Abstract
BackgroundCold atmospheric plasma (CAP), which is ionized gas produced at atmospheric pressure, could be a novel and potent antimicrobial therapy for the treatment of infected wounds. Previously we have shown that CAP generated with a flexible surface Dielectric Barrier Discharge (sDBD) is highly effective against bacteria in vitro and in ex vivo burn wound models. In the current paper, we determined the in vitro and in vivo safety and efficacy of CAP generated by this sDBD device.MethodsThe effect of CAP on DNA mutations of V79 fibroblasts was measured using a hypoxanthine–guanine-phosphoribosyltransferase (HPRT) assay. Furthermore, effects on cell proliferation, apoptosis and DNA damage in ex vivo burn wound models (BWMs) were assessed using immunohistochemistry. Next, 105 colony forming units (CFU) P. aeruginosa strain PAO1 were exposed to CAP in a 3D collagen-elastin matrix environment to determine the number of surviving bacteria in vitro. Finally, rat excision wounds were inoculated with 107 CFU PAO1 for 24 h. The wounds received a single CAP treatment, repeated treatments on 4 consecutive days with CAP, 100 µL of 1% (wt/wt) silver sulfadiazine or no treatment. Wound swabs and punch biopsies were taken to determine the number of surviving bacteria.ResultsExposure of V79 fibroblasts to CAP did not increase the numbers of mutated colonies. Additionally, the number of proliferative, apoptotic and DNA damaged cells in the BWMs was comparable to that of the unexposed control. Exposure of PAO1 to CAP for 2 min resulted in the complete elimination of bacteria in vitro. Contrarily, CAP treatment for 6 min of rat wounds colonized with PAO1 did not effectively reduce the in vivo bacterial count.ConclusionsCAP treatment was safe but showed limited efficacy against PAO1 in our rat wound infection model.
Highlights
Cold atmospheric plasma (CAP), which is ionized gas produced at atmospheric pressure, could be a novel and potent antimicrobial therapy for the treatment of infected wounds
In vitro efficacy of CAP against P. aeruginosa To determine the optimal exposure time to CAP for an effective bactericidal elimination under the same conditions as in the in vitro safety tests, 105 colony forming units (CFU) of PAO1 in Matriderm® were exposed to CAP for 1–4 min
After exposure to CAP for 1 min, 6.2 CFU/mL of PAO1 survived on average (Fig. 2)
Summary
Cold atmospheric plasma (CAP), which is ionized gas produced at atmospheric pressure, could be a novel and potent antimicrobial therapy for the treatment of infected wounds. We have shown that CAP generated with a flexible surface Dielectric Barrier Discharge (sDBD) is highly effective against bacteria in vitro and in ex vivo burn wound models. Plasma is the fourth state of matter in physics and consists of a mix of ions, electrons, highly reactive molecules, excited species, electric fields and ultraviolet radiation [6]. It can be artificially generated by subjecting a neutral gas to an extremely high temperature or a strong electromagnetic field. Plasma is accompanied by the production of heat due to the collision of electrons, and the subsequent excitation, ionization and dissociation processes of the gas particles [6]
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