We used the RF COST plasma jet, which was created as a ‘standard’ plasma jet. Firstly, we designed and built a reactor which allowed studying the sources of RONS induced in aqueous media by our plasma jet using various analytical techniques (electron paramagnetic and nuclear magnetic resonance spectroscopy, and UV-Vis spectrophotometry). We also developed a 3D fluid dynamics model and a 0D chemical kinetics model to study the gas phase phenomena in the plasma effluent. We then compared the experimentally obtained trends of RONS (H2O2, OH, H) concentrations with those predicted by the developed models. Our results have shown that unlike other types of plasma jets and devices, parallel field plasma jets, such as the RF COST jet, generate all RONS in the discharge region inside the plasma jet, with no extra species generated from ambient components in the effluent.
Furthermore, we developed analytical methods for the detection of the secondary species created in solutions upon interaction with plasma RONS. We demonstrated that chloride anions in aqueous media interact with LTP-induced O atoms, yielding hypochlorite anions ClO-.
Third, we studied the interaction of LTP with gel-like and tissue-like structures. 3D tumour models (spheroids) were generated, and the effects of LTP exposure on them was studied. We also showed that the short-lived LTP RONS (such as •OH radicals) were necessary to reduce the tumour size and prevent further re-growth. Additionally, we studied the interaction of LTP with gelatinous substrates: solutions of polymers (used to create nanofibers for applications in medicine) were studied with respect to the generation of short-lived RONS during LTP exposure. and their effect on the resulting nanofibers.
Finally, we studied the production and effects of peroxynitrite in LTP treatment of cancer. The goal was to investigate the possibility of ONOO- production using pulsed plasma sources. We developed a method to monitor the stability of ONOO- in aqueous media, and generated various RONS including peroxynitrite and studied their effects on tumours. We then identified which RONS were responsible for immunogenic cell death (ICD, a desired anti-tumour effect) in cancer cells. Overall, we showed that peroxynitrite can be efficiently used for decontamination, but not for ICD.
Throughout the project, we used different dissemination channels of our research. The non-industrial nature of the project implied that the main dissemination method was publication in scientific journals and participation in conferences. I published 7 peer-reviewed journal papers and 1 book chapter (of which 4 as the first author), with another submitted manuscript currently under revision. We succeeded in publishing both in specific journals targeting the plasma community (Plasma Processes and Polymers), and in journals of wider scientific interest (Physical Chemistry Chemical Physics, Analytical Chemistry, Cancers, Scientific Reports, Advanced Science). The aim of this was to bring more attention to the state-of-the-art of plasma research from different fields of science, including wide chemistry, biology and engineering readership. Our results were also presented to the scientific community in the form of 6 conference contributions at the major domestic and international conferences in the plasma domain.
To increase the impact of our work, a YouTube channel was created. We produced and published a video to communicate cold plasma medicine in general and my work in particular to a wide audience, not associated with science. I also participated in several popular science events aimed to reach the general public in different countries (Kurilka Gutenberga, Russia; Pint of Science, Belgium; invited public lecture at the Institute Cayetano Heredia, Peru). These efforts were very fruitful in introducing the LTP phenomenon to audiences with different backgrounds in different countries.
