# A Novel Method for Estimating the Dosage of Cold Atmospheric Plasmas in Plasma Medical Applications
###### Abstract  
Cold atmospheric plasmas (CAPs) used in plasma medicine have shown great potential in various aspects including wound healing, dermatology, cancer therapy, etc. It is one of the important issues to determine the plasma dosage in plasma medicine because it dominates the specific plasma treatment results. However, the multi-process interactions between CAPs and biological materials make it rather challenging to give an accurate and versatile definition for plasma dosage. In this study, the ratio of the discharge energy to the number of the treated in vitro kidney cells (m/cell) was employed as the unit of the plasma dosage. Additionally, inspired by basic knowledge of pharmacy, the median lethal dose (LD\({}_{50}\)) was employed to help estimate the plasma dosage. The experimental results show that the value of LD\({}_{50}\) using the newly designed CAP Bio-Med Platform for the kidney cells is 34.67 mJ/cell. This biology-based method has the advantages of easy operation, independence of specific CAP sources, and also independence of complex interactions between CAPs and the treated biological targets, and consequently, may provide a new direction to quantitatively define the plasma dosage in various plasma medical applications. plasma dosage; cold atmospheric plasma; plasma medicine; in vitro cell culture +
Footnote †: journal: Appl. Sci. 2021  
living tissues, cells, etc. Detailed descriptions and features of various kinds of CAP sources used in plasma medicine can be found in some topical reviews [7, 9, 10]. From the very beginning of the research on plasma medicine, the treatment safety issues have been widely investigated. The inactivation of microorganisms by plasma treatment has been proved and applied before 2000 [7], whereas [PERSON] et al. first reported the non-destructive CAP treatment on mammalian cells under moderate conditions in the early 2000s [11]. Later, they found that the CAP treatment for a too-long time period would cause mammalian cell necrosis [12]. Using different CAP generators, [PERSON] et al. came to a similar conclusion that the cells were hardly damaged with a relatively low CAP treatment energy density, whereas with a medium- to high-level treatment, the cells began to be harmed and even died [13]. That is to say, different CAP treatment intensities will lead to completely different results in plasma medicine. To quantitatively describe how much CAPs are interacting with the targets (e.g., living tissues, cells, etc. ), the concept of \"plasma dosage\" should be introduced. Additionally, only with a clear definition of the \"plasma dosage\" the users can accurately determine, and thus, carefully adjust, the action intensity of the CAPs to obtain the desired results in plasma medicine. Many studies have involved plasma dosage when investigating possible factors which intrinsically influence the CAP treatment effects. On the one hand, from the aspect of physical plasmas, various factors including power input into the CAP system, chemical compositions of the working gas, amplitudes and waveforms of discharge voltage and current, gas temperatures, treatment times and distances are all believed to be significant factors in plasma dosage [8, 9, 12, 13, 14, 15, 16]. In addition, some biological experimental parameters such as the thicknesses of the cell culture medium and the numbers of cells can also have obvious influences on the CAP treatment results [17]. A recent study by [PERSON] et al. provided an important attempt to define plasma dosage by the simplified equivalent total oxidation potential of several important RONS [8]. However, as shown in Figure 1, the interactions between the CAPs and the treated biological targets involve multiple physical, chemical and biological processes, leading to the significantly complicated, nonlinear, and multi-variable nature. These have made it extremely difficult to propose an accurate and versatile definition for plasma dosage, considering all the possible mechanisms.