A water-soluble fluorescent probe for real-time visualization of γ-glutamyl transpeptidase activity in living cells

A dual-site fluorescent probe for the detection of γ-glutamyl transpeptidase activity and its application in garlic

Developing convenient γ-glutamyl transpeptidase (GGT) activity detection methods is of great significance for soaking Laba garlic and human diseases detection. A dual-site fluorescent probe (probe 1) was developed for detection the activity of GGT. Probe 1 could recognize GGT by the enzymatic hydrolysis of peptide bond by GGT. There has a linear relationship between the fluorescence intensity of probe 1 at 416 nm and the activity of GGT. And the color of the probe solution gradually changed from colorless to blue with the increase of GGT activity under 365 nm ultraviolet light. Importantly, it has a linear relationship between the activity of GGT and the blue (B) value of probe solution photo. Therefore, probes can serve as a convenient tool for detecting GGT activity. More importantly, the probe has been successfully applied to detect of GGT activity in garlic.

Multifunctional fluorescence/photoacoustic bimodal imaging of γ-glutamyltranspeptidase in liver disorders under different triggering conditions

Hepatocellular carcinoma (HCC) seriously threatens the human health. Previous investigations revealed that γ-glutamyltranspeptidase (GGT) was tightly associated with the chronic injury, hepatic fibrosis, and the development of HCC, therefore might act as a potential indicator for monitoring the HCC-related processes. Herein, with the contribution of a structurally optimized probe ETYZE-GGT, the bimodal imaging in both far red fluorescence (FL) and photoacoustic (PA) modes has been achieved in multiple HCC-related models. To our knowledge, this work covered the most comprehensive models including the fibrosis and developed HCC processes as well as the premonitory induction stages (autoimmune hepatitis, drug-induced liver injury, non-alcoholic fatty liver disease). ETYZE-GGT exhibited steady and practical monitoring performances on reporting the HCC stages via visualizing the GGT dynamics. The two modes exhibited working consistency and complementarity with high spatial resolution, precise apparatus and desirable biocompatibility. In cooperation with the existing techniques including testing serum indexes and conducting pathological staining, ETYZE-GGT basically realized the universal application for the accurate pre-clinical diagnosis of as many HCC stages as possible. By deeply exploring the mechanically correlation between GGT and the HCC process, especially during the premonitory induction stages, we may further raise the efficacy for the early diagnosis and treatment of HCC.

γ-Glutamyltranspeptidase fluorescence lifetime response probe for precision tumor detection unveiling A549 cancer cell specificity

γ-Glutamyltranspeptidase (γ-GGT), as a key enzyme, exhibits markedly higher expression levels in tumor cells compared to normal cells. Under normal conditions, γ-GGT activity on the cell membrane is relatively low, but it undergoes a significant upregulation in cancer cells, making it a potential cancer biomarker. Particularly in A549 cells, a prominent cancer cell line, the pronounced upregulation of γ-GGT expression emphasizes its potential as a unique recognition target and a robust marker for A549 cells. This study successfully synthesized a highly selective γ-GGT fluorescent probe, the exhibits commendable sensitivity (LOD = 0.0021U/mL) and selectivity, achieving efficient detection at the cellular level and providing accurate insights into differential expression between normal and cancer cells. The alterations in fluorescence lifetime observed before and after the probe's reaction with γ-GGT serve as a crucial foundation for fluorescence lifetime imaging on living cells. The probe has become a powerful tool for precise localization of tumor cells, particularly demonstrating its capability for specific recognition in A549 cells. Overall, this research highlights the potential of γ-GGT as a target for fluorescent probes, emphasizing its prospects in specific recognition, particularly in A549 cells, with profound implications for advancing early cancer diagnosis and treatment methods.

A sensitive benzothiazole fluorescent probe for the detection of γ-glutamyl transpeptidase activity and its application

A sensitive benzothiazole fluorescent probe (PBZO) for the detection of γ-glutamyl transpeptidase (GGT) activity was developed. Based on the enzymatic hydrolysis of peptide bonds by glutamyl transpeptidase, it can be specifically recognized by PBZO. The PBZO has a good linear relationship with different gradients of GGT activity at the emission wavelength of 560 nm, the Stokes shift reached 215 nm, and the detection limit of GGT activity is 0.1644 U/ml. With the increase of GGT concentration in the probe solution, the color of the solution gradually changed from orange to dark yellow under the 365 nm UV lamp. The same color change was also observed on the probe test paper. In addition, there is a linear relationship between the GGT activity and the R-value of the probe solution. More importantly, the probe has a good recovery rate in serum. Therefore, this probe can be used as a convenient tool for detecting GGT activity.

Water-Soluble Small Organic Fluorophores for Oncological Theragnostic Applications: Progress and Development

Cancer is one of the major noncommunicable diseases, responsible for millions of deaths every year worldwide. Though various cancer detection and treatment modalities are available today, many deaths occur owing to its late-stage detection and metastatic nature. Noninvasive detection using luminescence-based imaging tools is considered one of the promising techniques owing to its low cost, high sensitivity, and brightness. Moreover, these tools are unique and valuable as they can detect even the slightest changes in the cellular microenvironment. To achieve this, a fluorescent probe with strong tumor uptake and high spatial and temporal resolution, especially with high water solubility, is highly demanded. Recently, several water-soluble molecules with emission windows in the visible (400-700 nm), first near-infrared (NIR-I, 700-1000 nm), and second near-infrared (NIR-II, 1000-1700 nm) windows have been reported in literature. This review highlights recently reported water-soluble small organic fluorophores/dyes with applications in cancer diagnosis and therapeutics. We systematically highlight and describe the key concepts, structural classes of fluorophores, strategies for imparting water solubility, and applications in cancer therapy and diagnosis, i.e., theragnostics. We discuss examples of water-soluble fluorescent probes based on coumarin, xanthene, boron-dipyrromethene (BODIPY), and cyanine cores. Some other emerging classes of dyes based on carbocyclic and heterocyclic cores are also discussed. Besides, emerging molecular engineering methods to obtain such fluorophores are discussed. Finally, the opportunities and challenges in this research area are also delineated.

In Vivo Imaging of γ-Glutamyl Transferase in Cardiovascular Diseases with a Photoacoustic Probe

In this work, a photoacoustic (PA) probe, HDS-GGT, was developed for the in vivo imaging of cardiovascular diseases by monitoring the γ-glutamyl transferase (GGT) dynamics. HDS-GGT exhibited a stable PA signal with auxiliary absorbance and NIRF variation after the trigger by GGT. In all three modalities of absorbance, NIRF, and PA, HDS-GGT could quantitatively reflect the GGT level. In PA modality, HDS-GGT indicated the practical advantages including high sensitivity, high stability, and high specificity. In living oxidized low-density lipoprotein-induced RAW264.7 cells, HDS-GGT indicated proper capability for imaging the plaques by visualizing the GGT dynamics. Moreover, during imaging in living model mice, HDS-GGT was achieved to distinguish the plaques from healthy blood vessels via a multiview PA presentation. HDS-GGT could also suggest the severity of plaques in the extracted aorta from the model mice, which was consistent with the histological staining results. The information herein might be useful for future investigations on cardiovascular diseases.

Advances and Perspectives of Responsive Probes for Measuring γ-Glutamyl Transpeptidase

Gamma-glutamyltransferase (GGT) is a plasma-membrane-bound enzyme that is involved in the γ-glutamyl cycle, like metabolism of glutathione (GSH). This enzyme plays an important role in protecting cells from oxidative stress, thus being tested as a key biomarker for several medical conditions, such as liver injury, carcinogenesis, and tumor progression. For measuring GGT activity, a number of bioanalytical methods have emerged, such as chromatography, colorimetric, electrochemical, and luminescence analyses. Among these approaches, probes that can specifically respond to GGT are contributing significantly to measuring its activity in vitro and in vivo. This review thus aims to highlight the recent advances in the development of responsive probes for GGT measurement and their practical applications. Responsive probes for fluorescence analysis, including "off-on", near-infrared (NIR), two-photon, and ratiometric fluorescence response probes, are initially summarized, followed by discussing the advances in the development of other probes, such as bioluminescence, chemiluminescence, photoacoustic, Raman, magnetic resonance imaging (MRI), and positron emission tomography (PET). The practical applications of the responsive probes in cancer diagnosis and treatment monitoring and GGT inhibitor screening are then highlighted. Based on this information, the advantages, challenges, and prospects of responsive probe technology for GGT measurement are analyzed.

A novel sensitive fluorescent probe with double channels for highly effective recognition of biothiols

Biothiols play a crucial role in maintaining redox balance in organisms, and anomalous levels of biothiols in human organs can lead to various sicknesses and biological disorders. This work developed a novel sensitive fluorescent probe TZ-NBD with double channels for highly efficient recognition of biothiols. TZ-NBD adopts 4-Chloro-7-nitrobenzofurazan (NBD-Cl) as the recognition moiety with simultaneous fluorescence output. By incorporating NBD-Cl with the other fluorophore, benzothiazole dihydrocyclopentachromene derivative (TZ-OH), the dual-channel sensitive fluorescence probe TZ-NBD was built. The existence of Cys/ Hcy could significantly trigger both the green and red fluorescent emissions, which were derived from fluorophores amine-substituted NBD and TZ-OH, respectively. While exposing to GSH, only the red-channel fluorescence signal could be detected, indicating the release of TZ-OH. The phenomena was mainly attributed to the fact that sulfur-substituted NBD has nearly no fluorescence, while amine-substituted NBD shows obvious green fluorescence. In our study, TZ-NBD exhibited dual-channel sensitivity, fast response, and excellent selectivity to biothiols in vitro. Moreover, TZ-NBD was favorably utilized for recognition of biothiols in vivo. We believe that the sensitive fluorescence probe with double channels can afford an alternate approach for monitoring biothiols in organisms and would be useful for studying diseases associated with biothiols.

An activatable near-infrared molecular reporter for fluoro-photoacoustic imaging of liver fibrosis

Noninvasive and accurate detection of liver fibrosis is extremely significant for well-timed intervention and treatment to prevent or reverse its progression. Fluorescence imaging probes hold great potential for imaging of liver fibrosis, but they always encounter the inherent limitation of shallow penetration depth, which compromises their ability of in vivo detection. To overcome this issue, an activatable fluoro-photoacoustic bimodal imaging probe (IP) is herein developed for specific visualization of liver fibrosis. The probe IP is constructed on a near-infrared thioxanthene-hemicyanine dye that is caged with gamma-glutamyl transpeptidase (GGT) responsive substrate and linked with integrin-targeted peptide (cRGD). Such molecular design permits IP to effectively accumulate in the liver fibrosis region through specific recognition of cRGD towards integrin and activate its fluoro-photoacoustic signal after interaction with overexpressed GGT to precisely monitor the liver fibrosis. Thus, our study presents a potential strategy to design dual-target fluoro-photoacoustic imaging probes for noninvasive detection of early-stage liver fibrosis.