Uncovering an effecient binary system as a chemosensor for visual and fluorescence detection of chromium (VI) in water samples.

There is an urgent requirement for the development of sensitive and quick sensors to monitor chromium (VI) due to its substantial carcinogenic and mutagenic properties. A coexisting system of coumarin 334 and diphenylcarbazide (C334/DPC) was used in this study as a fluorescent chemosensor to detect Cr(VI) ions. Upon the addition of Cr(VI), a purple chelate complex (Cr(III)-diphenylcarbazone) was produced, which resulted from the quantitative reaction between Cr(VI) ions and diphenylcarbazide (DPC), whereas no interaction between Cr(VI) and coumarin 334 took place. More interestingly, the absorption spectra of purple (Cr(III)-diphenylcarbazone) complex (λmax = 540 nm) were overlapped with emission and excitation spectra of coumarin 334 (λex/em = 453/492), resulting in the efficient quenching of coumarin 334 (C334) via the inner filter effect. Furthermore, the semi-quantitative estimation of Cr(VI) ion concentration may be achieved by visually watching the progressive color transformation of the probe from yellow to red after the addition different concentration of Cr(VI). The calibration plot for determination of Cr(VI) by this method is ranging from 0.048 to 268 µM. DFT calculations were conducted to enrich our understanding about the mechanism of action. This approach demonstrates an excellent selectivity and sensitivity for Cr(VI) including a detection limit of 48 nM. The new sensor was successfully applied to water samples (tap, mineral, and waste waters). The accuracy was confirmed by the atomic absorption spectroscopy.

Luminescent and time-resolved determination of gemifloxacin mesylate in pharmaceutical formulations and spiked blood plasma samples using a lanthanide complex as a probe.

A novel luminescence-based analytical methodology was established employing a europium(III) complex with 3-allyl-2-hydroxybenzohydrazide (HAZ) as the coordinating ligand for the quantification of gemifloxacin mesylate (GMF) in pharmaceutical preparations and human plasma samples spiked with the compound. The stoichiometry of the europium complex with HAZ was determined via the Job plot and exhibited a metal-to-ligand ratio of 1 : 2. The analytical procedure relies on a rapid and significant enhancement of luminescence by the Eu(AZ)2 complex when it interacts with gemifloxacin mesylate, which allowed for the rapid detection of 96 samples within approximately 2 minutes. The thermodynamic parameters of the complexation of GMF with Eu(AZ)2 were evaluated and showed that the complexation of GMF was spontaneous with a negative ΔG. The binding constant K was 4.27 × 105 L mol-1 and DFT calculations supported GMF binding and the formation of Eu(AZ)2-GMF without further ligand exchange. The calibration graph for the luminescence quantitation of GMF was linear over a wide concentration range of 0.11-16 µg mL-1 (2.26 × 10-7 to 3.30 × 10-5 mol L-1), with a limit of quantification (LOQ) of 110 ng mL-1 (230 nmol L-1) and a detection limit (LOD) of 40 ng mL-1 (82 nmol L-1). The proposed method showed good accuracy with an average recovery of 99% with relative standard deviations of less than 5% in spiking experiments, even in complex pharmaceutical dosage forms such as tablets and in human blood plasma. Herein, the ability of the suppression of the luminescence background by using the long lag times of the lanthanide probe in a time-resolved detection scheme provided reliable and precise results, which suggests its potential for use in further real or patient samples.

Development of an optical sensor for the determination of phenolic compounds in environmental samples.

A new optical sensor was developed for the rapid sensing of total phenolic content, which is simple, cheap, and sensitive, using the Eu(III)-(NTA)2-(Phen) complex [NTA = 1-(2-naphthoyl)-3,3,3-trifluoroacetone and Phen = 1,10 phenanthroline] as a luminescent probe at pH 7.5 using PIPES buffer. This method was based on luminescence quenching. The type of quenching during the reaction between the Eu(III)-(NTA)2-(Phen) complex and the phenolic compounds is dynamic quenching; the binding site is close to 1, and the reaction is endothermic, spontaneous, and involves hydrophobic attraction forces. The calibration curves were plotted using a sigmoidal fit giving an LOD of 0.01 µg mL-1, and the correlation coefficients are more than 0.99. For the first time, the time-resolved fluorescence technique was utilized in microtiter plates to enable the determination of 96 samples within two minutes with high sensitivity and selectivity. The proposed method was applied to three industrial wastewater samples and compared with the standard method for phenolic content determination, yielding high recoveries. This is the first luminescence method based on lanthanide complexes as probes for determining the total phenolic content in water samples.

Investigation of thymine as a potential cancer biomarker employing tryptophan with nanomaterials as a biosensor.

Tryptophan and tryptophan-based nanomaterials sensors in a solution have been developed to directly evaluate thymine. The determination of thymine has been done via quenching of the fluorescence of tryptophan and tryptophan-based nanomaterials such as graphene (Gr), graphene oxide (GO), gold nanoparticles (AuNPs), gold-silver nanocomposite (Au-Ag NC) in a physiological buffer. As the concentration of thymine rises, the fluorescence of tryptophan and tryptophan/nanomaterials becomes less intense. Trp, Trp/Gr, and tryptophan/(Au-Ag) NC systems' quenching mechanisms were dynamic, but tryptophan /GO and tryptophan/AuNPs' quenching mechanisms were static. The linear dynamic range for the determination of thy by tryptophan and tryptophan /nanomaterials is 10 to 200 µM. The detection limits for tryptophan, tryptophan /Gr, tryptophan /GO, tryptophan /AuNPs, and tryptophan/Au-Ag NC were 3.21, 14.20, 6.35, 4.67and 7.79 Μm, respectively. Thermodynamic parameters for the interaction of the Probes with Thy include the enthalpy (H°) and entropy (S°) change values, were assessed, as well as the binding constant (Ka) of Thy with Trp and Trp-based nanomaterials. A recovery study was conducted utilizing a human serum sample after the addition of the required quantity of the investigational thymine.

Sensitive ratiometric sensor for Al(III) detection in water samples using luminescence or eye-vision.

A facile, quick, and sensitive ratiometric luminescence sensor is designed for detection aluminum ions in water samples using luminescence or eye-vision. This approach relies on the emission change of the europium(III) complex with 3-(2-naphthoyl)-1,1,1,-trifluoro acetone (3-NTA) after interaction with various concentration of aluminum ions. The addition of aluminum ions suppressed the Eu(III) emission at 615 nm under 333 nm excitation, while simultaneously enhancing the ligand emission at 480 nm. Optimum detection was obtained in methanol. The quantification of aluminum ions using ratiometric method was determined by plotting the luminescence ratio (F480nm/F615nm) versus aluminum ions concentration. The calibration plot was obtained within the range 0.1-100 µM with LOD = 0.27 µM. Additionally, the concentration of aluminum ions can be estimated semi-quantitatively by visually observing the luminescence colour change of the probe from red to light green and then to dark green after being excited by a UV lamp with 365 nm. As far as we are aware, this is the first luminescent lanthanide complex-based ratiometric probe for the detection of aluminum ions. The probe showed remarkable aluminum ions selectivity relative to that of other metal ions. The suggested sensor was used effectively to identify aluminum ions in water samples with good results.

Fluorescence determination of Fe(iii) in drinking water using a new fluorescence chemosensor.

A new fluorescence chemosensor based on (Z)-2-(1-(3-oxo-3H-benzo[f]chromen-2-yl)ethylidene)hydrazine-1-carbothioamide (CEHC) has been developed for the determination of Fe(iii) in drinking water. The optimum conditions were acetate buffer solution with a pH 5.0. In this approach, the determination of Fe(iii) is based on static quenching of the luminescence of the probe upon increasing concentrations of Fe(iii). The CEHC sensor binds Fe(iii) in a 1 : 1 stoichiometry with a binding constant K a = 1.30 × 104 M-1. CEHC responds to Fe(iii) in a way that is more sensitive, selective, and quick to turn off the fluorescence than to other heavy metal ions. Selectivity was proved against seven other metal ions (Mn(ii), Al(iii), Cu(ii), Ni(ii), Zn(ii), Pb(ii), and Cd(ii)). The calibration curve was constructed based on the Stern-Volmer equation. The linear range was 2.50-150 µM with the correlation coefficient of 0.9994, and the LOD was 0.76 µM. The method was successfully applied to determine Fe(iii) in drinking water samples, and the accuracy of the chemosensor was validated by atomic absorption spectrometry.

Nanoparticles as a novel and promising antiviral platform in veterinary medicine.

Traditional veterinary virus vaccines, such as inactivated and live-attenuated vaccines, have achieved tremendous success in controlling many viral diseases of livestock and chickens worldwide. However, many recent viral outbreaks caused by different emerging and re-emerging viruses continue to be reported annually worldwide. It is therefore necessary to develop new control regimens. Nanoparticle research has received considerable attention in the last two decades as a promising platform with significant success in veterinary medicine, replacing traditional viral vector vaccines. However, the field of nanoparticle applications is still in its initial phase of growth. Here, we discuss various preparation methods, characteristics, physical properties, antiviral effects, and pharmacokinetics of well-developed nanoparticles and the potential of nanoparticles or nano-vaccines as a promising antiviral platform for veterinary medicine.

Validation of a Fluorescence Sensor Microtiterplate for Biogenic Amines in Meat and Cheese.

An optical sensor microtiterplate for quantitative analysis of the total content of biogenic amines (TAC) in meat and cheese was developed and validated for the first time. In the plate, a chameleon dye (Py-1) is embedded in a polymeric cocktail which is deposited on the bottom of the wells in a common microtiterplate. On reaction with biogenic amines (BAs), the fluorescence of Py-1 at 620 nm rapidly delivers a precise TAC. After 10 min incubation at 25 °C the determination of the TAC in various (real) samples is possible in high-throughput with a standard microplate reader. The optimized fluorescence method was validated for linearity, sensitivity, accuracy, precision (intraday and inter day repeatability) and recovery using histamine (HIS) as a representative BA. The sensor microtiterplate was successfully applied to quantitatively analyze the TAC in 10 real samples of cheese and meat obtained from various Egyptian markets. The TAC of these real samples obtained by the sensor microtiterplate was validated against the contents of BAs obtained by GC-MS at various times of storage. The data of the sensor microtiterplate agreed well with those of GC-MS. This demonstrates that the sensor microtiterplate is a reliable screening tool for the degradation status of food samples.

Fluorescence sensing of phosdrin pesticide by the luminescent Eu(III)- and Tb(III)-bis(coumarin-3-carboxylic acid) probes.

Luminescence quenching of the Eu(III)- and Tb(III)-bis (coumarin-3-carboxylic acid) (Ln(III)-(CCA)2) probes has been studied in the presence of organophosphorus or organochlorine pesticides; Phosdrin (P1), Malathion (P2), Profenofos (P3), Formothion (P4), Heptachlor (P5), and Endosulfan (P6). The luminescence intensity of lanthanide complex probes Ln(III)-(CCA)2 decreases as the concentration of the Phosdrin pesticide increases, while the other investigated pesticides have no significant influence on the lanthanide fluorescent intensities. It is observed that the quenching of Eu(III) and Tb(III)-coumarin-3-carboxylic acid by Phosdrin proceeds via static quenching processes according to Stern-Volmer plot. The binding constants (K) and the thermodynamic parameters of the interaction of Ln(III)-(CCA)2 with Phosdrin have been determined. A direct method for the determination of the Phosdrin in ethanol has been developed based on the luminescence changes of the Ln(III)-(CCA)2-phosdrin ternary complexes. The detection limits of P1 were 6.28 and 1.07 µM in case of Eu(III) and Tb(III)-complex, respectively. The influence of various interfering species on the detection of P1 has been investigated to assess the analytical applicability of the method. The new method was applied to determine the Phosdrin pesticide in different types of water samples.

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).