A turn on fluorescent assay for real time determination of β-galactosidase and its application in living cell imaging

A near-IR ratiometric fluorescent probe for the precise tracking of senescence: a multidimensional sensing assay of biomarkers in cell senescence pathways

Senescence is a complex physiological process that can be induced by a range of factors, and cellular damage caused by reactive oxygen species (ROS) is one of the major triggers. In order to learn and solve age-related diseases, tracking strategies through biomarkers, including senescence-associated β-galactosidase (SA-β-gal), with high sensitivity and accuracy, have been considered as a promising solution. However, endogenous β-gal accumulation is not only associated with senescence but also with other physiological processes. Therefore, additional assays are needed to define cellular senescence further. In this work, a fancy fluorescent probe SA-HCy-1 for accurately monitoring senescence is developed, with SA-β-gal and HClO as targets under high lysosomal pH conditions (pH > 6.0) specifically, on account of the role β-gal commonly played as an ovarian cancer biomarker. Therefore, precise tracking of cellular senescence could be achieved in view of these three dimensions, with response in dual fluorescence channels providing a ratiometric sensing pattern. This elaborate strategy has been verified to be suitable for biological applications by skin photo-aging evaluation and cellular passage tracing, displaying a significantly improved sensitivity compared with the commercial X-gal kit measurement.

Design strategies and biological applications of β-galactosidase fluorescent sensor in ovarian cancer research and beyond

Beta-galactosidase (β-galactosidase), a lysosomal hydrolytic enzyme, plays a critical role in the catalytic hydrolysis of glycosidic bonds, leading to the conversion of lactose into galactose. This hydrolytic enzyme is used as a biomarker in various applications, including enzyme-linked immunosorbent assays (ELISAs), gene expression studies, tuberculosis classification, and in situ hybridization. β-Galactosidase abnormalities are linked to various diseases, such as ganglioside deposition, primary ovarian cancer, and cell senescence. Thus, effective detection of β-galactosidase activity may aid disease diagnoses and treatment. Activatable optical probes with high sensitivity, specificity, and spatiotemporal resolution imaging capabilities have become powerful tools for visualization and real time tracking in vivo in the past decade. This manuscript reviews the sensing mechanism, molecular design strategies, and advances of fluorescence probes in the biological application of β-galactosidase, particularly in the field of ovarian cancer research. Current challenges in tracking β-galactosidase and future directions are also discussed.

Glycosidase-targeting small molecules for biological and therapeutic applications

Glycosidases are ubiquitous enzymes that catalyze the hydrolysis of glycosidic linkages in oligosaccharides and glycoconjugates. These enzymes play a vital role in a wide variety of biological events, such as digestion of nutritional carbohydrates, lysosomal catabolism of glycoconjugates, and posttranslational modifications of glycoproteins. Abnormal glycosidase activities are associated with a variety of diseases, particularly cancer and lysosomal storage disorders. Owing to the physiological and pathological significance of glycosidases, the development of small molecules that target these enzymes is an active area in glycoscience and medicinal chemistry. Research efforts carried out thus far have led to the discovery of numerous glycosidase-targeting small molecules that have been utilized to elucidate biological processes as well as to develop effective chemotherapeutic agents. In this review, we describe the results of research studies reported since 2018, giving particular emphasis to the use of fluorescent probes for detection and imaging of glycosidases, activity-based probes for covalent labelling of these enzymes, glycosidase inhibitors, and glycosidase-activatable prodrugs.

Molecularly Targeted Fluorescent Sensors for Visualizing and Tracking Cellular Senescence

Specific identification and monitoring of senescent cells are essential for the in-depth understanding and regulation of senescence-related life processes and diseases. Fluorescent sensors providing real-time and in situ information with spatiotemporal resolution are unparalleled tools and have contributed greatly to this field. This review focuses on the recent progress in fluorescent sensors for molecularly targeted imaging and real-time tracking of cellular senescence. The molecular design, sensing mechanisms, and biological activities of the sensors are discussed. The sensors are categorized by the types of markers and targeting ligands. Accordingly, their molecular recognition and fluorescent performance towards senescence biomarkers are summarized. Finally, the perspective and challenges in this field are discussed, which are expected to assist future design of next-generation sensors for monitoring cellular senescence.