Demonstration for cold atmospheric pressure plasma jet operation and antibacterial action in microgravity

Abstract

Cold atmospheric pressure plasma (ionized gas) is an innovative medical tool for the treatment of infected wounds thanks to its potential to inactivate drug-resistant microorganisms and promote tissue regeneration and vascularization. The low power consumption, compactness, and versatility of Cold Atmospheric Pressure Plasma (CAPP) devices make them an ideal tool for risk mitigation associated with human spaceflights. This work presents results in microgravity on the operability of CAPP and its antimicrobial effect. The experiments carried out in parabolic flights make it possible to optimize the treatment conditions (i.e., the distance, the gas mixture) and to obtain the rapid inactivation (<15 s) of Escherichia coli samples. Interestingly, the inactivation efficiency of CAPP was higher during parabolic flights than under terrestrial conditions. Overall, these results encourage the further development of CAPP medical devices for its implementation during human spaceflights.

Fig. 1. Plasma jet characterization in 0 g conditions.

a Plasma jet camera photographs in 1 g and 0 g versus O₂ concentration: 0%, 0.5%, 1%. Scale = 10 mm. b Plasma jet ICCD mean frame (30 frames) and mean length in 1 g and 0 g versus O₂ concentration. Scale = 10 mm.

Fig. 2. Inhibition of E. coli with the PG in 0 g conditions.

a Untreated sample in terrestrial condition. b Untreated sample in weightlessness condition, exposed to a 5 min He gas flow. c Example of a fully inactivated inhibition area” (blue) after PG treatment (He, 7 kV, 20 kHz, 5 s). d Example of a non-homogeneously inactivated area (red) due to PG treatment, thereafter named ”effect area” (He + 2%O₂, 7 kV, 20 kHz, 15 s).

Fig. 3. Bacterial inactivation analysis.

a Diameter of bacterial inactivation zone versus treatment time following He plasma exposure at 20 kHz and 7 kV, for a reactor-target gap of 15 and 25 mm, in 0 g conditions. b Diameter of bacterial inactivation versus treatment time following a He–0.5% O₂ plasma exposure at 20 kHz and 7 kV for a reactor-target gap of 15 and 25 mm in 0 g conditions. c Diameter of effect area following a 15 s-long He–O₂ plasma exposure with different dioxygen admixtures at 20 kHz and 7 kV for a reactor-target gap of 15 and 25 mm in 0 g conditions. d Diameter of bacterial inactivation versus treatment time following He plasma exposure at 20 kHz and 7 kV for a reactor-target gap of 15 and 25 mm in terrestrial conditions (1 g). a–d Presented values are means ± SD of n = 4 biological replicates.

Fig. 4. ICCD analysis and Ozone measurement in 1 g conditions.

a Filtered ICCD acquisitions of a plasma treatment of a grounded target at 15 mm. Contrast and the brightness adjustment are optimally set up for each acquisition. b ICCD acquisitions of a 7 kV, 20 kHz He plasma treatment of a grounded target versus different reactor-target gaps: 15 mm, 20 mm, 25 mm. Contrast and brightness adjustment are the same for each acquisition. c ICCD intensities of different transitions at the surface of a 15 mm far grounded target for a He (black) and a He + 0.5% O₂ (red) gas mixture for a plasma at 20 kHz and 7 kV. Presented values are means ± SD of n = 10 replicates. d Ozone measurement versus the O₂ concentration at 20 kHz and 7 kV. The target is at 15 mm, metallic, and grounded. Presented values are means of n = 10 replicates.

Fig. 5. Parabolic flight.

Airplane settings and gravity levels and duration during one parabola.

Fig. 6. In-flight experimental setup.

a In-plane photograph of GREMI experimental rack for cold plasma generation and bacteria exposure. b Plasma Gun reactor, side view. c Front view of the plasma jet and Optical setup.

Fig. 7. Bacterial sample analysis.

a Control sample. b Photograph an example of a treated Petri dish with the result of image treatment to measure the treated area (right corner).