Oral Presentation 24th Australian Conference on Microscopy and Microanalysis 2016

Do nanopillars kill bacteria by piercing the bacterial membrane? (#35)

Chaturanga D. Bandara 1 2 , Sanjleena Singh 3 , Annelena Wolff 3 , Jamie Riches 3 , Tuquabo Tesfamichael 1 , Adekunle Oloyede 1
  1. Science and Engineering Faculty, Queensland University of Technology (QUT), Brisbane, QLD 4000, Australia
  2. The Institute of Health and Biomedical Innovation (IHBI), Queensland University of Technology (QUT), Kelvin Grove, QLD 4059, Australia
  3. Central Analytical Research Facility, Queensland University of Technology (QUT), Brisbane, QLD 4000, Australia

Recently there has been increased interest in the potential of the surface topography of nanopillars to kill bacterial cells124 . It has been shown that bactericidal activity is independent of surface chemistry but rather is highly influenced by the properties of surface architecture24 . Nanopillars are also reported deadly to both eukaryotic and prokaryotic cells15 . Though it has reported that physical rupture of membrane by the nanopillars can be the cause of bacterial death using computational models6 , there is yet no direct experimental evidence which support the physical rupture of the membrane of cells. Physical rupture of the cell membrane was shown through indirect confocal imaging124 . Direct evidence for membrane rupture by nanopillars is important to conclude this bactericidal mechanism and to develop nanotopography as a tool to control bacterial adhesions on material surfaces. As biological samples are nonconductive, fragile under normal handling and display less image contrast, it is challenging to obtain desired information at the interface of the “bacterial membrane-nanotopgraphy” in high resolution imaging techniques without extensive processing of the samples which can potentially introduce artefacts and complicate interpretation. Here, the membrane of Escherichia coli on nanopillars of bactericidal dragonfly wing was characterised by TEM to determine whether any nanopillars pierced into bacterial cell. TEM micrographs have shown separation of inner cell plasma membrane from the outer membrane, which is a characteristic of cell death in bacteria as reported by Kim etal7   but none of images has showed bacterial membrane is pierced by nanopillars. TEM tomographic images have shown a gap of approximately 100 nm between the bacterial membrane and the tip of the nanopillars. This raises interesting question whether nanopillars pierce bacterial membrane when bacteria are dead on nanopillar topography. Future work is necessary to find the mechanism of which bacteria are being killed on nanotopography.

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