A fluorescein derivative FLTC as a chemosensor for Hg2+ and Ag+ and its application in living-cell imaging

Antimicrobial, antioxidant, cell imaging and sensing applications of fluorescein derivatives: A review

Fluorescein itself is a synthetic organic compound and a prominent member of the xanthene dye family. It exhibits strong fluorescence under ultraviolet (UV) or blue light excitation, making it widely used in various applications, including fluorescence microscopy, flow cytometry, immunoassays, and molecular biology techniques. One of the reasons fluorescein derivatives are highly valuable is their tunable fluorescence properties. Through chemical modifications of the fluorescein structure, different functional groups or substituents can be introduce, altering the compound's fluorescence characteristics such as emission wavelength, intensity, and photo stability. This flexibility allows for tailoring of fluorescent probes to specific experimental requirements, enhancing their utility in a range of scientific disciplines. Fluorescein derivatives also possess excellent antimicrobial and antioxidant activity. This review sheds light on the significant impact of fluorescein derivatives as biological active compounds, highlighting their potential in designing new therapeutic agents with antimicrobial properties. Additionally, their role as antioxidants is discussed. A major aspect covered in the review is the application of fluorescein derivatives as powerful cell imaging probes. Their unique fluorescent properties make them valuable tools for visualizing cellular structures and processes, opening up new possibilities for studying cellular dynamics and interactions.

New NIR spectroscopic probe with a large Stokes shift for Hg2+ and Ag+ detection and living cells imaging

A new near-infrared (NIR) probe based on a coumarinyl ligand (CL) was designed and synthesized. The probe CL can be used for simultaneous fluorescent turn-on and colorimetric detection of Hg²⁺ and Ag⁺ in ethanol/water medium. Colorless solution of probe CL changed to light yellow or dark yellow after addition of Hg²⁺ or Ag⁺ ions. Meanwhile the maximum absorption band shifted from 379 nm to 404 nm and the intensity increased enormously (for Hg²⁺) or moderately (for Ag⁺). Probe CL displayed an extraordinarily large Stokes shift of 316 nm and addition of Hg²⁺ or Ag⁺ to probe CL induced enhancement in the intensity of fluorescence emission at 695 nm by 15 or 8 fold. The detection limit of CL for Hg²⁺ and Ag⁺ ions is 0.83 and 8.8 μM, respectively. The applicable pH for sensing Hg²⁺ by probe CL is in a broad range of 2-12. Application of probe CL for in vitro U87MG cell imaging to detect Hg²⁺ ions was confirmed.

Recent Advances and Applications of Microfluidic Capillary Electrophoresis: A Comprehensive Review (2017-Mid 2019)

Microfluidic capillary electrophoresis (MCE) is the novel technique resulted from the CE mininaturization as planar separation and analysis device. This review presents and discusses various application fields of this advanced technology published in the period 2017 till mid-2019 in eight different sections including clinical, biological, single cell analysis, environmental, pharmaceuticals, food analysis, forensic and ion analysis. The need for miniaturization of CE and the consequence advantages achieved are also discussed including high-throughput, miniaturized detection, effective separation, portability and the need for micro- or even nano-volume of samples. Comprehensive tables for the MCE applications in the different studied fields are provided. Also, figure comparing the number of the published papers applying MCE in the eight discussed fields within the studied period is included. The future investigation should put into consideration the possibility of replacing conventional CE with the MCE after proper validation. Suitable validation parameters with their suitable accepted ranges should be tailored for analysis methods utilizing such unique technique (MCE).

A phenanthro[9,10-d]imidazole-based AIE active fluorescence probe for sequential detection of Ag+/AgNPs and SCN- in water and saliva samples and its application in living cells

Ag⁺ and SCN^- play extremely important roles in the fields of the physiology and environment. In this work, on the basis of phenanthro[9,10-d]imidazole derivative (DIPIP) which can exhibit the aggregation-induced emission (AIE) properties in aqueous solution, we achieved a sequential on-off-on switch for Ag⁺ and SCN^- with high selectivity and sensitivity. A remarkable fluorescence quenching effect of Ag⁺ on the probe DIPIP was observed with 1:2 stoichiometry, Subsequently, the fluorescence intensity of in situ generated DIPIP-Ag⁺ ensemble was easily switched on after the interaction between Ag⁺ and SCN^-, which was attributed to the stronger affinity of SCN^- to capture Ag⁺. In particular, the extreme limits of detection (LOD) for Ag⁺ and SCN^- in standard solutions were as low as to be 74.5 nM and 7.8 nM, respectively. Furthermore, the probe DIPIP and the DIPIP-Ag⁺ ensemble could be used to detect Ag⁺ in the real water and SCN^- in smoker saliva samples, respectively. In addition, the sequential "on-off-on" fluorescence mode of DIPIP to Ag⁺ and SCN^- were also successfully applied in living HeLa cells.

Microchip electrophoresis based multiplexed assay for silver and mercury ions simultaneous detection in complex samples using a stirring bar modified with encoded hairpin probes for specific extraction

It is crucially important to rapidly, simultaneously, and sensitively determine trace amounts of heavy metal ions in complex samples. Herein, a stirring bar modified with two kinds of encoded hairpin DNA probes (H₀ and H₀') was used in a multiplexed strategy allowing for specific extraction of Hg²⁺ and Ag⁺ coupled to microchip electrophoresis (MCE) separation and LED induced fluorescence (LIF) detection. The extraction step utilizes stir bars, which are functionalized with designed hairpin DNA probes (H₀ with TT and H₀' with CC mismatches in stems). This allows the specific capture of Hg²⁺ and Ag⁺ through CAg⁺C and THg²⁺T interactions. These complexes are then enzymatically degraded by the action of exonuclease III (Exo III). The ions released during this enzymatic reaction can initiate a new cycle of interactions with hairpin structures and enzymatic reactions and so on. This cyclic step is specific to the presence of Hg²⁺ and Ag⁺ and represents the first round of amplification of the presence of the selected ions. The resulting single strand DNAs on the stirring bars after enzymatic degradation were used in the second step as primers to trigger the catalytic hairpin assembly (CHA) in the presence of a couple of hairpin structures in solution. Such a reaction allows producing duplexes that can be monitored by MCE-LIF. The fluorescence intensity of CHA products (I_P) increased and that of hairpin DNAs (I_R) decreased with the increase of target concentrations. The signal ratios (I_P/I_R and I_P'/I_R') consisted of targets. The assay was employed for Hg²⁺ and Ag⁺ detection in several mediums including water, milk, and fish samples with complex matrices. The results showed that the assay could avoid matrix interference to increase the sensitivity. Therefore, the multiplexed assay was ideal to simultaneously and quickly detect metal ions in complex samples.

A multi-functional chemosensor for highly selective ratiometric fluorescent detection of silver(I) ion and dual turn-on fluorescent and colorimetric detection of sulfide

A multi-functional chemosensor 1 as silver and sulfide detector was synthesized by the combination of octopamine and 4-dimethylaminocinnamaldehyde. Sensor 1 exhibited a ratiometric fluorescence emission for Ag+ from blue to sky. The binding mode of 1 and Ag+ turned out to be a 1 : 1 ratio as determined using Job plot and electrospray ionization (ESI) mass spectral analyses. The sensing mechanism of 1 with silver ion was unravelled by 1H NMR titrations and theoretical calculations. Sensor 1 also discerned sulfide by enhancing fluorescence intensity and changing colour from yellow to colourless in aqueous solution. The sensing properties of 1 toward S2- were investigated by using ESI-mass analysis, Job plot and 1H NMR titrations. Moreover, 1 could be used as a detector for sulfide in a wide pH range.

A highly selective TPE-based AIE fluorescent probe is developed for the detection of Ag+

The detection of Ag⁺ in the environment is very important to determine the level of pollution from silver complexes, which have caused various human health problems. Herein, an aggregation-induced emission (AIE) chromophore (tetraphenylethane, TPE) attached to a benzimidazole group (tetra-benzimidazole, TBI–TPE) is synthesized and utilized to detect Ag⁺ in the environment. The strong chelating effect between the benzimidazole group and Ag⁺ leads to the formation of aggregates, and strong yellow fluorescence signals were observed after adding Ag⁺ into a TBI–TPE solution. The stoichiometry of the complex of TBI–TPE and Ag⁺ was established to be 1 : 2 using photochemical and mass spectra measurements. The detection limit of the Ag⁺ assay is 90 nM with a linear range from 100 nM to 6 μM. This study provides a facile method to determine Ag⁺ in real environmental samples with satisfactory results.

We develop a highly selective TPE-based AIE fluorescent probe containing a benzimidazole group for the detection of Ag⁺.

A New Reactive 1,8-Naphthalimide Derivative for Highly Selective and Sensitive Detection of Hg2

A 1,8-naphthalimide derivative with a reactive aliphatic hydroxyl was designed and synthesized as a fluorescent probe. Its structure was characterized by IR, ¹H NMR, ¹³C NMR, LC-MS and HPLC. The probe showed high selectivity and sensitivity to Hg²⁺ over other metal ions such as Pb²⁺, Na⁺, K⁺, Cd²⁺, Cr³⁺, Zn²⁺, Cu²⁺, Ni²⁺, Ca²⁺, Fe³⁺, Fe²⁺, Co²⁺, Mn²⁺ and Mg²⁺ in MeCN/H₂O (15/85, v/v). The increase in fluorescence intensity was linearly proportional to the concentration of Hg²⁺ in the range of 18-40 μM with a detection limit of 1.38 × 10^-7 mol/L. The probe could work in a pH span of 4.3-9.0 and respond to Hg²⁺ quickly with strong anti-interference ability. Job's plot suggested a 1:2 complex of the probe and Hg²⁺.

A fluorescence “turn-on” chemosensor for Hg2+and Ag+based on NBD (7-nitrobenzo-2-oxa-1,3-diazolyl)

A fluorescence “turn-on” chemosensor for the simultaneous detection of Hg²⁺and Ag⁺was developed and practically applied with test strips.

Transition metal based single chained surfactants: synthesis, aggregation behavior and enhanced photoluminescence properties of fluorescein

Four different transition metal based surfactants were synthesized. The effect of presence of metal as a part of counter ion on the aggregation behaviour of metallosurfactants and on the photophysical properties of fluorescein was explored.