Xing-Min Shi

Chemical Mechanisms of Bacterial Inactivation Using Dielectric Barrier Discharge Plasma in Atmospheric Air

Nonthermal plasma generated by parallel-plate dielectric-barrier discharge with 60-kHz high-voltage power was used to sterilize the bacteria in atmospheric air. Two kinds of typical bacteria, gram-negative E. coli (ATCC8099) and grampositive S. aureus (ATCC6538), were used as test strains. Bacteria cells held by cover-glass were placed on the bottom electrode. By adjusting the applied voltage, gap spacing, and treatment time, the effects of plasma and electric field on bacteria inactivation were investigated. The transmission electron microscope was used to observe the damage of cells treated by plasma. The concentrations of K+, protein, and nucleic acid leaked from cells were measured for detecting the cytoplasm status after plasma treatment. Experimental results showed that almost 100% of S. aureus and E. coli strains were killed in less than 10- and 7-s plasma treatment, respectively. It is concluded that the reactive oxygen species (ROS) in plasma play a dominant role in the inactivation process but not the electric field. It is supposed that the ROS can oxidize the cell membrane and then damage the protein and nucleic acid inside the cells and, thus, kill the bacteria.

Effect of Low-Temperature Plasma on Microorganism Inactivation and Quality of Freshly Squeezed Orange Juice

Dielectric barrier discharge is used to generate low temperature plasma (LTP) for the treatment of freshly squeezed orange juice, which was inoculated with and without three kinds of microorganisms, respectively. Four experiments were designed and conducted: 1) When freshly squeezed orange juice samples inoculated with either Staphylococcus aureus, Escherichia coli, or Candida albicans were treated with LTP for 12,8, and 25 s, respectively, the numbers of each microorganism decreased more than 5 logs; 2) when orange juices without the aforementioned microor ganism inoculation were treated with LTP for inactivating original microorganisms inside and then stored at 4°C refrigeration, the total plate count and the proliferation rate of original microor ganism were both reduced significantly (counting per each 4-d during storage); 3) when orange juice samples without microor ganism inoculation were treated with LTP, the LTP treatment had insignificant effect on the values of vitamin C, total acid, turbidity,°Brix, and pH of orange juice; 4) when orange juice samples were inoculated with S. aureus, E. coli, or C. albicans, respectively, and their pH values were slightly decreased by adding HC1 (similar to that after LTP treatment), there was no obvious inactivation effects due to the reduction of pH values. It was proposed that microorganism inactivation was mainly due to reactive species and charged particles instead of slight pH reduction, and LTP treatment was able to effectively inactivate microbes and maintain the quality of orange juice.

Dual effects of atmospheric pressure plasma jet on skin wound healing of mice.

Cold plasma has become an attractive tool for promoting wound healing and treating skin diseases. This article presents an atmospheric pressure plasma jet (APPJ) generated in argon gas through dielectric barrier discharge, which was applied to superficial skin wounds in BALB/c mice. The mice (n = 50) were assigned randomly into five groups (named A, B, C, D, E) with 10 animals in each group. Natural wound healing was compared with stimulated wound healing treated daily with APPJ for different time spans (10, 20, 30, 40, and 50 seconds) on 14 consecutive days. APPJ emission spectra, morphological changes in animal wounds, and tissue histological parameters were analyzed. Statistical results revealed that wound size changed over the duration of the experimental period and there was a significant interaction between experimental day and group. Differences between group C and other groups at day 7 were statistically significant (p < 0.05). All groups had nearly achieved closure of the untreated control wounds at day 14. The wounds treated with APPJ for 10, 20, 30, and 40 seconds showed significantly enhanced daily improvement compared with the control and almost complete closure at day 12, 10, 7, and 13, respectively. The optimal results of epidermal cell regeneration, granulation tissue hyperplasia, and collagen deposition in histological aspect were observed at day 7. However, the wounds treated for 50 seconds were less well healed at day 14 than those of the control. It was concluded that appropriate doses of cold plasma could inactivate bacteria around the wound, activate fibroblast proliferation in wound tissue, and eventually promote wound healing. Whereas, over doses of plasma suppressed wound healing due to causing cell death by apoptosis or necrosis. Both positive and negative effects may be related to the existence of reactive oxygen and nitrogen species (ROS and RNS) in APPJ.

Research on the Inactivation Effect of Low-Temperature Plasma on Candida Albicans

A dielectric barrier discharge was used to generate low-temperature plasma to treat Candida albicans. When the gap spacing was 3 mm, the killing log value (KLV) of the plasma on Candida albicans within 20 s of exposure was more than five, and for 4 and 5 mm gap spacing, the KLV within 25 s was more than five. With the extension of exposure time, the decrease in velocity of the number of living Candida albicans was fastest for the gap spacing of 3 mm, and then for 4 and 5 mm spacing. With 60 s of electric field treatment, as the applied voltage increases, the survival number of Candida albicans has no significant difference from that of the control sample. As for the inactivation mechanism of plasma on Candida albicans on the molecular microbiology side, transmission electron microscopic examination and the results of protein, nucleic acid and K+ detection in the extracellular environment showed that the plasma destroyed the outer structure of Candida albicans. Cytoplasm was also released, which caused Candida albicans to be dead. On the plasma physics side, the role of the electric field during Candida albicans inactivation by plasma is considered negligible. Therefore, charged particles and reactive species in plasma might play a dominant role in the process of destroying the outer structure of Candida albicans.

Effect of Low-Temperature Plasma on Deactivation of Hepatitis B Virus

In recent years, low-temperature plasma (LTP) has been widely applied in biological and medical fields. This paper is aimed to investigate the deactivation effect of LTP on hepatitis B virus (HBV). Dielectric barrier discharge (DBD) is employed to generate the atmospheric-pressure LTP for treatment of HBV. HBV serum collected from hepatitis B patients with HBsAg, HBeAg, and anti-HBc positive is used as the treatment model. LTP treatment time intervals are set as 10, 20, 30, and 40 s, respectively. Concentrations of HBsAg and S/N value for each different treatment are calculated. The liver function and HBV deoxyribonucleic acid (DNA) copy number are also detected. It is found that, compared with the control group, the concentrations of HBsAg and HBV DNA copy number of different treatment groups have statistically significant differences. With time going of LTP treatment, both the concentration of HBsAg and the copy number of HBV DNA gradually decrease, and all the S/N values are less than 2.1, indicating that HBsAg becomes negative after LTP treatment. Comparing the liver functions (i.e., enzymatic, proteinic, and bilirubin indicators) before and after LTP treatment, all the data are in the range of normal reference values. It is concluded that LTP induced by DBD is effective for HBV deactivation, and the liver function is kept normal during the process of plasma killing HBV.

Viability Reduction of Melanoma Cells by Plasma Jet via Inducing G1/S and G2/M Cell Cycle Arrest and Cell Apoptosis

This paper is aimed to investigate the inhibition effect and mechanism of low-temperature plasma (LTP) on melanoma cells. An argon atmospheric pressure plasma jet is used to generate LTP for the treatment of B16 murine melanoma cells cultured in vitro. LTP treatment time intervals are set as 5, 10, 15, and 20 s, respectively. After being treated with LTP, cell viability, cell apoptosis, cell cycle distribution, and cycle-related proteins expression of melanoma cells are, respectively, measured. It is found that, compared with the control cells, treatment of melanoma cells with 10, 15, and 20 s of plasma, result in a significant reduction in cell viability. Furthermore, investigation demonstrates that LTP may reduce cell viability of melanoma cells via inducing G1/S and G2/M cell cycle arrest and cell apoptosis, and alteration of cell cycle is due to down-modulation of the expression of CyclinB1 and CyclinD1 protein induced by LTP.

Effects of Atmospheric DBCD Plasma on Three Kinds of Typical Microorganisms

Dielectric barrier corona discharge (DBCD) is a robust plasma reactor with high efficiency and large scalable area. Nonthermal plasma is generated by DBCD in open condition under atmospheric pressure. Products of plasma are analyzed by using spectroscopy technology. The DBCD plasma is used to treat three kinds of typical microorganisms such as Escherichia coli, Staphylococcus aureus, and Candida albicans. Then, the inactivation effects of the plasma are discussed and compared with our formerly published results of parallel-plate dielectric barrier discharge (DBD) plasma. The results show that the DBCD plasma damages microbe cells by reactive species (RS) and lower pH values, while the parallel-plate DBD plasma works mainly through microdischarge channel and RS. In addition, different cell wall configurations result in different treatment effects.

Artemisinin ameliorated proteinuria in rats with adriamycin-induced nephropathy through regulating nephrin and podocin expressions.

OBJECTIVE To investigate the effects of artemisinin against proteinuria and glomerular filtration barrier damage in rats with adriamycin-induced nephropathy, and the potential mechanism underpinned the action. METHODS Forty adriamycin rats were randomly divided into two groups with the ratio of 1 : 3; the small-number group served as control group (n = 10), and the rats in the large-number group were treated with adriamycin to induce nephropathy; then they were further randomly assigned into 3 subgroups: benazepril group (n = 10), artemisinin group (n = 10), and adriamycin group (n = 10). The benazepril group and artemisinin group were treated with benazepril suspl (5.0 mg/kg daily) and artemisinin suspl (150 mg/kg daily) respectively after being modeled; those in the control group and adriamycin group were intragastrically administered an equivalent volume of distilled water every day. The treatment after model establishment lasted for a total of 4 weeks. The 24 h uric protein, blood biochemicals, renal pathological changes, renal ultrastrutural changes, Nephrin and Podocin proteins and gene expressions were measured by Coomassie brilliant blue assay, completely automatic biochemical analyzer, light microscope, electron microscopy, Western blot and reverse transcription polymerase chain reaction, respectively. RESULTS The rats in adriamycin group showed a significant increase in 24 h uric protein excretion, serum total cholesterol (TC), triglyceride (TG), blood urea nitrogen (BUN), serum creatinine (Scr) and decrease in albumin (Alb) (P < 0.05 or P < 0.01). Compared with adriamycin group, artemisinin could reduce uric protein excretion, decrease the serum TC, TG elevation, increase the serum Alb level, up-regulate the expressions of Nephrin and Podocin (P < 0.05 or P < 0.01), but no statistical significance effects on the levels of BUN, Scr in artemisinin group (P > 0.05). The renal pathological and ultrastrutural observation indicate that artemisinin could attenuate the severity of foot process effacement and fusion in the nephropathic rats. CONCLUSION Artemisinin might have an effect on the nephropathy in rats caused by adriamycin, which may be at least partly correlated with attenu- ation of the severity of foot process effacement and fusion, up-regulation of the expressions of Nephrin and Podocin in the glomeruli in the rats.

Low temperature plasma promoting fibroblast proliferation by activating the NF-κB pathway and increasing cyclinD1 expression

The potential applications of low temperature plasma (LTP) in wound healing have aroused the concern of many researchers. In this study, an argon atmospheric pressure plasma jet was applied to generate LTP for treatment of murine fibroblast cell (L929) cultured in vitro to investigate the effect of NF-κB pathway on fibroblast proliferation. The results showed that, compared with the control, L929 cells treated with plasma for less than 20 s had significant increases of proliferation; the productions of intracellular ROS, O2− and NO increased with prolongation of LTP treatment time; NF-κB pathway was activated by LTP in a proper dose range, and the expression of cyclinD1 in LTP-treated cells increased with the same trend as cell proliferation. After RNA interference to block p65 expression, with the same treatment time, RNAi-treated cells proliferated more slowly and expressed less cyclinD1 than normal cells. Furthermore, pretreatment with N-acetyl-L-cysteine (NAC) markedly prevented the plasma-induced changes in cells. In conclusion, the proliferation of L929 cells induced by LTP was closely related to NF-κB signaling pathway, which might be activated by appropriate level of intracellular ROS. These novel findings can provide some theoretical reference of LTP inducing cell proliferation and promoting wound healing.

Effects of low temperature atmospheric pressure plasma on skin wound healing of mice in vivo

Summary form only given. Low temperature plasma (LTP) has proven to be an effective way in wound healing, skin diseases, sterilization, and so on. This paper presented an atmospheric pressure discharge plasma jet in flowing argon by means of dielectric barrier discharge (DBD). Then, the effects of LTP on skin wound healing of mice in vivo were evaluated. Two wounds of 4 mm in diameter along the both sides of the spine were created on the back of each mouse (n=50). The mice were divided into fine groups equally. Five exposure time intervals of 10s, 20s, 30s, 40s and 50s were set, with the left side wound of each mouse was treated by LTP and the right one was left to heal naturally as a control part. The experiment last for 14 consecutive days, and sizes of the wounds were recorded every day. Finally, the wounds were removed, routinely fixed, paraffin-embedded, sectioned and hematoxylin-eosin stained. Experimental results showed that all wounds healing naturally as the control part were almost completely closed at day 14, and the wounds with 10-40s plasma exposure showed a significant daily improvement and almost complete closure at different days. Whereas, the wounds under 50s plasma exposure were still worse at day 14. Furthermore, it can be seen from images of pathological section, the number of fibroblast and blood capillary increased markedly within 30s exposure time, undergoing the course of reparative phase. However, lots of inflammatory cells infiltrated in the wound tissues with 50s exposure, meaning that the wounds were damaged by LTP. It was concluded that appropriate doses of LTP could inactivate bacteria around wound, activate fibroblast proliferation in wound tissue and eventually promote wound healing. Contrary, over doses of LTP could suppress wound healing through causing cell apoptosis or necrosis. Both positive and negative effects of LTP on mice skin wound healing were related to existence of reactive oxygen and nitrogen species (ROS and RNS) in the plasma jet, which were detected by optical emission spectroscopy.