Lipid A removal by a reduced pressure nitrogen afterglow

Hayat ZERROUKI1,2, Virginie RIZZATI3, Corinne BERNIS3, Jean-Philippe SARRETTE1,2, Sarah COUSTY4 and Anne NEGRE-SALVAYRE3

1 Université de Toulouse, UPS, INPT, LAPLACE (Laboratoire Plasma et conversion d'Energie), Bât. 3R2, 118 route de Narbonne, Toulouse cedex 9, F-31062, France

2 CNRS, LAPLACE, Toulouse, F-31062, France

3 INSERM UMR 1048, Université de Toulouse, Toulouse, F-31062, France

4 Université de Toulouse, UPS, Laboratoire Parodontites et Maladies Générales, Faculté de Chirurgie Dentaire de Toulouse, 3 chemin des Maraîchers, Toulouse, F-31062, France

Corresponding author's e-mail: sarrette@laplace.univ-tlse.fr

It was already demonstrated that the late afterglow region of flowing post-discharges at reduced pressure (1-20 Torr) can be used for the sterilization of surfaces and of the reusable medical instrumentation. Recently, the bactericidal efficiency of a pure nitrogen afterglow was established, demonstrating the synergistic effect existing between the treatment temperature and the concentration of nitrogen atoms present in the late afterglow [1].

In the first part of the present paper, new sets of experiments are presented in order to clarify the respective roles of the N-atoms and of the UV radiation in the inactivation mechanisms by the nitrogen afterglow. Inactivation kinetics are also correlated to morphologic changes observed on exposed gram negative E. coli bacteria.

Lipid A is a major hydrophobic component of lipopolysaccharides (endotoxins) present in the membrane of most Gram-negative bacteria. Liberated in large amounts during the bacterial death, it is the major responsible for the bioactivity and toxicity of endotoxins. In the second part of the paper, the ability of the nitrogen late afterglow for the neutralization and/or removal of lipid A is studied. The effect of the nitrogen afterglow is analysed on pure lipid A and on lipid A extracted from exposed E. coli bacteria.

Using the same afterglow conditions than for the inactivation experiments (nitrogen flow QN2 = 1 slpm, pressure p = 5 Torr, microwave injected power PMW = 200 W, exposure time : 40 minutes), it is shown that more than 60% of lipid A (pure or bacteria-extracted, 1 mg exposed at the concentration of 1 mg/ml) are loss.

The afterglow exposure also results in a loss of the lipid A pro-inflammatory activity, assessed by the net decrease of the redox-sensitive NFkB transcription factor nuclear translocation.

Aknowledgments

This work is supported by the French ANR project ‘PLASMAVIV'.

References

[1] Villeger S., Sarrette J.P., Rouffet B., Cousty S. and Ricard A., Eur. Phys. J. Appl. Phys. (2008), 42, 25-32