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.

Antimicrobial properties of ZnO nanomaterials: A review

The contribution of zinc ions to the antimicrobial activity of zinc oxide

In view of the emerging COVID-19 pandemic caused by SARS-CoV-2 virus, the search for potential protective and therapeutic antiviral strategies is of particular and urgent interest. Zinc is known to modulate antiviral and antibacterial immunity and regulate inflammatory response. Despite the lack of clinical data, certain indications suggest that modulation of zinc status may be beneficial in COVID-19. In vitro experiments demonstrate that Zn2+ possesses antiviral activity through inhibition of SARS-CoV RNA polymerase. This effect may underlie therapeutic efficiency of chloroquine known to act as zinc ionophore. Indirect evidence also indicates that Zn2+ may decrease the activity of angiotensin-converting enzyme 2 (ACE2), known to be the receptor for SARS-CoV-2. Improved antiviral immunity by zinc may also occur through up-regulation of interferon α production and increasing its antiviral activity. Zinc possesses anti-inflammatory activity by inhibiting NF-κB signaling and modulation of regulatory T-cell functions that may limit the cytokine storm in COVID-19. Improved Zn status may also reduce the risk of bacterial co-infection by improving mucociliary clearance and barrier function of the respiratory epithelium, as well as direct antibacterial effects against S. pneumoniae. Zinc status is also tightly associated with risk factors for severe COVID-19 including ageing, immune deficiency, obesity, diabetes, and atherosclerosis, since these are known risk groups for zinc deficiency. Therefore, Zn may possess protective effect as preventive and adjuvant therapy of COVID-19 through reducing inflammation, improvement of mucociliary clearance, prevention of ventilator-induced lung injury, modulation of antiviral and antibacterial immunity. However, further clinical and experimental studies are required.

https://www.spandidos-publications.com/10.3892/ijmm.2020.4575/download

Zinc and respiratory tract infections: Perspectives for COVID­19 (Review).

Bioactive glasses caused a revolution in healthcare and paved the way for modern biomaterial-driven regenerative medicine. The first 45S5 glass composition, invented by Larry Hench fifty years ago, was able to bond to living bone and to stimulate osteogenesis through the release of biologically-active ions. 45S5-based glass products have been successfully implanted in millions of patients worldwide, mainly to repair bone and dental defects and, over the years, many other bioactive glass compositions have been proposed for innovative biomedical applications, such as soft tissue repair and drug delivery. The full potential of bioactive glasses seems still yet to be fulfilled, and many of today’s achievements were unthinkable when research began. As a result, the research involving bioactive glasses is highly stimulating and requires a cross-disciplinary collaboration among glass chemists, bioengineers, and clinicians. The present article provides a picture of the current clinical applications of bioactive glasses, and depicts six relevant challenges deserving to be tackled in the near future. We hope that this work can be useful to both early-stage researchers, who are moving with their first steps in the world of bioactive glasses, and experienced scientists, to stimulate discussion about future research and discover new applications for glass in medicine.

https://www.mdpi.com/2079-4983/9/1/25/pdf

Bioactive Glasses: Where Are We and Where Are We Going?

Antimicrobial activity of zinc oxide particles on five micro-organisms of the Challenge Tests related to their physicochemical properties.

Zinc oxide as a new antimicrobial preservative of topical products: interactions with common formulation ingredients.

Film-forming cosmetic composition comprises 20-50 wt.% of a copolymer comprising (meth)acrylic acid and/or n-alkyl (meth)acrylate units.

Film-forming cosmetic composition, e.g. useful for treating acne-affected skin, comprises copolymer comprising (meth)acrylic acid and/or n-alkyl (meth)acrylate units

g r a p h i c a l a b s t r a c t a b s t r a c t Zinc ions (Zn 2+ ) exhibit antimicrobial activity against various bacterial and fungal strains. The partial dissolution of zinc oxide (ZnO) particles releases Zn2+ ions in aqueous suspension that contributes to the antimicrobial activity of ZnO. In addition to the activity of the soluble zinc species that is common with water-soluble zinc salts, ZnO combines two additional mechanisms of antimicrobial activity that supplement its activity as preservative in topical formulations: generation of reactive oxygen species and by direct contact to the cells walls. The present study aims at the evaluation of the contribution of the soluble zinc species to the antimicrobial activity of ZnO on microbial cultures in broth medium and the investigation of the dissolution of zinc from ZnO suspensions. The antimicrobial activities against the five microorganisms of the Challenge Tests were measured for suspensions of three ZnO grades in broth, and for the isolated liquid phase of the suspensions containing soluble zinc species. The Zn 2+ released

Emmanuelle Couval

Papers

The contribution of zinc ions to the antimicrobial activity of zinc oxide

Antimicrobial activity of zinc oxide particles on five micro-organisms of the Challenge Tests related to their physicochemical properties.

Zinc oxide as a new antimicrobial preservative of topical products: interactions with common formulation ingredients.

Film-forming cosmetic composition, e.g. useful for treating acne-affected skin, comprises copolymer comprising (meth)acrylic acid and/or n-alkyl (meth)acrylate units

Colloids and Surfaces A: Physicochemical and Engineering Aspects