Physicochemical properties of surface charge-modified ZnO nanoparticles with different particle sizes

Bio-adsorption of heavy metals from aqueous solution using the ZnO-modified date pits

The bio-adsorption of heavy metals (including Cu2+, Ni2+, and Zn2+) in aqueous solution and also in an industry wastewater using the ZnO-modified date pits (MDP) as the bio-adsorbent are investigated. The fresh and used bio-adsorbents were characterized by FT-IR, SEM, BET, and XRD. The bio-adsorption parameters (including the pH of solution, the particle size of MDP, the shaking speed, the initial concentration of heavy metals, the dosing of MDP, the adsorption time, and the adsorption temperature) were screened and the data were used to optimize the bio-adsorption process and to study the bio-adsorption isotherms, kinetics, and thermodynamics. Two adsorption models (Langmuir isotherm model and Freundlich isotherm model) and three kinetic models (pseudo-first-order model, pseudo-second-order model, and intra-particle diffusion model) were applied to model the experimental data. Results show that the maximum adsorption amount of Cu2+, Ni2+, and Zn2+ on a complete monolayer of MDP are 82.4, 71.9, and 66.3 mg g-1, which are over 4 times of those of date pits-based bio-adsorbents reported in literature. The bio-adsorption of heavy metals on MDP is spontaneous and exothermic, and is regulated by chemical adsorption on the homogeneous and heterogeneous adsorption sites of MDP surface. This work demonstrates an effective modification protocol for improved bio-adsorption performance of the date pits-based bio-adsorbent, which is cheap and originally from a waste.

Antibacterial and Photocatalytic Activity of ZnO/Au and ZnO/Ag Nanocomposites

The use of a combination of nanoparticles as antimicrobial agents can be one strategy to overcome the tendency of microbes to become resistant to antibiotic action. Also, the optimization of nano-photocatalysts to efficiently remove persistent pollutants from wastewater is a hot topic. In this study, two composites ZnO/Au (1% wt.) and ZnO/Ag (1% wt.) were synthesized by simple aqueous solution methods. The structure and morphology of the r nanocomposites were analyzed by structural and optical characterization methods. The formation of AuNPs and AgNPs in these experiments was also discussed. The antimicrobial properties of ZnO, ZnO/Au, and ZnO/Ag nanomaterials were investigated against Gram-negative bacteria (Pseudomonas aeruginosa) and Gram-positive bacteria (Staphylococcus aureus). The results showed an increase of 80% in the antimicrobial activity of ZnO/Au against Pseudomonas aeruginosa compared with 30% in the case of ZnO/Ag. Similarly, in the case of the S. aureus strain tests, ZnO/Au increased the antimicrobial activity by 55% and ZnO/Ag by 33%. The photocatalytic tests indicated an improvement in the photocatalytic degradation of methylene blue (MB) under UV irradiation using ZnO/Au and ZnO/Ag nanocomposites compared to bare ZnO. The photocatalytic degradation efficiency of ZnO after 60 min of UV irradiation was ∼83%, while the addition of AuNPs enhanced the degradation rate to ∼95% (ZP2), and AgNP presence enhanced the efficiency to ∼98%. The introduction of noble metallic nanoparticles into the ZnO matrix proved to be an effective strategy to increase their antimicrobial activity against P. aeruginosa and S. aureus, and their photocatalytic activity was evaluated through the degradation of MB dye. Comparing the enhancing effects of Au and Ag, it was found that ZnO/Au was a better antimicrobial agent while ZnO/Ag was a more effective photocatalyst under UV irradiation.

Mechanisms of regulation of motility of the gastrointestinal tract and the hepatobiliary system under the chronic action of nanocolloids

Modern cutting edge technologies of chemical synthesis enable the production of unique nanostructures with excess energy and high reactivity. Uncontrolled use of such materials in the food industry and pharmacology entail a risk for the development of a nanotoxicity crisis. Using the methods of tensometry, mechanokinetic analysis, biochemical methods, and bioinformatics, the current study showed that chronic (for six months) intragastrical burdening of rats with aqueous nanocolloids (AN) ZnO and TiO₂ caused violations of the pacemaker-dependent mechanisms of regulation of spontaneous and neurotransmitter-induced contractions of the gastrointestinal tract (GIT) smooth muscles (SMs), and transformed the contraction efficiency indices (AU, in Alexandria units). Under the same conditions, the fundamental principle of distribution of physiologically relevant differences in the numeric values of the mechanokinetic parameters of spontaneous SM contractions between different parts of GIT is violated, which can potentially cause its pathological changes. Using molecular docking, typical bonds in the interfaces of the interaction of these nanomaterials with myosin II, a component of the contractile apparatus of smooth muscle cells (SMC) were investigated. In this connection, the study addressed the question of possible competitive relations between ZnO and TiO₂ nanoparticles and actin molecules for binding sites on the myosin II actin-interaction interface. In addition, using biochemical methods, it was shown that chronic long-term exposure to nanocolloids causes changes in the primary active ion transport systems of cell plasma membranes, the activity of marker liver enzymes and disrupts the blood plasma lipid profile, which indicates the hepatotoxic effect of these nanocolloids.

Phytofabrication and Characterisation of Zinc Oxide Nanoparticles Using Pure Curcumin

Zinc oxide and curcumin, on their own and in combination, have the potential as alternatives to conventional anticancer drugs. In this work, zinc oxide nanoparticles (ZnO NPs) were prepared by an eco-friendly method using pure curcumin, and their physicochemical properties were characterised. ATR-FTIR spectra confirmed the role of curcumin in synthesising zinc oxide curcumin nanoparticles (Green-ZnO-NPs). These nanoparticles exhibited a hexagonal wurtzite structure with a size and zeta potential of 27.61 ± 5.18 nm and -16.90 ± 0.26 mV, respectively. Green-ZnO-NPs showed good activity towards studied bacterial strains, including Escherichia coli, Staphylococcus aureus and methicillin-resistant Staphylococcus aureus. The minimum inhibitory concentration of Green-ZnO-NPs was consistently larger than that of chemically synthesised ZnO NPs (Std-ZnO-NPs) or mere curcumin, advocating an additive effect between the zinc oxide and curcumin. Green-ZnO-NPs demonstrated an efficient inhibitory effect towards MCF-7 cells with IC50 (20.53 ± 5.12 μg/mL) that was significantly lower compared to that of Std-ZnO-NPs (27.08 ± 0.91 μg/mL) after 48 h of treatment. When Green-ZnO-NPs were tested against Artemia larvae, a minimised cytotoxic effect was observed, with LC50 being almost three times lower compared to that of Std-ZnO-NPs (11.96 ± 1.89 μg/mL and 34.60 ± 9.45 μg/mL, respectively). This demonstrates that Green-ZnO-NPs can be a potent, additively enhanced combination delivery/therapeutic agent with the potential for anticancer therapy.

Facile Preparation and Analytical Utility of ZnO/Date Palm Fiber Nanocomposites in Lead Removal from Environmental Water Samples

This study reports a facile approach for preparing low-cost, eco-friendly nanocomposites of ZnO nanoparticles (NPs) and date palm tree fiber (DPF) as a biomass sorbent. The hypothesis of this research work is the formation of an outstanding adsorbent based on the date palm fiber and ZnO nanoparticles. ZnO NP/DPF nanocomposites were synthesized by mixing the synthesized ZnO NPs and DPF in different mass ratios and evaluating their efficacy in adsorbing Pb2+ from aqueous solutions. The structure and surface morphology of the developed ZnO NP/DPF nanocomposite were critically characterized by XRD, FESEM, and TEM techniques. Compared to ZnO NPs, the ZnO NP/DPF nanocomposites displayed significantly enhanced Pb2+ uptake. Pb2+ adsorption was confirmed via various isotherm and kinetic models and thermodynamics. The computed Langmuir sorption capacity (qm) was found to be 88.76 mg/g (R2 > 0.998), and the pseudo-second-order R2 > 0.999 model was most appropriate for describing Pb2+ adsorption. Impregnating the biomass with ZnO NPs enhanced the spontaneity of the process, and the value (−56.55 kJ/mol) of ΔH displayed the exothermic characteristics of Pb2+ retention. Only the loaded ZnO NP/DPF achieved the removal of a high percentage (84.92%) of Pb2+ from the environmental water sample (seawater). This finding suggests the use of ZnO NP/DPF nanocomposites for removing heavy metals from environmental water samples to purify the samples.

Effects of Zinc Oxide Nanoparticles Synthesized Using Aspergillus niger on Carbapenem-Resistant Klebsiella pneumonia In Vitro and In Vivo

Currently, the mortality rate in Saudi Arabia's ICUs is increasing due to the spread of Klebsiella pneumoniae carbapenemase (KPC)-producing bacteria. This study was carried out to evaluate the ability of biologically synthesized zinc oxide nanoparticles (ZnO-NPs) using Aspergillus niger to overcome carbapenem-resistant K. pneumoniae (KPC) in vitro and in vivo. ZnO-NPs were synthesized via a biological method and characterized using UV-Vis spectroscopy, Zetasizer and zeta potential analyses, x-ray diffraction spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy (SEM), and energy-dispersive x-ray spectroscopy (EDX). In vitro sensitivity of KPC to ZnO-NPs was identified using the well diffusion method. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined by a macro-dilution method. The morphological alteration of KPC cells after ZnO-NPs treatment was observed by SEM. The in vivo susceptibility of KPC cells to ZnO-NPs ointment was evaluated using wound healing in experimental rats. The chemical characterization findings showed the formation, stability, shape, and size of the synthesized nanoparticles. The MIC and MBC were 0.7 and 1.8 mg/ml, respectively. The in vivo results displayed reduced inflammation and wound re-epithelialization of KPC-infected rats. These findings demonstrated that ZnO-NPs have great potential to be developed as antibacterial agents.

Preparation of Zinc Oxide Nanoparticles using Aspergillus niger as Antimicrobial and Anticancer Agents

In the current study, zinc oxide nanoparticles (ZnO-NP) were prepared using extracellular extracts of Aspergillus niger. Hence, the morphological structure, optical, and surface features of the synthesized nanoparticles were studied by X-ray diffraction, transmission electron microscopy, ultraviolet-visible and infrared absorption by Fourier transform. Use dynamic light scattering and zeta potential measurements to assess colloidal stability. The mean size of the synthetic particles is approximately 20 ± 5 nm and they have a hexagonal crystal structure. In addition, the prepared nanoparticles have strong light absorption in the ultraviolet region of λ = 265 and 370 nm. To achieve the goal of this study, the efficiency of ZnO-NP was determined as an antibacterial and antifungal against different bacterial and fungal strains. It was found that ZnO-NP showed significant antibacterial activity, where the inhibition zones were varied from 21 to 35mm in diameter against six bacterial species (i.e. K. pneumoniae, E. coli, A. baumannii, P. aeruginosa, S. aureus, and S. haemolyticus). In such a case, the minimal inhibitory concentration of zinc oxide nanoparticles against bacterial strains were 50, 12.5, 12.5, 50, 12.5, and 12.5μg/ml for K. pneumoniae, E. coli, A. baumannii, P. aeruginosa, S. aureus, and S. haemolyticus, respectively. Furthermore, ZnO-NP exhibits an antifungal behaviour against four fungal species (i.e., A. niger, P. marneffei, C. glabrata, and C. parapsilosis) with inhibition zone from 18 to 35mm in diameter. Whereas, the MICs for fungal isolates were 12.5μg/ml except A. niger was at 25μg/ml. Wi-38 cells were treated with ZnO-NPs exhibited different levels of cytotoxicity dependent upon the concentration of ZnO NPs using the MTT assay with IC50~800.42. Therefore, the present study introduces a facile and cost-effective extracellular green-synthesis of ZnO-NP to be used as antimicrobial and anticancer agents.

Chitosan Nanocomposite Coatings Containing Chemically Resistant ZnO-SnOx Core-shell Nanoparticles for Photocatalytic Antifouling

Functional nanocomposites with biopolymers and zinc oxide (ZnO) nanoparticles is an emerging application of photocatalysis in antifouling coatings. The reduced chemical stability of ZnO in the acidic media in which chitosan is soluble affects the performance of chitosan nanocomposites in antifouling applications. In this study, a thin shell of amorphous tin dioxide (SnO_x) was grown on the surface of ZnO to form ZnO–SnO_x core–shell nanoparticles that improved the chemical stability of the photocatalyst nanoparticles, as examined at pH 3 and 6. The photocatalytic activity of ZnO–SnO_x in the degradation of methylene blue (MB) dye under visible light showed a higher efficiency than that of ZnO nanoparticles due to the passivation of electronic defects. Chitosan-based antifouling coatings with varying percentages of ZnO or ZnO–SnO_x nanoparticles, with or without the glutaraldehyde (GA) crosslinking of chitosan, were developed and studied. The incorporation of photocatalysts into the chitosan matrix enhanced the thermal stability of the coatings. Through a mesocosm study using running natural seawater, it was found that chitosan/ZnO–SnO_x/GA coatings enabled better inhibition of bacterial growth compared to chitosan coatings alone. This study demonstrates the antifouling potential of chitosan nanocomposite coatings containing core–shell nanoparticles as an effective solution for the prevention of biofouling.

Biosynthesis of Zinc Oxide Nanoparticles from Acacia nilotica (L.) Extract to Overcome Carbapenem-Resistant Klebsiella Pneumoniae

Recently, concerns have been raised globally about antimicrobial resistance, the prevalence of which has increased significantly. Carbapenem-resistant Klebsiella pneumoniae (KPC) is considered one of the most common resistant bacteria, which has spread to ICUs in Saudi Arabia. This study was established to investigate the antibacterial activity of biosynthesized zinc oxide nanoparticles (ZnO-NPs) against KPC in vitro and in vivo. In this study, we used the aqueous extract of Acacia nilotica (L.) fruits to mediate the synthesis of ZnO-NPs. The nanoparticles produced were characterized by UV-vis spectroscopy, zetasizer and zeta potential analyses, X-ray diffraction (XRD) spectroscopy, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and transmission electron microscopy (TEM). The antimicrobial activity of ZnO-NPs against KPC was determined via the well diffusion method, and determining minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC), the results showed low MIC and MBC when compared with the MIC and MBC of Imipenem and Meropenem antibiotics. The results of in vitro analysis were supported by the results upon applying ZnO-NP ointment to promote wound closure of rats, which showed better wound healing than the results with imipenem ointment. The biosynthesized ZnO-NPs showed good potential for use against bacteria due to their small size, applicability, and low toxicity to human cells.

Investigating the Internalization and COVID-19 Antiviral Computational Analysis of Optimized Nanoscale Zinc Oxide

Global trials are grappling toward identifying prosperous remediation against the ever-emerging and re-emerging pathogenic respiratory viruses. Battling coronavirus, as a model respiratory virus, via repurposing existing therapeutic agents could be a welcome move. Motivated by its well-demonstrated curative use in herpes simplex and influenza viruses, utilization of the nanoscale zinc oxide (ZnO) would be an auspicious approach. In this direction, ZnO nanoparticles (NPs) were fabricated herein and relevant aspects related to the formulation such as optimization, structure, purity, and morphology were elucidated. In silico molecular docking was conducted to speculate the possible interaction between ZnO NPs and COVID-19 targets including the ACE2 receptor, COVID-19 RNA-dependent RNA polymerase, and main protease. The cellular internalization of ZnO NPs using human lung fibroblast cells was also assessed. Optimized hexagonal and spherical ZnO nanostructures of a crystallite size of 11.50 ± 0.71 nm and positive charge were attained. The pure and characteristic hexagonal wurtzite P63mc crystal structure was also observed. Interestingly, felicitous binding of ZnO NPs with the three tested COVID-19 targets, via hydrogen bond formation, was detected. Furthermore, an enhanced dose-dependent cellular uptake was demonstrated. The obtained results infer a rationale, awaiting validation from further biological and therapeutic studies.

Antibacterial Activity of Positively and Negatively Charged Hematite (α-Fe2O3) Nanoparticles to Escherichia coli, Staphylococcus aureus and Vibrio fischeri

In the current study, the antibacterial activity of positively and negatively charged spherical hematite (α-Fe2O3) nanoparticles (NPs) with primary size of 45 and 70 nm was evaluated against clinically relevant bacteria Escherichia coli (gram-negative) and Staphylococcus aureus (gram-positive) as well as against naturally bioluminescent bacteria Vibrio fischeri (an ecotoxicological model organism). α-Fe2O3 NPs were synthesized using a simple green hydrothermal method and the surface charge was altered via citrate coating. To minimize the interference of testing environment with NP's physic-chemical properties, E. coli and S. aureus were exposed to NPs in deionized water for 30 min and 24 h, covering concentrations from 1 to 1000 mg/L. The growth inhibition was evaluated following the postexposure colony-forming ability of bacteria on toxicant-free agar plates. The positively charged α-Fe2O3 at concentrations from 100 mg/L upwards showed inhibitory activity towards E. coli already after 30 min of contact. Extending the exposure to 24 h caused total inhibition of growth at 100 mg/L. Bactericidal activity of positively charged hematite NPs against S. aureus was not observed up to 1000 mg/L. Differently from positively charged hematite NPs, negatively charged citrate-coated α-Fe2O3 NPs did not exhibit any antibacterial activity against E. coli and S. aureus even at 1000 mg/L. Confocal laser scanning microscopy and flow cytometer analysis showed that bacteria were more tightly associated with positively charged α-Fe2O3 NPs than with negatively charged citrate-coated α-Fe2O3 NPs. Moreover, the observed associations were more evident in the case of E. coli than S. aureus, being coherent with the toxicity results. Vibrio fischeri bioluminescence inhibition assays (exposure medium 2% NaCl) and colony forming ability on agar plates showed no (eco)toxicity of α-Fe2O3 (EC50 and MBC > 1000 mg/L).

The Decoration of ZnO Nanoparticles by Gamma Aminobutyric Acid, Curcumin Derivative and Silver Nanoparticles: Synthesis, Characterization and Antibacterial Evaluation

Zinc oxide nanoparticles (ZnO NPs) are applied in various applications in catalysis, biosensing, imaging, and as antibacterial agents. Here we to prepare ZnO nanomaterials decorated by γ-amino butyric acid (GABA), curcumin derivatives (CurBF₂) and silver nanoparticles (CurBF₂-AgNPs). The structures of all ZnO nanostructures were characterized using Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), UV-VIS spectrophotometry, fluorescence spectrophotometry, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HR-TEM). Further, their antibacterial activities against Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria were investigated through analysis of minimum inhibitory concentration (MIC) method. Among the prepared nanostructures, the ZnO NPs-GABA/CurBF₂-AgNPs showed excellent antibacterial activity against both Gram-positive and -negative bacteria. ZnO NPs fabricated here may have potential use in future anti-bacterial compositions and coatings technologies.

Antibacterial and anticancer activity of ZnO with different morphologies: a comparative study

ZnO nanoparticles (NPS) with different morphologies were synthesized, and the antibacterial and anticancer activity was studied, herein. The physicochemical characterization was carried out by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR) and UV-visible. To study the antibacterial and anticancer capability of ZnO NPS, Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) bacteria and HeLa cancer cells were exposed at different doses of ZnO NPS (7-250 µg/mL). TEM analysis confirmed the obtention of spherical, hexagonal and rod ZnO NPS with an average diameter of 20 ± 4 nm, 1.17 ± 0.3 µm and 1.11 ± 1.2 µm, respectively. XRD diffractograms showed the characteristic pattern of crystalline ZnO in wurtzite phase. FTIR and UV-vis spectra showed slight differences of the main absorption peaks, revealing that different ZnO NPS morphologies may cause shifts in spectra. Biological essays showed that the number of E. coli and S. aureus bacteria as well as HeLa cells decreases linearly by increasing the nanoparticle concentration. However, the best anticancer and antibacterial activity was shown by spherical ZnO NPS at 100 µg/mL. The better capability of spherical ZnO NPS than hexagonal and rod ZnO NPS is related with its small particle size. The present results suggest that the spherical ZnO NPS has a great potential as an antibacterial and anticancer agent.

Investigation of Functionalized Surface Charges of Thermoplastic Starch/Zinc Oxide Nanocomposite Films Using Polyaniline: The Potential of Improved Antibacterial Properties

Improving the antibacterial activity of biodegradable materials is crucial for combatting widespread drug-resistant bacteria and plastic pollutants. In this work, we studied polyaniline (PANI)-functionalized zinc oxide nanoparticles (ZnO NPs) to improve surface charges. A PANI-functionalized ZnO NP surface was prepared using a simple impregnation technique. The PANI functionalization of ZnO successfully increased the positive surface charge of the ZnO NPs. In addition, PANI-functionalized ZnO improved mechanical properties and thermal stability. Besides those properties, the water permeability of the bionanocomposite films was decreased due to their increased hydrophobicity. PANI-functionalized ZnO NPs were applied to thermoplastic starch (TPS) films for physical properties and antibacterial studies using Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). The PANI-functionalized ZnO bionanocomposite films exhibited excellent antibacterial activity for both E. coli (76%) and S. aureus (72%). This result suggests that PANI-functionalized ZnO NPs can improve the antibacterial activity of TPS-based bionanocomposite films.

Effects of titanium dioxide and zinc oxide nano-materials on lipid order in model membranes

Engineered nano-materials (ENM) have been reported to affect lipid membrane permeability in cell models, but a mechanistic understanding of how these materials interact with biological membranes has not been described. To assess mechanisms of permeability, liposomes composed of DOPC, DOPS, or POPC, with or without cholesterol, were used as model membranes for measuring ENM-induced changes to lipid order to improve our understanding of ENM effects on membrane permeability. Liposomes were treated with either titanium dioxide (TiO₂) or zinc oxide (ZnO) ENM, and changes to lipid order were measured by time-resolved fluorescence anisotropy of a lipophilic probe, Di-4-ANEPPDHQ. Both ENM increased lipid order in two lipid models differing in headgroup charge. TiO₂ increased lipid order of POPC liposomes (neutral charge), while ZnO acted primarily on DOPS liposomes (negative charge). Addition of cholesterol to these models significantly increased lipid order while in some cases attenuated ENM-induced changes to lipid order. To assess the ability of ENM to induce membrane permeability, liposomes composed of the above lipids were assayed for membrane permeability by calcein leakage in response to ENM. Both ENM caused a dose-dependent increase in permeability in all liposome models tested, and the addition of cholesterol to the liposome models neither blocked nor reduced calcein leakage. Together, these experiments show that ENM increased permeability of small molecules (calcein) from model liposomes, and that the magnitude of the effect of ENM on lipid order depended on ENM surface charge, lipid head group charge and the presence of cholesterol in the membrane.

Greener synthesis of Rod Shaped Zinc Oxide Nanoparticles using Lilium ledebourii tuber and evaluation of their Leishmanicidal activity

Background

Nanoparticles (NPs) with unique chemical and physical properties can be used for therapeutic purposes because of their strong antimicrobial activates. Nanoparticles have been used as an antimicrobial agents to inhibit microbial growth.

Objectives

In view of the strong antimicrobial activity of nanoparticles, the biogenic synthesis and leishmanicidal activity of rod-shaped zinc oxide (R-ZnO) nanoparticles was explored using Lilium ledebourii tuber extract.

Materials and Methods

The ensuing nanoparticles are characterized by UV-visible spectroscopy, X-ray diffraction and transmission electron microscopy and their leishmanicidal activity evaluated against the Leishmania major (L. major) by MTT assay.

Results

The R-ZnO nanoparticles displayed excellent leishmanicidal activity against the L. major as they significantly inhibited the amastigotes. The IC₅₀ values of R-ZnO nanoparticles being ~ 0.001 mg.mL^-1. R-ZnO nanoparticles can inhibit L. major growth in a dose-dependent manner under in vitro conditions.

Conclusion

A simple, low-cost feasible and eco-friendly procedure was developed for biosynthesis of R-ZnO nanoparticles using natural bioresource that can inhibit human parasite cells growth in a dose-dependent manner under in vitro conditions.

Preparation and Application of Bioshell Calcium Oxide (BiSCaO) Nanoparticle-Dispersions with Bactericidal Activity

Scallop-shell powder (SSP) heated at high temperature exhibits high pH and broad antimicrobial activity. Bioshell calcium oxide (BiSCaO) is an SSP composed mainly of calcium oxide. It is poorly water-soluble under alkaline conditions and the generated precipitate can plug spray nozzles. The aim of this study was to establish that BiSCaO dispersion caused no significant CaO loss and plugging of spray nozzles, and to evaluate its deodorization and microbicidal abilities and its ability to reduce the concentrations of NO₂^- and NO₃^-. BiSCaO dispersions were prepared by mixing various concentrations of BiSCaO suspension, while phosphate compounds such as Na₃PO₄, Na₂HPO₄ or NaH₂PO₄ and the pH, average diameter, zeta potential, and form of the compounds with cryo-SEM were evaluated. We evaluated deodorization using tainted pork meat and microbicidal efficacy using contaminated suspension with normal bacterial flora. The concentration of NO₂^- and NO₃^- after mixing BiSCaO dispersion and pure water containing a high proportion of NO₂^- and NO₃^- were measured. BiSCaO dispersion formed with Na₂HPO₄, whose ratio to BiSCaO was 60%, showed a high pH (>12), a small particle diameter (>181 nm) and was stable for seven days. The BiSCaO dispersion showed higher deodorization and microbicidal activities than SSP-Ca(OH)₂, which was mainly composed of Ca(OH)₂. BiSCaO, but not SSP-Ca(OH)₂, could reduce the concentration of NO₂^- and NO₃^- by more than 90% within 15 min. We developed a stable BiSCaO dispersion, and it had high deodorization and microbicidal efficacy. These activities of BiSCaO might result from the high pH caused by CaO hydration and a reduction activity causing active radical species.

Enhancement of Thermal Diffusivity in Phase-Separated Bismaleimide/Poly(ether imide) Composite Films Containing Needle-Shaped ZnO Particles

Phase-separated polymer blend composite films exhibiting high thermal diffusivity were prepared by blending a soluble polyimide (BPADA-MPD) and a bismaleimide (BMI) with needle-shaped zinc oxide (n-ZnO) particles followed by high-temperature curing at 250 °C. Images recorded with a field-emission scanning electron microscope (FE-SEM) equipped with wavelength-dispersive spectroscopy (WDS) demonstrated that the spontaneously separated phases in the composite films were aligned along the out-of-plane direction, and the n-ZnO particles were selectively incorporated into the BMI phase. The out-of-plane thermal diffusivity of the composite films was significantly higher than those of the previously reported composite films at lower filler contents. Based on wide-angle X-ray diffraction (WAXD) patterns and image analysis, the enhanced thermal diffusivity was attributed to the confinement of the anisotropically shaped particles and their nearly isotropic orientation in one phase of the composite films.

Titanium Dioxide Nanoparticle-Biomolecule Interactions Influence Oral Absorption

Titanium dioxide (TiO₂) nanoparticles (NPs) have been widely applied in various industrial fields, such as electronics, packaging, food, and cosmetics. Accordingly, concerns about the potential toxicity of TiO₂ NPs have increased. In order to comprehend their in vivo behavior and potential toxicity, we must evaluate the interactions between TiO₂ NPs and biomolecules, which can alter the physicochemical properties and the fate of NPs under physiological conditions. In the present study, in vivo solubility, oral absorption, tissue distribution, and excretion kinetics of food grade TiO₂ (f-TiO₂) NPs were evaluated following a single-dose oral administration to rats and were compared to those of general grade TiO₂ (g-TiO₂) NPs. The effect of the interactions between the TiO₂ NPs and biomolecules, such as glucose and albumin, on oral absorption was also investigated, with the aim of determining the surface interactions between them. The intestinal transport pathway was also assessed using 3-dimensional culture systems. The results demonstrate that slightly higher oral absorption of f-TiO₂ NPs compared to g-TiO₂ NPs could be related to their intestinal transport mechanism by microfold (M) cells, however, most of the NPs were eliminated through the feces. Moreover, the biokinetics of f-TiO₂ NPs was highly dependent on their interaction with biomolecules, and the dispersibility was affected by modified surface chemistry.

In vitro cytotoxicity of SiO2 or ZnO nanoparticles with different sizes and surface charges on U373MG human glioblastoma cells

Silicon dioxide (SiO₂) and zinc oxide (ZnO) nanoparticles are widely used in various applications, raising issues regarding the possible adverse effects of these metal oxide nanoparticles on human cells. In this study, we determined the cytotoxic effects of differently charged SiO₂ and ZnO nanoparticles, with mean sizes of either 100 or 20 nm, on the U373MG human glioblastoma cell line. The overall cytotoxicity of ZnO nanoparticles against U373MG cells was significantly higher than that of SiO₂ nanoparticles. Neither the size nor the surface charge of the ZnO nanoparticles affected their cytotoxicity against U373MG cells. The 20 nm SiO₂ nanoparticles were more toxic than the 100 nm nanoparticles against U373MG cells, but the surface charge had little or no effect on their cytotoxicity. Both SiO₂ and ZnO nanoparticles activated caspase-3 and induced DNA fragmentation in U373MG cells, suggesting the induction of apoptosis. Thus, SiO₂ and ZnO nanoparticles appear to exert cytotoxic effects against U373MG cells, possibly via apoptosis.