A novel turn-on fluorescent probe based on berberine for detecting Hg2+ and ClO− with the different fluorescence signals

A Dual Functional Fluorescent Probe Based on Phenothiazine for Detecting Hg2+ and ClO- and its Applications

For the efficient detection of Hg2+ and ClO-, a double-analyte-responsive fluorescent probe PTB was successfully synthesized by combining N-butyl-3-formyl phenothiazine with hydrazine benzothiazole, and designing a specific reaction site for recognizing two analytes (Hg2+ and ClO-) in a compound. It was shown that probe PTB successfully formed a stable complex with Hg2+ in the coordination ratio of 2:1 by using the strong sulfur affinity of Hg2+, which resulted in a remarkable "turn-off" effect, with a quenching efficiency of 92.5% and four reversible cycles of Hg2+ fluorescence detection. For the fluorescence detection of Hg2+, the response time is fast (≤ 2 min) and the detection limit is low (7.8 nM), showing extremely high sensitivity, and the performance is obviously better than that of the reported fluorescent probes for detecting Hg2+. In particular, probe PTB has low toxicity and good biocompatibility, and has been successfully used for imaging of Hg2+ in living cells. Moreover, probe PTB uses thioether bond and carbon-nitrogen double bond as reaction sites to detect ClO-, which has large Stokes Shift (149 nm), good selectivity, high quenching efficiency (96.5%) and fast time response (about 10 s), and successfully detects ClO- in actual water samples. The dual functional fluorescent probe PTB is sensitive for Hg2+ and ClO-. It has been successfully used for making pH fluorescent test paper and imaging detection of exogenous Hg2+ in VSMC cells with low toxicity.

A sensitive ratiometric fluorescent chemosensor for visual and wearable mercury (II) recognition in river prawn and water samples

A novel ratiometric fluorescent probe p-RPT was prepared with triphenylamine and a rhodamine derivative. The probe displays high sensitivity and selectivity for Hg²⁺, which was applied in real water sample detection and biologic cell imaging. Hydrogel-coated paper sensors were fabricated with p-RPT, which displayed fluorescent colour change upon Hg²⁺ ion contact with a detection limit of 1.2 × 10^-8 M (∼10 ppb). In addition, flexible fluorescent p-RPT gloves were developed for visible and wearable Hg²⁺ detection and applied to detect mercury (II) in river prawn samples. In summary, the p-RPT probe not only shows great potential in mercury (II) detection for food and water, but also provides a new perspective for wearable sensing apparatus.

Molecular probes for fluorescent sensing of metal ions in non-mammalian organisms

While metal ions play an important role in the proper functioning of all life, many questions remain unanswered about exactly how different metals contribute to health and disease. The development of fluorescent probes, which respond to metals, has allowed greater understanding of the cellular location, concentration and speciation of metals in living systems, giving a new appreciation of their function. While the focus of studies using these fluorescent tools has largely been on mammalian organisms, there has been relatively little application of these powerful tools to other organisms. In this review, we highlight recent examples of molecular fluorophores, which have been applied to sensing metals in non-mammalian organisms.

Ratiometric and colorimetric probes with large stokes shift for sensing of exogenous hypochlorite in potato sprouts and industrial effluents

Being one of the important reactive oxygen species (ROS), hypochlorite ions (ClO^-) are involved in the control of several pathological and physiological processes. However, overexpression of ClO^- may prompt several disorders including cancer. Therefore, two fluorescein functionalized compounds with catechol (probe 1) and 2-naphthyl (probe 2) as substituents were synthesized through Schiff base reaction to recognize ClO^- in food items and industrial samples. While probe 2 exhibited turn-off fluorescent response towards ClO^- with limit of detection (LOD) of 86.7 nM, structurally alike probe 1 showed excellent ratiometric response with low detection limit (36.3 nM), large Stokes shift (353 nm), and 'fast' response time (15 s). ¹H NMR titration experiments favored spiroring opening of probe 1 upon the reaction with ClO^-. Probe 1 was successfully utilized for the monitoring of exogenous ClO^- in industrial samples. Further, fabrication of probe coated fluorescent paper strips and recognition of ClO^- in sprouting potato show diverse practical applicability of our probes.

Research Progress on Multifunctional Fluorescent Probes for Biological Imaging, Food and Environmental Detection

There has been rapid progress in the development of fast, sensitive, cheap and low-cytotoxicity micro-molecule fluorescent probes for application in various fields, including disease diagnosis, food safety and environmental safety. As an analytical tool, dual-function fluorescent probes with dual-emission responses have attracted considerable attention due to their cost-effectiveness and efficiency over single-function sensors. This review primarily describes research progress on multifunctional probes in terms of the reaction type and coordination type, as well as the general design principles of probes. The analytes include reactive oxygen species (ROS), reactive sulfur species (RSS), harmful cations and anions, etc. Multifunctional probes for food, medical and environmental applications are listed for future research. To improve the development of rapid detection methods, trends and strategies in the development of multifunctional fluorescent probes are also discussed.

Dicyanoisophorone-based fluorescent probe with large Stokes shift for ratiometric detection and imaging of exogenous/endogenous hypochlorite in cell and zebrafish

A novel dicyanoisophorone-based red-emissive fluorescence probe (YT) with large Stokes shift (230 nm) was synthesized for rapid (<20 s) and selective detection of hypochlorite ions in nearly 100% aqueous medium. YT responded to hypochlorite ions via the ClO^--promoted oxidative deprotection of thioacetal, leading to a red shift in its fluorescence maximum from 590 nm to 640 nm accompanied by naked-eye color change from orange to red. The emission response of the probe toward ClO^- presented a good linear relationship in the 5-160 μM concentration range, with the LOD of 4.64 μM. Further, the probe YT was successfully employed in exogenous and LPS-induced endogenous imaging of ClO^- in live cells and zebrafish, demonstrating its potential applications in biological science.