Bioelectrostatics Research Centre Use of volatile additives to increase the antimicrobial efficacy of a corona discharge Dr Lindsey Gaunt Bioelectrostatics Research Centre School of Electronics and Computer Science University of Southampton, UK

Bioelectrostatics Research Centre Use of volatile additives to increase the antimicrobial efficacy of a corona discharge Aim; rationale Methods Results Discussion Applications and further work

Bioelectrostatics Research Centre Introduction Electrical discharges historically used in disinfection. Intense plasma exposure for surface disinfection Broad spectrum sterilisation of biological media and surfaces Reactive oxygen species oxidise membrane macromolecules Electrical corona in nitrogen Effective concentration of ions and charged particles E. coli Enhance effects using volatile additives including essential oils

Bioelectrostatics Research Centre Methods Test organisms were Escherichia coli and Staphylococcus aureus Enclosed booths of 0.5m 3 E. coli exposed for 30 minutes, S. aureus exposed for 10 minutes Agar plates S. aureus

Bioelectrostatics Research Centre Methods (cont.) Electrical corona driven ion wind Fan – non-ionised air flow Control – unexposed plates Current at plate of 10pA and ozone concentration of 0.2ppm 50  l of either ethyl alcohol, cinnamon oil or tea tree oil Direction of air flow Ground electrode Corona electrode Mini crucible for volatiles Bacterial plate 150mm Mean cfu counts compared Standardised to 250 Mann-Whitney-U tests

Bioelectrostatics Research Centre Survivorship of E. coli following exposure to ionised and non-ionised regimes Non-ionised air and cinnamon had no effects Viability was reduced by ethyl alcohol (19%) and tea tree oil (45%) Ionisation reduced viability by 65% Mortality was increased to 89% with addition of ethyl alcohol and 92% with cinnamon oil Tea tree oil reduced ionic efficacy

Bioelectrostatics Research Centre Survivorship of S. aureus following exposure to ionised and non-ionised regimes Non-ionised air reduced viability by 23% Ethyl alcohol and cinnamon oil reduced viability by 28% and 45% respectively Ionisation reduced viability by 74% Mortality was increased to 82% with addition of either ethyl alcohol or cinnamon oil

Bioelectrostatics Research Centre Summary Non-ionised Air Volatiles Ionised No effect Vapour action Cinnamon oil no effect vs. E.coli Air Volatiles Ionic action Ionised volatiles E. coli least susceptible Tea tree oil reduced ionic disinfection Oils increased efficacy esp. E. coli

Bioelectrostatics Research Centre Conclusion Enhanced antibacterial activity through a reaction in the corona discharge with volatile molecules Additive effect seen between ionic and volatile disinfection (ethyl alcohol and cinnamon oil (E. coli)) Tea tree oil generates less effective species Gram-negative bacteria (E. coli) are less susceptible to ionisation and volatiles than Gram-Positive (S. aureus) Membrane damage invoked for ionic disinfection and essential oil effects; treatments compliment each other.

Bioelectrostatics Research Centre Applications and further work Proof of concept Aerial disinfection Optimise, characterise and scale up Pathogenic organisms Understand issues Heating, ventilation and air conditioning systems Protection for public buildings, offices, medical environments and animal rearing facilities