Preparation of Novel Composites of Polyvinyl Alcohol Containing Hesperidin Loaded ZnO Nanoparticles and Determination of Their Biological and Thermal Properties.

Hesperidin (HSP) is considered to be the most effective antimicrobial agent against SARS-CoV2 virus. The HSP was loaded onto ZnO nanoparticles that were successfully incorporated, via the hydrothermal method, into polyvinyl alcohol (PVA) for use as food packaging material. The hydrothermal method enabled the bioactive ZnO-HSP to be homogeneously dispersed in the PVA, which significantly increased the thermal stability of the matrix, while decreasing the softening temperature. The water holding capacity and water solubility of the obtained nanocomposites was reduced compared to the PVA. Finally, the ZnO-HSP antimicrobial agent contributed important antibacterial properties to the PVA and increased its antioxidant capacity against Staphylococcus aureus and Escherichia coli pathogens. In addition, the nanocomposites had no cytotoxic/proliferative effects on cancer cells. All results showed promise that the PVA/ZnO-HSP nanocomposites would be an excellent alternative for food packaging applications.

Synergistic effect of ZnO nanoparticles and hesperidin on the antibacterial properties of chitosan.

In this study, hesperidin (HSP) biological agent, which has strong antioxidant properties, was successfully transferred to ZnO nanoparticles, which were first synthesized by the hydrothermal method. Then, chitosan (CS)/ZnO-HSP nanocomposites were produced by adding different ratios of the ZnO-HSPs to the biodegradable CS biopolymer by hydrothermal method. The resulting materials were characterized using various biophysical strategies, including X-ray diffraction (XRD), Fourier transform infrared spectrometry, scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy. The mean particle size of ZnO was estimated to be 29 nm from the XRD calculations and SEM measurements. The effect of the ZnO-HSPs on the thermal properties of pure CS was investigated by thermogravimetric analysis and differential scanning calorimetry techniques, and improvements were noted in the thermal properties of CS. While the Tg value of CS was 81 °C, this value increased by 13-94 °C with the addition of 6 wt% by weight of the ZnO-HSP. The antibacterial effect of materials was determined by the disc diffusion method. The ZnO-HSPs added to the CS caused the nanocomposites to have a remarkable effect against Escherichia coli and Staphylococcus aureus microorganisms. While the inhibition diameter of the CS against E. coli was 18.3, the same value increased to 22.3 for the composite containing 6 wt% the ZnO-HSP. The HSP increased the antioxidant capacity of both the ZnO-HSP particles and the CS/ZnO-HSP nanocomposites, reducing the toxic effects of ZnO nanoparticles. Thus, it was determined that the CS/ZnO-HSP nanocomposites did not have any cytotoxicity in healthy human cells. The fact that the produced nanocomposites exhibit antibacterial activity and do not harm human cells shows that they can be a safe product for health. From all these results, this triple hybrid system is hoped that it will be used in biomedical applications as a naturally-sourced, environmentally friendly, and cost-effective composite biomaterial by combining its antimicrobial and strong antioxidant properties.

Synthesis of Moringa oleifera coated silver-containing nanocomposites of a new methacrylate polymer having pendant fluoroarylketone by hydrothermal technique and investigation of thermal, optical, dielectric and biological properties.

Firstly, silver nanoparticles were synthesized by green synthesis method from Moringa oleifera extract. Nanocomposites containing newly synthesized methacrylate polymer, poly 2-(4-fluorophenyl)-2-oxoethyl-2-methylprop-2-enoate (PFPAMA) and Ag nanoparticles from M. oleifera in different mass ratios (1, 3, and 5 wt%) were synthesized using the hydrothermal method. The morphological and structural properties of the materials have been examined by SEM, FTIR, UV, TGA, and XRD techniques. The activation energies (Ea) related to thermal decomposition of the nanocomposites were estimated by the Flynn-Wall-Ozawa and Kissinger-Akahira-Sunose methods by using non-isothermal TGA experiments. The thermal stability, glass transition temperature (Tg), and the thermal decomposition activation energy (Ea) values of nanocomposites were increased by increasing the Ag nanoparticles amount on the composite. The dielectric constant (ε'), the dielectric loss factor (ε″) and ac conductivity of neat PFPAMA and nanocomposites were also measured for the frequency range of 100 Hz to 2 kHz at 25 °C. It was seen that the frequency dependence of the dielectric constant and dielectric loss factor decreased with increasing frequency. The biological activities of nanocomposites against gram-positive (Staphylococcus aureus), gram-negative (Escherichia coli) bacteria and Candida krusei yeast were also tested. The antibacterial effect increased against both bacterial species as the amount of Ag nanoparticles from M. oleifera in the nanocomposites increased. In addition, the wound healing properties of nanocomposites were investigated by the scratch wound test.

Physical and chemical effects of acoustic cavitation in selected ultrasonic cleaning applications.

Acoustic cavitation in a liquid medium generates several physical and chemical effects. The oscillation and collapse of cavitation bubbles, driven at low ultrasonic frequencies (e.g., 20 kHz), can generate strong shear forces, microjets, microstreaming and shockwaves. Such strong physical forces have been used in cleaning and flux improvement of ultrafiltration processes. These physical effects have also been shown to deactivate pathogens. The efficiency of deactivation of pathogens is not only dependent on ultrasonic experimental parameters, but also on the properties of the pathogens themselves. Bacteria with thick shell wall are found to be resistant to ultrasonic deactivation process. Some evidence does suggest that the chemical effects (radicals) of acoustic cavitation are also effective in deactivating pathogens. Another aspect of cleaning, namely, purification of water contaminated with organic and inorganic pollutants, has also been discussed in detail. Strong oxidising agents produced within acoustic cavitation bubbles could be used to degrade organic pollutants and convert toxic inorganic pollutants to less harmful substances. The effect of ultrasonic frequency and surface activity of solutes on the sonochemical degradation efficiency has also been discussed in this overview.

Initial growth of sonochemically active and sonoluminescence bubbles at various frequencies.

The initial growth of acoustic cavitation activity is important in some applications such as therapeutic and diagnostic medicine. The initial growth of cavitation activity has been investigated using sonoluminescence and sonochemical activity (sonochemiluminescence) at 358 kHz, 647 kHz and 1062 kHz and at 5 W, 15 W and 30 W applied power levels. The growth of sonochemically active bubble population is found to be much faster than that of sonoluminescence bubble population at 358 kHz and 647 kHz whereas almost similar growth rate is observed at 1062 kHz for both bubble populations. This suggests that the cavitation bubble resonance size ranges of sonoluminescence and sonochemically active bubbles are different at 358 kHz and 647 kHz, whereas they have similar size range at 1062 kHz. At 358 kHz and 647 kHz, relatively smaller bubbles become chemically active. Possible reasons for such observations have been discussed. The data presented and discussed in this study may be useful in controlling the growth of cavitation bubble population in addition to enhancing the knowledge base in cavitation science.

Crystal structure of [[mu-bis(salicylidene)-1,3-propanediaminato]copper(II)]dibromozinc(II).

The title compound is a double oxygen-bridged dimeric heteronuclear metal complex. The coordination around the Cu atom is distorted square-planar involving two O and two N atoms from the bis(salicylidene)-1,3-propanediamine ligand. The Zn atom in the molecule has a distorted tetrahedral coordination sphere consisting of the two O atoms of the ligand and the two Br atoms. The bridging plane between the metal atoms is not planar.