# Applications of Plasma Produced with Electrical Discharges in Gases for Agriculture and Biomedicine
## 3 Review of Plasma Applications in Agriculture and Medicine
### Plasma Application in Biomedicine
#### 3.2.3 Tumour Treatment  
The most recent studies in the plasma oncology area are related to the direct application of different cold plasma techniques to tumour cells [196]. The most important task in tumour treatment lies in plasma-reactive species which are expected to penetrate several layers of cell membrane [197; 198; 199]. [PERSON] et al. [200] proposed a set of possible events underlying the apoptosis mechanism (cell self-destruction when stimulated by the appropriate trigger) in cancer treatment after cold plasma applications (Figure 8). Before the treatment (Figure 8a), the catalyse (commonly widespread enzyme) protects the tumour cell from the damage of oxidative ROS species. LTP plasma application activates the catalyse by the singlet molecular oxygen \({}^{1}\)O\({}_{2}\) (Figure 8b). When plasma treatment is finished, the cytotoxic effect, formation of apoptosis bodies, and apoptosis induction can, afterwards, be observed (Figure 8c).  
Figure 9 presents one the most successful approaches for plasma penetration into the tumour core. It allows the execution of an effective plasma application, focal with limited surgical invasion, and destroys the tumour radially from the inside. This concept was  
Figure 8: Proposed set of events forming the basis of the mechanism of apoptosis induction in selective LTP cancer treatment [200]: (**a**) before plasma treatment, (**b**) plasma treatment, (**c**) after plasma treatment.  
Figure 7: The interdependency of wound characteristics and gas plasma therapeutic schemes [62].  
proposed in [PERSON] et al. [196; 201]. The investigators suggested that this technique ensures enhanced targeted treatment of a tumour and controls tumour volume destruction. The efficiency of the concept depends on the plasma source and its synthesis parameters, such as voltage waveform, gas composition, and treatment duration.  
A group of Korean scientists conducted research on T98G brain cancer cells [202; 203; 204]. They observed the cytogenetic damage in T98G brain cancer cells upon exposure of DBD plasma discharge. They also reported the influence of exposure and incubation times on the studied cells [202]. The experiments show that the micronucleus formation rate is highly dependent on the plasma exposure time. During the experiment, the cells were exposed to 30, 60, 120 and 240 s plasma treatment. The first two exposure times show less effectiveness than the longer times of 120 and 240 s. The maximal effect was observed with 240 s exposure, which inhibited the growth of cells even up to 80% at 48 and 72 h incubation after treatment [203]. Plasma-treated cell viability was found to be significantly dependent on incubation time. The authors also compared the impact of DBD plasma exposure on cancer cells and normal human embryonic kidney cells (HEK). They concluded that the treatment is much more toxic on T98G cells than on HEK cells. The best results were obtained in the case of exposure times less than 120 s, which demonstrated viability above 75%. Plasma treatment of normal cells for a longer time duration reduces their viability to approximately 45%. Moreover, the researchers found that plasma exposure can lead to irreversible changes in DNA, mitochondrial impairment, and caspase activation resulting in cancer cell death [204].