peptide Ile-Leu-Thr-Glu-Arg showed the highest ACE inhibition rate.

CONCLUSION

Our findings demonstrate the potential use of MEPs as active components in functional foods designed to lower blood pressure.

Imaging and detection of sulfite in acute liver injury with a novel quinoxaline-based fluorescent probe

Herein, a novel fluorescent probe HZY was developed for monitoring the sulfite (SO₃^2-) dynamics. For the first time, the SO₃^2- triggered implement was applied in the acute liver injury (ALI) model. The levulinate was selected to achieve the specific and relatively steady recognition reaction. With the addition of SO₃^2-, the fluorescence response of HZY exhibited a large Stokes shift of 110 nm under the 380 nm excitation. The merits included high selectivity under various pH conditions. Compared with the reported fluorescent probes for sulfite, HZY indicated above-moderate performances including remarkable and rapid response (40 folds, within 15 min), and high sensitivity (limit of detection = 0.21 μM). Further, HZY could visualize the exogenous and endogenous SO₃^2- level in living cells. Moreover, HZY could gauge the changing levels of SO₃^2- in three types (induced by CCl₄, APAP, and alcohol) of ALI models. Both in vivo imaging and depth-of-penetration fluorescence imaging demonstrated that HZY could characterize the developmental and therapeutic status during the liver injury process by measuring the dynamic of SO₃^2-. The successful implementation of this project would promote the accurate in-situ detection of SO₃^2- in liver injury, which was expected to guide the pre-clinical diagnosis and clinical practice.

A sensing platform for on-site detection of glutathione S-transferase using oxidized Pi@Ce-doped Zr-based metal-organic frameworks(MOFs)

The development of point-of-care testing (POCT) for glutathione S-transferase (GST) is an effective way to establish the mechanism of targeted monitoring of cancer chemotherapy drug metabolism. Assays for GST with high sensitivity as well as on-site screening have been urgently required to monitor this process. Herein, we synthesized oxidized Pi@Ce-doped Zr-based metal-organic frameworks (MOFs) by electrostatic self-assembly between phosphate and oxidized Ce-doped Zr-based MOFs. It was found that the oxidase-like activity of oxidized Pi@Ce-doped Zr-based MOFs was substantially increased after phosphate ion (Pi) assembly. And a stimulus-responsive hydrogel-based kit was constructed by embedding oxidized Pi@Ce-doped Zr-based MOFs into a PVA (polyvinyl alcohol) hydrogel system, we integrated a portable hydrogel kit with a smartphone for real-time monitoring of GST for quantitative and accurate analysis. The color reaction was triggered based on oxidized Pi@Ce-doped Zr-based MOFs with 3,3',5,5'-tetramethylbenzidine (TMB). However, in the presence of glutathione (GSH), the above color reaction was hindered due to the reducibility of GSH. Catalyzed by GST, GSH can react with 1-chloro-2,4-dinitrobenzo (CDNB) to form an adduct, which caused the color reaction to occur again, resulting in the color response of the kit. In combination with ImageJ software, the kit image information acquired by smartphone could be converted into hue intensity, providing a direct quantitative tool for the detection of GST with a detection limit of 0.19mU·L^-1. Based on the advantages of simple operation and cost-effectiveness, the introduction of the POCT miniaturized biosensor platform will meet the requirements of on-site quantitative analysis of GST.

Improving reactivity of naphthalimide-based GST probe by imparting TPP cation: Development and application for live cell imaging

Glutathione S-transferases (GSTs) are a superfamily of multifunctional enzymes comprising multiple classes and subtypes. This paper describes the synthesis and characterization of TPPBN-1, a naphthalimide derivative conjugated with a triphenylphosphonium (TPP) cation. When 4-bromonaphthalimide (BrNaph), a previously characterized GST substrate, was conjugated to a TPP cation, the conjugate showed increased reactivity towards most alpha- and mu-class GSTs, particularly the GSTA2 subtype, compared to the parent compound, but hardly towards Pi-class GSTs. Using this probe with enhanced reactivity, the enzymatic activity of endogenous GSTA1/2 in HepG2 cells was visualized by confocal fluorescence microscopy. The results demonstrated that modification with TPP cations, which are often used as tags for targeting mitochondria, can be used to enhance the reactivity of probes for specific GST subtypes.

Pi-class Glutathione S-transferase (GSTP1)-selective fluorescent probes for multicolour imaging with various cancer-associated enzymes

Pi-class glutathione S-transferase (GSTP1) is highly expressed in a wide variety of human cancer tissues compared to the corresponding normal counterpart. Therefore, GSTP1 is a potential target enzyme for overcoming resistance to chemotherapeutic agents or visualizing specific lesions such as cancer. Here, we present orange and red fluorescence-emitting probes selective for GSTP1. Carbofluorescein and TokyoMagenta fluorophores were modified with a previously described GSTP1-selective chromogenic compound to generate orange and red fluorescence probes, respectively. Of these probes, Ps-CF , the orange fluorescence-emitting probe, was confirmed to be highly specific for detecting GSTP1 exogenously or endogenously expressed in various cancer cells. Additionally, it was demonstrated that Ps-CF is applicable for the simultaneous detection of GSTP1 and another cancer-associated enzymes by using a green fluorescence emitting γ-glutamyl transpeptidase (GGT) probe. In conclusion, the fluorescent probes developed in this study enable the simultaneous detection of multiple tumour markers such as GSTP1 with other cancer-associated enzymes by the concurrent use of spectrally distinguished fluorescent probes, potentially broadening the scope of cancer detection.

Dual-Channel Recognition of Human Serum Albumin and Glutathione by Fluorescent Probes with Site-Dependent Responsive Features

Design of chemical probes with high specificity and responses are particularly intriguing. In this work, a fluorescent probe (M-OH-SO₃) with dual-channel spectral responses toward human serum albumin (HSA) is presented. By employing dinitrobenzenesulfonate as a recognition site as well as a fluorescence quencher, probe M-OH-SO₃ displayed weak fluorescence, which, nevertheless, exhibits extensive yellow (575 nm) and red (660 nm) fluorescence emissions toward HSA under excitations at 400 and 500 nm, respectively. Interestingly, M-OH-SO₃ displayed the best performance toward HSA with distinctly higher selectivity than that of its counterparts M-SO₃, M-H-SO₃, and M-F-SO₃, which were prepared simply by modulating the functional group at the ortho position of the dicyanoisophorone core. Molecular docking results revealed that M-OH-SO₃ possesses the lowest binding energy among the tested derivatives and accordingly the strongest binding affinity. Probe M-OH-SO₃ showed a good linear relationship toward HSA in a range of 0.5-18 μM with a limit of detection of 35 nM. Cell imaging results demonstrated that probe M-OH-SO₃ could visualize the variation HSA levels in hepatocarcinoma cells. In addition, probe M-OH-SO₃ could also be employed for the recognition of glutathione through the cleavage of the dinitrobenzenesulfonate group along with an enhancement of emission at 575 nm. The site-dependent properties inspired a novel paradigm for design of fluorescent probes with optimized selectivity and responses.

Fluorescent probes for biomolecule detection under environmental stress

The use of fluorescent probes in visible detection has been developed over the last several decades. Biomolecules are essential in the biological processes of organisms, and their distribution and concentration are largely influenced by environmental factors. Significant advances have occurred in the applications of fluorescent probes for the detection of the dynamic localization and quantity of biomolecules during various environmental stress-induced physiological and pathological processes. Herein, we summarize representative examples of small molecule-based fluorescent probes that provide bimolecular information when the organism is under environmental stress. The discussion includes strategies for the design of smart small-molecule fluorescent probes, in addition to their applications in biomolecule imaging under environmental stresses, such as hypoxia, ischemia-reperfusion, hyperthermia/hypothermia, organic/inorganic chemical exposure, oxidative/reductive stress, high glucose stimulation, and drug treatment-induced toxicity. We believe that comprehensive insight into the beneficial applications of fluorescent probes in biomolecule detection under environmental stress should enable the further development and effective application of fluorescent probes in the biochemical and biomedical fields.

Chemical Probes and Activity-Based Protein Profiling for Cancer Research

Chemical probes can be used to understand the complex biological nature of diseases. Due to the diversity of cancer types and dynamic regulatory pathways involved in the disease, there is a need to identify signaling pathways and associated proteins or enzymes that are traceable or detectable in tests for cancer diagnosis and treatment. Currently, fluorogenic chemical probes are widely used to detect cancer-associated proteins and their binding partners. These probes are also applicable in photodynamic therapy to determine drug efficacy and monitor regulating factors. In this review, we discuss the synthesis of chemical probes for different cancer types from 2016 to the present time and their application in monitoring the activity of transferases, hydrolases, deacetylases, oxidoreductases, and immune cells. Moreover, we elaborate on their potential roles in photodynamic therapy.

A Novel Fluorescent Probe Strategy Activated by β-Glucuronidase for Assisting Surgical Resection of Liver Cancer

Liver cancer is a primary malignant tumor with a very high fatality rate, which has seriously threatened human health and life. In normal hepatocellular lesions, β-glucuronidase (GLU) activity in liver cancer tissues is significantly increased. Therefore, GLU has become one of the important biomarkers of primary liver cancer. Here, a series of fluorescent probes (DCDH, DCDCH₃, DCDOCH₃, and DCDNO₂) for early diagnosis of liver cancer and auxiliary surgical resection were successfully synthesized. Since the electron-withdrawing group -NO₂ connected to the probe DCDNO₂ accelerates the rapid cleavage of the glycosidic bond, DCDNO₂ exhibits superior fluorescence properties that are more sensitive and rapid than the other three probes DCDH, DCDCH₃, and DCDOCH₃ when detecting GLU. DCDNO₂ has been well-applied in real-time fluorescent visualization imaging for the detection of GLU activity in liver cancer cells and tumor tissues. In addition, DCDNO₂ has also been successfully used in the early diagnosis of liver cancer and real-time imaging to guide the surgical resection of liver cancer tumors. Therefore, DCDNO₂ has great potential for development in bioclinical medicine for the early detection and treatment of liver cancer.

A naphthimide fluorescent probe for the detection of selenols in selenium-enriched Tan sheep

An "off-on" fluorescent probe, Nap-DNB, which is based on naphthimide, was designed and developed for the detection of biological selenols in vitro. We have adopted a combination of a low-pH detection environment and reaction sites that are more difficult to destroy to avoid the interference of a large number of biological thiols in biological samples. Nap-DNB can completely respond to selenocysteine within 15 mins, with a detection limit of 92 nM. Nap-DNB was successfully used for the detection of selenols in the serum, liver, and longissimus dorsi of selenium-enriched Tan sheep. Through comparison, we found that the detection of selenols by the Nap-DNB is similar to that by thioredoxin reductase and glutathione peroxidase in a commercial kit method. Nap-DNB can be used for the detection of selenols in selenium-enriched Tan sheep.

Optical substrates for drug-metabolizing enzymes: Recent advances and future perspectives

Drug-metabolizing enzymes (DMEs), a diverse group of enzymes responsible for the metabolic elimination of drugs and other xenobiotics, have been recognized as the critical determinants to drug safety and efficacy. Deciphering and understanding the key roles of individual DMEs in drug metabolism and toxicity, as well as characterizing the interactions of central DMEs with xenobiotics require reliable, practical and highly specific tools for sensing the activities of these enzymes in biological systems. In the last few decades, the scientists have developed a variety of optical substrates for sensing human DMEs, parts of them have been successfully used for studying target enzyme(s) in tissue preparations and living systems. Herein, molecular design principals and recent advances in the development and applications of optical substrates for human DMEs have been reviewed systematically. Furthermore, the challenges and future perspectives in this field are also highlighted. The presented information offers a group of practical approaches and imaging tools for sensing DMEs activities in complex biological systems, which strongly facilitates high-throughput screening the modulators of target DMEs and studies on drug/herb‒drug interactions, as well as promotes the fundamental researches for exploring the relevance of DMEs to human diseases and drug treatment outcomes.

Biomarker-responsive Fluorescent Probes for In Vivo Imaging of Liver Injury

Liver injury-related diseases have aroused widespread concern due to its extreme unpredictability, acute onset, and severe consequences. Nowadays, the clinical prediction and assessment of liver injury mainly focus on histopathological and serological approaches, which undergoes a tedious process and sometimes requires invasive biopsy. Over the past decades, fluorescence imaging technique have emerged as a rising star for the diagnosis of diseases owing to its noninvasiveness, high fidelity and ease of operation. On regard to liver injury, the fluorescent probes have been delicately designed to response a variety of endogenous biomolecules to precisely offer comprehensive information about the lesion site. Herein, we make a brief summary and discussion about the design strategies and applications of the recently reported fluorescent biosensors responsive to a series of biomarkers involved in the liver injury. The potential prospects and remaining challenges are also discussed to promote the progression in this field.

Near-infrared frequency upconversion probe for revealing the relationship between glutathione S-transferase and drug-resistance

Drug resistance poses an enormous challenge for successful chemotherapy. Glutathione S-transferase (GST) has been confirmed to be involved in the progression of drug resistance to some anticancer drugs, thus revealing that the role of GST in anticancer drug resistance is necessary. Herein, by taking advantage of frequency upconversion luminescence (FUCL) technology, we reported an FUCL probe (NRh-NDs) that can detect GST based on a rhodamine derivative structure decorated with a 2,4-dinitrobenzenesulfonyl group (NDs). The NRh-NDs showed excellent sensitivity and high selectivity for GST and released the emissive dye NRh-NH₂, which showed emission and excitation wavelengths in vitro of 820 nm and 850 nm, respectively. The NRh-NDs probe successfully tested endogenic GST in U87, MCF-7 and A549 cells. The cell data showed that the increased levels of GST were positively related to cisplatin resistance but not to 5-fluorouracil resistance. These results suggested that the probe could be used as a visual tool to reveal the cause of drug resistance for cisplatin resistance in cancer treatment. Furthermore, it may serve as an effective tool to confirm the mechanism of antitumor drug resistance.

Construction of a Rational-Designed Multifunctional Platform Based on a Fluorescence Resonance Energy Transfer Process for Simultaneous Detection of pH and Endogenous Peroxynitrite

Peroxynitrite (ONOO^-), a kind of reactive oxygen species, plays an indispensable role in many physiological processes. The stability and reactivity of ONOO^- are significantly affected by the pH of the environment. A novel fluorescent probe RN-NA that can simultaneously respond to ONOO^- and pH was proposed and constructed based on a rational-designed multifunctional fluorescence resonance energy transfer (FRET) platform. The RN-NA probe exhibited a remarkably different fluorescence change in response to ONOO^- and pH. The fluorescence signals at 525 and 710 nm increased about 4-fold with a pH change from 8.0 to 3.0. The changes in fluorescence at 525 nm are mainly attributed to photo-induced electron transfer, and the fluorescence enhancement at 710 nm was mainly due to acid-induced open-closed circulation. In the presence of ONOO^-, the fluorescence at 525 nm increased 5-fold, while the fluorescence at 710 nm was almost completely diminished. Up to 70-fold fluorescence enhancement was observed in the ratiometric channel F₅₂₅/F₇₁₀. In the cell imaging experiment, the intracellular pH was adjusted using H⁺/K⁺ ionophore and nigericin, and the endogenous ONOO^- was generated by lipopolysaccharide (LPS) and γ-interferon (IFN-γ). The RN-NA probe can respond to cellular pH and endogenous ONOO^- with remarkable fluorescence changes in both red/green and ratiometric channels.

Proteome and transcriptome analysis revealed florfenicol via affected drug metabolism and lipid metabolism induce liver injury of broilers

In order to explore the mechanism of liver injury induced by florfenicol (FFC) in broilers. Sixty broilers were randomly divided into 2 groups: control group: normal drinking water and feed were given every d; FFC group: tap water containing FFC (0.15g/L) was given every d and feed was taken freely; each group was given 5 dd of continuous medication and feed was taken freely. The results showed that compared with the control group, FFC could significantly inhibit the weight gain of broilers (P < 0.05), and significantly inhibit the expression of CYP1A1 and CYP2H1 in liver tissue (P < 0.05). It was found that the expression of genes related to the effect of cytochrome P450 on the metabolism of exogenous substances, the peroxisome proliferators-activated receptors signal pathway, peroxisome pathway and glutathione metabolic pathway in the liver of broilers. The results of qPCR of UDP glucuronosyltransferase family 2A1 (UGT2A1), glutathione S-transferase-like 2 (GSTAL2), hematopoietic prostaglandin D synthase (HPGDS), glutathione S-transferase theta 1(GSTT1), isocitrate dehydrogenase (NADP(+)) 1 (IDH1), acyl-CoA oxidase 2 (ACOX2), fatty acid binding protein 1 (FABP1), adenylosuccinate lyase (ADSL), and phosphoribosyl aminoim idazolesuccino carboxamide synthase (PAICS) genes which were randomly selected from the most significant genes were consistent with those of RNA-seq. The results showed that FFC can affect the drug metabolism and lipid synthesis in the liver of broiler, thus impairing the normal function of liver and the growth and development of broiler.

Review on the recent progress in the development of fluorescent probes targeting enzymes

Enzymes are very important for biological processes in a living being, performing similar or multiple tasks in and out of cells, tissues and other organisms at a particular location. The abnormal activity of particular enzyme usually caused serious diseases such as Alzheimer's disease, Parkinson's disease, cancers, diabetes, cardiovascular diseases, arthritis etc. Hence, nondestructive and real-time visualization for certain enzyme is very important for understanding the biological issues, as well as the drug administration and drug metabolism. Fluorescent cellular probe-based enzyme detectionin vitroandin vivohas become broad interest for human disease diagnostics and therapeutics. This review highlights the recent findings and designs of highly sensitive and selective fluorescent cellular probes targeting enzymes for quantitative analysis and bioimaging.

Recent Progress in Fluorescent Sensors for Drug-Induced Liver Injury Assessment

Drug-induced liver injury (DILI) is a persistent concern in drug discovery and clinical medicine. The current clinical methods to assay DILI by analyzing the enzymes in serum are still not optimal. Recent studies showed that fluorescent sensors would be efficient tools for detecting the concentration and distribution of DILI indicators with high sensitivity and specificity, in real-time, in situ, and with low damage to biosamples, as well as diagnosing DILI. This review focuses on the assessment of DILI, introduces the current mechanisms of DILI, and summarizes the design strategies of fluorescent sensors for DILI indicators, including ions, small molecules, and related enzymes. Some challenges for developing DILI diagnostic fluorescent sensors are put forward. We believe that these design strategies and challenges to evaluate DILI will inspire chemists and give them opportunities to further develop other fluorescent sensors for accurate diagnoses and therapies for other diseases.

Fluorescent probes based on nucleophilic aromatic substitution reactions for reactive sulfur and selenium species: Recent progress, applications, and design strategies

Reactive sulfur species (RSS) and reactive selenium species (RSeS) are important substances for the maintenance of physiological balance. Imbalance of RSS and RSeS is closely related to a series of human diseases, so it is considered to be an important biomarker in early diagnosis, treatment, and stage monitoring. Fast and accurate quantitative analysis of different RSS and RSeS in complex biological systems may promote the development of personalized diagnosis and treatment in the future. One way to explore the physiological function of various types of RSS and RSeS in vivo is to detect them at the molecular level, and one of the most effective methods for this is to use fluorescent probes. Nucleophilic aromatic substitution (SNAr) reactions are commonly exploited as a detection mechanism for RSS and RSeS in fluorescent probes. In this review, we cover recent progress in fluorescent probes for RSS and RSeS based on SNAr reactions, and discuss their response mechanisms, properties, and applications. Benzenesulfonate, phenyl-O ether, phenyl-S ether, phenyl-Se ether, 7-nitro-2,1,3-benzoxadiazole (NBD), benzoate, and selenium-nitrogen bonds are all good detection groups. Moreover, based on an integration of different reports, we propose the design and synthesis of RSS- and RSeS-selective probes based on SNAr reactions, current challenges, and future research directions, considering the selection of active sites, the effect of substituents on the benzene ring, and the introduction of other functional groups.

Glutathione-S-transferase Fusion Protein Nanosensor

Fusion protein tags are widely used to capture and track proteins in research and industrial bioreactor processes. Quantifying fusion-tagged proteins normally requires several purification steps coupled with classical protein assays. Here, we developed a broadly applicable nanosensor platform that quantifies glutathione-S-transferase (GST) fusion proteins in real-time. We synthesized a glutathione-DNA-carbon nanotube system to investigate glutathione-GST interactions via semiconducting single-walled carbon nanotube (SWCNT) photoluminescence. We found that SWCNT fluorescence wavelength and intensity modulation occurred specifically in response to GST and GST-fusions. The sensor response was dependent on SWCNT structure, wherein mod(n - m, 3) = 1 nanotube wavelength and intensity responses correlated with nanotube diameter distinctly from mod(n - m, 3) = 2 SWCNT responses. We also found broad functionality of this sensor to diverse GST-tagged proteins. This work comprises the first label-free optical sensor for GST and has implications for the assessment of protein expression in situ, including in imaging and industrial bioreactor settings.

A fluorophore's electron-deficiency does matter in designing high-performance near-infrared fluorescent probes

The applications of most fluorescent probes available for Glutathione S-Transferases (GSTs), including NI3 which we developed recently based on 1,8-naphthalimide (NI), are limited by their short emission wavelengths due to insufficient penetration. To realize imaging at a deeper depth, near-infrared (NIR) fluorescent probes are required. Here we report for the first time the designing of NIR fluorescent probes for GSTs by employing the NIR fluorophore HCy which possesses a higher brightness, hydrophilicity and electron-deficiency relative to NI. Intriguingly, with the same receptor unit, the HCy-based probe is always more reactive towards glutathione than the NI-based one, regardless of the specific chemical structure of the receptor unit. This was proved to result from the higher electron-deficiency of HCy instead of its higher hydrophilicity based on a comprehensive analysis. Further, with caging of the autofluorescence being crucial and more difficult to achieve via photoinduced electron transfer (PET) for a NIR probe, the quenching mechanism of HCy-based probes was proved to be PET for the first time with femtosecond transient absorption and theoretical calculations. Thus, HCy2 and HCy9, which employ receptor units less reactive than the one adopted in NI3, turned out to be the most appropriate NIR probes with high-sensitivity and little nonenzymatic background noise. They were then successfully applied to detecting GST in cells, tissues and tumor xenografts in vivo. Additionally, unlike HCy2 with a broad isoenzyme selectivity, HCy9 is specific for GSTA1-1, which is attributed to its lower reactivity and the higher effectiveness of GSTA1-1 in stabilizing the active intermediate via H-bonds based on docking simulations.

An abnormal and intriguing phenomenon that the fluorophore's electron-deficiency could affect a probe's performance is now revealed for the first time.

A Highly Selective Fluorescent Probe for Hg2+ Based on a 1,8-Naphthalimide Derivative

Hg2+ has a significant hazardous impact on the environment and ecosystem. There is a great demand for new methods with high selectivity and sensitivity to determine mercury in life systems and environments. In this paper, a novel turn-on Hg2+ fluorescent probe has been reported with a naphthalimide group. The Hg2+ fluorescent probe was designed by the inspiration of the well-known specific Hg2+-triggered thioacetal deprotection reaction. A 1,2-dithioalkyl group was chosen as the specific recognition site of Hg2+. The probe showed weak fluorescence without Hg2+, and the color of the solution was light yellow. In the presence of Hg2+, the probe reacted specifically with the mercury ion to produce an aldehyde and emitted strong fluorescence, and the color of the solution also turned light green, thus realizing the monitoring of the mercury ion. The Hg2+ fluorescent probe showed outstanding sensitivity and selectivity toward Hg2+. Furthermore, the Hg2+ fluorescent probe could work in a wide pH range. The linear relationship between the fluorescence intensity at 510 nm and the concentration of Hg2+ was obtained in a range of Hg2+ concentration from 2.5 × 10-7 to 1.0 × 10-5 M. The detection limit was found to be 4.0 × 10-8 M for Hg2+. Furthermore, with little cell toxicity, the probe was successfully applied to the confocal image of Hg2+ in PC-12 cells.

Turn-on detection of glutathione S-transferase based on luminescence resonance energy transfer between near-infrared to near-infrared core-shell upconversion nanoparticles and organic dye

Glutathione S-transferase (GST) is a detoxification enzyme of the liver and kidney. Based on the toxicological effect of GST, it is of great significance to develop a rapid and sensitive detection method for GST. In this work, a new luminescence resonance energy transfer (LRET) system has been designed to detect glutathione S-transferase in the near-infrared (NIR) region by utilizing NaGdF₄:Yb³⁺,Tm³⁺@NaYF₄ upconversion nanoparticles (UCNPs) as the donor and NIR dye-806@Glutathione (IR806@GSH) as the acceptor. NaGdF₄:Yb³⁺,Tm³⁺@NaYF₄ UCNPs were synthesized by a coprecipitation method and surface modification of NOBF₄. The donor (positively charged) interacted with the acceptor (negatively charged) via electrostatic interactions to bring them into close proximity; then, LRET occurred and the luminescence was quenched. In the presence of GST, GST can specifically interact with the GSH of IR806@GSH molecule, making IR806@GSH far away from the donor surface, inhibiting the LRET, and restoring the luminescence of the UCNPs. There was a good linear relationship between the luminescence recovery intensity of UCNPs and GST concentration, ranging from 0.11 to 14.19 nM, and the detection of limit was 0.06 nM. The method has been used in the detection of GST in human serum samples and is expected to have potential applications in the biological field. Graphical abstract A luminescence resonance energy transfer system was developed for determination of glutathione S-transferase in the near-infrared region by utilizing NaGdF₄:Yb³⁺,Tm³⁺@NaYF₄ upconversion nanoparticles as the donor and NIR dye-806@Glutathione as the acceptor.

Evaluating Hyperthyroidism-Induced Liver Injury Based on In Situ Fluorescence Imaging of Glutathione and Phosphate via Nano-MOFs Sensor

Hyperthyroidism-induced liver injury is quite common in clinical settings. Therefore, developing rapid and simple methods for the assessment of hyperthyroid liver injury is of great significance. Considering phosphorus metabolism is disordered because of hyperthyroidism, and the hyperthyroid liver injury is closely related to the abnormal level of glutathione (GSH). Thus, development of a new method that can simultaneously detect changes in blood phosphorus and GSH levels of serum, liver, kidney, and other organs to assess the degree of hyperthyroid liver injury is necessary for clinical medical research. Herein, a novel fluorescent metal-organic frameworks (MOFs) nanoprobe using the UiO-66(OH)₂ as core and Cu-MOFs as shell was designed and synthesized. Through the specific action between Zr (IV) and phosphate, and the combine interaction of MOFs active center Cu (II) and GSH, high sensitivity and specific fluorescence detection of phosphate and GSH were achieved, respectively. Finally, the nanosensor was applied for evaluating different degrees of hyperthyroid liver injury in mice models and realized the monitoring of serum, liver, kidney, and other organs' blood phosphorus and GSH levels, and found that the levels of phosphate and GSH in serum were negatively correlated with the degree of hyperthyroid liver injury, while the changes of phosphate and GSH levels in the liver and kidney organs were positively correlated with the degree of hyperthyroid liver injury. In general, the present works provide a new way to effectively evaluate liver injury induced by hyperthyroidism in the early clinical stage.

Optimized Fluorescent Probe for Specific Imaging of Glutathione S-Transferases in Living Cells and Mice

GSTP1 has been considered to be a marker for malignancy in many tissues. However, the existing GST fluorescent probes are unfavorable for in vivo imaging because of the limited emission wavelength or insufficient fluorescence enhancement (six-fold). The limited fluorescence enhancement of GST fluorescent probes is mainly ascribed to the high background signals resulting from the spontaneous reaction between GSH and the probes. In this work, a highly specific GST probe with NIR emission has been successfully developed through optimization of the essential unit of the probe to repress the spontaneous reaction. The novel GST probe exhibits over 100-fold fluorescence enhancement upon incubation with GSTP1/GSH and high selectivity over other potential interference. In addition, the probe has been proved to be capable of tracking endogenous GST in A549 cells. Finally, the in vivo imaging results demonstrate that the probe can be used for effective imaging of endogenous GST activity in subcutaneous tumor mouse with high contrast.

Semi-Quantitatively Designing Two-Photon High-Performance Fluorescent Probes for Glutathione S-Transferases

Glutathione S-transferases (GSTs), detoxification enzymes that catalyze the addition of glutathione (GSH) to diverse electrophilic molecules, are often overexpressed in various tumor cells. While fluorescent probes for GSTs have often adopted the 2,4-dinitrobenzenesulfonyl (DNs) group as the receptor unit, they usually suffer from considerable background reaction noise with GSH due to excessive electron deficiency. However, weakening this reactivity is generally accompanied by loss of sensitivity for GSTs, and therefore, finely turning down the reactivity while maintaining certain sensitivity is critical for developing a practical probe. Here, we report a rational semiquantitative strategy for designing such a practical two-photon probe by introducing a parameter adopted from the conceptual density functional theory (CDFT), the local electrophilicity ω _k , to characterize this reactivity. As expected, kinetic studies established ω _k as efficient to predict the reactivity with GSH, and probe NI3 showing the best performance was successfully applied to detecting GST activities in live cells and tissue sections with high sensitivity and signal-to-noise ratio. Photoinduced electron transfer of naphthalimide-based probes, captured by femtosecond transient absorption for the first time and unraveled by theoretical calculations, also contributes to the negligible background noise.

Chemical probes for drug-induced liver injury imaging

Drug-induced liver injury (DILI) has been a long-standing concern of modern medicine, and the single most frequent reason for drug nonapprovals and postapproval restrictions or withdrawals. Chemical probes for early diagnosis of DILI has triggered a tremendous interest in the field of molecular imaging. In this review, we make a brief summary of the recently developed chemical probes and their applications in DILI imaging with special attention to the design of chemical probes, mechanism of their actions and their performances in DILI imaging.

Molecular Biomarkers in Drug-Induced Liver Injury: Challenges and Future Perspectives

Drug-induced liver injury (DILI) is one among the common adverse drug reactions and the leading causes of drug development attritions, black box warnings, and post-marketing withdrawals. Despite having relatively low clinical incidence, its potentially severe adverse events should be considered in the individual patients due to the high risk of acute liver failure. Although traditional liver parameters have been applied to the diagnosis of DILI, the lack of specific and sensitive biomarkers poses a major limitation, and thus accurate prediction of the subsequent clinical course remains a significant challenge. These drawbacks prompt the investigation and discovery of more effective biomarkers, which could lead to early detection of DILI, and improve its diagnosis and prognosis. Novel promising biomarkers include glutamate dehydrogenase, keratin 18, sorbitol dehydrogenase, glutathione S-transferase, bile acids, cytochrome P450, osteopontin, high mobility group box-1 protein, fatty acid binding protein 1, cadherin 5, miR-122, genetic testing, and omics technologies, among others. Furthermore, several clinical scoring systems have gradually emerged for the diagnosis of DILI including the Roussel Uclaf Causality Assessment Method (RUCAM), Clinical Diagnostic Scale (CDS), and Digestive Disease Week Japan (DDW-J) systems. However, currently their predictive value is limited with certain inherent deficiencies. Thus, perhaps the greatest benefit would be achieved by simultaneously combining the scoring systems and those biomarkers. Herein, we summarized the recent research progress on molecular biomarkers for DILI to improved approaches for its diagnosis and clinical management.

Precise Synthesis of GSH-Specific Fluorescent Probe for Hepatotoxicity Assessment Guided by Theoretical Calculation

Drug-induced hepatotoxicity is the main cause of acute liver injury, and its early diagnosis is indispensable in pharmacological and pathological studies. As a hepatotoxicity indicator, the GSH distribution in the liver could reflect the damage degree in situ. In this work, we have provided a theoretical design strategy to determine the generation of photo-induced electron transfer mechanism and achieve high selectivity for the target. After that, we precisely synthesized a novel near-infrared fluorescent probe BSR1 to specifically monitor endogenous GSH and hepatotoxicity in biosystem with a moderate fluorescent quantum yield (Φ = 0.394) and low detection limit (83 nM) under this strategy. Moreover, this mapping method for imaging GSH depletion in vivo to assay hepatotoxicity may provide a powerful molecular tool for early diagnosis of some diseases and contribute to assay hepatotoxicity for the development of new drugs. Importantly, this theoretical calculation-guided design strategy may provide an effective way for the precise synthesis of the target-specific fluorescent probe and change this research area from "trial-and-error" to concrete molecular engineering.

A highly selective fluorogenic substrate for imaging glutathione S-transferase P1: development and cellular applicability in epigenetic studies

Pi-class glutathione S-transferase (GSTP1) is a molecular marker enzyme whose expression level is altered in various malignant tumour tissues. Herein, we report the first highly selective fluorogenic GSTP1 substrate, Ps-TG, and its membrane-permeable derivative Ps-TAc, for specific visualization of intracellular GSTP1 activity in cancer cells or epigenetically regulated GSTP1 expression.

4-Bromo-1,8-naphthalimide derivatives as fluorogenic substrates for live cell imaging of glutathione S-transferase (GST) activity

Fluorogenic substrates are used to visualize the activity of cancer-associated enzymes and to interpret biological events. Certain types of glutathione S-transferase (GST), such as Pi class GST (referred to as GSTP1), are more highly expressed in a wide variety of human cancer tissues compared to their corresponding normal tissues. Pi class GST is thus a cancer cell molecular marker and potential target for overcoming resistance to chemotherapy. Here, we report that 4-bromo-1,8-naphthalimide (BrNaph) is a practical fluorogenic GST substrate. We have found that HE-BrNaph, an N-hydroxyethyl derivative, shows remarkable fluorescence enhancement upon GST-catalyzed S_NAr replacement of the bromo group with a glutathionyl group. This substitution was highly selective and occurred only in the presence of GSH/GSTs; no non-enzymatic reaction was observed. We demonstrated that HE-BrNaph allows visualization of GST activity in living cells and enables to distinguish cancer cells from normal cells. Further, various N-substitutions in BrNaph retain susceptibility to enzymatic activity and isozyme selectivity, suggesting the applicability of BrNaph derivatives. Thus, BrNaph and its derivatives are GST substrates useful for fluorescence imaging and the intracellular detection of GSTP1 activity in living cells.