GROWTH OF ESCHERICHIA COLI ON NANOCRYSTALLINE DIAMOND

Bacteria attached to solid surfaces are able to form bacterial biofilms which present serious problems both in healthcare and in industrial applications. Naturally, the development of anti-adhesive coatings that prevent bacterial attachment is of great importance nowadays. Nanocrystalline diamond (NCD) is one of the promising materials thanks its favourable mechanical and chemical properties. NCD appeared to be highly compatible with mammalian tissue cells; however, the knowledge on interactions between NCD and bacteria is rather scarce. In this contribution, we compared the attachment of gram-negative model bacterium Escherichia coli to uncoated glass and glass coated by NCD films. NCD films were grown by chemical vapour deposition on silica fused glass substrates. To achieve different wetting properties, the NCD were terminated by hydrogen or oxygen plasma. The NCD films were characterized by atomic force microscopy, scanning electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy and contact angle measurement. AFM confirmed differences in surface roughness between uncoated and NCD coated glass. Oxidized NCD films were hydrophilic compared to hydrogenated ones. Autoclaving was used for NCD samples sterilization; this method was shown to maintain original wetting properties of NCD films. For attachment experiments, continuous cultivation in commercially available CDC Bioreactor was used. Antibacterial tests indicated higher attachment of gram-negative model bacterium Escherichia coli to NCD surface compared to uncoated glass. We assign this effect to higher roughness of NCD surface compared to glass. Bacterial cells preferred the hydrophobic surface of hydrogenated NCD surface to hydrophilic oxidized NCD for their attachment.