Dec 12, 2012
Antibacterial coatings: taking lessons from nature
Chitosan films loaded with silver nanoparticles reduced in situ exhibit strong biocidal action against antibiotic-resistant and biofilm-forming strains of Staphylococcus aureus after short contact times. In a recent study, scientists from the University of Zaragoza in Spain and the Jagiellonian University in Poland have demonstrated how the antibacterial efficiency of these nanocomposite-based films depends on the size of the silver nanoparticles formed within the polymeric matrix and on the molecular weight/deacetylation degree of the chitosan used.
Direct contact between the bacteria and the film is required to completely eradicate the bacteria. On its own, the release of silver ions is not able to fully eliminate colonies of stationary growth bacteria, whereas upon contact the nanocomposite can eradicate a large bacteria count. Therefore, it is not only the cationic silver released from the film that is responsible for the biocidal action, but also the approach of the bacteria to the surface.
Finally, in view of their potential environmental impact, it seems clear that nanosilver-containing materials, while releasing silver ions to achieve bactericidal action, should keep the nanoparticles within the host structure to prevent an uncontrolled release of metallic nanoparticles into the environment. In this work, the researchers demonstrate that the uncontrolled release of silver is impaired by the strong attachment of the nanoparticles to the chitosan network.
The design of scaffolds or prosthesis with antibacterial characteristics is of interest in the broad fields of traumatology and orthopaedic surgery where a large variety of scaffolds or implants can suffer from bacterial colonization. Consequently, antibacterial coatings based on natural components on those surfaces could have a key role to play.
Full details can be found in the journal Nanotechnology.
About the author
Manuel Arruebo is a researcher based at the Institute of Nanoscience of Aragon in Spain.