Research On Mechanism Of Inactivated Candida Glabrata By Dc-driven Atmospheric Pressure Cold Plasma

Nowdays,plasma medicine has become a hot research direction.Among them,The most widely research is plasma sterilization and disinfection.Its essence is the interaction between plasma and cell.At present,it is believed that reactive nitrogen oxygen species(RONS)produced by the plasma play an important role in sterilization.However,we do not know the mechanism of interaction between these RONS and organisms.Meanwhile,it is difficult to determine the contribution of one or more RONS to sterilization and the inactivation effect,especially those important short-lived RONS.Therefore,in this paper,we have developed a dc-driven atmospheric pressure cold plasma source.And also we can selectively produce some of RONS by controlling the working gases,to study their contribution in the sterilization,in order to further reveal the mechanism of plasma sterilization.The main contents include the following five aspects:(1)Introduce the research background of this paper and four kinds of common cold plasma source.And summarize the research progress of plasma medicine at home and abroad.At the same time,I also introduce the experimental strain of this paper-Candida Glabrata and its status in clinical treatment.As Candida Glabrata is a kind of easily relapse refractory pathogenic fungi.So we introduce the dc-driven atmospheric pressure cold plasma technology to inactivate Candida Glabrata,as well as to provide a new idea for the treatment of diseases caused by Candida Glabrata.(2)Introduce the dc-driven atmospheric pressure cold plasma source that we designed.The high voltage electrode is a tungsten needle,and the grounding electrode is a metal net.The discharge is generated between the tungsten needle and the metal net under the DC voltage power.It will be produce the obvious luminous plasma plume in the air only when the working gas is Ar+N2.Through the detection of optical emission spectrum,it is found that different RONS can be selectively produced by controlling the working gases species(Ar+N2?Ar+O2?Ar+H2O?Ar+N2+O2?Ar+N2+H2O).At the same time,we measure the gas temperature along the plasma discharge afterglow with thermal couple,and also we measure the surface heating effect of the dc discharge afterglow in the treatment of objects with infrared thermal camera.Finally,combined with constant temperature water bath heat resistance test.It is confirmed that the effect of temperature with the dc-driven atmospheric pressure cold plasma that we dsigned on the survival rate of Candida Glabrata is negligible.In other words,the device is suitable for processing biological samples.(3)Introduce the effect of inactivated Candida Glabrata which growth in solid medium and suspension by the dc-driven plasma.and then the reason for the difference of sterilization effect in solid medium and suspension was explained by glucose and peptone experiments.It is mainly due to direct diffusion of RONS in the plasma discharge afterglow after the collision with the surface of solid medium.Secondly,altrough the surface of coated solid medium has a layer of water film,which makes RONS that produced by plasma can exist for a long time.However,the fungus coated on the culture medium is packaged by peptone and glucose.Due to the peptone and glucose have a certain reduction,they can react with the RONS in the water film,thus inhibiting the sterilization effect.Due to the co-existence of bacteria and fungi in actual clinical practice,So we used our plasma devices to kill three kinds of bacteria: Pseudomonas aeruginosa,Staphylococcus aureus and Escherichia coli.All good inactivation effect is obtained.(4)With Ar + H2 O plasma discharge afterglow is taken as an example to study the mechanism of plasma sterilization.It is found that the short-lived RONS is play an very important role in the process that the Ar+H2O plasma discharge afterglow inactivated Candida Glabrata.At the same time,the OHaq concentration in the treated physiological saline was measured and found that it plays an important role in the sterilization,and also the production of OHaq almost all comes from the ionization of the water vapor in the needle-net discharge area.In addition,we also found that ambient air is involved in Ar+H2O plasma afterglow discharge,and the participation of ambient air will increase the inactivation efficiency about 10%-20%.It is mainly due to the formation of a short-lived active substance ONOOHaq.However,the contribution of other short-lived active substances to sterilization can be neglected,such as O3 aq,O2-aq and so on.(5)Under the condition of shield,we study the mechanism of plasma discharge afterglow(Ar+O2?Ar+N2?Ar+N2+O2?Ar+N2+H2O)inactivated Candida albicans.The VUV play an important role in the pure Ar discharge sterilization,while the main role is O2-in the process of inactivated Candida albicans by Ar+O2 discharge.The long and short RONS play a synergistic role in the Ar+N2?Ar+N2+O2 and Ar+N2+H2O discharge sterilization.Ar+N2 is a kind of plume contact treatment,and a large amount of OHaq and a certain amount of ONOOHaq are generated.However,the nitrogen oxides play an very important role in the Ar+N2+O2 discharge sterilization.In the Ar+N2+H2O discharge inactivated Candida Glabrata,it is ONOOaq play an important role which is formed by NO2-aq and H2O2aq.