Development of a xanthene-based NIR fluorescent probe for accurate and sensitive detection of γ-glutamyl transpeptidase in cancer diagnosis and treatment

γ-Glutamyl transpeptidase (GGT) regulates glutathione (GSH), essential for cell functions and linked to cancer. High GGT levels in tumors make it a valuable cancer biomarker. Current GGT detection methods often lack sensitivity and specificity. To address this, we developed XM-Glu, a new near-infrared (NIR) fluorescent probe. XM-Glu features a xanthene-based structure with a hydroxy xanthene fluorophore and a malononitrile group for NIR emission and reduced background noise. It has a self-immolating linker masked with glutamate acid, which activates fluorescence when GGT is present. XM-Glu can detect GGT in the range of 1.0 to 20 mU with a low detection limit of 0.067 mU mL-1. It showed high specificity and minimal interference in cellular assays. In mice, XM-Glu effectively detected GGT in tumor, liver, and kidney tissues. Its NIR properties provide real-time insights into GGT activity, improving cancer diagnosis and monitoring. This new technology enhances cancer research and helps better understand GGT's role in cancer progression.

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.

Aggregation-Induced Emission of Curcuminoid-BF2 Complex for Phosphor-Converted Red Light-Emitting Diode

The incorporation of difluoroboron β-diketonate and tetraphenylethene under a facile Knoevenagel condensation reaction afforded one new D-π-A-π-D complex TCBF with high aggregation-induced emission (AIE) activity. The TCBF film can maintain a high photocurrent after long-term (500 min) photoelectronic measurements. The successful fabrication of a red LED device makes it a promising candidate for high-performance solid-state lighting.

γ-Glutamyltranspeptidase (GGT) Sensitive Fluorescence Probes for Cancer Diagnosis; Brief Review

Millions of deaths occur each year due to the late diagnosis of abnormal cellular growth within the body. However, the devastating impact of this can be significantly reduced if cancer metastasis is detected early through the use of enzymatic biomarkers. Among several biomarkers, γ-glutamyltranspeptidase (GGT) stands out as a member of the aminopeptidase family. It is primarily found on the surface of cancer cells such as glioma, ovarian, lung, and prostate cancer, without being overexpressed in normal cells or tissues. Recent years have witnessed significant progress in the field of cancer monitoring and imaging. Fluorescence sensing techniques have been employed, utilizing organic small molecular probes with enzyme-specific recognition sites. These probes emit a fluorescent signal upon interacting with GGT, enabling the imaging, identification, and differentiation of normal and cancerous cells, tissues, and organs. This review article presents a concise overview of recent progress in fluorescent probes developed for the selective detection of GGT, focusing on their applications in cancer imaging. It highlights the observed alterations in the fluorescence and absorption spectra of the probes before and after interaction with GGT. Additionally, the study investigates the changes in the probe molecule's structure following enzyme treatment, evaluates the sensor's detection limit, and consolidated imaging studies conducted using confocal fluorescence analysis. This comprehensive survey is expected to contribute to the advancement of sensing techniques for biomarker detection and cancer imaging, providing valuable insights for refining methodologies and inspiring future developments in this field.

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.

Crystal structure, photophysical properties, and DFT calculations of a boron difluoride curcumin complex

The crystal structure of a curcumin-BF2 complex has been successfully refined from single-crystal X-ray diffraction data of crystals with one molecule of co-crystallized dichloromethane. The complex has a nearly coplanar structure. The molecules form a mesh structure by intermolecular multiple hydrogen bonds, as well as weak hydrogen bonds with CH2Cl2 molecules. An investigation of the photo-physical properties has indicated that the curcumin-BF2 complex possesses a wide absorption band and an intense red emission in the solid state due to a strong electron-withdrawing effect of the BF2 groups. DFT calculations of a single molecule verify the relationships between the photo-physical properties and its intrinsic electronic features, but neglect the role of hydrogen bonding.

A ratiometric fluorescent probe for detection of γ-glutamyl transpeptidase in blood serum and living cells

γ-Glutamyl transpeptidase (GGT) is one of the biomarker of cancer, hepatitis, and numerous other diseases. The accurate analysis of GGT is useful for the early diagnosis of these diseases. In this work, Probe 1, a ratiometric fluorescent probe based on 2,3,5,6-tetrafluoroterephthalonitrile, was designed for GGT detection. The results indicated that Probe 1 can sensitively and selectively detect GGT in phosphate buffered solution and complex biological systems (e.g., blood serum). Furthermore, Probe 1 has been successfully applied for ratiometric imaging of GGT in cancer cells and normal cells.

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

γ-glutamyl transpeptidase (GGT) is a kind of cell-surface enzyme that is overexpressed in many cancer cells. It is of great significance to develop an ideal tool for the diagnosis of GGT-rich cancer cells. Here, we reported a simple-structured but effective imaging probe for the detection of GGT activity. In the presence of GGT, the γ-glutamyl linkage could be cleaved specifically to produce amino-substituted product, resulting in significant fluorescence enhancement at 578 nm. Moreover, we successfully employed the probe to monitor GGT activity in HepG2 cells. We envisaged that such a simple but effective imaging tool could improve the practical applications for bioimaging.

Recent advances in the synthesis of luminescent tetra-coordinated boron compounds

Tetra-coordinated boron compounds offer a plethora of luminescent materials. Different chelation around the boron center (O,O-, N,C-, N,O-, and N,N-) has been explored to tune the electronic and photophysical properties of tetra-coordinated boron compounds. A number of fascinating molecules with interesting properties such as aggregation induced emission, mechanochromism and tunable emission by changing the solvent polarity were realised. Owing to their rich and unique properties, some of the molecules have shown applications in making optoelectronic devices, probes and so on. This perspective provides an overview of the recent developments of tetra-coordinated boron compounds and their potential applications.

Recent advances in dioxaborine-based fluorescent materials for bioimaging applications

Fluorescent materials are continuously contributing to important advances in the field of bioimaging. Among these materials, dioxaborine-based fluorescent materials (DBFM) are arousing growing interest. Due to their rigid structures conferred by a cyclic boron complex, DBFM possess appealing photophysical properties including high extinction coefficients and quantum yields as well as emission in the near infrared, enhanced photostability and high two-photon absorption. We herein discuss the recent advances of DBFM that found use in bioimaging applications. This review covers the development of fluorescent molecular probes for biomolecules (DNA, proteins), small molecules (cysteine, H₂O₂, oxygen), ions and the environment (polarity, viscosity) as well as polymers and nanomaterials used in bioimaging. This review aims at providing a comprehensive and critical insight on DBFM by highlighting the assets of these promising materials in bioimaging but also by pointing out their limitations that would require further developments.

A two-photon fluorescent probe for sensitive detection and imaging of γ-glutamyl transpeptidase

A GGT-activated two-photon fluorescent probe (4F-2CN-GSH) was developed based on a cascade reaction. 4F-2CN-GSH could selectivily detect GGT with low detection limit and distinguish ovarian cancer cells from normal cells using both one-photon and two-photon fluorescence imaging.

Quicker, deeper and stronger imaging: A review of tumor-targeted, near-infrared fluorescent dyes for fluorescence guided surgery in the preclinical and clinical stages

Cancer is a public health problem and the main cause of human mortality and morbidity worldwide. Complete removal of tumors and metastatic lymph nodes in surgery is significantly beneficial for the prognosis of patients. Tumor-targeted, near-infrared fluorescent (NIRF) imaging is an emerging field of real-time intraoperative cancer imaging based on tumor-targeted NIRF dyes. Targeted NIRF dyes contain NIRF fluorophores and specific binding ligands such as antibodies, peptides and small molecules. The present article reviews recently updated tumor-targeted NIRF dyes for the molecular imaging of malignant tumors in the preclinical stage and clinical trials. The strengths and challenges of NIRF agents with tumor-targeting ability are also summarized. Smaller ligands, near infrared II dyes, dual-modality dyes and activatable dyes may contribute to quicker, deeper, stronger imaging in the nearest future. In this review, we highlighted tumor-targeted NIRF dyes for fluorescence-guided surgery and their potential clinical translation.

Ratiometric Imaging of γ-Glutamyl Transpeptidase Unperturbed by pH, Polarity, and Viscosity Changes: A Benzocoumarin-Based Two-Photon Fluorescent Probe

γ-Glutamyltransferase (GGT) is involved in maintaining the intracellular glutathione levels and, at its elevated levels, is associated with various diseases including cancer and myocardial infarction. To study this enzyme in biological systems, fluorescent probes have received significant attention recently. As fluorescence signal is sensitive to environmental fluctuations; however, it is challenging to address the signal fluctuation issue. Disclosed is the benzocoumarin-based probe that enables ratiometric imaging of GGT activity levels in cells as well as in tissues, essentially unperturbed by medium pH, viscosity, and polarity changes. Validity of the probe is demonstrated by determining the GGT activity level in HeLa cells directly through ratiometric imaging. Furthermore, the probe and its enzymatic product are two-photon absorbing, extending its applicability to tissue: an 8.5-fold higher level of GGT in cancerous tissue over the normal tissue is determined, and the GGT activity levels between different mouse organ tissues are quantitatively compared with the highest level in the kidney. The probe with practicality holds great promise for studying GGT-associated biological processes directly through ratiometric imaging by two-photon microscopy.

Self-Immolative Fluorescent and Raman Probe for Real-Time Imaging and Quantification of γ-Glutamyl Transpeptidase in Living Cells

Characterizing over-expressed enzymes or biomarkers in living cells is critical for the molecular understanding of disease pathology and consequently for designing precision medicines. Herein, a "switch-on" probe is designed to selectively detect γ-glutamyl transpeptidase (GGT) in living cells via a unique ensemble of enhanced fluorescence and surface-enhanced Raman scattering (SERS). In the presence of GGT, the γ-glutamyl bond in the probe molecule is cleaved, thereby activating a fluorescent probe molecule as well as a Raman reporter molecule. Consequently, the detection of GGT is achieved based on both plasmonic fluorescent enhancement and SERS with a detection limit as low as 1.2 × 10^-3 U/L (normal range for GGT levels in the blood is 9-48 U/L). The main advantage of this platform is that on the occasion of fluorescence signal interference, especially in the presence of free metal ions in cells, the SERS signals still hold high stability as a backup. This work highlights the benefits of the marriage of two complimentary sensing techniques into one platform that can overcome the major obstacles of detection of real-time biomarkers and imaging in living cells.