Influence of size scale and morphology on antibacterial properties of ZnO powders hydrothemally synthesized using different surface stabilizing agents

Adsorption of Polylactic-co-Glycolic Acid on Zinc Oxide Systems: A Computational Approach to Describe Surface Phenomena

Zinc oxide and polylactic-co-glycolic acid (ZnO-PLGA) nanocomposites are known to exhibit different biomedical applications and antibacterial activity, which could be beneficial for adding to wound dressings after different surgeries. However, possible cytotoxic effects along with various unexpected activities could reduce the use of these prominent systems. This is correlated to the property of ZnO, which exhibits different polymeric forms, in particular, wurtzite, zinc-blende, and rocksalt. In this study, we propose a computational approach based on the density functional theory to investigate the properties of ZnO-PLGA systems in detail. First, three different stable polymorphs of ZnO were considered. Subsequently, the abilities of each system to absorb the PLGA copolymer were thoroughly investigated, taking into account the modulation of electrical, optical, and mechanical properties. Significant differences between ZnO and PLGA systems have been found; in this study, we remark on the potential use of these models and the necessity to describe crucial surface aspects that might be challenging to observe with experimental approaches but which can modulate the performance of nanocomposites.

Zinc Oxide-Based Nanomaterials for Microbiostatic Activities: A Review

The world is fighting infectious diseases. Therefore, effective antimicrobials are required to prevent the spread of microbes and protect human health. Zinc oxide (ZnO) nano-materials are known for their antimicrobial activities. Because of their distinctive physical and chemical characteristics, they can be used in medical and environmental applications. ZnO-based composites are among the leading sources of antimicrobial research. They are effective at killing (microbicidal) and inhibiting the growth (microbiostatic) of numerous microorganisms, such as bacteria, viruses, and fungi. Although most studies have focused on the microbicidal features, there is a lack of reviews on their microbiostatic effects. This review provides a detailed overview of available reports on the microbiostatic activities of ZnO-based nano-materials against different microorganisms. Additionally, the factors that affect the efficacy of these materials, their time course, and a comparison of the available antimicrobials are highlighted in this review. The basic properties of ZnO, challenges of working with microorganisms, and working mechanisms of microbiostatic activities are also examined. This review underscores the importance of further research to better understand ZnO-based nano-materials for controlling microbial growth.

Optimizing Antimicrobial Efficacy: Investigating the Impact of Zinc Oxide Nanoparticle Shape and Size

Zinc oxide nanoparticles (ZnO NPs) have been investigated due to their distinct properties, variety of structures and sizes, and mainly for their antimicrobial activity. They have received a positive safety evaluation from the European Food Safety Authority (EFSA) for packaging applications as transparent ultraviolet (UV) light absorbers based on the absence of significant migration of zinc oxide in particulate form. ZnO NPs with different morphologies (spherical, flower, and sheet) have been synthesized via different sol-gel methods and extensively characterized by several solid-state techniques, namely vibrational spectroscopy, powder X-ray diffraction (XRD), scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDS), Fourier Transform Infrared Spectroscopy (FTIR), ultraviolet-visible spectroscopy (UV-VIS), electron paramagnetic resonance (EPR), and nitrogen adsorption-desorption isotherms. The ZnO NPs were assessed for their antibacterial activity against Escherichia coli (gram-negative bacteria) and Staphylococcus aureus (gram-positive bacteria) to study the influence of morphology and size on efficacy. ZnO NPs with different morphologies and sizes demonstrated antimicrobial activity against both bacteria. The highest microbial cell reduction rate (7-8 log CFU mL-1 for E. coli and 6-7 log CFU mL-1 for S. aureus) was obtained for the sheet- and spherical-shaped NPs as a result of the high specific surface area. In fact, the higher surface areas of the sheet- and spherical-shaped nanoparticles (18.5 and 13.4 m2 g-1, respectively), compared to the flower-shaped NPs (5.3 m2g-1), seem to promote more efficient bacterial cell reduction. The spherical-shaped particles were also smaller (31 nm) compared with the flower-shaped (233 × 249 nm) ones. The flower ZnO NP resulted in a 4-5 log CFU mL-1 reduction for E. coli and 3-4 log CFU mL-1 reduction for S. aureus. The lower apparent antibacterial activity of the flower-shaped could be associated with either the lack of defects on the particle core or the shape shielding effect. Compared to S. aureus, E. coli seems to be less resistant to ZnO NPs, which may be explained by the characteristics of its cell membrane. With simple synthesis techniques, which do not allow the size and shape of the nanoparticles to be controlled simultaneously, it is a challenge to elucidate the effect of each of these two parameters on antibacterial performance.

ZnO based 0-3D diverse nano-architectures, films and coatings for biomedical applications

Thin-film nano-architecting is a promising approach that controls the properties of nanoscale surfaces to increase their interdisciplinary applications in a variety of fields. In this context, zinc oxide (ZnO)-based various nano-architectures (0-3D) such as quantum dots, nanorods/nanotubes, nanothin films, tetrapods, nanoflowers, hollow structures, etc. have been extensively researched by the scientific community in the past decade. Owing to its unique surface charge transport properties, optoelectronic properties and reported biomedical applications, ZnO has been considered as one of the most important futuristic bio-nanomaterials. This review is focused on the design/synthesis and engineering of 0-3D nano-architecture ZnO-based thin films and coatings with tunable characteristics for multifunctional biomedical applications. Although ZnO has been extensively researched, ZnO thin films composed of 0-3D nanoarchitectures with promising thin film device bio-nanotechnology applications have rarely been reviewed. The current review focuses on important details about the technologies used to make ZnO-based thin films, as well as the customization of properties related to bioactivities, characterization, and device fabrication for modern biomedical uses that are relevant. It features biosensing, tissue engineering/wound healing, antibacterial, antiviral, and anticancer activity, as well as biomedical diagnosis and therapy with an emphasis on a better understanding of the mechanisms of action. Eventually, key issues, experimental parameters and factors, open challenges, etc. in thin film device fabrications and applications, and future prospects will be discussed, followed by a summary and conclusion.

Addressing Antimicrobial Properties in Guided Tissue/Bone Regeneration Membrane: Enhancing Effectiveness in Periodontitis Treatment

Guided tissue regeneration (GTR) and guided bone regeneration (GBR) are the two surgical techniques generally used for periodontitis disease treatment. These techniques are based on a barrier membrane to direct the growth of new bone and gingival tissue at sites with insufficient volumes or dimensions of bone or gingiva for proper function, esthetics, or prosthetic restoration. Numerous studies have highlighted biocompatibility, space-creation, cell-blocking, bioactivity, and proper handling as essential characteristics of a membrane's performance. Given that bacterial infection is the primary cause of periodontitis, we strongly believe that addressing the antimicrobial properties of these membranes is of utmost importance. Indeed, the absence of effective inhibition of periodontal pathogens has been recognized as a primary factor contributing to the failure of GTR/GBR membranes. Therefore, we suggest considering antimicrobial properties as one of the key factors in the design of GTR/GBR membranes. Antibiotics are potent medications frequently administered systemically to combat microbes and mitigate bacterial infections. Nevertheless, the excessive use of antibiotics has resulted in a surge in bacterial resistance. To overcome this challenge, alternative antibacterial substances have been developed. In this review, we explore the utilization of alternative substances with antimicrobial properties for topical application in membranes. The use of antibacterial nanoparticles, phytochemical compounds, and antimicrobial peptides in this context was investigated. By carefully selecting and integrating antimicrobial agents into GTR/GBR membranes, we can significantly enhance their effectiveness in combating periodontitis. These antibacterial substances not only act as barriers against pathogenic bacteria but also promote the process of periodontal healing.

Investigating the effect of acidic and basic precipitation on the antibacterial activity of ZnO nanoparticles against Gram-negative and Gram-positive bacteria

In the present work, acidic (direct) and basic precipitation (indirect) methods were used to demonstrate the influence of the mode of precipitation on the structural properties of ZnO nanoparticles (NPs). Four samples of ZnO nanoparticles were prepared, two samples via each mode of precipitation. DZOa and IZOa were the aged samples prepared via acidic and basic precipitation methods, and DZOwa and IZOwa were processed without aging. Both precipitation processes were carried out without using any surfactant reagents. Zinc hydroxide precipitate, which was formed during the basic precipitation method, could be critical in deciding the properties of ZnO NPs, unlike zinc hydroxide formed during acidic precipitation. Aging of zinc hydroxide, synthesised by basic precipitation method for 48 hours was found to be an added advantage in controlling the properties of ZnO NPs. The influence of the mode of precipitation on the structural properties and antibacterial activity of ZnO NPs against Gram-positive and Gram-negative bacterial strains was tested. The antibacterial activity of all four ZnO NPs was analysed via zone of inhibition measurements at a concentration dose of 200 μg ml-1. IZOa nanoparticles prepared using the basic precipitation method showed a higher antibacterial activity against three Gram-negative and one Gram-positive strains, namely, Klebsiella pneumoniae, Pseudomonas aeruginosa, Staphylococcus aureus, and Escherichia coli. DZOa nanoparticles synthesized through acidic precipitation showed relatively high antibacterial activity against Salmonella typhimurium, a Gram-negative strain. ZnO NPs prepared without aging, IZOwa and DZOwa, showed a higher antibacterial activity against E. coli and Bacillus sp. strains, respectively. All ZnO NPs were characterized via UV-visible, FTIR, XRD, and HRSEM techniques.

Antibacterial Gelatin Composite Hydrogels Comprised of In Situ Formed Zinc Oxide Nanoparticles

We report the feasibility of using gelatin hydrogel networks as the host for the in situ, environmentally friendly formation of well-dispersed zinc oxide nanoparticles (ZnONPs) and the evaluation of the antibacterial activity of the as-prepared composite hydrogels. The resulting composite hydrogels displayed remarkable biocompatibility and antibacterial activity as compared to those in previous studies, primarily attributed to the uniform distribution of the ZnONPs with sizes smaller than 15 nm within the hydrogel network. In addition, the composite hydrogels exhibited better thermal stability and mechanical properties as well as lower swelling ratios compared to the unloaded counterpart, which could be attributed to the non-covalent interactions between the in situ formed ZnONPs and polypeptide chains. The presence of ZnONPs contributed to the disruption of bacterial cell membranes, the alteration of DNA molecules, and the subsequent release of reactive oxygen species within the bacterial cells. This chain of events culminated in bacterial cell lysis and DNA fragmentation. This research underscores the potential benefits of incorporating antibacterial agents into hydrogels and highlights the significance of preparing antimicrobial agents within gel networks.

Enhancement of Antibacterial Properties, Surface Morphology and In Vitro Bioactivity of Hydroxyapatite-Zinc Oxide Nanocomposite Coating by Electrophoretic Deposition Technique

To develop medical-grade stainless-steel 316L implants that are biocompatible, non-toxic and antibacterial, such implants need to be coated with biomaterials to meet the current demanding properties of biomedical materials. Hydroxyapatite (HA) is commonly used as a bone implant coating due to its excellent biocompatible properties. Zinc oxide (ZnO) nanoparticles are added to HA to increase its antibacterial and cohesion properties. The specimens were made of a stainless-steel grade 316 substrate coated with HA-ZnO using the electrophoretic deposition technique (EPD), and were subsequently characterized using scanning electron microscopy (SEM), energy dispersive X-ray (EDX), stylus profilometry, electrochemical corrosion testing and Fourier transform infrared (FTIR) spectroscopy. Additionally, cross-hatch tests, cell viability assays, antibacterial assessment and in vitro activity tests in simulated body fluid (SBF) were performed. The results showed that the HA-ZnO coating was uniform and resistant to corrosion in an acceptable range. FTIR confirmed the presence of HA-ZnO compositions, and the in vitro response and adhesion were in accordance with standard requirements for biomedical materials. Cell viability confirmed the viability of cells in an acceptable range (>70%). In addition, the antibacterial activity of ZnO was confirmed on Staphylococcus aureus. Thus, the HA-ZnO samples are recommended for biomedical applications.

Cytotoxicity of PLGA-zinc oxide nanocomposite on human gingival fibroblasts

Background

Polylactic-co-glycolic acid and zinc oxide (PLGA-ZnO) nanocomposite has been investigated for its antibacterial properties, which could be beneficial for adding to wound dressings after periodontal surgery. However, its cytotoxicity against human gingival fibroblasts (HGFs) remains unclear and should be evaluated.

Methods

ZnO nanoparticles were synthesized using the hydrothermal method. These metallic nanoparticles were incorporated into the PLGA matrix by the solvent/non-solvent process. The nanomaterial was evaluated by field emission scanning electron microscopy (FESEM), Fourier transform infrared (FTIR), thermogravimetric analysis (TGA), and x-ray diffraction (XRD) analyses. HGF cells were acquired from the National Cell Bank and categorized into four groups: ZnO, PLGA, ZnO-PLGA, and control. The cells were exposed to different ZnO (1, 20, 40, 60, 80, and 100 µg/mL) and PLGA (0.2, 4, 8, 12, 16, and 20 µg/mL) concentrations for 24 and 48 hours. The cytotoxicity was tested using the MTT assay. The data were analyzed using SPSS 25, and P<0.05 was considered statistically significant.

Results

ZnO nanoparticles exhibited significant toxicity at≥40 µg/mL concentrations after 24 hours. Cell viability decreased significantly at all the tested concentrations after 48 hours of exposure. PLGA-ZnO cell viability in 24 hours was similar to the control group for all the concentrations up to 80 µg/mL.

Conclusion

ZnO nanoparticles could be toxic against HGF in high concentrations and with prolonged exposure. Therefore, incorporating ZnO nanoparticles into a biocompatible polymer such as PLGA could be a beneficial strategy for reducing their toxicity.

An alternative ZnO with large specific surface area: Preparation, physicochemical characterization and effects on growth performance, diarrhea, zinc metabolism and gut barrier function of weaning piglets

High-dose ZnO is widely used to prevent diarrhea and promote growth of weaning piglets, which has led to serious problems of animal toxicity, bacterial resistance and environmental pollution. In this study, a novel alternative ZnO (AZO) was prepared and its physicochemical properties were characterized. Animal experiments were further conducted to evaluate the effects of the ZnO forms, the dose of AZO and the combinations with AZO on the growth performance, diarrhea, zinc metabolism and gut barrier function of weaning piglets. The results showed that the AZO, compared with ordinary ZnO (OZO), nano ZnO (NZO) and porous ZnO (PZO), had the largest surface area and reduced the release of Zn²⁺ into the gastric fluid. AZO showed better antibacterial activity on Escherichia coli K88, Staphylococcus aureus and Salmonella enteritidis but lower cytotoxicity on porcine intestinal epithelial cells. Animal experiments suggested that low-dose AZO, NZO and PZO (300 mg/kg) improved growth performance and reduced diarrhea in weaning piglets as well as high-dose OZO (3000 mg/kg). Notably, low-dose AZO had the lowest diarrhea incidence. Additionally, low-dose AZO in combination with probiotics improved digestibility and digestive enzyme activities. Low-dose AZO in combination with probiotics also upregulated the expression of the intestinal zinc transporter proteins ZIP4 and DMT1, increased zinc bioavailability, reduced faecal zinc emissions, and avoided zinc overload in the liver and oxidative damage caused by high-dose ZnO. Moreover, low-dose AZO in combination with probiotics improved the gut barrier function of weaning piglets by promoting the expression of tight junction proteins, mucins and antimicrobial peptides and increasing gut microbiota diversity and beneficial Lactobacillus. This study proposed a novel strategy to replace high-dose ZnO and antibiotics with low-dose AZO and probiotics in weaning piglets, which effectively improved growth performance and prevented diarrhea while reducing animal toxicity, bacterial resistance, heavy metal residues and zinc emission pollution.

Ecological adaptation of earthworms for coping with plant polyphenols, heavy metals, and microplastics in the soil: A review

In recent years, soil pollution by massive accumulation of heavy metals (HMs), microplastics, and refractory hydrocarbon chemicals has become an emerging and global concern, drawing worldwide attention. These pollutants influence soil diversity by hindering the reproduction, abundance, thereby affecting aboveground productivity. The scientific community has recently emphasized the contribution of earthworms to heavy metal accumulation, microplastic degradation, and the decomposition of organic matter in the soil, which helps maintain the soil structure. This review paper aimed to compile scientific facts on how earthworms cope with the effect of HMs, microplastics, and plant polyphenols so that vermiremediation could be widely applied for well-being of the soil ecosystem by environmentalists. Earthworms have special surface-active metabolites in their guts called drilodefensins that help them defend themselves against the oxidative action of plant polyphenols. They also combat the effects of toxic microplastics, and other oxidative compounds by elevating the antioxidant activities of their enzymes and converting them into harmless compounds or useful nutrients. Moreover, earthworms also act as biofilters, bioindicators, bioaccumulators, and transformers of oxidative polyphenols, microplastics, toxic HMs, and other pollutant hydrocarbons. Microorganisms (fungi and bacteria) in earthworms' gut of also assist in the fixation, accumulation, and transformation of these toxicants to prevent their effects. As a potential organism for application in ecotoxicology, it is recommended to propagate earthworms in agricultural fields; isolate, and culture enormously in industry, and inoculate earthworms in the polluted soil, thereby abate toxicity and minimizing the health effect caused by these pollutants as well enhance the productivity of crops.

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.

HSBM-Produced Zinc Oxide Nanoparticles: Physical Properties and Evaluation of Their Antimicrobial Activity against Human Pathogens

This work examines the antibacterial and anticandidal activities of zinc oxide nanoparticles (ZNPs) synthesized by high-speed ball milling (HSBM), for short milling times: 0.5, 1, 1.5, and 2 h. First, ZNPs have been characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, and the Zetasizer analyzer. The HSBM results in semispherical ZNPs with some local agglomeration. We found that nanoparticles decrease in size continuously with milling time until they reach about 84% of their original size after only two hours; at 1000 rpm, HSBM reduces ZNP's average size by 6 nm/min. As particle size decreases, the X-ray diffracted patterns become broader and less intense while confirming that no phase transformation has occurred, proving HSBM's effectiveness in synthesizing nanoparticles on a large scale within a short period of time. According to FT-IR analysis, as material sizes change, the polarization charge of the ZNP surface changes as well, creating discrepancies in vibrational frequency, as demonstrated by the shifting of the IR spectra in the 300-600 cm^-1 frequency band. Raman responses have also been proven to depend on the particle size. Using the Agar well diffusion method, eleven microorganisms have been tested for the antimicrobial activity of ZNPs. Among the six Gram-negative tested bacteria, S. sonnei showed the largest inhibition zone of about 11.3 ± 0.6 mm with ZNPs measuring 148 nm in size (milled for 2 h), followed by E. coli ATCC 25922. Accordingly, S. aureus was the most susceptible Gram-positive bacteria, with inhibition zone size gradually increasing from 11.8 ± 0.3 mm to 13.5 ± 0.5 mm with decreasing nanoparticle size from 767 to 148 nm, while S. aureus ATCC 25923 was resistant to both milled and unmilled samples. Similar results were seen with candida, all milled ZNPs inhibited C. albicans, followed by C. tropicalis, whereas C. knisei was resistant to all ZNP sizes. In light of microorganism-ZNP interaction mechanisms, the obtained results have been discussed in depth.

ZnO@Polyvinyl Alcohol/Poly(lactic acid) Nanocomposite Films for the Extended Shelf Life of Pork by Efficient Antibacterial Adhesion

The proliferation of microorganisms is an important reason for meat spoilage and deterioration. Freezing and packaging by polymer films and preservatives are commonly used to preserve meat. While the energy consumption of freezing is very big, the polymer films made by petroleum bring up heavy environmental pressure. In the present study, biodegradable antibacterial ZnO@PLA (ZP) and ZnO@PVA/PLA (ZPP) nanocomposite films used as food packaging have been synthesized by the solvent evaporation method and coating method, respectively. Compared with films without ZnO NPs, ZP and ZPP both had long-term bacteriostasis for 24 and 120 h at temperatures of 25 and 4 °C, respectively. Moreover, the antibacterial effect showed positive relevance with the increase of the ZnO NP concentration. In addition, the antibacterial effect of ZPP was better than that of ZP in the same condition. Scanning electron microscopy showed that the numbers of methicillin-resistant staphylococcus aureus (MRSA) on ZP and ZPP were significantly reduced compared to that in the blank film, and ZPP caused the morphology of MRSA to change, which means that the antibacterial mechanism of ZP and ZPP composite films might be related to antibacterial adhesion. In conclusion, ZPP films have great potential to be regarded as the candidate of food packing to extend the shelf life of pork.

Anticancer effect of zinc oxide nanoparticles prepared by varying entry time of ion carriers against A431 skin cancer cells in vitro

Although, zinc oxide nanoparticles (ZRTs) as an anti-cancer agent have been the subject of numerous studies, none of the reports has investigated the impact of the reaction entry time of ion-carriers on the preparation of ZRTs. Therefore, we synthesized variants of ZRTs by extending the entry time of NaOH (that acts as a carrier of hydroxyl ions) in the reaction mixture. The anti-proliferative action, morphological changes, reactive oxygen species (ROS) production, and nuclear apoptosis of ZRTs on human A431 skin carcinoma cells were observed. The samples revealed crystallinity and purity by X-ray diffraction (XRD). Scanning electron microscopy (SEM) images of ZRT-1 (5 min ion carrier entry) and ZRT-2 (10 min ion carrier entry) revealed microtubule like morphology. On prolonging the entry time for ion carrier (NaOH) introduction in the reaction mixture, a relative ascent in the aspect ratio was seen. The typical ZnO band with a slight shift in the absorption maxima was evident with UV-visible spectroscopy. Both ZRT-1 and ZRT-2 exhibited non-toxic behavior as evident by RBC lysis assay. Additionally, ZRT-2 showed better anti-cancer potential against A431 cells as seen by MTT assay, ROS generation and chromatin condensation analyses. At 25 μM of ZRT-2, 5.56% cells were viable in MTT test, ROS production was enhanced to 166.71%, while 33.0% of apoptotic cells were observed. The IC50 for ZRT-2 was slightly lower (6 μM) than that for ZRT-1 (8 μM) against A431 cells. In conclusion, this paper presents a modest, economical procedure to generate ZRT nano-structures exhibiting strong cytotoxicity against the A431 cell line, indicating that ZRTs may have application in combating cancer.

Effect of polar/non-polar facets on the transformation of nanoscale ZnO in simulated sweat and potential impacts on the antibacterial activity

The use of nanoscale zinc oxide (n-ZnO) in the personal care products would cause interactions between n-ZnO and human sweat. Facet engineering has been applied to n-ZnO to improve its activity. Nevertheless, it is not clear whether the exposed facet would affect transformation of n-ZnO in sweat. Herein, we prepared ZnO nanoneedles with the dominant (1010) non-polar facet (i.e., ZnO-1010) and ZnO nanoflakes with the dominant (0001) polar facet (i.e., ZnO-0001), respectively. We found that n-ZnO can undergo chemical transformation in the simulated sweat within 168 h or 24 h, transforming into amorphous materials and Zn₃(PO₄)₂0.4 H₂O and/or Na(ZnPO₄)·H₂O. Given the rate constant (e.g., 0.093 h^-1 for ZnO-0001 vs. 0.033 h^-1 for ZnO-1010) of ZnO depletion and components of the precipitate from the simulated sweat, nevertheless, the transformation is highly dependent on the dominant exposed facet of n-ZnO. The ZnO-0001 relative to ZnO-1010 would likely undergo chemical transformation, demonstrating that the (0001) polar facet compared to (1010) non-polar facet had a superior activity to the dihydrogen phosphate anions in the simulated sweat, which is supported by density functional theory calculations. The chemical transformation can affect the antibacterial activity of n-ZnO to E. coli, moderating the toxicity due to a great decrease in the concentration of the dissolved zinc. In total, our findings provided insights into the facet-dependent transformation for n-ZnO in the simulated sweat, improving our understanding of potential risk of n-ZnO.

Hierarchical ZnO nano-spines grown on a carbon fiber seed layer for efficient VOC removal and airborne virus and bacteria inactivation

Air purification through fiber-based filters has become a fundamental requirement for air contamination control. However, conventional filters depend on polymeric fibrous filters with adequate particulate matter removal ability but fewer degassing and biocidal effects. This study presents the photocatalytic volatile organic compound (VOC) oxidation and antimicrobial properties of zinc oxide (ZnO) nano-spines sprouted activated-carbon nanofibers (I@ZnO/ACNFs) and their potential for air contamination control and infection prevention. By developing a novel technique that can induce phase separation of inorganic salts during electrospinning, nanofibers with zinc (Zn) components concentrated on the surface could be synthesized. I@ZnO/ACNFs exhibit a surface densely covered with high aspect-ratio ZnO nano-spines with significant lethality to airborne pathogens and enhanced photocatalytic activity toward VOCs. Moreover, excellent adhesion stability of ZnO to ACNFs under rapid airflow was observed in I@ZnO/ACNFs. In combination with intriguing antimicrobial activity and strong VOC removal capability derived from their unique morphology, novel I@ZnO/ACNFs hold potential for airborne microbial disinfection, effective and sustainable VOC purification, and the design of photomicrobicidal and photocatalytic materials.

Applications of Inorganic Nanoparticles in Food Packaging: A Comprehensive Review

Nanoparticles (NPs) have acquired significance in technological breakthroughs due to their unique properties, such as size, shape, chemical composition, physiochemical stability, crystal structure, and larger surface area. There is a huge demand for packaging materials that can keep food fresher for extended periods of time. The incorporation of nanoscale fillers in the polymer matrix would assists in the alleviation of packaging material challenges while also improving functional qualities. Increased barrier properties, thermal properties like melting point and glass transition temperatures, and changed functionalities like surface wettability and hydrophobicity are all features of these polymers containing nanocomposites. Inorganic nanoparticles also have the potential to reduce the growth of bacteria within the packaging. By incorporating nano-sized components into biopolymer-based packaging materials, waste material generated during the packaging process may be reduced. The different inorganic nanoparticles such as titanium oxide, zinc oxide, copper oxide, silver, and gold are the most preferred inorganic nanoparticles used in food packaging. Food systems can benefit from using these packaging materials and improve physicochemical and functional properties. The compatibility of inorganic nanoparticles and their various forms with different polymers make them excellent components for package fortification. This review article describes the various aspects of developing and applying inorganic nanoparticles in food packaging. This study provides diverse uses of metals and metal oxides nanoparticles in food packaging films for the development of improved packaging films that can extend the shelf life of food products. These packaging solutions containing nanoparticles would effectively preserve, protect, and maintain the quality of the food material.

Facile synthesis of silver modified zinc oxide nanocomposite: An efficient visible light active nanomaterial for bacterial inhibition and dye degradation

The present study reports the synthesis of silver (Ag) decorated zinc oxide (ZnO) nanocomposite via green synthesis method by using Acacia arabica plant leaves extract as both reducing and capping agent. The results clearly indicate a uniform distribution of Ag nanoparticles (NPs) over ZnO surface. Various analytical and spectroscopic techniques were used for investigating the formation and morphology of as-synthesized Ag/ZnO nanocomposites. Emergence of SPR at 424 and 378 nm confirmed the synthesis of AgNPs and ZnO respectively. The confirmation of elemental composition and crystal structure of prepared nanomaterials (NMs) was carried out via EDX and XRD analysis. Results obtained from HRTEM and SEM analysis indicated small sized spherically shaped NMs. The as-synthesized was checked for its photocatalytic activity towards degradation of MB in the presence as well as absence of light irradiation. Results of degradation study revealed that Ag/ZnO exhibits remarkable photocatalytic activity in the presence of light whereby removing 90% of MB within 80 min. Moreover, the antibacterial activity of synthesized nanocomposite was examined in both visible light and dark conditions. The experiment showed that nanomaterial depicts enhanced antibacterial activity in light in comparison to dark. The results showed that the inhibition diameter of Ag/ZnO nanocomposite in light was found to be 18 (±0.2), 22 (±0.3) against E. coli and S. aureus respectively. The inhibition zone of the said nanomaterial against E. coli and S. aureus in dark was 11 (±0.3), 14 (±0.5) respectively. These results conclude that activity is delivered both in the presence of visible light and dark but efficiency of antibacterial activity is found to be more in visible light in comparison.

Influence of Physical Dimension and Morphological-Dependent Antibacterial Characteristics of ZnO Nanoparticles Coated on Orthodontic NiTi Wires

White spot lesions (WSLs) are one of the adverse effects of fixed orthodontic treatments. They are the primary sign of caries, which means inhibiting this process by antibacterial agents will reverse the procedure. The current study tested the surface modification of nickel-titanium (NiTi) wires with ZnO nanoparticles (NPs), as antimicrobial agents. As the morphology of NPs is one of the most critical factors for their properties, the antibacterial properties of different morphologies of ZnO nanostructures coated on the NiTi wire were investigated. For the preparation of ZnO nanostructures, five coating methods, including chemical vapor deposition (CVD), chemical precipitation method, polymer composite coating, sol-gel synthesis, and electrospinning process, were used. The antibacterial activity of NPs was assessed against Streptococcus mutans by the colony counting method. The obtained results showed that all the samples had antibacterial effects. The antibacterial properties of ZnO NPs were significantly improved when the specific surface area of particles increased, by the ZnO nanocrystals prepared via the CVD coating method.

Effect of Polyethylene Film Thickness on the Antimicrobial Activity of Embedded Zinc Oxide Nanoparticles

Microbial contamination of most foods occurs primarily at the surface during postprocessing and handling; therefore, preventing cross-contamination by incorporation of antimicrobial substances in contact with the surface of the product is an efficient strategy in reducing food contamination risks. Zinc oxide nanoparticles (ZnONPs) have been used widely to achieve antimicrobial films in various applications including the food industry. This work describes the fabrication of antimicrobial polymeric films containing ZnONPs produced by the coextrusion and dip-coating techniques. Effects of skin layer thicknesses containing ZnONPs on the antimicrobial effectiveness of the film by their capability to inactivate Gram-positive and Gram-negative bacteria were studied for both methods. The antimicrobial properties of the coextruded multilayer LLDPE/ZnONP nanocomposite films evidenced antimicrobial activity in the range 0.5-1.5 log reductions, while in the case of a sandblasted multilayer film, it showed high antimicrobial properties as around 99.99%. The optical properties of coextruded multilayer films were measured and discussed. Furthermore, to achieve a thinner LLDPE thickness, ZnONPs were coated with different concentrations of LLDPE solution by the dip-coating method. TEM confirmed that a homogeneous layer is formed on the surface of ZnONPs. The thickness of the LLDPE layer estimated by TEM was about 2 nm and film produced 3 log and 4 log reductions for E. coli and S. aureus, respectively. The results show that developed films have the potential to be used as food packaging films and can extend shelf life, maintain quality, and assure the safety of food. The antimicrobial mechanisms of ZnONPs were also investigated. It was found that direct contact of particles with products is necessary to assure high antibacterial activity of the films.

Microbial inhibition and biosensing with multifunctional carbon dots: Progress and perspectives

Carbon dots (CDs) and their doped counterparts including nitrogen-doped CDs (N@CDs) have been synthesized by bottom-up or top-down approaches from different precursors. The attractiveness of such emerging 2D‑carbon-based nanosized materials is attributed to their excellent biocompatibility, preparation, aqueous dispersibility, and functionality. The antimicrobial, optical, and electrochemical properties of CDs have been advocated for two important biotechnological applications: bacterial eradication and sensing/biosensing. CDs as well as N@CDs act as antimicrobial agents as their surfaces encompass functional hydroxyl, carboxyl, and amino groups that generate free radicals. As a new class of photoluminescent nanomaterials, CDs can be employed in diversified analytics. CDs with surface carboxyl or amino groups form nanocomposites with nanomaterials or be conjugated with biorecognition molecules toward the development of sensors/biosensors. The deployment of conductive CDs in electrochemical sensing has also increased significantly because of their quantum size, excellent biocompatibility, enzyme-mimicking activity, and high surface area. The review also addresses the ongoing challenges and promises of CDs in pathogenesis and analytics. Perspectives on the future possibilities include the use of CDs in microbial viability assay, wound healing, antiviral therapy, and medical devices.

A state of the art review on the synthesis, antibacterial, antioxidant, antidiabetic and tissue regeneration activities of zinc oxide nanoparticles

Recently, zinc oxide nanoparticles (ZnONPs) are gaining much interest of nanobiotechnologists due to their profound biomedical applications. ZnONPs are used as antibacterial agents, which cause both gram-positive and negative bacterial cell death through the generation of reactive free radicals as well as membrane rupture. ZnONPs show excellent antioxidant properties in normal mammalian cells via the scavenging of reactive free radicals and up-regulation of antioxidant enzyme activities. Besides, it also shows hypoglycaemic effect in diabetic animals via pancreatic β-cells mediated increased insulin secretion and glucose uptake by liver, skeletal muscles and adipose tissues. Among the other potential applications, ZnONPs-induced bone and soft-tissue regeneration open a new horizon in the field of tissue engineering. Here, first we reviewed the complete synthesis routes of ZnONPs by physical, chemical, and biological pathways as well as outlined the advantages and disadvantages of the techniques. Further, we discussed the several important aspects of physicochemical analysis of ZnONPs. Additionally, we extensively reviewed the important biomedical applications of ZnONPs as antibacterial, antioxidant, and antidiabetic agents, and in the field of tissue engineering with special emphasis on their mechanisms of actions. Furthermore, the future perspectives of the ZnONPs are also discussed.

Unravelling the Role of Synthesis Conditions on the Structure of Zinc Oxide-Reduced Graphene Oxide Nanofillers

The diversity of zinc oxide (ZnO) particles and derived composites applications is highly dependent on their structure, size, morphology, defect amounts, and/or presence of dopant molecules. In this work, ZnO nanostructures are grown in situ on graphene oxide (GO) sheets by an easily implementable solvothermal method with simultaneous reduction of GO. The effect of two zinc precursors (zinc acetate (ZA) and zinc acetate dihydrate (ZAD)), NaOH concentration (0.5, 1 or 2 M), and concentration (1 and 12.5 mg/mL) and pH (pH = 1, 4, 8, and 12) of GO suspension were evaluated. While the ZnO particle morphology shows to be precursor dependent, the average particle size length decreases with lower NaOH concentration, as well as with the addition of a higher basicity and concentration of GO suspension. A lowered band gap and a higher specific surface area are obtained from the ZnO composites with higher amounts of GO suspension. Otherwise, the low concentration and the higher pH of GO suspension induce more lattice defects on the ZnO crystal structure. The role of the different condition parameters on the ZnO nanostructures and their interaction with graphene sheets was observed to tune the ZnO–rGO nanofiller properties for photocatalytic and antimicrobial activities.

ZnO Nanoparticles-Modified Dressings to Inhibit Wound Pathogens

Zinc oxide (ZnO) nanoparticles (NPs) have been investigated for various skin therapies in recent years. These NPs can improve the healing and modulate inflammation in the wounds, but the mechanisms involved in such changes are yet to be known. In this study, we have designed a facile ZnO nano-coated dressing with improved antimicrobial efficiency against typical wound pathogens involved in biofilm and chronic infections. ZnO NPs were obtained by hydrothermal method and characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and Fourier-transform infrared spectroscopy. Antibacterial and antibiofilm effects were evaluated against laboratory and clinical isolates of significant Gram-negative (Pseudomonas aeruginosa and Escherichia coli) and Gram-positive (Staphylococcus aureus and Enterococcus faecalis) opportunistic pathogens, by quantitative methods. Our results have shown that the developed dressings have a high antibacterial efficiency after 6–24 h of contact when containing 0.6 and 0.9% ZnO NPs and this effect is similar against reference and clinical isolates. Moreover, biofilm development is significantly impaired for up to three days of contact, depending on the NPs load and microbial species. These results show that ZnO-coated dressings prevent biofilm development of main wound pathogens and represent efficient candidates for developing bioactive dressings to fight chronic wounds.

A novel strategy of nanosized herbal Plectranthus amboinicus, Phyllanthus niruri and Euphorbia hirta treated TiO2 nanoparticles for antibacterial and anticancer activities

Titanium dioxide nanoparticles exhibit good anticancer and antibacterial activities. They are known to be environmentally friendly, stable, less toxic, and have excellent biocompatibility nature. Due to these properties, they are well suited for biological applications particularly in biomedical applications such as drug delivery and cancer therapy. In this research article, three medicinal herbs namely, Plectranthus amboinicus (Karpooravalli), Phyllanthus niruri (Keezhanelli), and Euphorbia hirta (Amman Pacharisi), were used to modify the surface of the TiO₂ nanoparticles. The synthesized nanoparticles were subjected to various characterization techniques. The samples are then subjected to MTT assay to determine cell viability. KB oral cancer cells are used for the determination of the anticancer nature of the pure and bio modified nanoparticles. It is observed that Plectranthus amboinicus-Phyllanthus niruri modified TiO₂ nanoparticles exhibit excellent anticancer activities among other bio modified and pure samples. The samples are then examined for antibacterial activities against three Gram-negative bacterial strains namely, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and two Gram-positive bacterial strains namely, Staphylococcus aureus and Streptococcus mutans, respectively. Among the modified and pure samples, Plectranthus amboinicus showed good antibacterial activity against Gram-positive and Gram-negative bacteria. In the Flow cytometry analysis, the generation of p53 protein expression from Plectranthus amboinicus-Phyllanthus niruri modified TiO₂ nano herbal particles shows the anti-cancerous nature of the sample. Then to determine the toxic nature of the Plectranthus amboinicus-Phyllanthus niruri modified TiO₂ nano herbal particles against normal cells, the NPs were subjected to MTT assay against normal L929 cells, and it was found to be safer and less toxic towards the normal cells.

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.

UV-initiated crosslinking of electrospun chitosan/poly(ethylene oxide) nanofibers doped with ZnO-nanoparticles: development of antibacterial nanofibrous hydrogel

UV-initiated crosslinking of electrospun poly(ethylene) oxide (PEO)/chitosan (CS) nanofibers doped with zinc oxide nanoparticles (ZnO-NPs) was performed using pentaerythritol triaclyrate (PETA) as the photoinitiator and crosslinker agent. The influence of the addition of PETA to the PEO/CS diameter and crosslinking of nanofibers was evaluated. The effect of irradiation time on the morphology and swelling properties of the crosslinked nanofibers were investigated. For ZnO-NPs, the minimum inhibitory concentrations were found at 1 mg/mL, and the minimum bactericidal concentrations at 2 mg/mL for all the strains tested. The nanofibrous hydrogel antibacterial effect was tested. This material enters the realm of fibrous hydrogels which have potential use in several applications as in the biomedical area.

SUPPLEMENTARY MATERIAL

The supplementary material for this article can be found at 10.1557/mrc.2020.74.

The Role of Metal Oxide Nanoparticles, Escherichia coli, and Lactobacillus rhamnosus on Small Intestinal Enzyme Activity

Engineered nanomaterials (ENMs) have become common in the food industry, which motivates the need to evaluate ENM effects on human health. Gastrointestinal (GI) in vitro models (e.g. Caco-2, Caco-2/HT29-MTX) have been used in nanotoxicology research. However, the human gut environment is composed of both human cells and the gut microbiota. The goal of this study is to increase the complexity of the Caco-2/HT29-MTX in vitro model by co-culturing human cells with the Gram-positive, commensal Lactobacillus rhamnosus or the Gram-negative, opportunistic Escherichia coli; with the hypothesis that the presence of bacteria would ameliorate the effects of exposure to metal oxide nanoparticles (NPs) such as iron oxide (Fe2O3), silicone dioxide (SiO2), titanium dioxide (TiO2), or zinc oxide (ZnO). To understand this relationship, Caco-2/HT29-MTX cell barriers were acutely co-exposed (4 hours) to bacteria and/or NPs (pristine or in vitro digested). The activity of the brush border membrane (BBM) enzymes intestinal alkaline phosphatase (IAP), aminopeptidase-N (APN), sucrase isomaltase (SI) and the basolateral membrane enzyme (BLM) Na+/K+ ATPase were assessed. Findings show that (i) the human digestion process alters the physicochemical properties of NPs, (ii) large agglomerates of NPs remain entrapped on the apical side of the intestinal barrier, which (iii) affects the activity of BBM enzymes. Interestingly, some NPs effects were attenuated in the presence of either bacterial strains. Confocal microscopy detected bacteria-NPs interactions, which may impede the NP-intestinal cell contact. These results highlight the importance of improving in vitro models to closely mimic the complexities of the human body.

Optimization of ZnO Nanorods Growth on Polyetheresulfone Electrospun Mats to Promote Antibacterial Properties

Zinc oxide (ZnO) nanorods grown by chemical bath deposition (CBD) on the surface of polyetheresulfone (PES) electrospun fibers confer antimicrobial properties to the obtained hybrid inorganic–polymeric PES/ZnO mats. In particular, a decrement of bacteria colony forming units (CFU) is observed for both negative (Escherichia coli) and positive (Staphylococcus aureus and Staphylococcus epidermidis) Grams. Since antimicrobial action is strictly related to the quantity of ZnO present on surface, a CBD process optimization is performed to achieve the best results in terms of coverage uniformity and reproducibility. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) provide morphological and compositional analysis of PES/ZnO mats while thermogravimetric analysis (TGA) is useful to assess the best process conditions to guarantee the higher amount of ZnO with respect to PES scaffold. Biocidal action is associated to Zn²⁺ ion leaching in solution, easily indicated by UV–Vis measurement of metallation of free porphyrin layers deposited on glass.

Biosynthesis and Antibacterial Activity of ZnO Nanoparticles by Artemisia aucheri Extract

Background

Green approach to nanoparticles, including metal oxides Because of an inevitable disadvantage of physical or chemical synthesis routes is attractive nowadays. ZnO nanoparticles play a key role in the medicals and drugs area.

Objectives

In this study, biosynthesis of ZnO nanoparticles with new approach to enhanced the Antimicrobial properties against gram-negative and gram-positive was performed by use of a new type of plant extract, Artemisia aucheri, in an environmentally friendly, cost-effective, simple procedure way.

Materials and Methods

By adding Zn(NO₃)₂ to A. aucheri methanol extract followed by stirring The resulted solution and final heat treatment in 200 °C the ZnO nanoparticles were synthesized. Disc diffusion method was applied to evaluation the Antimicrobial properties of the extract and nanoparticles towards resistance into Escherichia coli (gram-negative) and Staphylococcus aureus (gram-positive).

Results

X-ray diffraction pattern (XRD) result showed all of the peaks proportion to ZnO and no other peaks were detected, also demonstrated nanostructure nature with crystallite size about 9 nm. In the Fourier transform infrared spectroscopy (FTIR), there is a band in the 550 cm^-1 which is corresponded to ZnO. Also 76 nm average particle size obtained by DLS experiments. Energy-dispersive X-ray spectroscopy (EDS) analysis showed strong peaks for Zn and O, support supposition of ZnO nanoparticles. Field emission scanning electron microscopy (FESEM) images indicated spherical rounded particles with the size of average 30 nm. Antibacterial tests showed effective diameter about 11 and 10 mm for plant extract and also 7 and 5 mm for ZnO nanoparticles against E. coli (gram-negative) and S. aureus (gram-positive) in agar disc diffusion method, respectively.

Conclusions

Biosynthesized ZnO nanoparticles could be a good candidate for antibacterial activity, both against E. coli (gram-negative) and S. aureus (gram-positive) especially for versus E. coli.

Cellulose from sources to nanocellulose and an overview of synthesis and properties of nanocellulose/zinc oxide nanocomposite materials

Recently, environmental and ecological concerns are increasing due to the usage of petroleum-based products so the synthesis of ultra-fine chemicals and functional materials from natural resources is drawing a tremendous level of attention. Nanocellulose, a unique and promising natural material extracted from native cellulose, may prove to be most ecofriendly materials that are technically and economically feasible in modern times, minimizing the pollution generation. Nanocellulose has gained tremendous attention for its use in various applications, due to its excellent special surface chemistry, physical properties, and remarkable biological properties (biodegradability, biocompatibility, and non-toxicity). Various types of nanocellulose, viz. cellulose nanofibrils (CNFs), cellulose nanocrystals (CNCs), and bacterial nanocellulose (BNC), are deeply introduced and compared in this work in terms of sources, production, structures and properties. The metal and metal oxides especially zinc oxide nanoparticles (ZnO-NPs) are broadly used in various fields due to the diversity of functional properties such as antimicrobial and ultraviolet (UV) properties. Thus, the advancement of nanocellulose and zinc oxide nanoparticles (ZnO-NPs)-based composites materials are summarized in this article in terms of the preparation methods and remarkable properties with the help of recent knowledge and significant findings (especially from the past six years reports). The nanocellulose materials complement zinc oxide nanoparticles, where they impart their functional properties to the nanoparticle composites. As a result hybrid nanocomposite containing nanocellulose/zinc oxide composite has shown excellent mechanical, UV barrier, and antibacterial properties. The nanocellulose based hybrid nanomaterials have huge potential applications in the area of food packaging, biopharmaceuticals, biomedical, and cosmetics. Thus the functional composite materials containing nanocellulose and zinc oxide will determine the potential biomedical application for nanocellulose.

Electrospun Active Biopapers of Food Waste Derived Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) with Short-Term and Long-Term Antimicrobial Performance

This research reports about the development by electrospinning of fiber-based films made of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) derived from fermented fruit waste, so-called bio-papers, with enhanced antimicrobial performance. To this end, different combinations of oregano essential oil (OEO) and zinc oxide nanoparticles (ZnONPs) were added to PHBV solutions and electrospun into mats that were, thereafter, converted into homogeneous and continuous films of ~130 μm. The morphology, optical, thermal, mechanical properties, crystallinity, and migration into food simulants of the resultant PHBV-based bio-papers were evaluated and their antimicrobial properties were assessed against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) in both open and closed systems. It was observed that the antimicrobial activity decreased after 15 days due to the release of the volatile compounds, whereas the bio-papers filled with ZnONPs showed high antimicrobial activity for up to 48 days. The electrospun PHBV biopapers containing 2.5 wt% OEO + 2.25 wt% ZnONPs successfully provided the most optimal activity for short and long periods against both bacteria.

Construction of selenium-embedded mesoporous silica with improved antibacterial activity

In this work, different concentrations of Se-incorporated mesoporous silica nanospheres (MSNs) (5Se/MSNs and 10Se/MSNs) were successfully synthesized via an in-situ one-pot method. Their physicochemical properties were characterized by X-ray diffraction (XRD), transmission electron microscopy, and X-ray photoelectron spectroscopy (XPS). The release behaviors of Se and Si were investigated in a phosphate-buffered saline (pH = 5.5, 7.4) solution (PBS). In vitro antibacterial properties of the prepared samples were evaluated with Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). The cytocompatibilities of the samples were then assessed using L929 cells. Se nanoparticles were successfully loaded onto the outer and inner surfaces of hierarchical mesoporous silica. The sizes of the Se/MSNs nanoparticles were approximately 120 nm for 5Se/MSNs and 210 nm for 10Se/MSNs. The XRD and XPS results showed that Se mainly existed in the form of Se⁰ in the samples. The Se/MSNs exhibited stable and sustained release of both Si and Se in PBS solution. In vitro antibactericidal tests indicated that the Se/MSNs could exhibit better antibacterial activity against S. aureus than pure Se nanoparticles after 6 and 24 h of culturing. The minimal inhibitory concentration (MIC) of 10Se/MSN was 100 μg mL^-1. However, the Se/MSNs exhibited no inhibitory effect on E. coli bacteria. Furthermore, all the samples exhibited excellent cell viability. These studies demonstrate initial in vitro antibacterial activity and good cytocompatibility of Se/MSNs and their potential application in antibacterial nanomedicine.

Coupled Oxides/LLDPE Composites for Textile Effluent Treatment: Effect of Neem and PVA Stabilization

The polyvinyl alcohol (PVA) and neem extract were grafted onto coupled oxides (3ZT-CO) via reflux process to stabilize the particles to form 3ZT-CO/PVA and 3ZT-CO/Neem. These were then incorporated into LLDPE by melt blending process to give LLDPE/3ZT-CO/PVA and LLDPE/3ZT-CO/Neem composites. The Neem and PVA stabilized particles showed high zeta potential and dispersed homogeneously in water. The stabilization process altered the shape of the particles due to plane growth along the (002) polar direction. The stabilizers acted as capping agents and initiated the one-dimensional growth. The alkyl chain groups from PVA increased the polarity of the LLDPE/3ZT-CO/PVA and played a dominant role in the water adsorption process to activate the photocatalytic activity. This was further enhanced by the homogeneous distribution of the particles and low degree of crystallinity (20.87%) of the LLDPE composites. LLDPE/3ZT-CO/PVA exhibited the highest photodegradation (93.95%), which was better than the non-stabilized particles. Therefore, the photocatalytic activity of a polymer composite can be enhanced by grafting PVA and neem onto couple oxides. The LLDPE/3ZT-CO/PVA composite was further used to treat textile effluent. The results showed the composite was able to remove dye color by 93.95% and to reduce biochemical oxygen demand (BOD) and chemical oxygen demand (COD) by 99.99%.

Relationship Between Structure And Antimicrobial Activity Of Zinc Oxide Nanoparticles: An Overview

The inappropriate use of antimicrobials has resulted in the selection of resistant strains. Thus, a great number of studies have focused on the investigation of new antimicrobial agents. The use of zinc oxide nanoparticles (ZnO NPs) to optimise the fight against microbial resistance has been receiving increased attention due to the non-specific activity of inorganic antimicrobial agents. The small particle size and the high surface area of ZnO NPs can enhance antimicrobial activity, causing an improvement in surface reactivity. In addition, surface modifiers covering ZnO NPs can play a role in mediating antimicrobial activity since the surface properties of nanomaterials alter their interactions with cells; this may interfere with the antimicrobial effect of ZnO NPs. The possibility of using surface modifiers with groups toxic to microorganisms can improve the antimicrobial activity of ZnO NPs. Understanding the exact toxicity mechanisms is crucial to elucidating the antimicrobial activity of ZnO NPs in bacteria and fungi. Therefore, this review aims to describe the mechanisms of ZnO NPs toxicity against fungi and bacteria and how the different structural and physical-chemical characteristics of ZnO NPs can interfere in their antimicrobial activity.

Bio-modified TiO2 nanoparticles with Withania somnifera, Eclipta prostrata and Glycyrrhiza glabra for anticancer and antibacterial applications

Titanium dioxide nanoparticles exhibit good anticancer and antibacterial activities. They are known to be environmentally friendly and stable, less toxic and excellent biocompatibility nature. In this paper we report the biological properties of pure TiO₂ nanoparticles modified with Withania somnifera (Ashwagandha), Eclipta prostrata (Karisalankanni) and Glycyrrhiza glabra (Athimathuram) for biological applications. X-ray diffraction results revealed the anatase nature of the samples. From the TEM analyses, it is observed that there is an increase in the particle size of the bio modified samples. UV results show the red shift for the bio modified samples when compared with the pure samples. The samples are then subjected to MTT assay to determine the cell viability. KB oral cancer cells are used for the determination of anticancer nature of the pure and bio modified nanoparticles. It is observed that Withania somnifera - Eclipta prostrate modified TiO₂ nanoparticles exhibit excellent anticancer activities among other bio modified and pure samples. The samples are then examined for their antibacterial activities against three Gram-negative bacterial strains namely, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa and two Gram-positive bacterial strains namely, Staphylococcus aureus and Streptococcus mutans. Among the modified and pure samples, Withania somnifera - Eclipta prostrata showed good antibacterial nature against Gram-positive and Gram-negative bacteria.