# Anti-Bacterial Action of Plasma Multi-Jets in the Context of Chronic Wound Healing
## 1 Introduction  
When introducing new people to \"plasma\" as \"ionized gas\", one mentions that plasma is the fourth state of matter and represents more than 99% of the baryonic matter of the universe. Natural plasmas are fascinating (aurora), a unique source of energy on earth (sun power), at the origin of basic mater physics (stars, quark plasma, amino acid generation as the bricks of life), but they are also somehow \"hostile\", generating huge transientcurrents and overvoltage in lightning, electromagnetic disturbance in the pole region, intense energetic radiation fluxes constraining microorganisms, and life expansion. This was indeed one the first historical developments of plasma science and technology to try to benefit from the radiative (UV, X-rays) and chemical compounds (oxidants, metastable states, charged particles with high energy) of plasmas for decontamination or sterilization purposes. Besides the pioneer works [1; 2; 3] and industrial device development [4; 5] based on plasma generation, innovative ongoing research works are still continuously reported on this topic [6; 7; 8; 9]. New eco-friendly alternatives pushed by consumer needs and environmental challenges, such as the use of natural ingredients for cosmetics, the design of innovative food product packaging, food product shelf life lengthening, and also the emergence of antibiotic-resistant pathogens or new viruses are key examples where an increasing need for new decontamination strategies are continuously required. Many among them are based on plasma technology [10; 11; 12; 13]. Indeed, plasma are known to be a potential and likely unique strategy for resistant microorganism reduction, mostly due to plasma's multifaceted features, merging energetic radiation, energetic particles, and chemically active compound cocktails likely combining short and long-lived oxidants. In this context, non-thermal plasma, or so-called cold plasma, has been developed in the past decade for plasma biomedical applications. Among them, the therapeutic applications in \"plasma medicine\" [14; 15] emerge, the two probably more advanced fields being wound care [16; 17; 18; 19; 20; 21; 22; 23] and new approaches for cancer treatment [24; 25; 26; 27; 28; 29; 30; 31]. Clinical studies dedicated to wound healing indicate that pathogen abatement, tissue growth stimulation and immune response are three of the modes of action that plasma delivery can trigger and control. Pathogen reduction is a key issue in hospitals where more and more multidrug-resistant strains of bacteria are emerging, thus limiting or even preventing the use of conventional disinfectants or drugs. [PERSON] et al. [32] reported on plasma's antibacterial effect with an RF helium afterglow on multi resistant _Pseudomonas aeruginosa_ and methicillin-resistant _Staphylococcus aureus_ exposed in vitro samples. Planktonic or biofilm growth on borosilicate slides cultured in 24-well plates were considered in this work, and a combination of plasma treatment with antibiotics was also evaluated. In [33], a dielectric barrier discharge (DBD) plasma torch generated with an air flow at 3.5 L/min and delivering a plasma jet 4 mm in diameter was used to study the sensitivity of antibiotic-resistant and non-resistant bacteria. The microorganisms were set in a thin liquid layer covering a glass substrate. The authors conclude that plasma degrades components (DNA) of the bacteria so that the plasma method may be useful in eliminating bacteria that are resistant to conventional antibiotic therapy. The application of DBD plasma was also demonstrated as a valuable decontamination technique for the removal from inert surfaces of planktonic and biofilm-embedded bacteria such as methicillin-sensitive _S. aureus_ (MRSA-USA 300, MRSA-USA 400) and _E. coli_, the most common hospital contaminants [34]. A plasma source named FlatPlaSter2.0., consisting of surface micro-discharges generated in air over a surface of 13 \(\times\) 9 cm\({}^{2}\) was assessed as an alternative disinfectant for dry surfaces [35].