Browsing by Author "Christofferson, AJ"

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    Biochemical interaction of few layer black phosphorus with microbial cells using synchrotron macro-ATR-FTIR
    (Materials Australian and The Australian Ceramic Society, 2022-06-01) Shaw, ZL; Cheeseman, S; Huang, LZY; Penman, R; Ahmed, T; Bryant, SJ; Bryant, G; Christofferson, AJ; Orwell-Twigg, R; Dekiwadia, C; Truong, VK; Vongsvivut, JP; Walia, S; Elbourne, A
    In the fight against drug-resistant pathogenic microbial cells, low dimensional materials are emerging as a promising alternative treatment. Specifically, few-layer black phosphorus (BP) has demonstrated its effectiveness against a wide range of pathogenic microbial cells with studies suggesting low cytotoxicity towards healthy mammalian cells. However, the antimicrobial mechanism of action of BP is not well understood and further in-depth investigations are required. In this work, the complex biochemical interaction between BP and a series of microbial cells is investigated using advanced, high-resolution microscopy techniques to provide a greater understanding of the antimicrobial mechanism. Synchrotron macro-attenuated total reflection–Fourier transform infrared (ATR-FTIR) micro-spectroscopy is used to elucidate the chemical changes occurring outside and within the cell of interest after exposure to BP nanoflakes. The ATR-FTIR data, coupled with microscopy, reveals chemical changes to the cellular phospholipids, proteins, structural polysaccharides and nucleic acids when compared to untreated cells. These changes can be attributed to the physical interaction combined with the oxidative stress induced by the degradation of the BP nanoflakes. This study provides an insight into the biochemical interaction of BP nanoflakes with microbial cells, allowing for a better understanding of the antimicrobial mechanism of action.
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    Gold nanoparticle adsorption alters the cell stiffness and cell wall bio-chemical landscape of Candida albicans fungal cells
    (Elsevier, 2024-01-15) Penman, R; Kariuki, R; Shaw, ZL; Dekiwadia, C; Christofferson, AJ; Bryant, G; Vongsvivut, JP; Bryant, SJ; Elbourne, A
    Hypothesis Nanomaterials have been extensively investigated for a wide range of biomedical applications, including as antimicrobial agents, drug delivery vehicles, and diagnostic devices. The commonality between these biomedical applications is the necessity for the nanoparticle to interact with or pass through the cellular wall and membrane. Cell-nanomaterial interactions/uptake can occur in various ways, including adhering to the cell wall, forming aggregates on the surface, becoming absorbed within the cell wall itself, or transversing into the cell cytoplasm. These interactions are common to mammalian cells, bacteria, and yeast cells. This variety of interactions can cause changes to the integrity of the cell wall and the cell overall, but the precise mechanisms underpinning such interactions remain poorly understood. Here, we investigate the interaction between commonly investigated gold nanoparticles (AuNPs) and the cell wall/membrane of a model fungal cell to explore the general effects of interaction and uptake. Experiments The interactions between 100 nm citrate-capped AuNPs and the cell wall of Candida albicans fungal cells were studied using a range of advanced microscopy techniques, including atomic force microscopy, confocal laser scanning microscopy, scanning electron microscopy, transmission electron microscopy, and synchrotron-FTIR micro-spectroscopy. Findings In most cases, particles adhered on the cell surface, although instances of particles being up-taken into the cell cytoplasm and localised within the cell wall and membrane were also observed. There was a measurable increase in the stiffness of the fungal cell after AuNPs were introduced. Analysis of the synchrotron-FTIR data showed significant changes in spectral features associated with phospholipids and proteins after exposure to AuNPs. © 2023 The Author(s). Published by Elsevier Inc. This is an open access article under the CC BY license.
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    Molecular mechanism of stabilization of thin films for improved water evaporation protection
    (American Chemical Society, 2013-11-26) Yiapanis, G; Christofferson, AJ; Plazzer, M; Weir, MP; Prime, EL; Qiao, GG; Solomon, DH; Yarovsky, I
    All-atom molecular dynamics simulations and experimental characterization have been used to examine the structure and dynamics of novel evaporation-suppressing films where the addition of a water-soluble polymer to an ethylene glycol monooctadecyl ether monolayer leads to improved water evaporation resistance. Simulations and Langmuir trough experiments demonstrate the surface activity of poly(vinyl pyrrolidone) (PVP). Subsequent MD simulations performed on the thin films supported by the PVP sublayer show that, at low surface pressures, the polymer tends to concentrate at the film/water interface. The simulated atomic concentration profiles, hydrogen bonding patterns, and mobility analyses of the water-polymer-monolayer interfaces reveal that the presence of PVP increases the atomic density near the monolayer film, improves the film stability, and reduces the mobility of interfacial waters. These observations explain the molecular basis of the improved efficacy of these monolayer/polymer systems for evaporation protection of water and can be used to guide future development of organic thin films for other applications. © 2013, American Chemical Society.