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

Abstract

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.

High-fidelity imaging of a tumour-associated lysosomal enzyme with an acceptor engineering-boosted near-infrared fluorescent probe

“…Fluorescence imaging has revolutionized fundamental studies in life sciences by enabling the visualization, characterization, and measurement of biological processes at the molecular and cellular levels in living systems. 14–18 In particular, activatable fluorescent probes in the near-infrared (NIR) window have shown a higher signal-to-noise ratio for in vivo imaging. 19–23 Unfortunately, when it comes to the subcellular dimension, existing NIR activable probes are prone to dispersing throughout the cell, which largely compromises the fidelity of imaging for biomarkers within specific organelles.…”