Experimental Study On The Interaction Of Cold Atmospheric Plasma And Perilla Seed Oil

The interaction between cold atmospheric plasma(CAP)and liquids is a current research hotspot.Compared with the direct plasma treatment,plasma-activated liquid has more advantages in safety and convenience.Studies have shown that vegetable oil can be transformed into plasma-activated oil with high activity and stable existence for several months under the treatment of CAP,which shows broad application prospects in plasma medicine.However,there are very few studies on plasma-activated oil at home and abroad,and there are also a large number of gaps in the reaction mechanism.In this thesis,the interaction between CAP and vegetable oil is deeply studied based on several diagnostic methods of CAP and plasmaactivated oil,the main contents are as follows:(1)A self-made plasma jet device was used to produce CAP to react with perilla seed oil(PSO),and the interaction mechanism and final product of CAP and PSO were analyzed according to the diagnostic results.Experimental results show that there are a large number of high-energy species and reactive species in CAP,and PSO is gradually activated under the treatment of plasma.Gas chromatography showed that the contents of various fatty acids especially unsaturated fatty acids in plasma-activated perilla seed oil(PAPSO)decreased significantly,the breaking of C=C double bond and C-H bond,and the formation of O-H and C-O bonds were found in infrared spectroscopy and proton nuclear magnetic resonance spectroscopy,the change of physicochemical properties indicated the formation of peroxides and carboxylic acids in PAPSO.Based on the results,the reaction mechanism between plasma and PSO was proposed:On the one hand,the C=C double bond is broken by high-energy species,and further oxidized by reactive species to generate H2O2,carboxylic acid,and some other reactive substances.On the other hand,the reactive species seize the hydrogen atoms on the carbon chain and form reactive groups such as alcohols,aldehydes and carboxyl groups at the corresponding sites.Experiments have shown that these newly formed reactive substances can be stable for more than half a year.(2)Based on the diagnosis of CAP and PAPSO,the influence of different discharge parameters on reactive species in plasma and PAPSO activity were studied,and the regulation of PAPSO activity was realized.The experimental results show that a higher gas flow rate is helpful to improve the argon concentration ratio in the jet and enhance the discharge intensity,but too high gas flow rate will lead to the instability of the discharge,so that an optimal gas flow rate exists,which makes the OH radical density in plasma maximum and the PAPSO activity highest.When the gas flow rate is constant,the OH radical density in the plasma gradually decreases along the jet direction,while the PAPSO activity increases first and then decreases with the increase of treatment distance.This is because the too close distance will intensify the return of the air flow,and reduce the stability of the gas flow and the water vapor content.The study of electrical parameters found that the voltage amplitude and pulse frequency were positively correlated with the density of OH radicals and the activity of PAPSO,which was very favorable for the regulation of PAPSO activity.(3)PAPSO was used to kill MC38 cancer cells in vitro,preliminarily verified the anticancer effect of PAPSO-The experimental results showed that the inhibition rate of PAPSO on MC38 cells was more than 50%,and the inhibition rate even reached 80%when the volume concentration ratio of PAPSO was 1/100 and treated by plasma for 6 h,while the inhibition rate of PSO on MC38 cells was less than 10%.At the same time,the apoptosis rate of the PAPSO groups was also significantly higher than that of the PSO groups.The longer time treated by plasma,the higher the volume concentration of the PAPSO,and the stronger the killing ability of MC38 cells.The carboxylic acid produced in PAPSO provides an acidic environment for cells,and the reactive species such as H2O2 make the concentration of intracellular ROS exceed the tolerance range,which are the main reasons why PAPSO inhibits MC38 cells proliferation and induces MC38 cells apoptosis.In this thesis,the basic characteristics of CAP,the interaction mechanism between CAP and PSO,and the activity regulation of PAPSO were comprehensively studied,and the activity of PAPSO was verified by in vitro experiments.This study deepens the understanding of plasma-activated oils,which is conducive to further promoting the development of plasma medicine and plasma pharmacy.