BIOPLASMAS & PLASMAS WITH LIQUIDS - Joint Conference of COST ACTIONS TD1208 “Electrical discharges with liquids for future
applications” & MP1101 Biomedical Applications of Atmospheric Pressure Plasma Technology, Bertinoro, Italy, 13th-17th September 2015
A Uniform Plasma Dose Treatment of Individual Isolated
Bacteria Cells
D. Rutherford1, C. Mahony1, S. Spence1, F. Macias-Montero1, C.
Kelsey1, N. Hamilton1, E. Bennet2, H. Potts2, D. Diver2, D.
McDowell1, D. Mariotti1, P. Maguire1
1Nanotechnology
& Integrated BioEngineering Centre, Ulster University, Shore
Road, Newtownabbey, BT37 0QB, N. Ireland
2School of Physics & Astronomy, Kelvin Building, University of Glasgow, G12
8QQ, Scotland
rutherford-d1@email.ulster.ac.uk
Research into the interactions between bacteria cells and gas plasmas has predominantly
focussed on investigating plasma exposure as a means of decontaminating a wide range of
materials and environments. However, not all cells that are subjected to plasma treatment are
inactivated, and there is a knowledge gap with regards to the fundamental mechanisms that
govern plasma’s anti-bacterial effects. Progress in this area is hampered because not all cells
receive identical treatment in terms of plasma exposure and treatment duration, termed ‘plasma
dose’. We have demonstrated that individual bacteria cells subjected to a uniform plasma dose
can retain cell viability.
Each bacterial cell (E. coli) is contained within an aerosol droplet (d ~ 10 µm) and transported
through an atmospheric pressure plasma (3.0 mm x 2.0 mm ID). Gas temperature is estimated
to be <400 K, plasma density 1E13-1E14 cm-3 and exposure times vary between 0.04 – 0.1 ms,
dependent on the droplet velocity [1]. The bacteria-loaded aerosol droplet undergoes some
evaporation inflight (~2 µm) and the plasma-cell interactions are facilitated by the liquid droplet,
where it is known that plasma-induced charging and surface chemistry can occur. We report on
the viabilities and growth kinetics of individual aerosolised, plasma-exposed bacteria, and the
impact of the treatment on bacterial biomolecules with reference to measured plasma
parameters.
Figure 1. Numbers of plasma treated bacteria
(CFUs) detected on Nutrient Agar &
Chromocult Agar, after incubation (37oC/24h)
Figure 2. Optical densities (OD600 nm) of suspensions
of treated bacteria, incubated at 37 oC, for up to 24
hours. Inset graph shows the lag phase only.
[1] P. Maguire et al., “Controlled Microdroplet Transport in an Atmospheric Pressure
Microplasma”, Appl. Phys. Lett. 106, 224101 (2015)