An excimer process induced a turn-on fluorescent probe for detection of ultra-low concentration of mercury ions.

The accumulation of mercury pollution in plants can induce severe injury to human beings. It is a great challenge to monitor ultra-low concentrations of mercury in complicated matrixes. In this study, we successfully developed a strategy via Hg2+-triggered naphthalene-based fluorescent probe 1, which formed excimer that subsequently emitted fluorescence for the successful detection of ultra-low concentrations of Hg2+. The coordination of N and S atoms with Hg2+ facilitated the formation of excimer from the naphthalene-conjugated planes that were in sufficiently close proximity. Suppression of CN bond rotation also induced the chelation-enhanced fluorescence (CHEF) effect, and the cumulative result of these effects was obvious fluorescent enhancement. Compared with probe 2, the other key factor for detection of Hg2+ is that the electrons of the hydroxyl group can easily transfer to a naphthalene moiety, resulting in an augmented π-electron density that enhanced the π-π stacking of the naphthalene-conjugated excimer. After detailed spectral studies and mechanism discussions, it was realized that probe 1 was able to detect ultra-low concentrations of Hg2+ in PBS buffer solution. The detection limit was calculated to be 1.98 nM. On account of the excellent performances, the probe was successfully applied in monitoring Hg2+ in water and pea sprouts with the potential for application as an advanced warning of contamination.

Coordination Synergistic-Induced J-Aggregation Enhanced Fluorescent Performance of HBT-Excimers and Imaging Applications.

Developing a novel strategy to improve the optical performances of fluorescent probes is a vital factor in elevating its practical application; viz., novel biocompatible fluorescent probes with excellent multifunctions exhibited unparalleled advantages in probing functions of intracellular molecules to elucidate intracellular events in living systems. Herein, we have successfully constructed a new strategy that aggregation and coordination synergistically induce (2-hydroxylphenyl-benzothiazole) HBT derivatives to form excimers with large red-shifted fluorescence and application for insight into stress-response zinc fluctuations in living systems. We have synthesized four HBT-based derivatives and deeply investigated the response mechanism by fluorescent spectral studies, demonstrating that probes 3 and 4 showcased large red shifts in emission wavelength due to J-aggregation. More interestingly, the fluorescence of probe 4 was significantly enhanced in the presence of a zinc ion, suggesting that zinc coordination synergistically induced J-aggregation. Probe 4 was successfully applied to image zinc fluctuations in different models of living systems, proving that this probe is a powerful tool to unveil the relationship between invasive stress and diseases by monitoring endogenous zinc fluctuations.

Insight into sulfur dioxide and its derivatives metabolism in living system with visualized evidences via ultra-sensitive fluorescent probe.

Sulfur dioxide (SO2) and its derivatives have long been considered as hazardous environmental pollutants but commonly used as food additives in safe dose range. They also could be produced from biological metabolism process of sulfur-containing amino acids. However, their physiological roles remain extremely obscure mainly due to lack of efficient tools for monitoring and imaging strategy establishment. Furthermore, most of current studies of this aspect focus on novel probe design or just imaging them rather than on the ins and outs. Therefore, there is a high significance of establishing highly sensitive detection strategy for monitoring SO2 derivatives in living systems, food and environment. Herein, we design a fluorescent probe MS-Bindol for sensitively detecting SO2 derivatives with a low detection limit (0.2 nM). We have established an imaging strategy for investigation of SO2 derivatives metabolism in living cells and zebrafish, providing visualize evidences and verified that SO2 derivatives could be synthetized from thiosulfate and glutathione(GSH) and be hardly consumed by using sulfite oxidase inhibitors (ferricyanide or arsenite). Moreover, the probe also exhibits excellent practicability in food as well as environmental samples. Our studies may help biologist for better understanding SO2 derivatives metabolism and deeply explore their physiological roles in biological systems.

A small molecule fluorescent probe for mercury ion analysis in broad low pH range: Spectral, optical mechanism and application studies.

Development of new fluorescent probes for mercury ion analysis in environmental or living organism is undergoing quick growth due to its detrimental toxicity to environmental safety, ecological security, and human being. However, in most cases, the industrial waste water is acidic whereas it remains a great challenge to real-time monitor mercury ion directly at low pH using small molecule fluorescence probe. In this study, we have successfully designed and synthesized the Naph (1, 8-Naphthalimide derivative) -based small molecule probe termed as Naph-NSS capable of monitoring mercury ion in a broad range at low pH (from 2.0 to 7.0). The solid spectral studies demonstrated the high sensitivity and selectivity of the probe towards mercury ion among various species. After binding with Hg2+, the fluorescence of Naph-NSS greatly enhanced, and the mechanism of which was investigated by DFT studies. The probe was able to be loaded on paper strip for instant and fast detection of mercury ions. In addition, the probe is also suitable for detection of mercury ion in environmental samples, living cells and in vivo.

A cysteine-selective fluorescent probe for monitoring stress response cysteine fluctuations.

Rare studies provided evidence for the real-time monitoring of stress response cysteine fluctuations. Here, we have successfully designed and synthesized a cysteine-selective fluorescent probe 1 to monitor stress response Cys fluctuations, providing visual evidence of Hg2+ regulated cysteine fluctuations for the first time, which may open a new way to help researchers to reveal the mechanism of heavy metal ion poisoning.

A chemical covalent tactic for bio-thiol sensing and protein labeling agent design.

Discovering novel chemical reactions is important for bioanalysis. Herein, we report a tactic for bio-thiol sensing and protein labeling agent design by the installation of a sulfoxide group onto the skeleton of various fluorophores, and powerfully validate its abilities, which may shed light on the development of specific protein tags to give insight into their biological functions.

A reaction-based ratiometric fluorescent probe for mercury ion detection in aqueous solution.

Mercury ions are crucially harmful to ecosystem and human being due to their characters of bioaccumulation and difficulty of biochemical degradation. Therefore, development of mercury ion detection methods has attracted increasing interests recently. In this study, we successfully synthesized a hydroxyphenylbenzothiazole (HBT)-based fluorescent probe HBT-Hg in an extremely simple manner for mercuric ions detection. The spectral studies revealed that the probe HBT-Hg could react with Hg2+ selectively and sensitively in PBS buffer (10 mM, pH = 7.40), showing ratiometric fluorescent changes from blue to light green. The response mechanism of the probe HBT-Hg and Hg2+ was finally confirmed by HPLC analysis, viz., the probe HBT-Hg converted to its precursor compound 1. Finally, the probe HBT-Hg was successfully applied in monitoring Hg2+ in living A549 cells.

A colorimetric method for determination of the prostate specific antigen based on enzyme-free cascaded signal amplification via peptide-copper(II) nanoparticles.

Biotinylated peptide-Cu2+ nanoparticles (Cu-P NPs) were synthesized via "one-pot" self-assembly. The peptide P conststs of a hydrophobic dipeptide (FF), a tripeptide (KGH), and a biotin moiety attached to the terminal amino group of the Lys residue. The Cu-P NPs contain abundant catalytically active Cu2+ ions which are liberated by acid-induced dissolution. The released Cu2+ ions catalyze the oxidization of 3,3',5,5'-tetramethylbenzidine (TMB) by H2O2 because of their intrinsic peroxidase activity, and this results in the formation of a blue-green coloration. Based on the streptavidin-biotin interaction, the Cu-P NPs were employed to establish an enzyme-free colorimetric method for determination of prostate-specific antigen (PSA) as a model biomarker. Under optimal conditions, the linear response range is 0.001-1 ng mL-1, with a limit of detection as low as 1 pg mL-1. Graphical abstract Schematic illustration of a colorimetric immunoassay for the prostate specific antigen (PSA) with biotinylated peptide-Cu2+ nanoparticle (Cu-P NP) as the signal label based on the streptavidin (SA)-biotin interaction. The signal was produced by Cu2+-catalyzed oxidization of 3,3',5,5'-tetramethylbenzidine (TMB). P: KGHFF.

A ratiometric fluorescent probe of methionine sulfoxide reductase with an improved response rate and emission wavelength.

A ratiometric fluorescent probe of methionine sulfoxide reductase, Msr-Ratio, was disclosed for monitoring the enzyme activity in vitro and in live cells. The probe displayed favorable properties such as a nearly 400-fold fluorescence change, fast response rate (<30 min), large Stokes shift (120 nm), and green emission (550 nm).

A novel ratiometric AIEE/ESIPT probe for palladium species detection with ultra-sensitivity.

Existing fluorescent probes for palladium (Pd) species detection have revealed their vulnerabilities, such as low sensitivity, poor anti-interference ability and long reaction time. In order to develop a faster and more accurate detection method for palladium species at extremely low concentrations, in this study, we designed a novel ratiometric AIEE/ESIPT probe (HPNI-1) based on the Tsuji-Trost reaction for Pd. According to the data obtained, the probe was able to detect Pd species with an ultra-high anti-interference ability (Pd : other metals = 1 : 1000), rapid detection time (within 2 minute) and ratiometric fluorescent signal changes with a 1.34 nM detection limit. This study not only proves that existing methods can be improved but also provides future prospects for HPNI-1 as one of the greatest probes for Pd species detection.

Recovery of uranium(VI) from aqueous solution by 2-picolylamine functionalized poly(styrene-co-maleic anhydride) resin.

A 2-picolylamine functionalized poly(styrene-co-maleic anhydride) resin was synthesized and characterized by FT-IR, elemental analysis, SEM and XPS. To recover uranium from aqueous solution, the influence factors such as pH values, contact time, temperature and initial uranium concentration were optimized. Adsorption kinetics fitted well with the pseudo-second-order model, whereas adsorption isotherm matched well with the Langmuir isothermal adsorption model, with the maximum sorption capacity of 518.39mgg-1 at pH 5.30 and 298K. The uptake of uranium could be implied in 0.01M coexisted ions environment. Besides, the resin could be regenerated by 0.1M HNO3 and repeatedly utilized in circles. The study proved that the resin has potential application prospects for disposal of uranium(VI).