## 3 Applications of Cold Atmospheric Pressure Plasma
### Medicine
Besides decontamination, cold plasma technology can also be used for direct therapeutic intervention. With the help of plasma, the medical treatment process could be markedly shortened. Other benefits of CAPP treatment are good tolerability (painless), biocompatibility and biosecurity (it is assumed that CAPP treatment can be applied to living cells and tissues without causing any damage) [47, 78]. First of all, CAPP is a promising tool for wound healing because it has antimicrobial effects. Furthermore, it can enhance the proliferation of skin fibroblasts and angiogenesis [49, 79]. [PERSON] et al. demonstrated that plasma treatment using an open jet plasma device has strong bactericidal and fungicidal properties. Different bacteria strains (_Staphylococcus aureus_, _Pseudomonas aeruginosa_) and yeasts (_Candida albicans_ and _Malassezia pachydematis_) were treated which are associated with wound and skin infections. After the CAPP treatment, differences were observed due to the diverse structures of the cell wall of the microbes (e.g., Gram-positive bacteria have thicker cell walls then Gram-negative bacteria). The study concentrated on the influence of various process parameters of the plasma treatment. Nitrogen-based plasma was more effective than air. Increased input power and treatment time had higher antimicrobial efficacy against the tested microorganisms. [42]. The CAPP application has been intensively studied in dermatology [47]. Clinical trials have focused on onychomycosis (fungal infection of the nail), oncology (melanoma, actinic keratosis), viral warts (caused by infection with human papillomavirus), wound healing (different kinds of chronic infectious, microbiologically infected/contaminated wounds, herpes zoster-related pain), hair loss (increased hair follicle diameter), biofilm disruption (atopic dermatitis, itch), cosmetic applications (skin rejuvenation, reduction of wrinkles) and other ailments [26, 51]. The treatment requires careful dosage (fast treatment and gentle heating) in order to prevent unwanted skin burns or damage deeper tissues. For example, longer exposure of the skin (>43 \({}^{\circ}\)C) can cause blisters [47]. CAPP also exhibits a promising future in dentistry for bonding to dentin and ceramics, surface activation of dental implants, tooth bleaching, removing dental plaque/biofilms from teeth, composite restoration and disinfection of root canals [80]. Plasma can reach inaccessible areas of the tooth surface such as fissures and grooves, furthermore the procedure is painless because plasma does not cause thermal damage to the tissue [41, 81]. The promising effects of CAPP treatment useful in various areas of dentistry, for instance, cardiology (cariogenic microorganisms, e.g., _Streptococcus mutans_, _Lactobacillus acidophilus_), periodonontology (_Porphyromonas gingivalis_, _Tannerella forysthia_ and _Treponema danticola_), endodontics (_Enterococcus faecalis_,) and oral oncology, was reviewed by [PERSON] et al. [82]. [PERSON] et al. investigated the antibacterial effect of CAPP treated dental titanium implants on Gram-positive and Gram-negative bacteria with different cell wall structures. The biofilm formation rate and adhesion of Gram-negative bacteria were significantly lower than Gram-positive bacteria on samples treated with the APPJ. Gram-positive bacteria are more resistant to plasma than Gram-negative bacteria. This is related to the thickness of the peptidoglycan layer in the bacterial cell wall, which may reduce the antibacterial effects [83]. Cold plasma has shown promising results in cancer therapy because it can selectively induce apoptosis in cancer cells, reduce tumor volume and vasculature and halt metastasis [49; 58; 84]. CAPP has shown substantial anticancer capability over a wide range of cancer cells, for instance, melanoma [47; 85], carcinoma [86; 87] and osteosarcoma [88]. Cancer cells vary from normal cells, e.g., they produce higher amounts of reactive oxygen species. Thus, cancer cells are more susceptible to plasma-generated ROS than normal cells.