Open access peer-reviewed chapter

Cold Atmospheric Pressure Plasmas (CAPs) for Skin Wound Healing

Written By

Zilan Xiong

Submitted: 17 April 2017 Reviewed: 01 March 2018 Published: 16 May 2018

DOI: 10.5772/intechopen.76093

From the Edited Volume

Plasma Medicine - Concepts and Clinical Applications

Edited by Yusuf Tutar and Lutfi Tutar

Chapter metrics overview

2,679 Chapter Downloads

View Full Metrics

Abstract

In the past 20 years, cold atmospheric pressure plasmas (CAPs) have become a new promising way for many biomedical applications, such as disinfection, cancer treatment, root canal treatment, wound healing, and other medical applications. Among these applications, investigations of plasma for skin wound healing has gained huge success both in vitro and in vivo experiments, and also the mechanism behind it has been studied by many groups. In this chapter, we summarize the state-of-the-art progress in wound healing by CAPs. The plasma devices developed for wound healing, the interactions between plasmas and microorganisms/cells/tissues, the in vitro and in vivo treatments, the clinical trials, and biosafety issues are all included.

Keywords

  • atmospheric pressure plasma
  • plasma devices
  • wound healing
  • disinfection
  • cell proliferation
  • clinical trials

1. Introduction

Wound healing is a complex process involved with infection, cell proliferation/migration, and skin remodeling, see Figure 1 [1]. For normal wounds, generally the first-stage inflammation occurs in 24–48 h after tissue damage. Bacteria, neutrophils, and platelets are abundant with normal skin appendages present outside the wound. The second stage lasts from after 48 h to around 10 days, during which scab would form on the skin and cell migration and proliferation vigorously occurs. New blood vessels populate the wound area. Skin remodeling starts in the following stage and usually lasts a year or even longer. A scar is usually left and the healed area does not contain normal skin appendages. Wounds can typically be categorized as acute and chronic wounds. Acute wounds contain abrasions, scalds, burns, or post-operative incisions; however, chronic wound does not heal in an orderly set of stages and often remain in the inflammatory stage for too long and associated with systemic illnesses, age, and repeated trauma such as diabetic ulcers, venous ulcers, arterials ulcers, and pressure sores. The number of patients undergoes chronic wounds increases constantly. It has been reported that around 4.5–5 million people in Germany are concerned with chronic non-healing wounds [2]. Traditional treatments of chronic wounds are expensive and time-consuming; patients usually undergo long-term hospitalization with a poor quality of life.

Figure 1.

Classic stages of wound repair: (a) inflammation (b) new tissue formation; and (c) remodeling [1].

The first step of chronic wound treatment begins with bacterial disinfection. However, with involvement of multidrug-resistant bacteria like methicillin-resistant Staphylococcus aureus (MRSA), treatment of chronic wound encounters more challenges, because the effect of traditional medical antiseptics is largely restrained. Therefore, there is a huge demand for new methods and strategies for skin disinfection and improving wound healing process. One of the potential candidates is cold atmospheric pressure plasmas (CAPs) [36].

Plasma, known as the fourth state of matter, other than plasma from blood, has been studied for centuries. Nevertheless, cold atmospheric pressure plasmas (CAPs) also called nonthermal plasmas have attracted huge attention during last two decades for its unique advantage in a new special field—plasma medicine. In 1996, the first paper of plasma medicine came out, which developed a promising way to solve the problems with traditional medical therapies [7]. Since then, related research groups in the entire world started to follow this new field; they extended the research field from initial decontamination to mechanism study, plasma cell interaction, cancer treatment, skin disinfection, blood coagulation, chronic wound healing, and so on, and since then thousands of peer-reviewed research and review papers have been published. There also have been various CAP devices developed [813], based on which, in recent years several commercial plasma devices have started to be used in hospital, for example, RF Argon plasma jet-based products by Leibniz Institute for Plasma Science and Technology (INP Greifswald)—kINPen MED has gained Conformité Européenne (CE) marketing certification in 2013 [14].

We report the latest progress of atmospheric pressure plasma for skin wound healing in this chapter and the sections have been arranged as follows: in Section 2, basic plasma components and typical plasma sources for skin treatment are summarized; in Sections 3 and 4, fundamental studies of plasmas interaction with microorganism and cell/tissue are included; in Sections 5 and 6, in vitro and in vivo studies of CAP treatment of skin wounds on animal model are presented; and in Section 6, clinical trials and a very important issue—plasma biosafety—are presented.

Advertisement

2. Plasma generation and designed devices for skin disinfection

CAPs could be generated in lab using plasma source and driven by power supplies with working gas. Working gases such as noble gases (He, Ar), N2, O2, air, or their mixtures could be used to ignite the plasma. Typical constituents of plasma include electrons, ions, neutral particles (background gas molecules), UV radiation (UBA, UVB, UVC), heat, reactive oxygen, nitrogen species (RONS), and so on (see Figure 2). All these components within plasma make CAPs highly reactive. The constituents and concentration of species in plasma depends on the plasma source, the power input as well as the working gas. When contacting with microorganisms or cell/tissue, components of plasma will play different roles in the treating processes; however, the mechanism has not been fully understood yet. It is well known that UVB (280–320 nm) and UVC (100–280 nm) could be able to cross the epidermis, and UVA (320–400 nm) can even reach the dermis. UVB and UVA can also trigger skin cancer. However, a lot of reports claimed that UV radiation in plasma is low and does not play a significant role in anti-microorganism process except that from microwave-driven discharge [1518]. Charged particles in plasma were concluded to play an essential role in bacterial inactivation by rupturing the outer layer of cell membrane [19, 20]. Mendis et al. reported the electrostatic force caused by charge accumulation on the cell membrane could overcome the tensile strength which leads to rupture [15]. However, other researchers claimed different viewpoints that the anti-bacterial effect of the charged particles is due to the chemical modification of the membrane surface [21]. CAPs are usually designed to operate in near room temperature (less than 40°C); therefore, there would not be substantial thermal effects on microbial cells [22]. The effect of heat can be ignored. The microorganism is under indirect plasma treatment which means that plasma does not directly contact with the target; the electric field was too weak to contribute to the inactivation process. In some cases, when plasma is in direct contact with the samples, the electric field could become high enough to take effect [23]. However, in most of the cases, there is a rare possibility to put the samples within 300 μm away from the electrode to cause damage by the electric field [24]. If the plasma device is using air or O2-containing mixture or operating in the open air, RONS such as O, O3, NO, NO2, OH, and H2O2 would present. These highly active species are believed to play an important role in all the plasma treatment processes and have already been reported by many researchers [18, 2628]. The detailed discussion of the roles of reactive species can be found in [29].

Figure 2.

Plasma components.

Figure 3 summarizes several typical plasma sources used in different research groups. (a) is called plasma pencil designed by Laroussi group [30]. This device driven by sub-microsecond high-voltage pulse uses He gas flowing through a modified DBD device (with holes in the center of dielectric plates), therefore the plasma created between electrode panels comes out and forms a plasma plume up to 5 cm. Another famous plasma source construct is a floating-electrode DBD device (FE-DBD) which uses the treating object as the second electrode and could generate plasma between the electrode surface and the substrate [31]. FE-DBD could directly use the air inside the short gap as working gas. Safety and stability of FE-DBD largely depends on the power supply, the gas gap, and the electrode shape. Kolb et al. introduced a DC-driven micro-hollow cathode discharge to generate plasma plume outside the tiny hole (c) [32]. It could use air or other gas as working gas. A 51 KΩ ballast resistor is connected to the circuit to restrain the current to 20 mA. The dimension of the plume changes with the gas flow rate as well as the gas temperature. Lu et al. reported a single-electrode plasma jet powered by nanosecond pulse DC [33]. Helium is used as working gas and the length of plasma plume could reach up to 4 cm. The gas temperature is about 300 K and species like O, OH, and N2+ are all detected by optical emission spectra (OES) (d). Another structure called plasma needle usually uses bare metal needle as electrode, see (e) and (f) [9, 34]. (g) is a portable DC-driven plasma needle array device called plasma flashlight [35]. This device can directly use a DC battery to power up and create plasma in the open air. (h) is a plasma brush of relatively large area [36]. (i) is also a classical design (surface micro-discharge, SMD) representing ‘indirect plasma’ [37]. This type of plasma generates on the surface of the electrode, and the plasma does not directly contact with the treatment target. When using air as working gas, SMD could operate in three modes: call ozone mode, transition mode, and NOx mode, respectively. The transition between these modes depends on the input power. More detailed information of the different plasma sources can be found in [38, 39].

Figure 3.

Typical CAP sources.

With the development of the lab-made plasma sources and fundamental studies, many commercial plasma device products have been delivered into the market. Figure 4 shows three famous products for skin wound healing based on plasma jet device, FE-DBD and SMD, respectively. Figure 4(a) is the world famous kINPen plasma device, which is based on a RF argon plasma jet source and gained CE marketing certification in 2013. (b) is called PlasmaDerm based on FE-DBD. And (c) is MicroPlasma β, which origins from SMD device. The wound healing effect of these three products will be presented in the following sections.

Figure 4.

Three commercialized CAPs medical devices.

Advertisement

3. Plasma interaction with microorganisms

Plasma sterilization is the first research field of plasma medicine. Since Professor Laroussi published the first paper of plasma sterilization in 1996 on IEEE Transactions on Plasma Science [7], there came out thousands of studies on inactivation of bacteria, fungi, and virus using different plasma sources. At the same time, mechanism of plasma interaction with microorganism was studied by using physical, chemical, and biomedical diagnostic methods, such as optical emission spectra (OES), laser-induced fluorescence (LIF), Fourier transform infrared spectroscopy (FTIR), flow cytometry, electrophoresis, ELISA, chemiluminescence assay, and so on. However, the exact mechanism of plasma inactivation microorganisms still remains unclear. Possible mechanisms proposed by researchers are: (1) electroporation- and oxidation-induced cell wall/membrane dysfunction, which leads to leakage of cellular components; (2) intracellular oxidation and nitrification causing protein damage and gene expression disorder; and (3) direct DNA damage such as causing double-strand breaking.

Bacterial killing effect by CAPs has been investigated for more than 20 years. It is found that CAPs could effectively inactivate different type of bacteria, including gram-positive and gram-negative, anaerobic, aerobic, or facultative anaerobic bacteria [40]. The response of bacteria to CAPs is species-dependent and the Gram-positive bacteria is usually more susceptible to CAPs treatment because of the difference of cell-wall components, which indicates that the CAP-induced damage to the cell membrane and cell wall may be a key factor of antibacterial effect. The most common bacteria found in skin and wound infection are Staphylococcus aureus, Staphylococcus epidermidis, Bacillus cereus, and so on, which have been proved to be effectively inactivated by CAPs [41, 42]. Unlike drugs, another advantage of CAPs is that plasma does not show any resistance after multi-treatment against bacteria. Maisch et al. reported significant decolonization of methicillin-resistant Staphylococcus aureus (MRSA) and Escherichia coli without cell damage of a pig skin sample [43]. Alkawareek et al. also found complete inactivation of MRSA [44].

Many fungi are common constituents of skin flora, and under certain conditions, they would cause diseases. The effects of traditional tools such as chemicals, UV radiation, or heat are often unsatisfactory and sometimes accompanied by undesirable side effects. Unlike bacteria, fungus is more resistance to plasma treatment because of the much more complex cell biology. In 2008, Akishev et al. published the first paper of CAP decontamination of Aspergillus niger and Candida lipolytica on agar surface using N2 + O2 plasma jet. After 30–60 treatments, inhibition zone of 30–40 mm was observed [45]. Xiong et al. also inactivated Candida albicans on agar surface using a He + O2 plasma jet [46]. They compared the antifungal effect of with/without a cap on the petri dish and found that restraining active species inside the chamber largely improved the antifungal effect. Daeschlein et al. used a low-temperature atmospheric pressure plasma jet to treat clinical isolates of Trichophyton interdigitale, Trichophyton rubrum, Microsporum canis, and Candida albicans. They found that plasma irradiation could eradicate fungal growth and no isolate exhibited resistance to plasma treatment [47]. In a new research area of plasma treatment of onychomycosis, Xiong et al. used three kinds of CAPs to treat E. coli and Trichophyton rubrum living on the back side of a nail model and found that bacteria is easier to inactivate than fungus and the inactivation effect also related to the structure of plasma sources [48].

Researchers also use CAPs successfully inactivate various virus and mechanism has been investigated as well [4951].

It is known that more than 60% of all infections are caused by bacteria in the form of bacteria which could become resistant to treatment and often develop into a chronic state. A biofilm is often formed by a cluster of cells encapsulated by a 3D extracellular matrix (ECM), [52] which forms a good protection barrier for antibiotics and plasma agents. Therefore, cells inside this community have been demonstrated to exhibit higher antibiotic resistance than planktonic cells. However, CAPs have also shown great decontamination effect against biofilms with longer time than treating planktonic cells under same condition [53, 54]. Koban et al. compared the anti-biofilm (Candida albicans) effect by dielectric barrier discharge and plasma jet, and used 0.1% chlorhexidine digluconate (CHX) and 0.6% sodium hypochlorite (NaOCl) as positive control. They found plasma treatment reduced the colony-forming units CFU significantly compared to chemical disinfectants [55]. In a later research, they investigated the synergistic effect of nonthermal plasma and disinfecting agents against single and multispecies dental biofilms. They found that the combination of plasma and agents increases the antimicrobial efficacy of all tested compounds [56]. Xiong et al. firstly used Laser Confocal Scanning Microscopy (LCSM) technology to obtain the depth of biofilm that plasma could penetrate through [57]. A He-O2 mixture nanosecond pulse DC-driven plasma jet was used to treat a 10-day growth of Porphyromonas gingivalis biofilm, and found that 5-min plasma treatment could at least inactivate the bacteria under 15 μm. In their following work, they successfully inactivated a 25.5 μm biofilm using a plasma flashlight [35]. Puligundla and Mok reviewed the potential application of nonthermal plasmas against biofilm-associated microorganism in 2017. For more details about plasma interaction with biofilms, refer [58].

Advertisement

4. Plasma interaction with skin-related cells/tissues in vitro

The interaction between plasma and human cells largely depends on the plasma source, plasma doses as well as cell type. Researches on plasma cells interaction have been studied by several groups [5961]. For a unique mixed state with electrical field, charged particles, and controllable reactive species, the response of eukaryotic cell to plasma treatment is very different. It is generally accepted that low dose of plasma treatment could stimulate cell viability and enhance proliferation, differentiation, and migration, while high dose induces cell apoptosis/necrosis [6265]. It has been found that the resistance against plasma treatment is different between cancer cells and normal cells, which makes plasma selectively killing cancer cells while bring less damage to normal cells and become a potential and powerful tool against cancers [6668].

As mentioned earlier, the second stage of wound repair is related to cell proliferation and migration as well as angiogenesis. Cell types involved in wound healing are mainly fibroblasts and keratinocytes, among which keratinocytes contribute to the major healing processes and fibroblast cells play a guiding role [69, 70]. It has already been reported that CAPs could increases fibroblast cell proliferation and migration by using N2/Ar microplasma through simulated release of fibroblast growth factor-7 [71], as seen in Figure 5. Researchers from INP have done series of investigations of plasma interaction of keratinocyte. They used different plasma sources including plasma jet (kINPen), SMD and DBD, and different keratinocyte cell models/tissues to study the response after treatment. They found increased b1-integrin expression and reduced E-cadherin and EGFR expression of HaCaT-keratinocytes after 30 s treatment [72]. Intracellular level of ROS increased after SMD treatment without dependence on the treatment time or different treatment regimens [73] and DBD and kINPen 09 plasma treatments could also induce oxidative stress in human keratinocytes [71, 72]. Plasma treatment could not only induce cell reactions of stress-sensing but also of proliferative nature, and they propose that stimulating doses of plasma treatment may protect epithelial skin cells in wound healing by promoting proliferation and differentiation through triggering hormesis-like processes [7478]. Other groups also found the evidence that short-term plasma exposure could enhance keratinocyte proliferation [79].

Figure 5.

The progression and statistical analyses of cell migration or coverage, 6 and 12 h after plasma exposure times of 5, 10, and 15 s [71].

Angiogenesis is a very important process in the second stage of wound healing involving with growth factors, cytokines, ROS, and NO which could be provided by CAPs. Studies of plasma-inducing angiogenesis have been reported by many groups. Arjunan et al. found that FE-DBD treatment could induce angiogenesis by FGF-2 release regulated by plasma-produced ROS [80]. Hirata et al. used a mouse burn model to investigate the healing process by plasma irradiation, and they found that healing process was improved and the quantity of neovascular vessels was increased after plasma treatment [81]. Kim et al. used angiographic optical coherence tomography (OCT), which successfully captured the plasma-induced angiogenesis process. Figure 6 shows the en face vascular projections acquired from the angiographic OCT and matched stereoscopic images of the plasma and control wounds over 14 days. They found that the vascular wound area decease of plasma treated wound was more significant [82]. Up to date, very little is known about plasma-induced angiogenesis formation and a lot of work needs to be done in the future to understand the mechanism of plasma effect on angiogenesis.

Figure 6.

(a) Non-invasive angiographic OCT images and (b) stereoscopic images longitudinally acquired over 14 days after wound generation; relative depth in angiographic OCT images is color-coded as from yellow (superficial) to red (deep) [82].

Advertisement

5. CAPs treatment of in vivo animal m`odels

Based on previous fundamental research of plasma treatment on would healing, treatments on animal models with various wounds and clinical trials are also conducted. Ermolaeva et al. used an argon plasma, which tested the antibacterial effect on both vitro and on the animal model of infected wounds. They found that the 10-min treatment significantly reduced bacterial loads on wound surface and 5-day daily plasma treatment could eliminate bacteria from the infected surface 2 days earlier than the control. Wound closure was accelerated in the plasma-treated animals [41]. Nastuta et al. established a burned wounds model on Wistar rat’s skin and used a helium plasma jet to stimulate the wound healing process. They found that both polyurethane wound dressing and plasma-assisted epithelization are positive for the recovery process of burned wounds [83]. Alcantara et al. and Hung et al. also found accelerated wound healing after argon and helium plasma needle and plasma jet treatment [84, 85]. Anke Schmidt used kINPen argon plasma jet device to investigate the wound healing activity on a murine model of full-thickness ear wound; a significant acceleration of wound re-epithelization was observed in days 3–9 [86]. Same results were found by Kubinova et al. without noticeable effects and concomitant activation of pro-inflammatory signaling [87]. Shao et al. investigated the efficacy of a nonthermal N2/Ar treatment of a laser-induced partial thickness skin wound on a mouse model. Wound-closure kinetics, optical coherence tomography (OCT) and laser Doppler scanning methods were used to measure the healing efficiency and results also show the promotion of wound healing by micro-plasma treatment [88]. Wound healing process in diabetic patients is relatively slow and current therapeutic methods are not completely successful. Fathollah et al. studied the wound healing process by plasma in diabetic rats and found enhanced wound healing rate in the nondiabetic rats and significant wound contraction in diabetic rats after plasma treatment, as seen in Figure 7. And also histological analyses show the formation of epidermis layer, neovascularization, and cell proliferation [89].

Figure 7.

Wound observation for days 3, 7, 15 and 30 after the treatment [89].

Advertisement

6. Clinic trials and biosafety concern

Beside animal studies, clinical trials have also been done on patients, especially by using several commercialized products. The world’s first plasma source used for clinical trials was the microwave plasma torch MicroPlaSter. Using the first-generation product named MicroPlaSter α, they treated 38 chronic infected wounds on 36 patients with 291 5-min daily treatments and standard wound care, and obtained a significant reduction (34%) of bacterial load without any side effects [90]. In the following study, they compared plasma treatment on various etiologies (Group A), all chronic ulcers (Group B) and Group C for 5-min plasma treatment of chronic venous ulcers. They found a greater reduction in width and length in Group A than control. In Groups B and C, significant reduction in width was found with plasma treatment but not in length [91]. Figure 8 shows a modified version of MicroPlaSter β and results of treating inflamed ulcer [92]. Isbary et al. reported a successful treatment of Hailey-Hailey disease by a daily 5-min cold plasma treatment and significant improvement was found after 11 treatments [93]. The argon plasma jet device kINPen MED and DBD plasma source PlasmaDerm successively got the CE marketing for medical devices in 2013. Based on the previous fundamental studies in vitro and on animals, they both reported series clinical trials on human beings focusing on wound healing treatment, especially for the treatment of chronic/infected wounds and microorganism-caused skin diseases. For example, PlasmaDerm was reported to reduced more than tenfold in bacterial colonization on an adult patient with atopic eczema by 30-day treatment of 1 min/day [94]. kINPen MED was reported to significantly reduce the wound volume compared to octenisept in 16 patients with ulcer [95].

Figure 8.

Inflamed ulcer of the right lower leg treatment with cold atmospheric argon plasma generated by MicroPlaSter β [92].

Plasma biosafety is definitely a big issue in clinical application. Both of these commercialized products showed tolerable properties (temperature, UV radiation, reactive species, electrical currents, mutagenicity, penetration depth, subjective sensations, cytotoxicity, and histocompatibility) on human skin under controlled conditions and exhibited accelerated wound healing rate [9598]. Systematic review work of these two devices could be found in [14, 92].

Advertisement

7. Conclusion

Atmospheric pressure cold plasmas could affect different stages of wound healing by helping to activate microorganisms in the first stage and stimulate skin-related cell proliferation and migration in the following period. CAPs have demonstrated high wound healing abilities and may become a promising therapy to replace or assist traditional methods in clinics for wound healing process, especially in chronic wounds. With the certification of several CAP products, more standards and procedures for clinical treatments should be cleared in the future to guide the plasma treatment under an effective and safe way.

Advertisement

Acknowledgments

The author would like to thank for the support from Huazhong scholar program.

References

  1. 1. Gurtner GC, Werner S, Barrandon Y, Longaker MT. Wound repair and regeneration. Nature. 2008;453(7193):314-321
  2. 2. Werdin F, Tennenhaus M, Schaller H-E, Rennekampff H-O. Evidence-based management strategies for treatment of chronic wounds. Eplasty. 2009;9:e19
  3. 3. Lloyd G, Friedman G, Jafri S, Schultz G, Fridman A, Harding K. Gas plasma: Medical uses and developments in wound care. Plasma Processes and Polymers. 2010;7(3-4):194-211
  4. 4. Haertel B, von Woedtke T, Weltmann K-D, Lindequist U. Non-thermal atmospheric-pressure plasma possible application in wound healing. Biomolecules & Therapeutics. 2014;22(6):477-490
  5. 5. Weltmann K-D, von Woedtke T. Plasma medicine—Current state of research and medical application. Plasma Physics and Controlled Fusion. 2017;59(1):14031
  6. 6. Yousfi M, Merbahi N, Pathak A, Eichwald O. Low-temperature plasmas at atmospheric pressure: Toward new pharmaceutical treatments in medicine. Fundamental & Clinical Pharmacology. 2014;28(2):123-135
  7. 7. Laroussi M. Sterilization of contaminated matter with an atmospheric pressure plasma. IEEE Transactions on Plasma Science. 1996;24(3):1188-1191
  8. 8. Stoffels E, Kieft IE, Sladek REJ. Superficial treatment of mammalian cells using plasma needle. Journal of Physics D: Applied Physics. 2003;36(23):2908-2913
  9. 9. Stoffels E, Kieft IE, Sladek REJ, van den Bedem LJM, van der Laan EP, Steinbuch M. Plasma needle for in vivo medical treatment: Recent developments and perspectives. Plasma Sources Science and Technology. 2006;15(4):S169-S180
  10. 10. Laroussi M, Akan T. Arc-free atmospheric pressure cold plasma jets: A review. Plasma Processes and Polymers. 2007;4(9):777-788
  11. 11. Iza F et al. Microplasmas: Sources, particle kinetics, and biomedical applications. Plasma Processes and Polymers. 2008;5(4):322-344
  12. 12. Xinpei L et al. An $RC$ plasma device for sterilization of root canal of teeth. IEEE Transactions on Plasma Science. 2009;37(5):668-673
  13. 13. Weltmann K-D, von Woedtke T. Basic requirements for plasma sources in medicine. European Physical Journal Applied Physics. 2011;55(1):13807
  14. 14. Bekeschus S, Schmidt A, Weltmann K-D, von Woedtke T. The plasma jet kINPen—A powerful tool for wound healing. Clinical Plasma Medicine. 2016;4(1):19-28
  15. 15. Moreau S et al. Using the flowing afterglow of a plasma to inactivate Bacillus subtilis spores: Influence of the operating conditions. 2000. http://oasc12039.247realmedia.com/RealMedia/ads/click_lx.ads/www.aip.org/pt/adcenter/pdfcover_test/L-37/386502181/x01/AIP-PT/JAP_ArticleDL_092017/scilight717-1640x440.gif/434f71374e315a556e61414141774c75?x
  16. 16. Boudam MK, Moisan M, Saoudi B, Popovici C, Gherardi N, Massines F. Bacterial spore inactivation by atmospheric-pressure plasmas in the presence or absence of UV photons as obtained with the same gas mixture. Journal of Physics D: Applied Physics. 2006;39(16):3494-3507
  17. 17. Shimizu T et al. Characterization of microwave plasma torch for decontamination. Plasma Processes and Polymers. 2008;5(6):577-582
  18. 18. Lu X et al. The roles of the various plasma agents in the inactivation of bacteria. Journal of Applied Physics. 2008;104(5):53309
  19. 19. Dobrynin D, Fridman G, Friedman G, Fridman A. Physical and biological mechanisms of direct plasma interaction with living tissue. New Journal of Physics. 2009;11(11):115020
  20. 20. Fridman G et al. Comparison of direct and indirect effects of non-thermal atmospheric-pressure plasma on bacteria. Plasma Processes and Polymers. 2007;4(4):370-375
  21. 21. Digel I, Artmann AT, Nishikawa K, Cook M, Kurulgan E, Artmann GM. Bactericidal effects of plasma-generated cluster ions. Medical & Biological Engineering & Computing. 2005;43(6):800-807
  22. 22. Laroussi M, Leipold F. Evaluation of the roles of reactive species, heat, and UV radiation in the inactivation of bacterial cells by air plasmas at atmospheric pressure. International Journal of Mass Spectrometry. 2004;233(1-3):81-86
  23. 23. Shi JJ, Kong MG. Cathode fall characteristics in a dc atmospheric pressure glow discharge. Journal of Applied Physics. 2003;94(9):5504-5513
  24. 24. Shi JJ, Kong MG. Evolution of discharge structure in capacitive radio-frequency atmospheric microplasmas. Physical Review Letters. 2006;96(10):105009
  25. 25. Huang C, Yu Q, Hsieh F, Duan Y. Bacterial deactivation using a low temperature argon atmospheric plasma brush with oxygen addition. Plasma Processes and Polymers. 2007;4(1):77-87
  26. 26. Uhm HS, Lim JP, Li SZ. Sterilization of bacterial endospores by an atmospheric-pressure argon plasma jet. Applied Physics Letters. 2007;90(26):261501
  27. 27. Kim SJ, Chung TH, Bae SH, Leem SH. Bacterial inactivation using atmospheric pressure single pin electrode microplasma jet with a ground ring. Applied Physics Letters. 2009;94(14):141502
  28. 28. Eto H, Ono Y, Ogino A, Nagatsu M. Low-temperature sterilization of wrapped materials using flexible sheet-type dielectric barrier discharge. Applied Physics Letters. 2008;93(22):221502
  29. 29. Graves DB. The emerging role of reactive oxygen and nitrogen species in redox biology and some implications for plasma applications to medicine and biology. Journal of Physics D: Applied Physics. 2012;45(26):263001
  30. 30. Laroussi M, Lu X. Room-temperature atmospheric pressure plasma plume for biomedical applications. Applied Physics Letters. 2005;87(11):113902
  31. 31. Fridman G et al. Blood coagulation and living tissue sterilization by floating-electrode dielectric barrier discharge in air. Plasma Chemistry and Plasma Processing. 2006;26(4):425-442
  32. 32. Kolb JF et al. Cold atmospheric pressure air plasma jet for medical applications. Applied Physics Letters. 2008;92(24):241501
  33. 33. Lu X, Jiang Z, Xiong Q, Tang Z, Pan Y. A single electrode room-temperature plasma jet device for biomedical applications. Applied Physics Letters. 2008;92(15):151504
  34. 34. Lu X et al. A simple atmospheric pressure room-temperature air plasma needle device for biomedical applications. Applied Physics Letters. 2009;95(18):181501
  35. 35. Pei X et al. Inactivation of a 25.5 μm Enterococcus faecalis biofilm by a room-temperature, battery-operated, handheld air plasma jet. Journal of Physics D: Applied Physics. 2012;45(16):165205
  36. 36. Lu X, Wu S, Chu PK, Liu D, Pan Y. An atmospheric-pressure plasma brush driven by sub-microsecond voltage pulses. Plasma Sources Science and Technology. 2011;20(6):65009
  37. 37. Morfill GE, Shimizu T, Steffes B, Schmidt H-U. Nosocomial infections—A new approach towards preventive medicine using plasmas. New Journal of Physics. 2009;11(11):115019
  38. 38. Isbary G et al. Cold atmospheric plasma devices for medical issues. Expert Review of Medical Devices. 2013;10(3):367-377
  39. 39. Laroussi M, Lu X, Keidar M. Perspective: The physics, diagnostics, and applications of atmospheric pressure low temperature plasma sources used in plasma medicine. Journal of Applied Physics. 2017;122(2):020901
  40. 40. Scholtz V, Pazlarova J, Souskova H, Khun J, Julak J. Nonthermal plasma ? A tool for decontamination and disinfection. Biotechnology Advances. 2015;33(6):1108-1119
  41. 41. Ermolaeva SA et al. Bactericidal effects of non-thermal argon plasma in vitro, in biofilms and in the animal model of infected wounds. Journal of Medical Microbiology. 2011;60(1):75-83
  42. 42. Daeschlein G et al. Skin decontamination by low-temperature atmospheric pressure plasma jet and dielectric barrier discharge plasma. The Journal of Hospital Infection. 2012;81(3):177-183
  43. 43. Maisch T et al. Decolonisation of MRSA, S. aureus and E. coli by cold-atmospheric plasma using a porcine skin model in vitro. PLoS One. 2012;7(4):e34610
  44. 44. Alkawareek MY, Gormana SP, Graham WG, Gilmore BF. Potential cellular targets and antibacterial efficacy of atmospheric pressure non-thermal plasma. International Journal of Antimicrobial Agents. 2014;43(2):154-160
  45. 45. Akishev Y et al. Atmospheric-pressure, nonthermal plasma sterilization of microorganisms in liquids and on surfaces. Pure and Applied Chemistry. 2008;80(9):1953-1969
  46. 46. Xiong Z, Lu XP, Feng A, Pan Y, Ostrikov K. Highly effective fungal inactivation in He + O2 atmospheric-pressure nonequilibrium plasmas. Physics of Plasmas. 2010;17(12):123502
  47. 47. Daeschlein G et al. In vitro killing of clinical fungal strains by low-temperature atmospheric-pressure plasma jet. IEEE Transactions on Plasma Science. 2011;39(2):815-821
  48. 48. Xiong Z, Roe J, Grammer TC, Graves DB. Plasma treatment of onychomycosis. Plasma Processes and Polymers. 2016;13(6):588-597
  49. 49. Xiong Z et al. Room-temperature, atmospheric plasma needle reduces adenovirus gene expression in HEK 293A host cells. Applied Physics Letters. 2011;99(25):253703
  50. 50. Sakudo A, Toyokawa Y, Imanishi Y. Nitrogen gas plasma generated by a static induction Thyristor as a pulsed power supply inactivates adenovirus. PLoS One. 2016;11(6):e0157922
  51. 51. Sakudo A, Toyokawa Y, Imanishi Y, Murakami T. Crucial roles of reactive chemical species in modification of respiratory syncytial virus by nitrogen gas plasma. Materials Science and Engineering: C. 2017;74:131-136
  52. 52. Costerton JW, Stewart PS, Greenberg EP. Bacterial biofilms: A common cause of persistent infections. Science. 1999;284(5418):1318-1322
  53. 53. Joaquin JC, Kwan C, Abramzon N, Vandervoort K, Brelles-Marino G. Is gas-discharge plasma a new solution to the old problem of biofilm inactivation? Microbiology. 2009;155(3):724-732
  54. 54. Xu L, Tu Y, Yu Y, Tan M, Li J, Chen H. Augmented survival of Neisseria gonorrhoeae within biofilms: Exposure to atmospheric pressure non-thermal plasmas. European Journal of Clinical Microbiology & Infectious Diseases. 2011;30(1):25-31
  55. 55. Koban I et al. Treatment of Candida albicans biofilms with low-temperature plasma induced by dielectric barrier discharge and atmospheric pressure plasma jet. New Journal of Physics. 2010;12(7):73039
  56. 56. Koban I et al. Synergistic effects of nonthermal plasma and disinfecting agents against dental biofilms in vitro. ISRN Dentistry. 2013;2013:573262
  57. 57. Xiong Z, Du T, Lu X, Cao Y, Pan Y. How deep can plasma penetrate into a biofilm? Applied Physics Letters. 2011;98(22):221503
  58. 58. Puligundla P, Mok C. Potential applications of nonthermal plasmas against biofilm-associated micro-organisms in vitro. Journal of Applied Microbiology. 2017;122(5):1134-1148
  59. 59. Kim SJ, Chung TH, Bae1 SH. Induction of apoptosis in human breast cancer cells by a pulsed atmospheric pressure plasma jet. Applied Physics Letters. 2010;97:23702
  60. 60. Kalghatgi S et al. Effects of Non-Thermal Plasma on Mammalian Cells. PLoS One. Jan 2011;6(1):e16270
  61. 61. O’Connell D et al. Cold atmospheric pressure plasma jet interactions with plasmid DNA. Applied Physics Letters. Jan 2011;98(4):43701
  62. 62. Weiss M et al. Cold atmospheric plasma treatment induces anti-proliferative effects in prostate cancer cells by redox and apoptotic Signaling pathways. PLoS One. 2015;10(7):e0130350
  63. 63. Nakai N et al. Retardation of C2C12 myoblast cell proliferation by exposure to low-temperature atmospheric plasma. The Journal of Physiological Sciences. 2014;64(5):365-375
  64. 64. Siu A et al. Differential effects of cold atmospheric plasma in the treatment of malignant glioma. PLoS One. 2015;6:10
  65. 65. Xiong Z et al. Selective neuronal differentiation of neural stem cells induced by nanosecond microplasma agitation. Stem Cell Research. 2014;12(2):387-399
  66. 66. Wang M, Holmes B, Cheng X, Zhu W, Keidar M, Zhang LG. Cold atmospheric plasma for selectively ablating metastatic breast cancer cells. PLoS One. 2013;8(9):e73741
  67. 67. Ja Kim S, Min Joh H, Chung TH. Production of intracellular reactive oxygen species and change of cell viability induced by atmospheric pressure plasma in normal and cancer cells. Applied Physics Letters. 2013;103(15):153705
  68. 68. Hirst AM, Frame FM, Arya M, Maitland NJ, O’Connell D. Low temperature plasmas as emerging cancer therapeutics: The state of play and thoughts for the future. Tumor Biology. 2016;37(6):7021-7031
  69. 69. Tipa RS, Kroesen GMW. Plasma-stimulated wound healing. IEEE Transactions on Plasma Sciences. 2011;39(11(Part 1)):2978-2979
  70. 70. Grose R, Werner S. Wound-healing studies in transgenic and knockout mice. Molecular Biotechnology. 2004;28(2):147-166
  71. 71. Ngo M-HT, Liao J-D, Shao P-L, Weng C-C, Chang C-Y. Increased fibroblast cell proliferation and migration using atmospheric N2/Ar micro-plasma for the stimulated release of fibroblast growth factor-7. Plasma Processes and Polymers. 2014;11(1):80-88
  72. 72. Haertel B, Wende K, Von Woedtke T, Weltmann KD, Lindequist U. Non-thermal atmospheric-pressure plasma can influence cell adhesion molecules on HaCaT-keratinocytes. Experimental Dermatology. 2011;20(3):282-284
  73. 73. Haertel B, Hähnel M, Blackert S, Wende K, von Woedtke T, Lindequist U. Surface molecules on HaCaT keratinocytes after interaction with non-thermal atmospheric pressure plasma. Cell Biology International. 2012;36(12):1217-1222
  74. 74. Blackert S, Haertel B, Wende K, von Woedtke T, Lindequist U. Influence of non-thermal atmospheric pressure plasma on cellular structures and processes in human keratinocytes (HaCaT). Journal of Dermatological Science. 2013;70(3):173-181
  75. 75. Wende K et al. Atmospheric pressure plasma jet treatment evokes transient oxidative stress in HaCaT keratinocytes and influences cell physiology. Cell Biology International. 2014;38(4):412-425
  76. 76. Schmidt A et al. Non-thermal plasma treatment is associated with changes in transcriptome of human epithelial skin cells. Free Radical Research. 2013;47(8):577-592
  77. 77. Schmidt A et al. Non-thermal plasma activates human keratinocytes by stimulation of antioxidant and phase II pathways. The Journal of Biological Chemistry. 2015;290(11):6731-6750
  78. 78. Schmidt A, Von Woedtke T, Bekeschus S. Periodic exposure of keratinocytes to cold physical plasma: An in vitro model for redox-related diseases of the skin. Oxidative Medicine and Cellular Longevity. 2016. p. 17. Article ID: 9816072
  79. 79. Korolov I, Fazekas B, Széll M, Kemény L, Kutasi K. The effect of the plasma needle on the human keratinocytes related to the wound healing process. Journal of Physics D: Applied Physics. 2016;49(3):35401
  80. 80. Arjunan KP, Friedman G, Fridman A, Clyne AM. Non-thermal dielectric barrier discharge plasma induces angiogenesis through reactive oxygen species. Journal of the Royal Society Interface. 2012;9(66):147-157
  81. 81. Hirata T, Kishimoto T, Tsutsui C, Kanai T, Mori A. Healing burns using atmospheric pressure plasma irradiation. Japanese Journal of Applied Physics. 2014;53(1):010302
  82. 82. Kim DW, Park TJ, Jang SJ, You SJ, Oh WY. Plasma treatment effect on angiogenesis in wound healing process evaluated in vivo using angiographic optical coherence tomography. Applied Physics Letters. 2016;109(23):233701
  83. 83. Nastuta AV, Topala I, Grigoras C, Pohoata V, Popa G. Stimulation of wound healing by helium atmospheric pressure plasma treatment. Journal of Physics D: Applied Physics. 2011;44(10):105204
  84. 84. García-Alcantara E et al. Accelerated mice skin acute wound healing in vivo by combined treatment of argon and helium plasma needle. Archives of Medical Research. 2013;44(3):169-177
  85. 85. Hung YW, Lee LT, Peng YC, Chang CT, Wong YK, Tung KC. Effect of a nonthermal-atmospheric pressure plasma jet on wound healing: An animal study. Journal of the Chinese Medical Association. 2016;79(6):320-328
  86. 86. Schmidt A, Bekeschus S, Wende K, Vollmar B, von Woedtke T. A cold plasma jet accelerates wound healing in a murine model of full-thickness skin wounds. Experimental Dermatology. 2017;26(2):156-162
  87. 87. Kubinova S et al. Non-thermal air plasma promotes the healing of acute skin wounds in rats. Scientific Reports. 2017;7:45183
  88. 88. Shao P-L, Liao J-D, Wong T-W, Wang Y-C, Leu S, Yip H-K. Enhancement of wound healing by non-thermal N2/Ar micro-plasma exposure in mice with fractional-CO2-laser-induced wounds. PLoS One. 2016;11(6):e0156699
  89. 89. Fathollah S et al. Investigation on the effects of the atmospheric pressure plasma on wound healing in diabetic rats. Scientific Reports. 2016;6:19144
  90. 90. Isbary G et al. A first prospective randomized controlled trial to decrease bacterial load using cold atmospheric argon plasma on chronic wounds in patients. The British Journal of Dermatology. 2010;163(1):78-82
  91. 91. Isbary G et al. Cold atmospheric argon plasma treatment may accelerate wound healing in chronic wounds: Results of an open retrospective randomized controlled study in vivo. Clinical Plasma Medicine. 2013;1(2):25-30
  92. 92. Heinlin J et al. Plasma applications in medicine with a special focus on dermatology. Journal of the European Academy of Dermatology and Venereology. 2011;25(1):1-11
  93. 93. Isbary G, Morfill G, Zimmermann JL, Shimizu T, Stolz W. Cold atmospheric plasma—A successful treatment of lesions in Hailey-Hailey disease. Archives of Dermatology. 2011;147(4):388-390
  94. 94. Emmert S et al. Atmospheric pressure plasma in dermatology: Ulcus treatment and much more. Clinical Plasma Medicine. 2013;1(1):24-29
  95. 95. Lademann J et al. Risk assessment of the application of tissue-tolerable plasma on human skin. Clinical Plasma Medicine. 2013;1(1):5-10
  96. 96. Tiede R, Hirschberg J, Daeschlein G, von Woedtke T, Vioel W, Emmert S. Plasma applications: A dermatological view. Contributions to Plasma Physics. 2014;54(2):118-130
  97. 97. Kluge S et al. Investigating the mutagenicity of a cold argon-plasma jet in an HET-MN model. PLoS One. 2016;9:11
  98. 98. Schmidt A et al. One year follow-up risk assessment in SKH-1 mice and wounds treated with an argon plasma jet. International Journal of Molecular Sciences. 2017;18(4):868

Written By

Zilan Xiong

Submitted: 17 April 2017 Reviewed: 01 March 2018 Published: 16 May 2018