Lidé

David Rutherford, Ph.D.

Všechny publikace

Correlative atomic force microscopy and scanning electron microscopy of bacteria-diamond-metal nanocomposites

  • DOI: 10.1016/j.ultramic.2023.113909
  • Odkaz: https://doi.org/10.1016/j.ultramic.2023.113909
  • Pracoviště: Katedra fyziky
  • Anotace:
    Research investigating the interface between biological organisms and nanomaterials nowadays requires multi-faceted microscopic methods to elucidate the interaction mechanisms and effects. Here we describe a novel approach and methodology correlating data from an atomic force microscope inside a scanning electron microscope (AFM-in-SEM). This approach is demonstrated on bacteria-diamond-metal nanocomposite samples relevant in current life science research. We describe a procedure for preparing such multi-component test samples containing E. coli bacteria and chitosan-coated hydrogenated nanodiamonds decorated with silver nanoparticles on a carbon-coated gold grid. Microscopic topography information (AFM) is combined with chemical, material, and morphological information (SEM using SE and BSE at varied acceleration voltages) from the same region of interest and processed to create 3D correlative probe-electron microscopy (CPEM) images. We also establish a novel 3D RGB color image algorithm for merging multiple SE/BSE data from SEM with the AFM surface topography data which provides additional information about microscopic interaction of the diamond-metal nanocomposite with bacteria, not achievable by individual analyses. The methodology of CPEM data interpretation is independently corroborated by further in-situ (EDS) and ex-situ (micro-Raman) chemical characterization as well as by force volume AFM analysis. We also discuss the broader applicability and benefits of the methodology for life science research.

Enhanced antimicrobial and photocatalytic effects of plasma-treated gallium-doped zinc oxide

  • DOI: 10.1016/j.apsusc.2024.159567
  • Odkaz: https://doi.org/10.1016/j.apsusc.2024.159567
  • Pracoviště: Katedra fyziky
  • Anotace:
    We characterize gallium-doped zinc oxide (ZnO:Ga) after exposure to hydrogen or oxygen plasma for potential use as a novel antibacterial and photocatalytic material. ZnO:Ga were composed of smooth rods with a thick central portion and tapered nanometre-sized ends alongside clusters of thin disk particles. Plasma treatment removed material from the rod surface and introduced features such as small holes or pits that increased the surface roughness and reduced the zinc ion concentration measured from colloidal suspensions. The surface charge of ZnO:Ga was influenced by plasma treatment: hydrogen plasma induced a positive surface charge whereas oxygen plasma resulted in a negative surface charge. However, electrostatic interactions with negatively charged bacteria were not the predominant mechanism underlying the antibacterial effect of ZnO:Ga. Treatment with oxygen or hydrogen plasma enhanced the antibacterial effect of ZnO:Ga against gram-positive bacteria, yet only oxygen plasma caused an enhancement against gram-negative bacteria. The photocatalytic effect of ZnO:Ga was enhanced after oxygen plasma treatment but supressed by hydrogen plasma treatment. The results indicate that plasma treatment of ZnO:Ga can successfully alter material properties to provide enhancement of the antibacterial and photocatalytic effects, however the type of feed gas used should be carefully chosen based upon the desired application.

Generation and delivery of free hydroxyl radicals using a remote plasma

  • Autoři: McQuaid, H., David Rutherford, Ph.D., Mariotti, D., Maguire, P.
  • Publikace: Plasma Sources Science and Technology. 2023, 32(1), ISSN 0963-0252.
  • Rok: 2023
  • DOI: 10.1088/1361-6595/acb07f
  • Odkaz: https://doi.org/10.1088/1361-6595/acb07f
  • Pracoviště: Katedra fyziky
  • Anotace:
    We demonstrate a new gas-based O H ∙ generation source using a low power radio frequency driven atmospheric pressure plasma configured to deliver the radical flux into the far effluent region, well away from interference from other plasma factors such as electric fields, currents, and ultraviolet radiation. Using He-H2O gas chemistry isolated from the laboratory air, the plasma generated flux contains O H ∙ and other radicals including, O and HO2 as well as H2O2 which, along with, was found to vary with H2O vapour content and absorbed power density. Peak flux values were 2.3 nmol s−1 and 0.23 nmol s1 for H2O2 and O H ∙ respectively at a distance of 50 mm from the plasma, with 790 ppmv H2O and a power density of ∼108 W m−3. The maximum O H ∙ flux density was 4.5 × 1019 m−2s−1 falling to 1.7 × 1019 m2 s1 at 110 mm, equivalent to generation rates of 74 µM s1 and 28 µM s−1. Despite high O H ∙ recombination rates at the plasma exit, the escaping flux is still significant, indicating a viable delivery capability to downstream targets. Its performance with regard to O H ∙ generation rates compares well with traditional O H ∙ generation techniques such as radiolysis, advanced oxidation processes and enhanced Fenton-chemistry approaches where O H ∙ production rates are sub-µM s−1. Delivering precisely quantifiable O H ∙ fluxes provides new opportunities for scientific studies and technological opportunities in cell biology, atmospheric chemistry, protein unfolding and systematic dose studies for plasma-based and other O H ∙ related potential medical treatments.

Bactericidal effect of zinc oxide nanoparticles on Gram-positive and Gram-negative strains in reverse spin bioreactor

  • DOI: 10.1088/1757-899X/1050/1/012013
  • Odkaz: https://doi.org/10.1088/1757-899X/1050/1/012013
  • Pracoviště: Katedra fyziky
  • Anotace:
    We present an experimental study investigating the efficacy of zinc oxide nanoparticle use for bacterial decontamination of water using reverse spin technology. The number of viable bacteria reduced with treatment time and the rate of inactivation was dependent on zinc oxide concentration. Gram-positive S. aureus bacteria were more resistant to zinc oxide nanoparticles compared to Gram-negative E. coli, however both strains were completely eradicated after 4 hours using a concentration of 10 μg/mL. Nanoparticles did not inhibit growth of bacteria when added to an agar surface, neither when in liquid before bacteria inoculation nor when loaded onto filter paper disks after bacteria inoculation. These results emphasise the importance of efficient reactor mixing to enhance interaction capability for ZnO use in water decontamination.

Effect of ZnO nanoparticle sizes and illumination on growth inhibition of Escherichia coli and Staphylococcus aureus bacteria in cultivation medium

  • DOI: 10.1088/1757-899X/1050/1/012007
  • Odkaz: https://doi.org/10.1088/1757-899X/1050/1/012007
  • Pracoviště: Katedra fyziky
  • Anotace:
    We study antibacterial effects of the zinc oxide nanoparticles (ZnO NPs) in cultivation medium (Mueller-Hinton broth) on Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria models. We compare synthesized ZnO hedgehog NPs and commercial ZnO NPs (50 nm and 20 μm nominal size) in different concentrations (1 mg/mL and 0.1 mg/mL). Results show that E. coli are more sensitive to the ZnO presence in the cultivation media than S. aureus. We also characterize influence of visible and UV light on the ZnO NP effects.

Growth Inhibition of Gram-Positive and Gram-Negative Bacteria by Zinc Oxide Hedgehog Particles

  • DOI: 10.2147/IJN.S300428
  • Odkaz: https://doi.org/10.2147/IJN.S300428
  • Pracoviště: Katedra fyziky
  • Anotace:
    Purpose: Nanomaterials for antimicrobial applications have gained interest in recent years due to the increasing bacteria resistance to conventional antibiotics. Wound sterilization, water treatment and surface decontamination all avail from multifunctional materials that also possess excellent antibacterial properties, eg zinc oxide (ZnO). Here, we assess and compare the effects of synthesized hedgehog-like ZnO structures and commercial ZnO particles with and without mixing on the inactivation of bacteria on surfaces and in liquid environments.

Microscopic Study of Bovine Serum Albumin Adsorption on Zinc Oxide (0001) Surface

  • DOI: 10.1002/pssa.202000558
  • Odkaz: https://doi.org/10.1002/pssa.202000558
  • Pracoviště: Katedra fyziky
  • Anotace:
    Properties and functions of various ZnO materials are intensively investigated in biological systems for diagnostics, therapy, health risks assessment as well as bactericidal and decontamination purposes. Herein, the interface between ZnO and biological environment is studied by characterizing adsorption of bovine serum albumin (BSA) and fetal bovine serum (FBS) using atomic force microscopy with CF4-treated tips. Similar molecular morphologies (thickness around 2 nm) yet different binding forces to ZnO (10–25 nN) are observed. These observations are corroborated by atomic scale simulations of BSA on (0001) ZnO surface using force-field method and showing rearrangements of Zn surface atoms. Such binding may have an impact also on other properties of ZnO–BSA complex.

PLASMA-SYNTHESISED ZINC OXIDE NANOPARTICLE BEHAVIOR IN LIQUIDS

  • DOI: 10.37904/nanocon.2021.4318
  • Odkaz: https://doi.org/10.37904/nanocon.2021.4318
  • Pracoviště: Katedra fyziky
  • Anotace:
    Zinc oxide nanoparticles have been synthesized using non-thermal atmospheric pressure plasma (ZnO-NTP). We investigated the behavior of these ligand-free as a colloid suspension using different solvents, from deionized water to physiological saline and microbial culture broth. We found that the zeta potential of ZnO-NTP became more negative after exposure to microbial culture broth relative to water, which suggests increased colloid stability. Photoluminescence spectra of ZnO-NTP were similar regardless of liquid type, yet optical and fluorescent images of samples showed different agglomeration behavior depending on liquid type. Scanning electron microscopy images revealed large agglomerates of ZnO-NTP interacting with the surface of bacteria cells, ranging in size from 200 nm up to 2 µm. We also studied effect of sub-lethal concentrations of ZnO-NTP on bacteria under illumination. There was no significant difference in viable bacteria concentration after 24h exposure to 10 µg/mL ZnO-NTP relative to untreated control irrespective of sample illumination.

COMPARISON OF MICROBIAL INTERACTIONS OF ZINC OXIDE NANOMATERIALS IN VARIOUS SIZE AND SHAPE

  • DOI: 10.37904/nanocon.2019.8666
  • Odkaz: https://doi.org/10.37904/nanocon.2019.8666
  • Pracoviště: Katedra fyziky
  • Anotace:
    Zinc oxide nanoparticles (ZnO NP) have shown great potential as a novel antibacterial material at a time when resistance towards conventional antibiotics is becoming more prevalent. We report bacteria inactivation by ZnO NP with novel hedgehog-like morphology using model gram-negative (E. coli) and gram-positive (S. aureus) bacteria. E. coli exposed to the novel ZnO hedgehog NP during growth resulted in 4 orders of magnitude reduction in viable cell concentration after 24 h, which is more than 2 orders higher reduction compared to commercially available ZnO NPs with nominal sizes from 50 nm to 20 um. There was a positive correlation between hedgehog NP concentration and bacteria cell concentration reduction within the range tested 0.1 – 1.0 mg/mL. S. aureus was less sensitive to ZnO NP exposure and inactivation effect of various ZnO NP was comparable. The effect can be thus atrributed to direct mechanical damage of the bacterial mebrane that is the most effective for the novel hedgehog ZnO NP. This conclusion was corroborated also by disk diffusion assays

Longitudinal dynamics of herd-level Mycobacterium bovis MLVA type surveillance in cattle in Northern Ireland 2003–2016

  • Autoři: Skuce, R., Breadon, E., Allen, A., Milne, G., McCormick, C., Hughes, C., David Rutherford, Ph.D., Smith, G., Thompson, S., Graham, J., Harwood, R., Byrne, A.
  • Publikace: Infection, Genetics and Evolution. 2020, 79(1), ISSN 1567-1348.
  • Rok: 2020
  • DOI: 10.1016/j.meegid.2019.104131
  • Odkaz: https://doi.org/10.1016/j.meegid.2019.104131
  • Pracoviště: Katedra fyziky
  • Anotace:
    Investigating genetically-structured diversity in pathogen populations over time is important to better understand disease maintenance and spread. Herd-level surveillance of Mycobacterium bovis genotypes (multi-locus VNTR analysis types, MLVA types) from all culture-confirmed bovine tuberculosis (TB) herd cases was undertaken in Northern Ireland (NI), generating an unparalleled, longitudinal, population-level 14-year survey for this pathogen.

Continuous In-Flight Synthesis for On-Demand Delivery of Ligand-Free Colloidal Gold Nanoparticles

  • Autoři: Maguire, P., David Rutherford, Ph.D., Macias-Montero, M., Mahony, C., Kelsey, C., Tweedie, M., Pérez-Martin, F., McQuaid, H., Diver, D., Mariotti, D.
  • Publikace: Nano Letters. 2017, 17(3), 1336-1343. ISSN 1530-6984.
  • Rok: 2017
  • DOI: 10.1021/acs.nanolett.6b03440
  • Odkaz: https://doi.org/10.1021/acs.nanolett.6b03440
  • Pracoviště: Katedra fyziky
  • Anotace:
    We demonstrate an entirely new method of nanoparticle chemical synthesis based on liquid droplet irradiation with ultralow (<0.1 eV) energy electrons. While nanoparticle formation via high energy radiolysis or transmission electron microscopy-based electron bombardment is well-understood, we have developed a source of electrons with energies close to thermal which leads to a number of important and unique benefits. The charged species, including the growing nanoparticles, are held in an ultrathin surface reaction zone which enables extremely rapid precursor reduction. In a proof-of-principle demonstration, we obtain small-diameter Au nanoparticles (∼4 nm) with tight control of polydispersity, in under 150 μs. The precursor was almost completely reduced in this period, and the resultant nanoparticles were water-soluble and free of surfactant or additional ligand chemistry. Nanoparticle synthesis rates within the droplets were many orders of magnitude greater than equivalent rates reported for radiolysis, electron beam irradiation, or colloidal chemical synthesis where reaction times vary from seconds to hours. In our device, a stream of precursor loaded microdroplets, ∼15 μm in diameter, were transported rapidly through a cold atmospheric pressure plasma with a high charge concentration. A high electron flux, electron and nanoparticle confinement at the surface of the droplet, and the picoliter reactor volume are thought to be responsible for the remarkable enhancement in nanoparticle synthesis rates. While this approach exhibits considerable potential for scale-up of synthesis rates, it also offers the more immediate prospect of continuous on-demand delivery of high-quality nanomaterials directly to their point of use by avoiding the necessity of collection, recovery, and purification. A range of new applications can be envisaged, from theranostics and biomedical imaging in tissue to inline catalyst production for pollution remediation in automobiles.

Za stránku zodpovídá: Ing. Mgr. Radovan Suk