Precision Imaging of Biothiols in Live Cells and Treatment Evaluation during the Development of Liver Injury via a Near-Infrared Fluorescent Probe

Design and Synthesis of two novel carbazole-based fluorescent probes and their application in detecting Hg2

Mercury is a highly toxic and non-degradable heavy metal pollutant that poses great harm to human health and the ecological environment. Two novel carbazole based thioacetal fluorescent probes 4a and 4b for highly sensitive and selective detection of Hg2+ have been designed and synthesized. Though both probes 4a and 4b can detect Hg2+ through thioacetal deprotection reaction, due to the difference in structural stability and the AIE effect of probe 4a, probe 4a has higher selectivity and sensitivity, with a detection limit as low as 5.1 × 10-8 M and a response time of approximately 25 s. In addition, probe 4a can detect Hg2+ under the solvent systems with high water content, thus we have successfully applied probe 4a to the detection of Hg2+ in actual water and soil samples, and used it as test strips.

Screening Anti-Parkinson's Disease Drugs in Living Mouse Brains via a Peroxynitrite-Activated Fluorescent Probe

Screening anti-Parkinson's disease (PD) drugs at in vivo brain level is imperative for managing PD yet currently remains unaccomplished. Peroxynitrite (ONOO-) has been implicated in PD progression. Thus, developing in vivo ONOO--based imaging tools for anti-PD drug screening holds promise for early prognosis and treatment of PD. Consequently, a near-infrared (NIR) fluorescence probe, BOB-Cl-PN, with high specificity, good sensitivity (LOD = 24 nM), and rapid response (<60 s), was devised to investigate ONOO- and PD relationships. Utilizing NIR fluorescence imaging, BOB-Cl-PN effectively monitored ONOO- fluctuations in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD cell models, establishing a cellular high throughput screening (cHTS) system for anti-PD drugs. In live animal imaging, BOB-Cl-PN's ability to penetrate the blood-brain barrier enabled ONOO- flux imaging of PD mouse brains. Moreover, BOB-Cl-PN served as an imaging contrast for in vivo screening of potential traditional Chinese medicines for PD therapy, identifying fisetin as having the best therapeutic index among 10 Chinese medicines. This study constructs a sensitive, efficient imaging contrast for monitoring ONOO- dynamics in PD brains and provides a valuable platform for cellular and in vivo screening of anti-PD drugs.

Benzimidazole-Derived B2 as a Fluorescent Probe for Bacterial Outer Membrane Vesicle (OMV) Labeling: Integrating DFT, Molecular Dynamics, Flow Cytometry, and Confocal Microscopy

Bacterial outer membrane vesicles (OMVs) are nanoscale extracellular structures produced by Gram-negative bacteria that are critical for microbial biology and host-pathogen interactions and have great potential in biotechnological applications. Despite the availability of fluorescent dyes for OMV studies, many are repurposed from eukaryotic extracellular vesicle research and are not explicitly optimized for OMVs, leading to challenges in achieving consistent labeling, minimizing background noise, and preserving vesicle integrity during analyses. This study evaluates B2, a benzimidazole-derived fluorophore, for OMV labeling in advanced techniques like flow cytometry and confocal microscopy. OMVs were isolated from Escherichia coli strains BL21 and O157, and their integrity was confirmed using transmission electron microscopy (TEM). B2 staining protocols were optimized for OMVs, and fluorescence analyses revealed specific interactions with the vesicle membranes, reducing aggregation and enhancing signal uniformity. Flow cytometry indicated near-complete labeling efficiency (98-100%) with minimal background interference. Confocal microscopy further validated B2's effectiveness, showing evident OMV internalization into epithelial HT-29 cells and compatibility with other fluorophores. Density functional theory (DFT) calculations, including Fukui function analysis, identified key electrophilic and nucleophilic regions in B2 that facilitate specific hydrogen bonding and polar interactions with membrane components. Non-covalent interaction (NCI) analysis revealed pronounced intramolecular hydrogen bonding along with discrete regions of weak van der Waals interactions. Molecular dynamics simulations suggest that B2 exhibits an affinity for both the hydrophobic core of the lipid bilayer and the core oligosaccharide region of the LPS layer, which collectively ensures sustained retention of the dye. The findings presented in this study position B2 as a valuable fluorophore for OMV research.