Silicon Nanopillars Have Antibacterial Properties

Nanostructures present both in nature (on dragonfly wings) and in the lab (on a synthetic silicon mimic) kill bacteria, suggesting new approaches to antibacterial surfaces for biomedical and industrial applications, reports a group led by Elena P. Ivanova of Swinburne University of Technology, in Australia (Nat. Commun. 2013, DOI: 10.1038/ncomms3838). Dragonfly wing surfaces are patterned with lipids that form vertical pillars a few hundred nanometers tall and less than 90 nm in diameter. So-called black silicon—named for its light absorption properties—has similarly sized pillars, made up of largely amorphous silicon. When Ivanova and colleagues incubated either material with suspensions of Pseudomonas aeruginosa,Staphylococcus aureus, or Bacillus subtilis, as well as with B. subtilis spores, they found that the surfaces killed the cells and spores. In prior work with cicada wing surfaces, which also have bactericidal nanopillars, Ivanova and colleagues showed that when P. aeruginosa cells adsorb onto nanopillar surfaces, parts of the cell walls located between individual pillars stretch, leading to cell rupture. The authors note that black silicon is readily made using standard semiconductor etching techniques.