Zirconium-based hydrophobic-MOFs as innovative electrode modifiers for flibanserin determination: Exploring the electrooxidation mechanism using a comprehensive spectroelectrochemical study.

Three different types of Zr-based MOFs derived from benzene dicarboxylic acid (BDC) and naphthalene dicarboxylic acid as organic linkers (ZrBDC, 2,6-ZrNDC, and 1,4-ZrNDC) were synthesized. They were characterized using X-ray diffraction analysis (XRD), X-ray photoelectron spectroscopy (XPS), Fourier-transform IR spectroscopy (FT-IR), and Transmission electron microscopy (TEM). Their hydrophilic/hydrophobic nature was investigated via contact angle measurements; ZrBDC MOF was hydrophilic and the other two (ZrNDC) MOFs were hydrophobic. The three MOFs were combined with MWCNTs as electrode modifiers for the determination of a hydrophobic analyte, flibanserin (FLB), as a proof-of-concept analyte. Under the optimized experimental conditions, a significant enhancement in the oxidation peak current of FLB was observed when utilizing 2,6-ZrNDC and 1,4-ZrNDC, being the highest when using 1,4-ZrNDC. Furthermore, a thorough investigation of the complex oxidation pathway of FLB was performed by carrying out simultaneous spectroelectrochemical measurements. Based on the obtained results, it was verified that the piperazine moiety of FLB is the primary site for electrochemical oxidation. The fabricated sensor based on 1,4-ZrNDC/MW/CPE showed an oxidation peak of FLB at 0.8 V vs Ag/AgCl. Moreover, it showed excellent linearity for the determination of FLB in the range 0.05 to 0.80 µmol L-1 with a correlation coefficient (r) = 0.9973 and limit of detection of 3.0 nmol L-1. The applicability of the developed approach was demonstrated by determination of FLB in pharmaceutical tablets and human urine samples with acceptable repeatability (% RSD values were below 1.9% and 2.1%, respectively) and reasonable recovery values (ranged between 97 and 103% for pharmaceutical tablets and between 96 and 102% for human urine samples). The outcomes of the suggested methodology can be utilized for the determination of other hydrophobic compounds of pharmaceutical or biological interest with the aim of achieving low detection limits of these compounds in various matrices.

In vitro assessment of PEG-6000 coated-ZnO nanoparticles: modulating action to the resisted antibiotic activity against APEC.

BACKGROUND: Avian pathogenic Escherichia coli (APEC) are considered a growing health problem to both poultry and the public, particularly due to its multi-drug resistance. Zinc oxide nanoparticles (ZnO-NPs) are a promising multi-benefit candidate. This study focused on boosting the antimicrobial effect of the chemically synthesized ZnO-NPs using Polyethylene glycol-6000 (PEG-6000) and evaluating their potential to recover the sensitivity of Florfenicol and Streptomycin-resistant APEC to these drugs in a concentration range of 0.1-0.4 mg/mL. Four samples of ZnO-NPs were formulated and tested microbiologically. RESULTS: The physicochemical characterization showed well-crystallized spherical in situ synthesized ZnO-NPs using PEG-6000 (surfactant) and ethanol (co-surfactant) of ∼19-67 nm particle size after coating with PEG-6000 molecules. These ZnO-NPs demonstrated a strong concentration-dependent antibacterial effect against multidrug-resistant APEC strains, with a minimum inhibitory concentration of 0.1 mg/mL, Combining PEG-6000 coated in situ synthesized ZnO-NPs and Florfenicol induced 60% high sensitivity (30 mm inhibitory-zone), 30% intermediate sensitivity, and 10% resistance against APEC strains. The combination with Streptomycin revealed 50% high sensitivity, 30% intermediate sensitivity, and 20% resistance with a 20 mm maximum zone of inhibition using agar well diffusion test. CONCLUSION: In situ preparation of ZnO-NPs using PEG-6000 and ethanol followed by coating with PEG-6000 enhanced its antibacterial activity in minimum inhibitory concentration and regained the efficacy of Florfenicol and Streptomycin against APEC, referring to a non-antibiotic antimicrobial alternative and an effective combination regimen against multidrug-resistant APEC E. coli in veterinary medicine.

Structural, optical and photocatalytic properties of mesoporous CuO nanoparticles with tunable size and different morphologies.

Nanomaterials with controllable particle size and shape have fascinating properties. Herein, CuO nanoparticles (NPs) with controlled particle size and morphology are obtained via a simple co-precipitation approach. Variation of the reaction medium composition steers the variation of both particle size and morphology of the CuO NPs. The reaction was performed in ethanol-water solutions with different volume to volume ratios (v/v%) i.e. 0, 25, 50, and 100%. XRD of the obtained samples revealed a drop in their particle size from ∼13 to ∼7 nm when the aqueous medium is entirely replaced by the ethanolic medium. TEM and HR-TEM investigations have pointed to the formation of CuO NPs with rod-like shapes in water (diameter = 15 nm and length = 200 nm). Whereas, spherical NPs with a diameter of 7.2 nm are obtained in ethanol. Structural analysis of CuO samples obtained in different media was done applying the Rietveld method. The volume of the monoclinic unit cell of CuO is increased to 81.869 Å3 when water (81.207 Å3) is completely substituted by ethanol. Moreover, the internal local strain (ε) and the dislocation density (δ) values increase from 2.78 × 10-3 to 4.64 × 10-3 and 0.592 × 106 to 1.93 × 106 line per m2, respectively by changing from aqueous to ethanolic medium. The optical band gap (E g) determined using Tauc's equation for the direct transition is increased from 2.2 to 2.65 eV when water is totally replaced by ethanol. The feasibility of both CuO samples as photocatalysts for the degradation of Congo red was tested. CuO prepared in pure water showed remarkably high efficiency during the first 25 min of illumination. Both samples showed complete dye removal after 35 min. Ultimately, this work presents a simple and green approach for the preparation of CuO NPs with tunable particle size, varied morphological shapes, high surface area, and different structural and optical properties merely through controlling the ethanol content in water.

ε-MnO2-modified graphite electrode as a novel electrochemical sensor for the ultrasensitive detection of the newly FDA approved Hepatitis C antiviral drug ledipasvir.

A novel, simple and sensitive electrochemical method for the determination of ledipasvir (LED), the newly FDA approved Hepatitis C antiviral drug was developed and validated using ε-MnO2-modified graphite electrode. Two different MnO2 polymorphs (γ- and ε-MnO2 nanoparticles) were synthesized and characterized using X-ray powder diffraction (XRD), Fourier transform infrared (FTIR), energy dispersive X-ray (EDX) and thermogravimetric analysis (TGA). Surface area measurements show that ε-MnO2 NPs have large surface area of 345 m2/g, which is extremely high if compared to that of γ-MnO2 NPs (38 m2/g). In addition, a comprehensive study of the difference in the electrochemical behavior of LED while using pencil graphite electrode (PGE) modified with either γ- or ε-MnO2 NPs is carried out. It was found that surface area and percentage of surface hydroxyls of MnO2 NPs are the key factors governing the sensitivity of the fabricated electrode toward the oxidation of the positively charged LED. Scanning electron microscopy (SEM) was employed to investigate the morphological shape of MnO2 NPs and the surface of the bare and modified electrodes. Moreover, cyclic voltammetry and electrochemical impedance spectroscopy (EIS) were used for the surface analysis of the modified electrodes. Based on the obtained results, ε-MnO2/PGE was applied as a selective and sensitive electrode for determination of LED. Under the optimized experimental conditions, ε-MnO2/PGE provides a linear response over the concentration range of 0.025-3.60 µmol L-1 LED with a low limit of detection, which was found to be 5.10 nmol L-1 (4.50 ng mL-1) for the 1st peak and 9.20 nmol L-1 (8.10 ng mL-1) for the 2nd one. In addition, the oxidation behavior of LED is discussed with a full investigation of the oxidized product using FT-IR and LC/MS. The fabricated sensor exhibits a good precision, selectivity and stability and was applied successfully for the determination of LED in its tablets and real rat plasma samples with a good recovery using a simple extraction technique.

Ultrasound assisted facile synthesis of Mn(II) and Cu(II) coordination polymers and their use as precursors for α-Mn3O4 and CuO nanoparticles: Synthesis, characterization and catalytic properties.

A self-assembly of pyridine-2,6-dicarboxylate with Cu(II) and Mn(II) under ultrasonic and microwave irradiation gave the two coordination polymers [Cu(PDA)(H2O)1.5]n (1) and [Mn(PDA)(H2O)1.5]n (2). Their structures were characterized using IR, elemental analysis, X-ray diffraction (XRD) and spectroscopic methods. The corresponding α-Mn3O4 and CuO nanoparticles were synthesized by calcination of 1 and 2 in air at 600 °C. Transmission electron microscopy (TEM) reveals a sphere-like morphology for the Mn3O4 nanoparticles. Shrinkage of the particle size from 90 nm (by conventional synthesis of the precursor) to 19 nm (ultrasonic-assisted) takes place, indicating the great effect of ultrasonication. CuO nanoparticles were of semispherical (conventional and ultrasonic-assisted methods) and hexagonal shapes (microwave irradiation) with an average diameter of 7, 15 and 25 nm, respectively. The catalytic performance of the coordination polymers towards degradation of methylene blue and methyl orange in the presence of hydrogen peroxide was studied. Using the same dose, catalyst 1 proved to be more efficient in color removal of both MB and MO than catalyst 2 did. Recycling test for 2 showed that it is a recyclable catalyst with no structural changes over three recycling experiments.

Fabrication of novel electrochemical sensors based on modification with different polymorphs of MnO2 nanoparticles. Application to furosemide analysis in pharmaceutical and urine samples.

A novel MnO2 nanoparticles/chitosan-modified pencil graphite electrode (MnO2 NPs/CS/PGE) was constructed using two different MnO2 polymorphs (γ-MnO2 and ε-MnO2 nanoparticles). X-ray single phases of these two polymorphs were obtained by the comproportionation reaction between MnCl2 and KMnO4 (molar ratio of 5 : 1). The temperature of this reaction is the key factor governing the formation of the two polymorphs. Their structures were confirmed by powder X-ray diffraction (XRD), Fourier transform infrared (FTIR) and energy dispersive X-ray (EDX) analysis. Scanning electron microscopy (SEM) was employed to investigate the morphological shape of MnO2 NPs and the surface of the bare and modified electrodes. Moreover, cyclic voltammetry and electrochemical impedance spectroscopy (EIS) were used for surface analysis of the modified electrodes. Compared to bare PGE, MnO2 NPs/CS/PGE shows higher effective surface area and excellent electrocatalytic activity towards the oxidation of the standard K3[Fe(CN)6]. The influence of different suspending solvents on the electrocatalytic activity of MnO2 was studied in detail. It was found that tetrahydrofuran (THF) is the optimum suspending solvent regarding the peak current signal and electrode kinetics. The results reveal that the modified γ-MnO2/CS/PGE is the most sensitive one compared to the other modified electrodes under investigation. The modified γ-MnO2/CS/PGE was applied for selective and sensitive determination of FUR. Under the optimized experimental conditions, γ-MnO2/CS/PGE provides a linear response over the concentration range of 0.05 to 4.20 µmol L-1 FUR with a low limit of detection, which was found to be 4.44 nmol L-1 (1.47 ng mL-1) for the 1st peak and 3.88 nmol L-1 (1.28 ng mL-1) for the 2nd one. The fabricated sensor exhibits a good reproducibility and selectivity and was applied successfully for the determination of FUR in its dosage forms and in spiked urine samples with good accuracy and precision.