A novel ratiometric fluorescence probe based on the FRET-ICT mechanism for detecting fluoride ions and viscosity

Fluoride ion is not only important for dental health, but also a contributing factor in a variety of diseases. At the same time, fluoride ions and cell viscosity are both important to the physiological environment of mitochondria. We developed a dual-response ratiometric fluorescent probe BDF based on Förster resonance energy transfer (FRET) and intramolecular charge transfer (ICT) mechanism for the detection of F- and viscosity. BDF has an outstanding intramolecular energy transfer efficiency of 97.7% and shows excellent performance for fluorine ion detection. In addition, when the system viscosity increases, the fluorescence emission intensity of BDF is greatly heightened, indicating the possibility of viscosity detection. Finally, based on the fluorescence properties of BDF, we used the probe to detect F- in the toothpaste sample and image exogenous fluoride ions in HeLa cells.

Fluoride-activated photothermal system for promoting bacteria-infected wound healing

Although photothermal therapy (PTT) employing nanozymes has shown excellent antibacterial potential, excessive heating generally harms host cells and hinders recovery. Herein, we report an innovative technique for acquiring the programmed temperature by managing the catalytic activity of nanozymes. The photothermal system of CeO2 + F- + TMB can obtain precise photothermal temperature by adjusting the concentration of fluoride ions under near-infrared irradiation. At the optimized photothermal temperature, the photothermal system affords fine photothermal antibacterial treatment with high-efficiency antibacterial effects against Staphylococcus aureus and Escherichia coli in vitro. In vivo wound healing experiments confirm that the system can effectively promote fibroblast proliferation, angiogenesis and collagen deposition with remarkable wound healing efficiency. This strategy offers a novel design concept for creating a new generation of PTT and opens the way for the creation of alternative antibiotics.

Fluoride ions detection in aqueous media by unprecedented ring opening of fluorescein dye: A novel multimodal sensor for fluoride ions and its utilization in live cell imaging

Imidazole functionalized on fluorescein dye was developed as an efficient probe for naked eye and fluorescence determination of fluoride ions. The probe is dramatic color change and very exciting fluorescence turn-on response with the addition fluoride ions. Moreover, fluoride ions triggering leads to the fissure of the spirolactam ring that causes drastic color makes feasible for the naked eye detection of fluoride ions. The mode of binding of fluoride with the probe was proved by ¹H NMR titration experiments and the observed photophysical changes were rationalized by use of DFT calculations. This sensor was more applied to detect fluoride ions in real samples and imaging of fluoride ions through fluorescence imaging in living cells.

A coumarin based Schiff Base: An effective colorimetric sensor for selective detection of F- ion in real samples and DFT studies

Chemosensors are molecular devices which react with target and give a visible signal, which is a degree of its sensitivity. Herein, a novel coumarin based Schiff Base has been synthesized for F^- ions detection. The chemosensor showed an intense color change upon the addition of F^- ions (light yellow to purple). The chemosensor has fewer effects of competing anions. The limit of detection is calculated as low as 1.1 × 10^-6 and the binding constant was determined as 1.61 × 10⁴. The job's plot confirmed 1:1 stoichiometry between chemosensor and F^- ion. The reverse reaction of chemosensor with MeOH is useful to construct a combinatorial logic circuit gates. The interaction mechanism of chemosensor was deliberated by ¹H NMR, FTIR, and DFT studies. Finally, the chemosensor was useful to detect F^- ions in tooth-paste sample and test strip is prepared for F^- ions detection.

Development of carbazole-based fluorescent probe for highly sensitive application in fluoride ion detection

Fluorine is a necessary element for human, which is closely related to life activities, such as metabolism of teeth and bone tissue. A small amount of fluoride ions can promote the strengthen of our body. However, a large amount of fluoride ions will damage the human immune system to produce organ diseases. Sensitive and rapid detection of fluoride ions has attracted great interests for researchers. In this work, a reactive fluorescent probe SCP for detection of fluoride ions with high quantum yield was designed and synthesized based on the carbazole ring. Subsequently, the photophysical properties of the probe SCP were carefully studied. At last, SCP performed 62.8% quantum yield in physiological condition, excellent ability of quantitative analysis, well selectivity, and distinguishing features for HepG2 cell imaging.

Mitochondria targeted dual-fluorescent probe for bio-imaging viscosity and F- with different fluorescence signals

The F^- ion and viscosity both affect the physiological state of mitochondria and to the best of our knowledge no fluorescent probe is reported for the dual detection of mitochondrial viscosity and F^- ion through different signals. DMAS-Si is weakly red fluorescent due to free intramolecular rotation between dimethylaminophenyl and pyridinium moieties and PET from silyloxy to the pyridinium moiety. In viscous medium (glycerol 90 %), the rotation is restricted and 18-fold increase in red-fluorescence (λ_em 637 nm) is observed. On reaction with F^- ion, the desilylations followed by release of quinone-methide from DMAS-Si gives intense green fluorescence (λ_em 515 nm) due to formation of DMAS. DMAS-Si can detect as low as 50 nM F^-. DMAS-Si shows good permeability to HeLa cells and preferably targets mitochondria. It has been used for imaging of increased viscosity in mitochondria of HeLa cells in the presence of nystatin through red fluorescence and exogenous F^- ion by appearance of green fluorescence.

Ultrafast fluorescent probe with near-infrared analytical wavelength for fluoride ion detection in real samples

The first ultrafast fluorescence probe with response time in seconds (10 s) for fluoride ions (F^-) has been proposed by conjugating dimethylthiophosphoryl group as a recognition unit with the near-infrared fluorophore of hemicyanine. The response mechanism is the F^--induced cleavage of the dimethylthiophosphoryl group, along with the liberation of the fluorophore, which results in a distinctly enhanced fluorescence intensity at 730 nm (λ_ex = 680 nm). The fluorescence enhancement of the probe is directly proportional to the F^- concentration in the range of 10-300 µM with the detection limit of 4.28 µM. The probe has been successfully used to determine F^- concentration in real water and toothpaste samples as well as image F^- in living cells. The simplicity and quick response of this probe endow it with the ability of detecting F^- rapidly in real samples.

Presence of fluoride in water diminishes fast the SPR peak of silver nanocrystals showing large red shift with quick sedimentation - A fast sensing and fast removal case

The medicinal use of fluoride is beneficial up to a low ppm level but regular ingestion at high doses show many adverse effects in human. Fluoride may get ingested through drinking water specially through ground water near the hilly regions, where fluoride content is huge. Hence, fluoride sensing and removal of it from water is very important as fluoride contaminated water is transparent and not easily detectable. Here, we have studied colorimetric and spectrophotometric techniques for sensing of fluoride along with its fast removal from water by using prepared saponin capped silver nanoparticles (AgNPs). Colorimetric study has confirmed the presence of fluoride ions in water samples above the colorimetric detection limit of 10 ppm. But spectroscopic sensing further provides more lower limit of sensing with the total removal of fluoride ions up to 1.2 ppm level. On repeating this this study 15 times, sensing and removal of fluoride is found to be well reproducible. The interaction of fluoride ions with silver nanoparticles has resulted in sedimentation of fluoride ions in the form of fluoride-nanoparticles complex and that interaction has been confirmed by FTIR spectral study of the sedimented part. EDX analysis has also provided the information of easy removal of the fluoride ions from water as presence of fluoride peak has been found in EDX spectra.

Enhanced fluoride removal from water by rare earth (La and Ce) modified alumina: Adsorption isotherms, kinetics, thermodynamics and mechanism

The removal of F^- from aqueous solution using lanthanum and cerium modified mesoporous alumina (La/MA and Ce/MA) was studied, and characteration of the adsorbents by XRD, BET, XRF, FTIR, TEM, XPS and the pH_ZPC measurements were carried out. The adsorption was investigated in both batch and column adsorption systems. Batch experimental results showed that adsorption capacities of adsorbents were recorded in the following order: La/MA > Ce/MA > mesoporous alumina (MA). Besides, adsorption datas were fitted well by Sips isotherm model and Elovich kinetics model, and the maximum adsorption capacity of La/MA was 26.45 mg·g^-1 in Sips model at the dosage of 2.0 g·L^-1 and near neutral condition (pH = 6.0 ± 0.1). Moreover, thermodynamic parameters were illustrated that adsorption process of fluoride ion over La/MA was spontaneous and endothermic. In the adsorption process, the interaction between metal and fluoride, the adsorption capacity was increased due to form the bond of M···F (M = La or Ce). Furthermore, the influence of coexisted anions on F^- removal was investigated, and it was indicated that removal efficiency was slightly affected by the presence of Cl^- and NO₃^-, while SO₄^2- and CO₃^2- caused a sharp fall in removal efficiency. Column experiments results were indicated that time of break-through of La/MA was twice as much as that of MA.

1,6-Elimination reaction induced detection of fluoride ions in vitro and in vivo based on a NIR fluorescent probe

Near-Infrared "turn on" type fluorescent probes are attractive and promising in the fields of chemical sensing and bioimaging. Here, a new dicyanomethylene-4H-pyran derivative (DCM-Si) NIR fluorescent probe was designed and synthesized for specific lighting up F^- in living cells and bodies. SiO bond was used as F^- trigger, and the release of fluorophore (DCM-NH₂) occurred after substituent reaction and subsequent 1,6-elimination. This NIR probe displayed high sensitivity and selectivity for the sensing of F^-, and the detection limit was calculated to be as low as 157 nM. Moreover, the "off-on" fluorescent signal changes can be realized by adding F^- in living cells and zebrafish embryos.

A targetable fluorescent probe for real-time monitoring of fluoride ions in mitochondria

Fluorion are pivotal anions in biology because they play an important role in dental care, treating osteoporosis, preventing tooth decay and promoting the healthy growth of bone. Studies have shown that high levels of fluoride will lead to the inactivation of the mitochondria. Therefore, it is urgent to develop a method to detect the fluoride anions in the mitochondria. Herein, we have developed a novel mitochondrial-target fluorescent probe for detecting F^- in living cells. The probe exhibited excellent sensitivity and high selectivity for F^- over the other relative species. With changing fluoride ions, the fluorescence spectrum of the probe changed significantly with a large turn-on fluorescence signal. Cell imaging indicated that the probe can penetrate viable cell membranes and rapidly detects and images fluorion over other anions in the mitochondria.

A near-infrared fluorescent probe for selective and quantitative detection of fluoride ions based on Si-Rhodamine

A highly selective fluorescent probe (SiROPS) based on Si-rhodamine (SiR) towards F^- was investigated. SiROPS can realize the NIR detection of F^- because of the long fluorescent wavelength (λ_ex = 650 nm, λ_em = 669 nm). The near-IR optical and the ratiometric fluorescence type signaling were realized by employing fluoride-selective cleavage of the latent thiophosphinated probe in mixed aqueous media. The cleavage of F^- to the ortho positions of dimethylphosphinothionyl group in the meso aryl involves the suppression of internal rotation upon phosphorylation of a reactive phenolate and the activating rotation of o-OH, which resulting in a large fluorescence "Turn-Off" response. The detection limit of the probe to F^- was 48 nM in the dynamic range of 0.5 μM-20 μM. In addition, the proposed probe has been used to detect F^- in water samples and toothpaste samples with satisfying results.

Synthesis of adsorbent from Tamarix hispida and modified by lanthanum metal for fluoride ions removal from wastewater: Adsorbent characteristics and real wastewater treatment data

This data article describes a facile method for production of an adsorbent from Tamarix hispida wasted wood and modified by lanthanum metal for fluoride ions removal from wastewater. The main characteristics of the adsorbent consist of BET surface area, functional groups, and elemental analysis is presented. The data for attenuating the pollutants from a real wastewater treatment which was provided from a glass factory is also represented. More than 90% of fluoride content of the real wastewater was treated by the adsorbent. Generally, these data would be informative for extend research aim to industrial wastewater treatment and those who work in the wastewater treatment plants.

Long-term release of fluoride from fissure sealants-In vitro study

The intensity of the cariostatic activity of fluoride ions can be attributed to their multidirectional influence on the caries process. They are an irreplaceable factor that helps sustain mineral balance of dental tissues, simultaneously demonstrating antibacterial properties. As a consequence, many manufacturers of fissure sealants include fluoride ions in their products. The aim of this in vitro study was to determine long-term fluoride release from four fissure sealants (Conseal F, Fissurit FX, Delton Fs+, Admira Seal). During a 14-week-long observation, all the materials showed a relatively constant level of F- release; however, it is crucial to mention that within the first 48h, the most significant increase in fluoride release was found for Fissurit and Delton sealants. Based on the overall assessment, the highest total amount of the released fluoride ions was observed for Delton, and the lowest level was reported for Admira Seal.

Geochemical controls of high fluoride groundwater in Umarkot Sub-District, Thar Desert, Pakistan

Groundwater samples (n=152) were collected in the Thar Desert of the Umarkot Sub-District, Pakistan to evaluate the geochemical controls on the occurrence of high fluoride (F(-)) levels within the study area. Fluoride concentrations range from 0.06 to 44.4 mg/L, with mean and median values of 5.22 and 4.09 mg/L, respectively; and roughly 84% of the samples contain fluoride concentrations that exceed the 1.5mg/L drinking water standard set by WHO. The overall groundwater quality reflects the influences of silicate mineral weathering and evaporation. Fluoride originates from the weathering of minerals derived from Type-A granite and possibly anion exchange (OH(-) for F(-)) on clays and weathered micas under high pH conditions. High fluoride levels are associated with Na-HCO3 type water produced by calcite precipitation and/or base ion exchange. Depleted calcium levels in groundwater allow higher fluoride concentrations to occur before the solubility limit for fluoride is reached.

A highly selective colorimetric and ratiometric fluorescent chemodosimeter for detection of fluoride ions based on 1,8-naphthalimide derivatives

A high selective colorimetric and ratiometric fluorescent probe based on 4-hydroxy-1, 8-naphthalimide was designed and synthesized to detect fluoride ions (F(-)). The sensing behavior of this probe was studied by UV-visible and fluorescence spectroscopy. The probe displays an 110 nm red-shift of fluorescence emission and the color changes from colorless to yellow by virtue of the strong affinity of F(-) toward silicon which can act as a new visual sensor for F(-).