Among multidrug-resistant bacteria, the toughest ones to beat make biofilms. These films shield bacteria and stick to surface wounds like burn injuries or bed sores. As modern medicines fail against resistant bacteria, some scientists propose turning to ancient yet proven remedies: essential oils. The challenge, however, is getting the greasy oils into water-based bacterial environments. Researchers led by Vincent M. Rotello at the University of Massachusetts, Amherst, engineered cross-linked poly(oxanorborneneimide) nanocomposites (X-BNCs) loaded with the compound carvacrol, which can be extracted from the essential oil of oregano. These nanocomposites smuggle the oil into biofilms grown on the surface of mouse cells (J. Am. Chem. Soc. 2018, DOI: 10.1021/jacs.8b03575). Within hours, the oil-soaked nanocomposites killed four pathogenic Gram-negative and Gram-positive strains of bacteria commonly found in hospitals, including two multidrug-resistant strains. The team also tested the bacteria’s ability to develop resistance to the nanocomposites. The researchers treated the bacteria with the nanocomposites until only a fraction survived, then regrew the bacterial culture in an iterative fashion and found that the bacteria was susceptible to the treatment even after 20 cycles. After the nanocomposite has ferried the antimicrobial agent behind bacterial enemy lines, the composite is degraded by biomolecules such as glutathione and esterase enzymes. The resulting fragments should then be safely expelled by the body, Rotello says.
This article was corrected on June 11, 2018, to clarify that carvacrol is itself not an essential oil but rather a compound in the essential oil of oregano.