Antimicrobial and Photocatalytic Degradation Activities of Chitosan-coated Magnetite Nanocomposite

Nanofillers in Novel Food Packaging Systems and Their Toxicity Issues

Background: Environmental concerns about petroleum-based plastic packaging materials and the growing demand for food have inspired researchers and the food industry to develop food packaging with better food preservation and biodegradability. Nanocomposites consisting of nanofillers, and synthetic/biopolymers can be applied to improve the physiochemical and antimicrobial properties and sustainability of food packaging. Scope and approach: This review summarized the recent advances in nanofiller and their applications in improved food packaging systems (e.g., nanoclay, carbon nanotubes), active food packaging (e.g., silver nanoparticles (Ag NPs), zinc oxide nanoparticles (ZnO NPs)), intelligent food packaging, and degradable packaging (e.g., titanium dioxide nanoparticles (e.g., TiO2 NPs)). Additionally, the migration processes and related assessment methods for nanofillers were considered, as well as the use of nanofillers to reduce migration. The potential cytotoxicity and ecotoxicity of nanofillers were also reviewed. Key findings: The incorporation of nanofillers may increase Young's modulus (YM) while decreasing the elongation at break (EAB) (y = -1.55x + 1.38, R2 = 0.128, r = -0.358, p = 0.018) and decreasing the water vapor (WVP) and oxygen permeability (OP) (y = 0.30x - 0.57, R2 = 0.039, r = 0.197, p = 0.065). Meanwhile, the addition of metal-based NPs could also extend the shelf-life of food products by lowering lipid oxidation by an average of approx. 350.74% and weight loss by approx. 28.39% during the longest storage period, and significantly increasing antibacterial efficacy against S. aureus compared to the neat polymer films (p = 0.034). Moreover, the migration process of nanofillers may be negligible but still requires further research. Additionally, the ecotoxicity of nanofillers is unclear, as the final distribution of nanocomposites in the environment is unknown. Conclusions: Nanotechnology helps to overcome the challenges associated with traditional packaging materials. Strong regulatory frameworks and safety standards are needed to ensure the appropriate use of nanocomposites. There is also a need to explore how to realize the economic and technical requirements for large-scale implementation of nanocomposite technologies.

Synthesis, theoretical studies, antibacterial, and antibiofilm activities of novel azo-azomethine chelates against the pathogenic bacterium Proteus mirabilis

2-((1-(4-((2,4,6-trioxohexahydropyrimidin-5-yl)diazenyl) phenyl) ethylidene) amino) benzoic acid (H3L), and its V(IV), Co(II), Ni(II), Cu(II), Pd(II) and Ag(I) chelates were synthesized. They were defined using multiple spectral and analytical techniques. With the exception of Ag(I) chelate, all chelates possessed non-electrolytic character. Square pyramidal shape was proposed for V(IV) chelate and Square planar for the other chelates. The analysis of functional group bands of H3L and its coordination compounds alludes that H3L chelated as neutral tetradentate via nitrogen atoms of azo and azomethine groups, oxygen atom of carbonyl of barbituric acid and OH of the carboxylic group. TG/DTG predicted the thermal behaviors of all compounds. The antibacterial activity of H3L and its coordination compounds was conducted against Proteus mirabilis at concentrations of 250, 500, and 1000 µg/mL. Ag(I) at 1000 µg/mL, showed the most inhibiting potency against P. mirabilis and registered zone of inhibition of 28.33 ± 0.84 mm and highest biofilm inhibition of 70.31%. At 50 Gy of gamma irradiation, the reducing effect of Ag(I) chelate was improved. The protein interruption of P. mirabilis was greatly interrupted by increasing the concentration of the chaletes. Also, Ag(I) showed the highest cytotoxicity with IC50 value of 11.5 µg/ mL. The novelty of this study is the synthesis of a new azo-Schiff base and this is almost the first publication of the effect of azo-Schiff ligands against that bacterial strain P. mirabilis.

Potential antibacterial, antibiofilm, and photocatalytic performance of gamma-irradiated novel nanocomposite for enhanced disinfection applications with an investigated reaction mechanism

BACKGROUND

Water scarcity is now a global challenge due to the population growth and the limited amount of available potable water. In addition, modern industrialization, and microbial pathogenesis is resulting in water pollution on a large scale.

METHODS

In the present study, reusable Co0.5Ni0.5Fe2O4/SiO2/TiO2 composite matrix was incorporated with CdS NPs to develop an efficient photocatalyst, and antimicrobial agents for wastewater treatment, and disinfection purpose. The antibacterial performance of the gamma-irradiated samples was evaluated against various types of Gram-positive bacteria using ZOI, MIC, antibiofilm, and effect of UV-exposure. Antibacterial reaction mechanism was assessed by bacterial membrane leakage assay, and SEM imaging. In addition, their photocatalytic efficiency was tested against MB cationic dye as a typical water organic pollutant.

RESULTS

Our results showed that, the formed CdS NPs were uniformly distributed onto the surface of the nanocomposite matrix. While, the resulted CdS-based nanocomposite possessed an average particle size of nearly 90.6 nm. The antibacterial performance of the prepared nanocomposite was significantly increased after activation with gamma and UV irradiations. The improved antibacterial performance was mainly due to the synergistic effect of both TiO2 and CdS NPs; whereas, the highest photocatalytic efficiency of MB removal was exhibited in alkaline media due to the electrostatic attraction between the cationic MB and the negatively-charged samples. In addition, the constructed heterojunction enabled better charge separation and increased the lifetime of the photogenerated charge carriers.

CONCLUSION

Our results can pave the way towards the development of efficient photocatalysts for wastewater treatment and promising antibacterial agents for disinfection applications.

Synthesis and characterization of a novel magnetic chitosan-nickel ferrite nanocomposite for antibacterial and antioxidant properties

A novel nanomagnet modified with nickel ferrite nanoparticles (NPs) coated with hybrid chitosan (Cs-NiFe2O4) was synthesized using the co-precipitation method. The resulting nanomagnets were characterized using various techniques. The size of the nanomagnetic particles was estimated to be about 40 nm based on the transmission electron microscopy (TEM) image and X-ray diffraction analysis (XRD) pattern (using the Debye-Scherrer equation). Scanning electron microscopy (SEM) images indicated that the surface of Cs-NiFe2O4 NPs is flatter and smoother than the uncoated NiFe2O4 NPs. According to value stream mapping (VSM) analysis, the magnetization value of Cs-NiFe2O4 NPs (17.34 emu/g) was significantly lower than NiFe2O4 NPs (40.67 emu/g). The Cs-NiFe2O4 NPs indicated higher antibacterial properties than NiFe2O4 NPs and Cs. The minimum inhibitory concentrations of Cs-NiFe2O4 NPs against S. aureus and E. coli were 128 and 256 mg/mL, respectively. Antioxidant activity (evaluated by 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging test) for NiFe2O4 NPs and Cs-NiFe2O4 NPs at the concentration of 100 µg/mL were 35% and 42%, respectively. Consequently, the synthesized Cs-NiFe2O4 NPs can be proposed as a viable material for biomedical applications.

Magnetically responsive chitosan-pectin films incorporating Fe3O4 nanoparticles with enhanced antimicrobial activity

Chitosan-pectin films with iron oxide (Fe₃O₄) magnetic nanoparticles were prepared by solution casting in order to produce biopolymer based magnetically active materials. Infrared (FTIR) spectra indicated physical interactions between the matrix and nanoparticles, corroborated by differential scanning calorimetry (DSC) results. In addition, thermal characterization suggested that the interactions between chitosan, pectin and the nanoparticles resulted in a less compact structure, influencing the film mechanical properties. Regarding vibrating-sample magnetometry (VSM) and electrical analysis, chitosan-pectin films with Fe₃O₄ nanoparticles showed ferrimagnetic behavior, with an increase of the dielectric constant as the nanoparticle concentration increased. Furthermore, films displayed enhanced antimicrobial activity against Escherichia coli (Gram-negative) and Staphylococcus epidermidis (Gram-positive) bacteria. Therefore, chitosan-pectin films with Fe₃O₄ magnetic nanoparticles provide promising results for active and intelligent food packaging applications.

Antimicrobial, and Antibiofilm Activities of Silver Doped Hydroxyapatite: A Novel Bioceramic Material for Dental Filling

Even though hydroxyapatite (HA) is the most common biocompatible material; it has limited antibacterial resistance. HA experiences a tailor-made structure depending on the desired applications. In this regard, silver (Ag) is of particular interest to inhibit wide spectrum of pathogenic bacteria and other microorganisms. Silver doped hydroxyapatite (Ag-HA) was developed via wet co-precipitation with subsequent hydrothermal processing to hinder the growth and multiplication of pathogenic microbes. Ag-HA demonstrated mono-dispersed nano-rods of 70 nm length and 7 nm diameters. Even though silver dopant induced stresses within the crystal lattice; Ag-HA maintained the crystallographic structure of HA with no change. Ag-HA nanocomposite demonstrated Ca/P value of 1.238 compared with 1.402 for virgin HA via XPS spectroscopy. The reduction of Ca/P value was correlated to the partial replacement of Ca+2 with Ag+1; Silver content was reported to be of 1 atomic %. Elemental mapping using EDAX confirmed uniform dispersion of silver ion within HA lattice. Antimicrobial results indicated that, Ag-HA nanocomposite demonstrated the most potent zone of inhibition (ZOI) against Staphylococcus aureus, and Candida albicans. Antibiofilm results indicated that Ag-HA nanocomposite at 10.0 µg/mL, experienced the highest percentage for S. aureus and C. albicans of 96.09%, and 77.77%, respectively. Ag-HA nanocomposite demonstrated an excellent disinfectant agent once it had excited by UV light. In growth curve assay, the OD600 value of Ag- HA were lower, showing the repression impact on the growth of S. aureus. It was observed that the quantity of cellular protein discharged from S. aureus is directly proportional to the concentration of Ag-HA, which proves the antibacterial characteristics of the Ag-HA nanocomposite, and explains the creation of holes in the bacterial membrane producing the oozing out of the proteins from the S. aureus cytoplasm. Ag-HA nanocomposite achieved the complete lysis of the bacterial cell and cell malformation, decreasing the total viable number, so the outstanding antimicrobial results encouraged the tooth filling biomedical applications.

Graphical Abstract

Enhanced photocatalytic and antimicrobial performance of a multifunctional Cu-loaded nanocomposite under UV light: theoretical and experimental study

Due to modern industrialization and population growth, access to clean water has become a global challenge. In this study, a metal-semiconductor heterojunction was constructed between Cu NPs and the Co_0.5Ni_0.5Fe₂O₄/SiO₂/TiO₂ composite matrix for the photodegradation of potassium permanganate, hexavalent chromium Cr(VI) and p-nitroaniline (pNA) under UV light. In addition, the electronic and adsorption properties after Cu loading were evaluated using density functional theory (DFT) calculations. Moreover, the antimicrobial properties of the prepared samples toward pathogenic bacteria and unicellular fungi were investigated. Photocatalytic measurements show the outstanding efficiency of the Cu-loaded nanocomposite compared to that of bare Cu NPs and the composite matrix. Degradation efficiencies of 44% after 80 min, 100% after 60 min, and 65% after 90 min were obtained against potassium permanganate, Cr(VI), and pNA, respectively. Similarly, the antimicrobial evaluation showed high ZOI, lower MIC, higher protein leakage amount, and cell lysis of nearly all microbes treated with the Cu-loaded nanocomposite.

Potential Impact of Reduced Graphene Oxide Incorporated Metal Oxide Nanocomposites as Antimicrobial, and Antibiofilm Agents Against Pathogenic Microbes: Bacterial Protein Leakage Reaction Mechanism

In the current study, nanocomposites-based reduced graphene oxide (RGO) and metal oxides (AgO, NiO, and ZnO) were fabricated. The starting precursor and RGO were characterized by XRD, Raman, SEM, and HRTEM, while SEM and EDX mapping validated the synthesized nanocomposites. In addition, ZOI, MIC, antibiofilm, and growth curve were tested. The antimicrobial reaction mechanism was investigated by protein leakage assay and SEM imaging. Results revealed that all synthesized nanocomposites (RGO-AgO, RGO-NiO, and RGO-ZnO) have outstanding antimicrobial activity against pathogenic bacteria and unicellular fungi. Moreover, RGO-AgO, RGO-NiO, and RGO-ZnO nanocomposites exhibited an antibiofilm activity percentage against Staphylococcus aureus (91.72%), Candida albicans  (91.17%), and Escherichia coli (90.36%). The SEM analysis of S. aureus after RGO-AgO treatment indicated morphological differences, including the whole lysis of the outer surface supported by deformations of the bacterial cells. It was observed that the quantity of cellular protein leakage from S. aureus is directly proportional to the concentration of RGO-AgO, RGO-NiO, and RGO-ZnO nanocomposites and found to be 260.25 µg/mL, 110.55 µg/mL, and 99.90 µg/mL, respectively. The prepared nanocomposites promise to treat resistant microbes as a new strategy for managing infectious diseases.

Engineered magnetic oxides nanoparticles as efficient sorbents for wastewater remediation: a review

The rapid urbanization and industrialization is causing worldwide water pollution, calling for advanced cleaning methods. For instance, pollutant adsorption on magnetic oxides is efficient and very practical due to the easy separation from solutions by an magnetic field. Here we review the synthesis and performance of magnetic oxides such as iron oxides, spinel ferrites, and perovskite oxides for water remediation. We present structural, optical, and magnetic properties. Magnetic oxides are also promising photocatalysts for the degradation of organic pollutants. Antimicrobial activities and adsorption of heavy metals and radionucleides are also discussed.