Design and Development of an HBT-Based Ratiometric Fluorescent Probe to Monitor Stress-Induced Premature Senescence

Abstract

Stress-induced premature senescence (SIPS) can be induced in tumor cells by reactive oxygen species (ROS) or oncogenes. The antineoplastic drugs cause apoptosis and senescence by damaging the DNA. Although the detection of cellular senescence is important to monitor drug response during anticancer therapy, only a few probes have been studied for imaging SIPS. In this study, we developed 2-(2′-hydroxyphenyl)benzothiazole (HBT)-based fluorescent probes to determine SIPS by monitoring the oxidative stress and β-galactosidase activity. HBT is a commonly used fluorophore because of its luminescence mechanism via excited-state intramolecular proton transfer, and it has attractive properties, such as a four-level photochemical process and large Stokes shift (151 nm). A novel fluorescent probe, (2-(benzo[d]thiazol-2-yl)phenyl)boronic acid, was prepared for the detection of ROS, including H 2 O 2 , via the oxidation reaction of arylboronic acids to form the fluorescent phenol, HBT. In addition, to determine the enzymatic activity of β-galactosidase, a 2-(4′-chloro-2′-hydroxyphenyl)benzothiazole (CBT)-based enzymatic turn-on probe (CBT-β-Gal) was designed and synthesized. β-Galactosidase catalyzed the hydrolysis of β-galactopyranoside from CBT-β-Gal to release the fluorescent CBT. These probes were capable of ratiometric imaging the accumulation of H 2 O 2 and the degree of β-galatosidase activity in contrast to H 2 O 2 -untreated and H 2 O 2 -treated HeLa cells. Furthermore, these probes were successfully employed for imaging the increased levels of ROS and β-galactosidase activity in the doxorubicin-treated HeLa cells.

Chromo-fluorogenic probes for β-galactosidase detection

“…Finally, Mizuta and co-workers prepared probe 70, based on 2-(2'-hydroxyphenyl)benzothiazole fluorophore, for the measurement of β-Gal activity in senescent cells. [85] PBS solutions of probe 70 showed negligible fluorescence when excited at 356 nm (quantum yield of 0.045), whereas a marked emission band at 508 nm (quantum yield of 0.339) was formed in the presence of β-Gal enzyme. This marked emission enhancement was ascribed to the enzymatic hydrolysis of probe 70, which generated a highly emissive 2-(2'-hydroxyphenyl)benzothiazole fluorophore.…”

Small-molecule fluorescence-based probes for aging diagnosis

“…Typically, the ROS levels increase in various types of cancers and cellular senescence [37]. Mizuta et al have developed two fluorescent probes to detect oxidative stress and the activity of β-gal to evaluate stress-induced premature senescence [38]. The authors first synthesized six candidate fluorescent probes 1a-f for ROS detection and screened the optimal probe 1a (Figure 14A,B [39].…”

Molecular Dynamics Simulation of the Excited-State Proton Transfer Mechanism in 3-Hydroxyflavone Using Explicit Hydration Models

“…Excited-state proton transfer (ESPT) − is a fascinating process playing an important role in biological systems − and having interesting applications in materials science as ultraviolet stabilizers, luminescence and storage materials, fluorescent probes, , and chemosensors . Intramolecular ESPT (ESIPT) can usually occur through intramolecular hydrogen bonding between proton donor (e.g., −OH and −NH 2 ) and proton acceptor (e.g., −CO and −CN−) groups within a molecule.…”