| AVS 59th Annual International Symposium and Exhibition | |
| Biofilms and Biofouling: Marine Medical Energy Focus Topic | Thursday Sessions |
| Session MB+BI-ThM |
| Session: | Biofilms and Biofouling in Medicine |
| Presenter: | A. Pegalajar-Jurado, Swinburne University of Technology, Australia |
| Authors: | A. Pegalajar-Jurado, Swinburne University of Technology, Australia C.D. Easton, CSIRO Materials Science and Engineering, Australia S.L. McArthur, Swinburne University of Technology, Australia |
| Correspondent: | Click to Email |
Essential oils such as tea tree oil are known for their antibacterial properties. They have been used extensively as effective topical antimicrobial agents and are active against a wide range of micro-organisms. Traditionally, the antimicrobial properties of tea tree oil has been linked to the constituents of the oil including terpinen-4-ol and 1,8-cineole. To translate these antimicrobial properties into medical devices, methods for incorporating or coating materials are required. Recently, thin polymer films from terpinen-4-ol have been fabricated using plasma polymerisation. Initial data suggests that some antimicrobial activity was maintained. While plasma polymer films of 1,8-cineole have been fabricated previously, little focus has been placed on the antibacterial activity of this constituent.
The activity of 1,8-cineole against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) was evaluated based on the time-kill approach. Several concentrations of the oil (0.05 %, 0.2 %, 0.3 % and 0.5 % v/v) were added to broth media containing 3x108 CFU/mL of each bacterium. The optical density of the resulting solutions was measured at intervals over 24-hrs to monitor bacterial growth rates. The results demonstrated that concentrations above 0.35% v/v gave a 90% kill rate in the gram-negative E. coli after 8-hrs. Interestingly, the oil was less effective against the gram-positive S. aureus, producing a lower kill rate and rapid growth recovery in a 24-hour period.
Plasma polymers thin films of 1,8-cineole and 1,7-octadiene (hydrophobic control) were prepared using a stainless steel plasma reactor as described previously, while uncoated glass slides were used as a hydrophilic, positive control. Samples were then exposed to broth media containing 3x108 CFU/mL of each bacteriumto determine the effects of the coatings on bacterial attachment and growth. In this work, bacterial studies of the coating behaviour have focused on the attachment of S.aureus and E. coli, and biofilm formation of E. coli. Comparison of the plasma polymerised cineole (ppCineole) coating with the two controls demonstrated a reduction in bacterial attachments over 18-hrs. The reduction in bacterial attachment was more obvious in the case of E.coli in comparison with S. aureus. There were not significant differences between plasma polymerised cineole and octadiene in the inhibition of E.coli attachment and growth over a period of 18-hours. However, the biofilm studies indicated that only the 1,8-cineole film demonstrated antimicrobial behaviour over a period of time of 5 days.
Keywords: plasma polymerisation, antibacterial activity, cineole