Hassan A. Azab

Synthesis and fluorescence properties of Eu-anthracene-9-carboxylic acid towards N-acetyl amino acids and nucleotides in different solvents

Europium (III) complex with anthracene-9-carboxylic acid (9-AA) has been synthesized and characterized by elemental analysis, FT-IR, and TG-DTG techniques. The results indicated that the composition of this complex is Eu (9-AA)(3). The luminescence properties of the complex in different solvents and at different pH values have been investigated. The results show that the complex exhibits more efficient luminescence in THF and ethyl acetate. The interactions of Eu-complex with different N-acetyl amino acids and nucleotides in different solvents have been investigated by fluorescence measurements. Enhancement of the fluorescence intensities has been observed in cyclohexane, acetone, acetonitrile, and tetrahydrofuran whereas the fluorescence intensities of the investigated complex in ethanol, water, and ethyl acetate exhibit relatively low intensity.

Luminescence recognition of different organophosphorus pesticides by the luminescent Eu(III)–pyridine-2,6-dicarboxylic acid probe

Luminescence quenching of a novel long lived Eu(III)-pyridine-2,6-dicarboxylic acid probe of 1:2 stoichiometric ratio has been studied in 0.10 volume fraction ethanol-water mixture at pH 7.5 (HEPES buffer) in the presence of the organophosphorus pesticides chlorfenvinphos (P1), malathion (P2), azinphos (P3), and paraxon ethyl (P4). The luminescence intensity of Eu(III)-(PDCA)(2) probe decreases as the concentration of the pesticide increases. It was observed that the quenching due to P3 and P4 proceeds via both diffusional and static quenching processes. Direct methods for the determination of the pesticides under investigation have been developed using the luminescence quenching of Eu(III)-pyridine-2,6-dicarboxylic acid probe in solution. The linear range for determination of the selected pesticides is 1.0-35.0 μM. The detection limits were 0.24-0.55 μM for P3, P4, and P1 and 2.5 μM for P2, respectively. The binding constants (K), and thermodynamic parameters of the OPs with Eu(III)-(PDCA)(2) were evaluated. Positive and negative values of entropy (ΔS) and enthalpy (ΔH) changes for Eu(III)-(PDCA)(2)-P1 ternary complex were calculated. As the waters in this study do not contain the above mentioned OPs over the limit detectable by the method, a recovery study was carried out after the addition of the adequate amounts of the organophosphorus pesticides under investigation.

High-throughput sensing microtiter plate for determination of biogenic amines in seafood using fluorescence or eye-vision

A new optical sensing microplate was developed for rapid screening for the presence of biogenic amines (BAs) in seafood samples with high sensitivity. The deposition of a sensing spot (containing a chameleon dye (Py-1) in a polymeric cocktail) on the bottom of the wells of a standard microplate renders the plate a new sensing tool for a rapid and parallel detection of up to 96 (real) samples. This sensing microplate enables (1) a semi-quantitative readout of analyte concentration by eye-vision, (2) a rapid fluorescence readout of 96 samples with standard instrumentation in less than two minutes (unlike chromatographic and electrophoretic methods), (3) a statistically robust data evaluation (with 8-12 replicates) and (4) a rapid parallel sample preparation with standard 8 or 12-channel micropipettes. On reaction with biogenic amines, the dye shows a significant visible color change from blue over green to red color. The appearance of red color favorably coincides with the concentration of BAs that can induce symptoms of poisoning. The linear ranges of fluorescence calibration data for six biogenic amines cover the clinical toxicological relevant range of BAs that is too low to be detected by the human nose. The LODs range from 0.16 to 0.56 μg mL(-1), with correlation coefficients (r(2)) between 0.985 and 0.999. Finally, the evolution of spoilage of four fish samples (monitored by determination of their BA status) and the increase of their total amine content were found to agree well with previous data on time-dependent evolution of BAs in fish.

A novel luminescent terbium-3-carboxycoumarin probe for time-resolved fluorescence sensing of pesticides methomyl, aldicarb and prometryne

The luminescence arising from lanthanide cations offers several advantages over organic fluorescent molecules: sharp, distinctive emission bands allow for easy resolution between multiple lanthanide signals; long emission lifetimes (μs-ms) make them excellent candidates for time-resolved measurements; and high resistance to photo bleaching allow for long or repeated experiments. A time-resolved (gated) luminescence-based method for determination of pesticides methomyl, aldicarb and prometryne in microtiterplate format using the long-lived terbium-3-carboxycoumarin in 1:3 metal:ligand ratio has been developed. The limit of detection is 1.20×10(6), 5.19×10(5) and 2.74×10(6)ng L(-1) for methomyl, prometryne and aldicarb, respectively. The quantum yield (QY=0.08) of Tb(III)-3-carboxycoumarin was determined using 3-(2-benzothiazolyl)-7-diethylamino-coumarin (coumarin 6). Stern-volmer studies at different temperatures indicate that collisional quenching dominates for methomyl, aldicarb and prometryne. Binding constants were determined at 303, 308 and 313 K by using Lineweaver-Burk equation. A thermodynamic analysis showed that the reaction is spontaneous with negative ΔG. Effect of some relevant interferents on the detection of pesticides has been investigated.

A novel anti-tumor agent, Ln(III) 2-thioacetate benzothiazole induces anti-angiogenic effect and cell death in cancer cell lines.

New complexes with a potent DNA-binding anti-tumor agent, europium(III)- and terbium(III)-2-thioacetate benzothiazole were synthesized and characterized. These complexes showed strong binding affinity to calf thymus DNA using fluorometric and electronic absorption spectroscopy. The synthesized complexes resulted in inhibition of proliferation of EAC cells and ascites formation. Their anti-tumor effect was found to be through anti-angiogenic activity as was evident by the reduction of microvessel density and down-regulation of VEGF receptor type-2 (Flk-1). It was found that EAC cells had distinct DNA fragmentation patterns analyzed by capillary electrophoresis in the treated animals. Moreover, the synthesized complexes exhibited significant cytotoxic activity against HepG2 and MCF7 cell lines. Furthermore, complexes showed a potent anti-bacterial activity against two pathogenic bacteria Escherichia coli and Salmonella.

Time-resolved fluorescence sensing of pesticides chlorpyrifos, crotoxyphos and endosulfan by the luminescent Eu(III)-8-allyl-3- carboxycoumarin probe

This work describes the application of time resolved fluorescence in microtiter plates for investigating the interactions of europium-allyl-3-carboxycoumarin with pesticides chlorpyrifos, endosulfan and crotoxyphos. Stern-Volmer studies at different temperatures for chlorpyrifos and crotoxyphos shows dynamic and static quenching mechanisms respectively. Direct methods for the determination of the pesticides under investigation have been developed using the luminescence variations of the probe in solution. The detection limits are 6.53, 0.004, 3.72 μmol/L for chlorpyrifos, endosulfan, and crotoxyphos, respectively. The binding constants and thermodynamic parameters of the pesticides with probe were evaluated. A thermodynamic analysis showed that the reaction is spontaneous with negative ΔG. Effect of some relevant interferents on the detection of pesticides has been investigated. The new method was applied to the determination of the pesticides in different types of water samples (tap, mineral, and waste water).

Bis(acridine-9-carboxylate)-nitro-europium(III) dihydrate complex a new apoptotic agent through Flk-1 down regulation, caspase-3 activation and oligonucleosomes DNA fragmentation

New bis(acridine-9-carboxylate)-nitro-europium(III) dihydrate complex was synthesized and characterized. In vivo anti-angiogenic activities of bis(acridine-9-carboxylate)-nitro-europium(III) dihydrate complex against Ehrlich ascites carcinoma (EAC) cells are described. The newly synthesized complex resulted in inhibition of proliferation of EAC cells and ascites formation. The anti-tumor effect was found to be through anti-angiogenic activity as evident by the reduction of microvessel density in EAC solid tumors. The anti-angiogenic effect is mediated through down-regulation of VEGF receptor type-2 (Flk-1). The complex was also found to significantly increase the level of caspase-3 in laboratory animals compared to the acridine ligand and to the control group. This was also consistent with the DNA fragmentation detected by capillary electrophoresis that proved the apoptotic effect of the new complex. Our complex exhibited anti-angiogenic and apoptotic activity in vivo, a thing that makes it a potential effective chemotherapeutic agent. The interaction of calf thymus DNA (ct-DNA) with bis(acridine-9-carboxylate)-nitro-europium(III) dihydrate complex has been investigated using fluorescence technique. A competitive experiment of the europium(III)-acridine complex with ethidium bromide (EB) to bind DNA revealed that interaction between the europium(III)-acridine and DNA was via intercalation. The interaction of the synthesized complex with tyrosine kinases was also studied using molecular docking simulation to further substantiate its mode of action.

PHYSICO-CHEMICAL PROPERTIES OF Nd(III) AND Er(III) COMPLEXES WITH SOME BIOLOGICAL BUFFER LIGANDS

The new Nd(III) and Er(III) complexes with the zwitterionic buffer ligands N-tris[hydroxymethyl]methyl-3-aminopropanesulfonic acid sodium salt (NaTAPS) and 3-[N,N-bis(2-hydroxyethyl) amino]-2-hydroxypropanesulfonic acid sodium salt (NaDIPSO) have been prepared and characterized by IR, DTA, TG, mass, elemental analyses and electrical conductivity measurements. The Nd(III) complexes may be formulated as [Nd(DIPSO)2H2O)n]NO3· mH2O, where n = 1 and m = 1 for NaDIPSO as ligand while n = 2 and m = 0 for NaTAPS as ligand, [Nd(TAPS)2(H2O)n]NO3. The Er(III) complexes may be described as [Er(DIPSO)2(H2O)n]Cl · mH2O, where n = m = 2 for NaDIPSO as ligand while n = 2 and m = 0 for NaTAPS as ligand. Thermogravemetric studies show that the Er(III) complexes are thermally more stable than the Nd(III) complexes. The electrical conductivity of DMF solutions of these complexes indicate 1:1 electrolytic behavior.