With the advent of nanotechnology, there has been an extensive interest in the antimicrobial potential of metals. The rapid and widespread development of antimicrobial-resistant and multidrug-resistant bacteria has prompted recent research into developing novel or alternative antimicrobial agents. In this study, the antimicrobial efficacy of metallic copper, cobalt, silver and zinc nanoparticles was assessed against Escherichia coli (NCTC 10538), S. aureus (ATCC 6538) along with three clinical isolates of Staphylococcus epidermidis (A37, A57 and A91) and three clinical isolates of E. coli (Strains 1, 2 and 3) recovered from bone marrow transplant patients and patients with cystitis respectively. Antimicrobial sensitivity assays, including agar diffusion and broth macro-dilution to determine minimum inhibitory and bactericidal concentrations (MIC/MBC) and time-kill/synergy assays, were used to assess the antimicrobial efficacy of the agents. The panel of test microorganisms, including antibiotic-resistant strains, demonstrated a broad range of sensitivity to the metals investigated. MICs of the type culture strains were in the range of 0.625-5.0 mg ml −1. While copper and cobalt exhibited no difference in sensitivity between Gram-positive and Gram-negative microorganisms, silver and zinc showed strain specificity. A significant decrease (p < 0.001) in the bacterial density of E. coli and S. aureus was demonstrated by silver, copper and zinc in as little as two hours. Furthermore, combining metal nanoparticles reduced the time required to achieve a complete kill.

Original languageEnglish
Article number045003
Number of pages11
JournalBiomedical Materials
Issue number4
Early online date9 May 2023
Publication statusPublished - Jul 2023

Bibliographical note

Copyright © 2023 The Author(s). Published by IOP Publishing Ltd. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence [https://creativecommons.org/licenses/by/4.0/]. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.


  • antimicrobial
  • antimicrobial resistance
  • heavy metals
  • nanoparticles
  • synergism


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