Nitric Oxide-Emitting Nanomaterials Kill Microbes

Nanomaterials modified to release nitric oxide, a compound produced by inflammatory cells to kill invading microbes, might be future therapeutics for fighting antibiotic-resistant pathogens, according to a research team led by Mark H. Schoenfisch of the University of North Carolina, Chapel Hill. Building on previous work showing that NO-releasing nanoparticles kill bacteria more efficiently than small-molecule NO donors (ACS Nano, DOI: 10.1021/nn700191f), grad student Yuan Lu and postdoc Bin Sun reported that NO-releasing silica nanorods and polystyrene-capped dendrimers have even better biocidal activity. The researchers modified these materials with N-diazeniumdiolate moieties that break down to form NO when exposed to water. They found that long, thin silica rods (1,100 nm by 100 nm) kill bacteria at a lower dosage and with less NO than do spherical nanoparticles. “We don’t yet know whether the rods pierce the bacteria,” Schoenfisch said. But he thinks a greater contact area between the nanorods and bacteria surfaces leads to better NO delivery. The researchers also found that hydrophobic, polystyrene-capped dendrimers are more effective bacteria killers than are hydrophilic dendrimers, likely because the hydrophobic compounds interact with the bacteria better to locally transfer cargo, he added.