A colorimetric and fluorescence turn-on probe for the detection of palladium in aqueous solution and its application in vitro and in vivo

Two-photon fluorescence probe for palladium with perchlorate induced quenching mechanism and its application in smartphone-based rapid detection

We propose a new approach for detecting palladium using a two-photon fluorescent probe quenched by perchlorate. This newly developed method has the potential to overcome some of the limitations of the currently available methods for detecting palladium. This article provides a detailed introduction to the design and synthesis of fluorescent probe, as well as the fluorescence performance in aqueous solutions. The results demonstrate the probe is highly sensitive, selective, and efficient in detecting palladium. The study also includes a thorough analysis of the quenching mechanism of the probe by perchlorate, and obtained different results from previous literatures. Moreover, the probe can easily identify and differentiate between palladium being present in the valence states 0, + 2/+ 4, and accomplish detecting palladium in convoluted solutions such as wastewater, environmental water, Hela cells and zebrafish. Due to its excellent performance, using self-developed optical device, the possibility of detecting palladium in aqueous solutions based on smartphone was explored.

A 1,8-naphthimide-based Fluorescent Probe for Analyzing DMF/H2O Composition

A novel 1,8-naphthalimide fluorescent probe (BNAS) containing 2-thiopheneethylamine moiety was designed and synthesized for analyzing the composition of N,N-dimethylformamide (DMF)/deionized water (H2O) mixtures. With the increase of DMF content, the fluorescence of the system was enhanced from dark to bright yellow-green. Taking 15% (volume) DMF content as the dividing point, the fluorescence intensity of the system at 535 nm showed two good linear relationships with the DMF content 1-15% and 15-99%, based on which the composition of the DMF/H2O mixtures with a volume ratio of 1/99-99/1 could be quickly and efficiently analyzed with high selectivity and sensitivity. BNAS can be applied in real sample assay and further be loaded onto filter paper to make a portable sensor. The mechanism of BNAS response to DMF/H2O composition was also explored.

Novel Crown Ether Amino Acids as Fluorescent Reporters for Metal Ions

Unnatural amino acids with enhanced properties, such as increased complexing ability and luminescence, are considered to be highly attractive building blocks for bioinspired frameworks, such as probes for biomolecule dynamics, sensitive fluorescent chemosensors, and peptides for molecular imaging, among others. Therefore, a novel series of highly emissive heterocyclic alanines bearing a benzo[d]oxazolyl unit functionalized with different heterocyclic π-spacers and (aza)crown ether moieties was synthesized. The new compounds were completely characterized using the usual spectroscopic techniques and evaluated as fluorimetric chemosensors in acetonitrile and aqueous mixtures in the presence of various alkaline, alkaline-earth, and transition metal ions. The different crown ether binding moieties as well as the electronic nature of the π-bridge allowed for fine tuning of the sensory properties of these unnatural amino acids towards Pd²⁺ and Fe³⁺, as seen by spectrofluorimetric titrations.

New nano materials-based optical sensor for application in rapid detection of Fe(II) and Pd(II) ions

For the analytical determination of Fe(II) and Pd(II) concentrations, a novel optical sensor based on spectrophotometric technique was used. The optical sensor was prepared by direct immobilization of a novel synthesized chromophore, 5-amino-phenanthrolin-3 formyl salicylic acid, onto nanocellulose. Human vision can identify the color associated with Fe II ions, and spectrophotometric methods can measure it with detection and quantification limits of 0.239 and 0.796 ppb, respectively. Pd(II) detection and quantification limits were 0.318 ppb and 1.06 ppb, respectively. The effects of various parameters on the detection of Fe(II) or Pd(II) ion content were investigated and optimized. The optical phenanthroline-nanocellulose (5-Phen) sensor could be reproduced multiple times and used with a higher capacity each time. The results demonstrated that the 5-Phen sensor could measure Fe(II) in human blood serum accurately and successfully even without any pre-concentration.

Tm3+ Ion Blue Emission Quenching by Pd2+ Ions in Barium Phosphate Glasses: Fundamental Analysis toward Sensing Applications

The quenching effect of Pd²⁺ ions on the blue emission from Tm³⁺ was investigated for the first time using barium phosphate glass as model matrix. Glasses containing fixed Tm₂O₃ at 0.5 mol % and PdO up to 0.3 mol % (added relative to P₂O₅) were prepared by melting and first characterized for basic structural properties by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and Raman spectroscopy. Thermal properties were then evaluated by differential scanning calorimetry (DSC). The focus was thereafter on evaluating the optical properties by absorption and photoluminescence (PL) spectroscopy with decay kinetics assessment. XRD confirmed the amorphous nature of the glasses synthesized. The vibrational spectroscopy assessment consistently exhibited the IR- and Raman-active bands characteristic of phosphate glasses, showing no significant variation with PdO codoping. The DSC analysis revealed all glasses possessed high thermal stability assessed by the differences (ΔT = T_g - T_x ≥ 154 °C) between glass transition temperatures (T_g) and onset of crystallization (T_x). A tendency of the T_g values to increase with PdO contents was however exhibited. In addition, specific enthalpies of crystallization showed magnitudes decreasing with increasing PdO concentration, thus suggesting crystallization suppression by Pd²⁺. Concerning the optical properties, it was observed that codoping the glasses with PdO (0.1-0.3 mol %) led to the development of the visible Pd²⁺ d-d absorption band (peak ≈415-410 nm). In addition, drastic PL quenching of the Tm³⁺ blue emission around 452 nm (¹D₂ → ³F₄ transition) was induced by Pd²⁺. Analyzing PL decay curves obtained by exciting Tm³⁺ ions at 359 nm while monitoring 452 nm emission revealed decreased ¹D₂ state lifetimes. Thus, a potential of Tm³⁺ for analytical sensing of Pd²⁺ in various matrices was suggested. Ultimately determining quenching constants from the PL data and based on the comparison of results from emission intensity and decay rates, likely Tm³⁺ → Pd²⁺ energy transfer processes underlying the PL quenching were proposed.

A highly selective turn-on fluorescence probe with large Stokes shift for detection of palladium and its applications in environment water and living cells

Nowadays, palladium has been widely used in many fields, which facilitates all aspects of our life. However, it may cause water and soil pollution and bring irreversible damage to the environment and organisms. Developing a fluorescence probe for rapid, highly sensitive and selective detection of palladium is still a poser. In this work, we designed and synthesized a novel fluorescence probe (RHS) for specific detection of palladium. Based on Pd⁰-mediated Tsuji-Trost reaction, the fluorescence probe was constructed by a rhodol derivative as thefluorophore and an allyl carbonate moiety as the specific palladium reactive site. The probe displayed excellent properties for detecting palladium, such as high selectivity and sensitivity, rapid response (20 min) and large Stokes shift (155 nm). The detection limit was determined to be as low as 0.140 μM with a linear range from 20 to 80 μM. After addition of palladium in RHS solution, the color of the solution turned from yellow to blue, indicating palladium could be monitored by the naked eyes. Moreover, probe RHS was successfully applied to palladium detection in environmental water samples. Importantly, with low cytotoxicity and good biocompatibility, the probe could monitor palladium in living cells.

A highly sensitive and selective fluorescence turn-on probe for the sensing of H2S in vitro and in vivo

A fluorescence turn-on probe, 2-butyl-1,3-dioxo-2,3-dihydro-1H-benzo[de]isoquinolin-6-yl 2,4-dinitrobenzenesulfonate (NT-SH), has been constructed for sensing of hydrogen sulfide (H₂S). NT-SH exhibited excellent detection performance including favorable water solubility, low fluorescence background, high enhancement (45-fold), large linear response range (0-50 μM) and low detection limit (80.01 nM) for H₂S in aqueous. In addition, the response mechanism of NT-SH for H₂S was confirmed by the theoretical calculation and mass spectral analysis. More importantly, the imaging experiments of H₂S in vitro and in vivo confirmed that NT-SH had low cytotoxicity, and favorable biocompatibility. In addition, it illustrated that NT-SH was able to detected exogenous H₂S in living cells and zebrafish. These results suggested that NT-SH can be act as a potential molecular tool for detecting of H₂S in aqueous solution, in vitro and in vivo.

A multiple acetal chalcone-BODIPY-based fluorescence: synthesis, physical property, and biological studies

Fluorescent probes with outstanding physical and biological properties are superior for functional fluorescent dyes design. However, few studies pay attention to the stability of specific groups in fluorescent probes. The aldehyde group in the fluorescent probe is highly active but unstable under certain conditions. Therefore, we introduced ethoxy groups to realize the conversion to aldehyde groups under acidic conditions and avoid the instability of straightforward aldehyde groups. In this work, two fluorophores based on the multi acetal difluoroboraindacene (BODIPY) units with combination of the pharmaceutical intermediate chalcone have been firstly developed. In the design part, chalcone was introduced as a medium for fluorophore and multiple acetal. The mild synthesis strategy is based on the ligand ((Z)-2-chloro-1-(difluoroboranyl)-5-((4-ethyl-3,5-dimethyl-2H-pyrrol-2-ylidene)(phenyl)methyl)-1H-pyrrole) and connects with chalcone in (2E,2'E)-3,3'-(1,3-phenylene)bis(1-(2,4-bis(2,2-diethoxyethoxy)phenyl)prop-2-en-1-one). The emission wavelengths of the products are around 530 nm with high fluorescence intensity. To highlight the biological characteristics of these novel BODIPY fluorescents, we further demonstrated biological analysis studies on MTT and flow cytometry assays. The IC₅₀ values of BODIPY 5 ranged from 79 ± 6.11 to 63 ± 5.67 μM and BODIPY 6 were found to be 86 ± 4.07 to 58 ± 10.51 μM in tested cell lines. Flow cytometry data analysis shows that the representative agent 6 and reference have similar rational apoptosis rates in first quadrant. Last but not least, 6 shows outstanding biological compatibility and cell imaging potential in live cell imaging and in vivo assay, not only is the fluorescence prominent enough, but also rapidly distributes. Thus, our study reports a mild synthesis strategy and full biological analysis on BODIPY fluorescents, and the subtle modulation of the physical and biological properties by pharmaceutical substituents makes these designed chalcone-BODIPY-based dyes hopeful to realize drug functional fluorescent dyes. Two new highly sensitive BODIPY fluorophores are synthesized based on the ligand ((Z)-2-chloro-1-(difluoroboranyl)-5-((4-ethyl-3,5-dimethyl-2H-pyrrol-2-ylidene)(phenyl)methyl)-1H-pyrrole), which connects with chalcone in (2E,2'E)-3,3'-(1,3/4-phenylene)bis(1-(2,4-bis(2,2-diethoxyethoxy)phenyl)prop-2-en-1-one). Multiple acetals were introduced and the physical and biological properties of BODIPYs are described with MTT assay and in vitro and in vivo imaging.