## 3 Results
### Quantification of the Generated (Reactive) CAP Species
#### 3.1.3 Generation of Intracellular Reactive Oxygen Species (ROS)  
The fluorescence measurements obtained for the DCFH2-DA and CAP treated _Listeria monocytogenes_ and _Salmonella_ Typhimurium model biofilms can be observed in Figure 5. Separate ANOVA tests have been performed for each biofilm forming species to (i) make a comparison between the untreated control and all examined combinations of plasma characteristics, and (ii) to examine the influence of a certain plasma characteristic on the intracellular ROS generation while keeping the other characteristics constant.  
Figure 4: pH values (-) obtained following CAP treatment of 500 \(\upmu\)L of sterile water using each possible combination of plasma characteristics (\(n=3\)). Significant differences between all examined conditions (ANOVA test 1), including the untreated control, have been indicated by means of a different small letter, with ‘a’ bearing the lowest value. The influence of the oxygen level (ANOVA tests 2–5), the electrode configuration (ANOVA tests 6–9), and the discharge power (ANOVA tests 10–13) on the pH of the CAP treated water have been indicated as well by means of a different small letter, with ‘a’ again bearing the lowest value.  
For _Listeria monocytogenes_, it can be observed that only four conditions resulted in significantly higher fluorescence values compared with the untreated control, i.e., DBD-1.0% (_v/v_)-21.88 V, DBD-0.0% (_v/v_)-13.88 V, DBD-1.0% (_v/v_)-13.88 V, SBD-1.0% (_v/v_)-21.88 V. Regarding the influence of the oxygen level, it can be concluded that the addition of oxygen favors the creation of intracellular ROS, although not always significantly proven. For the influence of the electrode configuration, the DBD electrode resulted in (significantly) higher values, or no significant differences were observed compared with the SBD electrode. Finally, the discharge power had no major influence on the formation of intracellular ROS when applying the DBD electrode. For the SBD electrode, on the other hand, a lower discharge power was favorable when no oxygen was added, while the opposite trend was observed with the addition of 1.0% (_v/v_) oxygen.  
For _Salmonella_ Typhimuriumium, only one condition did not result in a significant increase in fluorescence i.e., SBD-0.0% (_v/v_)-21.88 V, indicating that the _Salmonella_ Typhimuriumium cells are generally more vulnerable to the generation of intracellular ROS and/or have a higher permeability for extracellularly created ROS. As for _Listeria monocytogenes_, the addition of oxygen to the gas flow generally resulted in a (significant) increase in intracellular ROS. For the influence of the electrode configuration, the DBD resulted in significantly higher fluorescence values while applying the highest discharge power. For the lowest discharge power, on the other hand, no significant differences were observed between both electrode configurations. Finally, for the influence of the discharge power, (significantly) higher values were obtained at the highest value while applying the DBD electrode. For the SBD electrode, on the other hand, the opposite trend was observed.