E-Poster Presentation Australian Society for Microbiology Annual Scientific Meeting 2021

Superior antimicrobial properties of electron rich zinc oxide-reduced graphene oxide functionalised nanocomposite materials towards producing bacteria free safe water (#361)

Piumie Rajapaksha 1 , Khanh B. Vu 2 , Son Ngo 3 , Rebecca Orrell-Trigg 1 , Samuel Cheeseman 1 , Billy Murdoch 4 , Namita Choudhury 5 , Daniel Cozzolino 6 , Aaron Elbourne 1 , Yen Truong 7 , Vi Khanh Truong 1 , James Chapman 1
  1. School of Science, RMIT University, Melbourne, VIC, Australia
  2. Department of Chemical Engineering, International University, Ho Chi Minh City, Vietnam
  3. Laboratory of Theoretical and Computational Biophysics, Ton Duc Thang University, Ho Chi Minh City, Vietnam
  4. RMIT Microscopy & Microanalysis Facility, RMIT University, Melbourne, VIC, Australia
  5. School of Engineering, RMIT University, Melbourne, VIC, Australia
  6. Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, Brisbane, Australia
  7. CSIRO Manufacturing, Commonwealth Scientific and Industrial Research Organization (CSIRO), Clayton, VIC, Australia

Antimicrobial-resistant (AMR) bacterial strains known more colloquially as ‘superbugs’ have caused global health challenges. These so-called superbugs are pathogenic microorganisms that are resistant to classical disinfecting methods. Therefore, innovations in water purification using materials are required to treat these superbugs. This study fabricates a multi-functional, and multi-mechanistic antimicrobial water purifying nanomaterial. The nanomaterial is based on theoretical measurements which demonstrated an electron-rich carbon nanomaterial. These electron dense features can therefore interact with the microbial cell walls on the biointerface. Many methods exist as viable solutions for destroying microbes, but many of these approaches are uni-dimensional in their disinfection approach. In this work we combine zinc oxide (ZnO) and graphene oxide (GO); producing ZnO metal nanoparticle (NPs) doped reduced-GO (40% w/w ZnONP/rGO) materials. The materials are significantly effective in killing a range of Gram-positive and Gram-negative bacterial strains. The antimicrobial performance of the ZnONP-rGO (2 mg/mL) was evaluated against ~106 CFU/mL of concentrations of methicillin-resistant Staphylococcus aureus (MRSA) (ATCC 700699), Escherichia coli 0157:H7 (ATCC 43888) and Salmonella typhimurium (ATCC 14028) bacteria following a standard plate count method. The ZnONP-rGO performed at 98%, 82%, 79% total kill rates, while the unmodified-GO recorded 28%, 54%, 49% against S. typhimurium, E. coli 0157:H7, and MRSA, respectively.

The ZnONP-rGO was found to be highly antibacterial, because of the ZnONP-rGO; which through modelling demonstrated an electron-rich nanocomposite material. Additionally, the electron rich ZnONP-rGO physically perforates the microbial membranes over the edges and surfaces, which can be seen in the SEM data and corroborated through confocal laser scanning microscopy. The study concludes that the electron rich ZnONP-rGO nanomaterial physically induces the microbial cellular deaths and exhibits superior antimicrobial properties.