Inactivation of Myeloma Cancer Cells by Helium and Argon Plasma Jets: The Effect Comparison and the Key Reactive Species

In plasma cancer therapy, the inactivation of cancer cells under plasma treatment is closely related to the reactive oxygen and nitrogen species (RONS) induced by plasmas. Quantitative study on the plasma-induced RONS that related to cancer cells apoptosis is critical for advancing the research of plasma cancer therapy. In this paper, the effects of several reactive species on the inactivation of LP-1 myeloma cancer cells are comparatively studied with variable working gas composition, surrounding gas composition, and discharge power. The results show that helium plasma jet has a higher cell inactivation efficiency than argon plasma jet under the same discharge power. By comparing the concentration of aqueous phase reactive species and the cell inactivation efficiency under different working gases and discharge powers, it is demonstrated that the inactivation efficiency of LP-1 myeloma cancer cells is strongly correlated with the concentration of peroxynitrite (ONOOH/ONOO-). Published by AIP Publishing

Production and Correlation of Reactive Oxygen and Nitrogen Species in Gas- and Liquid-Phase Generated by Helium Plasma Jets Under Different Pulse Widths

In this paper, we present the effects of the pulse width (PW) on the plasma jet\u27s discharge characteristics, particularly focusing on the production and correlation of the reactive oxygen and nitrogen species (RONS) in gas- and liquid-phase. It is found that the length of plasma jet plume first increases before the PW of 10 μs, then gradually decreases and finally almost remains unchanged beyond 150 μs. The plasma bullet disappears after the falling edge of the voltage pulse at low PW, while it terminates far ahead of the falling edge of voltage pulse at high PW. This is mainly attributed to accumulation of space charges that lead to weakening of the reduced electric field with an increase of PW from low to high. More important, it is found that the excited reactive species, the positive and negative ions from plasma jet, and the concentrations of NO2– and NO3– in deionized water exposed to plasma jet so display the first increasing and then decreasing change trend with increase of PW, while the concentration of H2O2 in water almost displays the linearly increasing trend. This mainly results from the formation of the H3O+ and HO2–, as well as their ion water clusters that can produce more OH radicals to be converted into H2O2, while the NO2– and NO3– in gas phase can transport into water and exist most stably in water. The water cluster formation at gas-liquid interface is an important key process that can affect the chemical nature and dose of aqueous RONS in water; this is beneficial for understanding how the RONS are formed in liquid-phase. Published by AIP Publishing

Alteration of Metabolite Profiling by Cold Atmospheric Plasma Treatment in Human Myeloma Cells

BACKGROUND: Despite new progress of chemotherapy in multiple myeloma (MM) clinical treatment, MM is still a refractory disease and new technology is needed to improve the outcomes and prolong the survival. Cold atmospheric plasma is a rapidly developed technology in recent years, which has been widely applied in biomedicine. Although plasma could efficiently inactivate various tumor cells, the effects of plasma on tumor cell metabolism have not been studied yet. METHODS: In this study, we investigated the metabolite profiling of He plasma treatment on myeloma tumor cells by gas-chromatography time-of-flight (GC-TOF) mass-spectrometry. Meanwhile, by bioinformatic analysis such as GO and KEGG analysis we try to figure out the metabolism pathway that was significantly affected by gas plasma treatment. RESULTS: By GC-TOF mass-spectrometry, 573 signals were detected and evaluated using PCA and OPLS-DA. By KEGG analysis we listed all the differential metabolites and further classified into different metabolic pathways. The results showed that beta-alanine metabolism pathway was the most significant change after He gas plasma treatment in myeloma cells. Besides, propanoate metabolism and linoleic acid metabolism should also be concerned during gas plasma treatment of cancer cells. CONCLUSIONS: Cold atmospheric plasma treatment could significantly alter the metabolite profiling of myeloma tumor cells, among which, the beta-alanine metabolism pathway is the most susceptible to He gas plasma treatment. © The Author(s) 2018

p-Type Co Interstitial Defects in Thermoelectric Skutterudite CoSb_3 Due to the Breakage of Sb_4-Rings

Skutterudite CoSb_3 based thermoelectric devices have high potential for engineering applications because both n- and p-type doped CoSb_3 demonstrate excellent thermoelectric performance. A crucial point concerning the application of CoSb_3 is to understand and control its defect chemistry. To reveal the native conductivity behavior of nonstoichiometric CoSb_3, we investigated the intrinsic point defects in CoSb_3 using density functional theory. We found CoSb_3 is p-type in either Co or Sb rich regions of phase stability. Interstitial Co (Co_i) and interstitial Co-pair (Co_(i-p)) are the dominant point defects in the Co rich region. However, Co_(i-p) will be difficult to form because the formation temperature of Co_(i-p) is much lower than the synthesis temperature of CoSb_3. The unexpected acceptor nature of the Co_i or Co_(i-p) defects is explained by the breakage of multiple Sb_4-rings. Co vacancy (Co_v) is found to be the p-type defect in the Sb rich region. Furthermore, the solubility of excess Co in CoSb_3 is expected to be larger than that of Sb because of the lower formation energy and higher carrier concentration of Co_i compared with those of Co_v

Alteration of Metabolite Profiling by Cold Atmospheric Plasma Treatment in Human Myeloma Cells

BACKGROUND: Despite new progress of chemotherapy in multiple myeloma (MM) clinical treatment, MM is still a refractory disease and new technology is needed to improve the outcomes and prolong the survival. Cold atmospheric plasma is a rapidly developed technology in recent years, which has been widely applied in biomedicine. Although plasma could efficiently inactivate various tumor cells, the effects of plasma on tumor cell metabolism have not been studied yet. METHODS: In this study, we investigated the metabolite profiling of He plasma treatment on myeloma tumor cells by gas-chromatography time-of-flight (GC-TOF) mass-spectrometry. Meanwhile, by bioinformatic analysis such as GO and KEGG analysis we try to figure out the metabolism pathway that was significantly affected by gas plasma treatment. RESULTS: By GC-TOF mass-spectrometry, 573 signals were detected and evaluated using PCA and OPLS-DA. By KEGG analysis we listed all the differential metabolites and further classified into different metabolic pathways. The results showed that beta-alanine metabolism pathway was the most significant change after He gas plasma treatment in myeloma cells. Besides, propanoate metabolism and linoleic acid metabolism should also be concerned during gas plasma treatment of cancer cells. CONCLUSIONS: Cold atmospheric plasma treatment could significantly alter the metabolite profiling of myeloma tumor cells, among which, the beta-alanine metabolism pathway is the most susceptible to He gas plasma treatment. © The Author(s) 2018

NO2- and NO3- Enhance Cold Atmospheric Plasma Induced Cancer Cell Death by Generation of ONOO-

Cold atmospheric plasma (CAP) is a rapidly developed technology that has been widely applied in biomedicine especially in cancer treatment. Due to the generation of various active species in plasma, CAP could induce various tumor cells death and showed a promising potential in cancer therapy. To enhance the biological effects of gas plasma, changing the discharging parameters is the most commonly used method, yet increasing discharging power will lead to a higher possibility of simultaneously damage surrounding tissues. In this study, by adding nontoxic concentration of additional nitrite and nitrate in the medium, we found that anti-tumor effect of CAP treatment was enhanced in the same discharging parameters. By microplate reader and cell flow cytometer we measured several extracellular and intracellular RONS and found that ONOO- was mostly correlated with the enhanced cancer cell killing effect. We proposed that more nitrogen supplies such as nitrite and nitrate could increase the production of RNS especially ONOO- and resulted in a better killing effect to cancer cells. Our results provided a new strategy to enhance the antitumor effect by plasma jet treatment without changing the discharging parameters. © 2018 Author(s)

Superstrengthening Bi_2Te_3 through Nanotwinning

Bismuth telluride (Bi_2Te_3) based thermoelectric (TE) materials have been commercialized successfully as solid-state power generators, but their low mechanical strength suggests that these materials may not be reliable for long-term use in TE devices. Here we use density functional theory to show that the ideal shear strength of Bi_2Te_3 can be significantly enhanced up to 215% by imposing nanoscale twins. We reveal that the origin of the low strength in single crystalline Bi_2Te_3 is the weak van der Waals interaction between the Te1 coupling two Te1─Bi─Te2─Bi─Te1 five-layer quint substructures. However, we demonstrate here a surprising result that forming twin boundaries between the Te1 atoms of adjacent quints greatly strengthens the interaction between them, leading to a tripling of the ideal shear strength in nanotwinned Bi_2Te_3 (0.6 GPa) compared to that in the single crystalline material (0.19 GPa). This grain boundary engineering strategy opens a new pathway for designing robust Bi_2Te_3 TE semiconductors for high-performance TE devices

Effect of Cold Atmospheric Plasma Treatment on the Metabolites of Human Leukemia Cells

Background Acute myeloid leukemia (AML) is a typically fatal malignancy and new drug and treatment need to be developed for a better survival outcome. Cold atmospheric plasma (CAP) is a novel technology, which has been widely applied in biomedicine, especially in various of cancer treatment. However, the changes in cell metabolism after CAP treatment of leukemia cells have been rarely studied. Methods In this study, we investigated the metabolite profiling of plasma treatment on leukemia cells based on Gas Chromatography Tandem Time-of-Flight Mass Spectrometry (GC-TOFMS). Simultaneously, we conducted a series of bioinformatics analysis of metabolites and metabolic pathways with significant differences after basic data analysis. Results 800 signals were detected by GC-TOF mass-spectrometry and then evaluated using PCA and OPLS-DA. All the differential metabolites were listed and the related metabolic pathways were analyzed by KEGG pathway. The results showed that alanine, aspartate and glutamate metabolism had a significant change after plasma treatment. Meanwhile, d-glutamine and d-glutamate metabolism were significantly changed by CAP. Glutaminase activity was decreased after plasma treatment, which might lead to glutamine accumulation and leukemia cells death. Conclusions We found the above two metabolic pathways vulnerable to plasma treatment, which might result in leukemia cells death and might be the cornerstone of further exploration of plasma treatment targets

Dramatically reduced lattice thermal conductivity of Mg_2Si thermoelectric material from nanotwinning

Tuning phonon transport to reduce the lattice thermal conductivity (κ_L) is crucial for advancing thermoelectrics (TEs). Traditional strategies on κ_L reduction focus on introducing scattering sources such as point defects, dislocations, and grain boundaries, that may degrade the electrical conductivity and Seebeck coefficient. We suggest here, a novel twin boundary (TB) strategy that can decrease the κ_L of Mg_2Si by ∼90%, but which may not degrade the electrical properties significantly. We validate this suggestion using density functional theory (DFT). We attribute the mechanism of TB induced κ_L reduction to (i) the lower phonon velocities and larger Grüneisen parameter, (ii) “rattling” of the Mg--Mg pair induced soft acoustic and optical modes, (iii) shorter phonon lifetime and higher phonon scattering rate. We predict that the size of nanotwinned structure should be controlled between 3 nm and 100 nm in the Mg2Si matrix for the most effective κ_L reduction. These results should be applicable for other TE or non TE energy materials with desired low thermal conductivity, suggesting rational designs of high-performance Mg_2Si TE materials with low κ_L for the energy conversion applications

A construction of multidimensional Dubrovin-Novikov brackets

A method for the construction of classes of examples of multi-dimensional, multi-component Dubrovin-Novikov brackets of hydrodynamic type is given. This is based on an extension of the original construction of Gelfand and Dorfman which gave examples of Novikov algebras in terms of structures defined from com- mutative, associative algebras. Given such an algebra, the construction involves only linear algebra