Mechano-bactericidal nanopillars require external forces to effectively kill bacteria
Nanopillars are known to mechanically damage bacteria, suggesting a promising strategy for highly-effective anti-bacterial surfaces. However, the mechanisms underlying this phenomena remain unclear, which ultimately limits translational potential towards real-world applications. Using real-time and end-point analysis techniques, we demonstrate that in contrast to expectations, bacteria on multiple "mechano-bactericidal" surfaces remain viable, unless exposed to a moving air-liquid interface which caused considerable cell death. Reasoning that normal forces arising from surface tension may underlie mechano-bactericidal activity, we developed computational and experimental models to estimate, manipulate, and recreate the impact of these forces. Our experiments together demonstrate that nanopillar surfaces alone do not cause cell death, but require a critical level of external force to deform and rupture bacteria. These studies hence provide fundamental physical insight into the mechanisms by which nanopillar surfaces can serve as effective antibacterial strategies, and describe the use-conditions under which such nanotechnological approaches may provide practical value. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=107 SRC="FIGDIR/small/012153v1_ufig1.gif" ALT="Figure 1"> View larger version (29K): org.highwire.dtl.DTLVardef@1cfded2org.highwire.dtl.DTLVardef@2dc47dorg.highwire.dtl.DTLVardef@bf002dorg.highwire.dtl.DTLVardef@1a49c2d_HPS_FORMAT_FIGEXP M_FIG Graphical Abstract C_FIG