An effective fluorescent optical sensor: Thiazolo-thiazole based dye exhibiting anion/cation sensitivities and acidochromism

Fluorescence-based ratiometric sensors as emerging tools for CN- detection: Chemical structures, sensing mechanisms and applications

Hazardous cyanide anions (CN-) are increasingly threatening the environment and human health due to their widespread use in industry and many other fields. Over the past three decades, a large number of probes have been reported to sensitively and selectively detect this toxic anion, while a rather limited number of ratiometric fluorescent probes have been developed. The ratiometric probes have significant potential in bio-imaging and biomedical applications because of the ability to detect CN- in a quick, convenient and affordable way. In this review, we introduce 42 ratiometric fluorescent probes reported in the past 6 years (2018-2023) for CN- detection. Our description includes the chemical structures, photo-physical properties, CN- sensing mechanisms, solution color changes, limits of detection (LODs) and/or various applications of these chemical probes. This review provides guidelines for design and development of a new ratiometric probe for effective CN- detection.

Design, Synthesis and Evaluation of Fluorescent Properties of Benzothiazole Derivatives

Fluorescence imaging is conducive to establish a bridge between molecular biology and clinical medicine, and provides new tools for disease process research, early diagnosis, and efficacy evaluation, because of the advantages of rapid imaging and nondestructive detection. Herein, a series of fluorescent molecules with thiadiazole, or thiazole, or benzothiazole cores were designed and synthesized to develop more excellent fluorescent molecules in bio-imaging. According to theoretical and experimental methods, we found that benzothiazole derivative 14 B with conjugate expansion by (4-aminophenyl) ethynyl group was the most excellent fluorescent molecule among all the investigated compounds and exhibited low cytotoxicity and strong blue and green fluorescence by confocal cell imaging.

The syntheses, photophysical properties and pH-sensitive studies of heterocyclic azo dyes bearing coumarin-thiophene-thiazole

This study reports the synthesis of two novel thiazolylazo dyes (4 and 5) bearing coumarin-thiophene moiety. UV-Vis spectroscopy was used to investigate the photophysical properties of 4 and 5 in different solvents. The dyes displayed good potential for hydroxide sensing in different mediums. The reversibility was also studied, and it was found that 4 and 5 could be reverted to their original state by adding acid. Furthermore, the acidochromic properties were studied in protic and aprotic media. Both dyes displayed a good acidochromic response in DCM. Moreover, 4 and 5 were investigated for pH sensing, and it was found that both compounds displayed changes in absorption spectra in a basic media. The theoretical calculations were carried out to investigate the deprotonation and protonation mechanisms using density functional theory (DFT). The thermal properties of the dyes were investigated using thermogravimetric analysis (TGA). The results showed good thermal stability up to around 200 °C.

In-situ formation of fluorophore cross-linked micellar thick films and usage as drug delivery material for Propranolol HCl

Polyethylene glycol monomethyl ether-block-poly(glycidyl methacrylate)-block-poly[2-(diethylamino)ethyl methacrylate] triblock copolymer was synthesized to prepare self-assembled micron sized films via a novel approach named as "phase separated micellar self assembly method". Liquid-air interface self assembly method via slow solvent evaporation was used to obtain micellar films. Cross-linking of polymer films was carried out by diffusion of fluorophore cross-linker into polymer solution from subphase. In-situ micellar formation was triggered via driven forces such as molecular interactions and slow evaporation of solvent. Thiazolo[5,4-d]thiazole based cross-linker fluorophores containing alkali subphases were used to prepare highly fluorescent cross-linked micellar films. Micellar morphologies of the films were characterized with SEM while the cross-sections of fluorophore cross-linked films were observed with TEM analysis to examine diffusion of the dye as nano-sized particles into the polymer film. Convenience and usability of the micellar films as drug delivery material were demonstrated with Propranolol HCl release via UV-Vis spectroscopic studies. Optical properties of the films before and after drug release were determined via photoluminescence spectroscopy to be able to sense the completion of the drug release process. Swelling and shrinkage properties of the films were also determined in different pH values. These highly fluorescent polymer films have great potential as drug delivery materials and biomedical sensing applications.

Partnered Excited-State Intermolecular Proton Transfer Fluorescence (P-ESIPT) Signaling for Nitrate Sensing and High-Resolution Cell-Imaging

Nitrite (NO₂⁻) is a common pollutant and is widely present in the environment and in human bodies. The development of a rapid and accurate method for NO₂⁻ detection is always a very important task. Herein, we synthesized a partnered excited-state intermolecular proton transfer (ESIPT) fluorophore using the “multi-component one pot” method, and used this as a probe (ESIPT-F) for sensing NO₂⁻. ESIPT-F exhibited bimodal emission in different solvents because of the solvent-mediated ESIPT reaction. The addition of NO₂⁻ caused an obvious change in colors and tautomeric fluorescence due to the graft of NO₂⁻ into the ESIPT-F molecules. From this basis, highly sensitive and selective analysis of NO₂⁻ was developed using tautomeric emission signaling, achieving sensitive detection of NO₂⁻ in the concentration range of 0~45 mM with a detection limit of 12.5 nM. More importantly, ESIPT-F showed the ability to anchor proteins and resulted in a recognition-driven “on-off” ESIPT process, enabling it to become a powerful tool for fluorescence imaging of proteins or protein-based subcellular organelles. MTT experimental results revealed that ESIPT-F is low cytotoxic and has good membrane permeability to cells. Thus, ESIPT-F was further employed to image the tunneling nanotube in vitro HEC-1A cells, displaying high-resolution performance.

Analyte Interactions with Oxoporphyrinogen Derivatives: Computational Aspects

Abstract:

The binding of anions by highly-coloured chromophore compounds is of interest from the point-of-view of the development of optical sensors for analyte species. In this review, we have summarised our work on the interactions between oxoporphyrinogen type host compounds and different analyte species using computational methods. The origin of our interest in sensing using oxoporphyrinogens stems from an initial finding involving anion-host interactions involving a conjugated oxoporphyrinogen molecule. This review starts from that point, introducing some additional exemplary anion binding data, which is then elaborated to include descriptions of our synthesis work towards multitopic and ion pair interactions. In all the projects, we have consulted computational data on host structure and host-guest complexes in order to obtain information about the interactions occurring during complexation. Density functional theory and molecular dynamics simulations have been extensively used for these purposes. Oxoporphyrinogens are highly colored synthetically flexible compounds whose interactions with anions, ion pairs, and other species have been modelled using computational methods.