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Study: Black Silicon Mechanically Kills Pseudomonas aeruginosa, Other Pathogens

Australian scientists have revealed the bacterial killing potential of black silicon, a type of silicon that has been etched to create long narrow nanoprotrusions on its surface.

The Wandering Percher dragonfly (Diplacodes bipunctata). Insets show 3D reconstruction of the upper surface of black silicon, upper left, and the surface of the dragonfly forewings.

The Wandering Percher dragonfly (Diplacodes bipunctata). Insets show 3D reconstruction of the upper surface of black silicon, upper left, and the surface of the dragonfly forewings.

Earlier this year the team discovered that the wing of the cicada Psaltoda claripennis can shred certain types of rod-shaped bacteria through a process that arises from its physical structure.

“Based on this discovery, we investigated other insects that may possess similar surface architectures that might kill more bacteria, in particular the deadly strains of the Staphylococcus aureus or golden staph bacterium,” explained Prof Elena Ivanova from Swinburne University of Technology, who is the lead author of the study published in the journal Nature Communications.

In the new study, Prof Ivanova and her colleagues set out to study the wings of the Wandering Percher dragonfly (Diplacodes bipunctata), whose spike-like nanostructure kills both rod-shaped and spherical bacteria, and mimic the surface structure of the dragonfly wing on the silicon surface.

The researchers compared the two surfaces and their bacteria-killing capacity. They demonstrated that both create a spike-like structure through the formation of clusters of multiple neighboring nanoprotrusions.

“This structure generates a mechanical bacteria killing effect which is unrelated to the chemical composition of the surface,” said senior author Prof Russell Crawford, also from Swinburne University of Technology.

Black silicon and Wandering Percher dragonfly wing surfaces were effective against the gram-negative Pseudomonas aeruginosa cells, gram-positive Staphylococcus aureus cells and both the vegetative cells and spores of Bacillus subtilis.

“Both surfaces were found to be highly effective against a range of bacteria, as well as endospores. They exhibited estimated average bacteria killing rates of up to 450,000 cells per minute of exposure, for every square centimeter of available surface.”

“This represents an exciting prospect for the development of a new generation of antibacterial nanomaterials that could be applied to the surfaces of medical implants, making them far safer.”

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Bibliographic information: Ivanova EP et al. 2013. Bactericidal activity of black silicon. Nature Communications 4, article number: 2838; doi: 10.1038/ncomms3838