Anat Lipovsky

Bio: Anat Lipovsky is an academic researcher from Bar-Ilan University. The author has contributed to research in topics: Visible spectrum & Nanoparticle. The author has an hindex of 21, co-authored 40 publications receiving 2583 citations. Previous affiliations of Anat Lipovsky include National Cheng Kung University & Center for Advanced Materials.

Enhanced Antibacterial Activity of Nanocrystalline ZnO Due to Increased ROS-Mediated Cell Injury

Abstract: An innovative study aimed at understanding the influence of the particle size of ZnO (from the microscale down to the nanoscale) on its antibacterial effect is reported herein. The antibacterial activity of ZnO has been found to be due to a reaction of the ZnO surface with water. Electron-spin resonance measurements reveal that aqueous suspensions of small nanoparticles of ZnO produce increased levels of reactive oxygen species, namely hydroxyl radicals. Interestingly, a remarkable enhancement of the oxidative stress, beyond the level yielded by the ZnO itself, is detected following the antibacterial treatment. Likewise, an exposure of bacteria to the small ZnO nanoparticles results in an increased cellular internalization of the nanoparticles and bacterial cell damage. An examination of the antibacterial effect is performed on two bacterial species: Escherichia coli (Gram negative) and Staphylococcus aureus (Gram positive). The nanocrystalline particles of ZnO are synthesized using ultrasonic irradiation, and the particle sizes are controlled using different solvents during the sonication process. Taken as a whole, it is apparent that the unique properties (i.e., small size and corresponding large specific surface area) of small nanometer-scale ZnO particles impose several effects that govern its antibacterial action. These effects are size dependent and do not exist in the range of microscale particles.

Understanding the Antibacterial Mechanism of CuO Nanoparticles: Revealing the Route of Induced Oxidative Stress

Abstract: To date, there is still a lack of definite knowledge regarding the interaction of CuO nanoparticles with bacteria and the possible permeation of the nanoparticles into bacterial cells. This study was aimed at shedding light on the size-dependent (from the microscale down to the small nanoscale) antibacterial activity of CuO. The potent antibacterial activity of CuO nanoparticles was found to be due to ROS-generation by the nanoparticles attached to the bacterial cells, which in turn provoked an enhancement of the intracellular oxidative stress. This paradigm was confirmed by several assays such as lipid peroxidation and reporter strains of oxidative stress. Furthermore, electron microscopy indicated that the small nanoparticles of CuO penetrated the cells. Collectively, the results reported herein may reconcile conflicting concepts in the literature concerning the antibacterial mechanism of CuO nanoparticles, as well as highlight the potential for developing sustainable CuO nanoparticles-based devices for inhibiting bacterial infections.

Antifungal activity of ZnO nanoparticles--the role of ROS mediated cell injury.

Abstract: Metal oxide nanoparticles have marked antibacterial activity. The toxic effect of these nanoparticles, such as those comprised of ZnO, has been found to occur due to an interaction of the nanoparticle surface with water, and to increase with a decrease in particle size. In the present study, we tested the ability of ZnO nanoparticles to affect the viability of the pathogenic yeast, Candida albicans (C. albicans). A concentration-dependent effect of ZnO on the viability of C. albicans was observed. The minimal fungicidal concentration of ZnO was found to be 0.1 mg ml(-1) ZnO; this concentration caused an inhibition of over 95% in the growth of C. albicans. ZnO nanoparticles also inhibited the growth of C. albicans when it was added at the logarithmic phase of growth. Addition of histidine (a quencher of hydroxyl radicals and singlet oxygen) caused reduction in the effect of ZnO on C. albicans depending on its concentration. An almost complete elimination of the antimycotic effect was achieved following addition of 5 mM of histidine. Exciting the ZnO by visible light increased the yeast cell death. The effects of histidine suggest the involvement of reactive oxygen species, including hydroxyl radicals and singlet oxygen, in cell death. In light of the above results it appears that metal oxide nanoparticles may provide a novel family of fungicidal compounds.

EPR Study of Visible Light-Induced ROS Generation by Nanoparticles of ZnO

Abstract: Nanoparticles of ZnO have been shown to have marked antibacterial and anticancerous activities. The toxic effect of ZnO has been found to exist due to a reaction of the ZnO surface with water. In the present work electron-spin resonance measurements revealed that aqueous suspensions of small nanoparticles of ZnO produce increased levels of reactive oxygen species, namely hydroxyl radicals and singlet oxygen. Interestingly, a remarkable enhancement of the oxy radicals, was detected when the ZnO water suspension had been irradiated with blue (400−500 nm) light. The characterization of the mechanism of light-induced oxy radicals formation by ZnO nanoparticles would contribute to its use as a sterilization agent.

Eradication of multi-drug resistant bacteria by a novel Zn-doped CuO nanocomposite.

Abstract: Zinc-doped copper oxide nanoparticles are synthesized and simultaneously deposited on cotton fabric using ultrasound irradiation. The optimization of the processing conditions, the specific reagent ratio, and the precursor concentration results in the formation of uniform nanoparticles with an average size of ≈30 nm. The antibacterial activity of the Zn-doped CuO Cu0.88Zn0.12O in a colloidal suspension or deposited on the fabric is tested against Escherichia coli (Gram negative) and Staphylococcus aureus (Gram positive) bacteria. A substantial enhancement of 10 000 times in the antimicrobial activity of the Zn–CuO nanocomposite compared to the pure CuO and ZnO nanoparticles (NPs) is observed after 10 min exposure to the bacteria. Similar activities are observed against multidrug-resistant bacteria (MDR), (i.e., Methicillin-resistant S. aureus and MDR E. coli) further emphasizing the efficacy of this composite. Finally, the mechanism for this enhanced antibacterial activity is presented.

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

Abstract: 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.

Generation and Detection of Reactive Oxygen Species in Photocatalysis

Abstract: The detection methods and generation mechanisms of the intrinsic reactive oxygen species (ROS), i.e., superoxide anion radical (•O2–), hydrogen peroxide (H2O2), singlet oxygen (1O2), and hydroxyl radical (•OH) in photocatalysis, were surveyed comprehensively. Consequently, the major photocatalyst used in heterogeneous photocatalytic systems was found to be TiO2. However, besides TiO2 some representative photocatalysts were also involved in the discussion. Among the various issues we focused on the detection methods and generation reactions of ROS in the aqueous suspensions of photocatalysts. On the careful account of the experimental results presented so far, we proposed the following apprehension: adsorbed •OH could be regarded as trapped holes, which are involved in a rapid adsorption–desorption equilibrium at the TiO2–solution interface. Because the equilibrium shifts to the adsorption side, trapped holes must be actually the dominant oxidation species whereas •OH in solution would exert the reactivity...

The antimicrobial activity of nanoparticles: present situation and prospects for the future

Abstract: Nanoparticles (NPs) are increasingly used to target bacteria as an alternative to antibiotics. Nanotechnology may be particularly advantageous in treating bacterial infections. Examples include the utilization of NPs in antibacterial coatings for implantable devices and medicinal materials to prevent infection and promote wound healing, in antibiotic delivery systems to treat disease, in bacterial detection systems to generate microbial diagnostics, and in antibacterial vaccines to control bacterial infections. The antibacterial mechanisms of NPs are poorly understood, but the currently accepted mechanisms include oxidative stress induction, metal ion release, and non-oxidative mechanisms. The multiple simultaneous mechanisms of action against microbes would require multiple simultaneous gene mutations in the same bacterial cell for antibacterial resistance to develop; therefore, it is difficult for bacterial cells to become resistant to NPs. In this review, we discuss the antibacterial mechanisms of NPs against bacteria and the factors that are involved. The limitations of current research are also discussed.

Titanium dioxide-based nanomaterials for photocatalytic fuel generations.

Abstract: Generations Yi Ma,† Xiuli Wang,† Yushuai Jia,† Xiaobo Chen,‡ Hongxian Han,*,† and Can Li*,† †State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences and Dalian National Laboratory for Clean Energy, 457 Zhongshan Road, Dalian 116023, China ‡Department of Chemistry, College of Arts and Sciences, University of Missouri-Kansas City, 5100 Rockhill Road, Kansas City, Missouri 64110, United States

Antimicrobial activity of metals: mechanisms, molecular targets and applications

Abstract: Metals have been used as antimicrobial agents since antiquity, but throughout most of history their modes of action have remained unclear. Recent studies indicate that different metals cause discrete and distinct types of injuries to microbial cells as a result of oxidative stress, protein dysfunction or membrane damage. Here, we describe the chemical and toxicological principles that underlie the antimicrobial activity of metals and discuss the preferences of metal atoms for specific microbial targets. Interdisciplinary research is advancing not only our understanding of metal toxicity but also the design of metal-based compounds for use as antimicrobial agents and alternatives to antibiotics.