Antibacterial activity of zinc oxide nanoparticles (ZnO-NPs) has received significant interest worldwide particularly by the implementation of nanotechnology to synthesize particles in the nanometer region. Many microorganisms exist in the range from hundreds of nanometers to tens of micrometers. ZnO-NPs exhibit attractive antibacterial properties due to increased specific surface area as the reduced particle size leading to enhanced particle surface reactivity. ZnO is a bio-safe material that possesses photo-oxidizing and photocatalysis impacts on chemical and biological species. This review covered ZnO-NPs antibacterial activity including testing methods, impact of UV illumination, ZnO particle properties (size, concentration, morphology, and defects), particle surface modification, and minimum inhibitory concentration. Particular emphasize was given to bactericidal and bacteriostatic mechanisms with focus on generation of reactive oxygen species (ROS) including hydrogen peroxide (H2O2), OH− (hydroxyl radicals), and O2 −2 (peroxide). ROS has been a major factor for several mechanisms including cell wall damage due to ZnO-localized interaction, enhanced membrane permeability, internalization of NPs due to loss of proton motive force and uptake of toxic dissolved zinc ions. These have led to mitochondria weakness, intracellular outflow, and release in gene expression of oxidative stress which caused eventual cell growth inhibition and cell death. In some cases, enhanced antibacterial activity can be attributed to surface defects on ZnO abrasive surface texture. One functional application of the ZnO antibacterial bioactivity was discussed in food packaging industry where ZnO-NPs are used as an antibacterial agent toward foodborne diseases. Proper incorporation of ZnO-NPs into packaging materials can cause interaction with foodborne pathogens, thereby releasing NPs onto food surface where they come in contact with bad bacteria and cause the bacterial death and/or inhibition.

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Review on Zinc Oxide Nanoparticles: Antibacterial Activity and Toxicity Mechanism.

The major strategies for designing surfaces that prevent fouling due to proteins, bacteria, and marine organisms are reviewed. Biofouling is of great concern in numerous applications ranging from biosensors to biomedical implants and devices, and from food packaging to industrial and marine equipment. The two major approaches to combat surface fouling are based on either preventing biofoulants from attaching or degrading them. One of the key strategies for imparting adhesion resistance involves the functionalization of surfaces with poly(ethylene glycol) (PEG) or oligo(ethylene glycol). Several alternatives to PEG-based coatings have also been designed over the past decade. While protein-resistant coatings may also resist bacterial attachment and subsequent biofilm formation, in order to overcome the fouling-mediated risk of bacterial infection it is highly desirable to design coatings that are bactericidal. Traditional techniques involve the design of coatings that release biocidal agents, including antibiotics, quaternary ammonium salts (QAS), and silver, into the surrounding aqueous environment. However, the emergence of antibiotic- and silver-resistant pathogenic strains has necessitated the development of alternative strategies. Therefore, other techniques based on the use of polycations, enzymes, nanomaterials, and photoactive agents are being investigated. With regard to marine antifouling coatings, restrictions on the use of biocide-releasing coatings have made the generation of nontoxic antifouling surfaces more important. While considerable progress has been made in the design of antifouling coatings, ongoing research in this area should result in the development of even better antifouling materials in the future.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/adma.201001215

Antifouling coatings: recent developments in the design of surfaces that prevent fouling by proteins, bacteria, and marine organisms.

The antibacterial properties of zinc oxide nanoparticles were investigated using both Gram-positive and Gram-negative microorganisms. These studies demonstrate that ZnO nanoparticles have a wide range of antibacterial activities toward various microorganisms that are commonly found in environmental settings. The antibacterial activity of the ZnO nanoparticles was inversely proportional to the size of the nanoparticles in S. aureus. Surprisingly, the antibacterial activity did not require specific UV activation using artificial lamps, rather activation was achieved under ambient lighting conditions. Northern analyses of various reactive oxygen species (ROS) specific genes and confocal microscopy suggest that the antibacterial activity of ZnO nanoparticles might involve both the production of reactive oxygen species and the accumulation of nanoparticles in the cytoplasm or on the outer membranes. Overall, the experimental results suggest that ZnO nanoparticles could be developed as antibacterial agents agai...

Size-Dependent Bacterial Growth Inhibition and Mechanism of Antibacterial Activity of Zinc Oxide Nanoparticles

https://www.tandfonline.com/doi/pdf/10.1088/1468-6996/9/3/035004

Enhanced bioactivity of ZnO nanoparticles?an antimicrobial study

The antibacterial behaviour of suspensions of zinc oxide nanoparticles (ZnO nanofluids) against E. Coli has been investigated. ZnO nanoparticles from two sources are used to formulate nanofluids. The effects of particle size, concentration and the use of dispersants on the antibacterial behaviour are examined. The results show that the ZnO nanofluids have bacteriostatic activity against E. coli. The antibacterial activity increases with increasing nanoparticle concentration and increases with decreasing particle size. Particle concentration is observed to be more important than particle size under the conditions of this work. The results also show that the use of two types of dispersants (Polyethylene Glycol (PEG) and Polyvinylpyrolidone (PVP)) does not affect much the antibacterial activity of ZnO nanofluids but enhances the stability of the suspensions. SEM analyses of the bacteria before and after treatment with ZnO nanofluids show that the presence of ZnO nanoparticles damages the membrane wall of the bacteria. Electrochemical measurements using a model DOPC monolayer suggest some direct interaction between ZnO nanoparticles and the bacteria membrane at high ZnO concentrations.

Investigation into the antibacterial behaviour of suspensions of ZnO nanoparticles (ZnO nanofluids)

Influence of particle size on the antibacterial activity of zinc oxide

Change in antibacterial characteristics with doping amount of ZnO in MgO–ZnO solid solution

The effects of shape, crystallinity and specific surface area of ZnO powder on antibacterial activity were studied by measuring the change in the electrical conductivity with bacterial growth. From the results, it was clarified that the antibacterial activity increased with the increase of powder concentration in the physiological saline. The antibacterial activity against Escherichia coli strongly depended on the specific surface area of the powder; the activity increased with the increase of the surface area, irrespective of the shape and the crystallinity of their powders. In the case of Staphylococcus aureus, however, it was found that there was no difference in the activity according to the characteristic of the powders. The appearance of antibacterial activity was found to be due to the generation of H2O2 from the surface of ZnO powder.

https://www.jstage.jst.go.jp/article/jcersj1988/106/1238/106_1238_1007/_pdf

Influence of Powder Characteristic of ZnO on Antibacterial Activity

Adsorption and growth inhibition of bacteria on carbon materials containing zinc oxide

Several 9-methyltriptycene derivatives have been synthesized and the PMR spectra examined at low temperatures. The compounds which have a methoxy or a methyl group at a peri position showed only broadening of methyl signals, whereas those with a chlorine at a peri position and another substituent at some other peri position showed a splitting of methyl signals. The compounds which have a halogen atom at a peri position are the intermediary cases in a sense that they show separation of the signal into two with 1 : 2 relative intensities but fail to show fine splittings. Activation parameters for the rotation were obtained by total line shape analysis. Substituent effects have been discussed.

Osamu Yamamoto

Papers

Influence of particle size on the antibacterial activity of zinc oxide

Change in antibacterial characteristics with doping amount of ZnO in MgO–ZnO solid solution

Influence of Powder Characteristic of ZnO on Antibacterial Activity

Adsorption and growth inhibition of bacteria on carbon materials containing zinc oxide

Restricted Rotation Involving the Tetrahedral Carbon. X. Barriers to Rotation of Methyl Groups in 9-Methyltriptycene Derivatives.