Development of injection gas heating system for introducing large droplets to inductively coupled plasma

Fundamental studies on droplet throughput and the analysis of single cells using a downward-pointing ICP-time-of-flight mass spectrometer

Capabilities of the downwardly oriented inductively coupled plasma mass spectrometer (ICP-MS) recently reported (Vonderach et al. 2021) were studied using a time-of-flight mass spectrometer (TOFMS) yielding benefits for the fast detection of short transient signals containing multi-element information. The previously reported sample inlet configuration for the analysis of microdroplets was equipped with two extra gas inlets for the supply of argon and helium, which enabled a more precise optimization of the sample introduction and operating conditions of the plasma. Furthermore, the sample supply system was operated at elevated temperatures to enhance the desolvation of the droplets prior to their introduction into the plasma. Transient droplet signals with frequencies of up to 1000 Hz were recorded for 74 μm (diameter) sized droplets. The upper detectable droplet size was limited by the droplet generator used and was measured at 93 μm (diameter). The droplets served as the transporter for biological cells so that the described setup could be used to analyze single cells. Mouse lung cells embedded into droplets were detected successfully according to their Cs droplet tracer, Ir nucleus marker, surface markers and the phosphorus content. Transient signals were recorded at a time resolution of 33 μs in order to investigate the signal structure of single droplet-cell events containing multiple elements. Signals between 200-400 μs (FW base) and ≤100 μs (FWHM) in duration were measured. To ensure that the droplet formation process did not affect the sampled cells, different types of cells were localized within the droplets using optical inspection directly after droplet formation and it was possible to observe that cells remained intact with random sampling. The results indicate that a downward-pointing ICP-MS in combination with the microdroplet-based approach can be considered as an alternative to commonly used ICP-MS systems for single cell analysis, and might be suitable for online coupling to flow cytometry.

Influence of Gas Temperature in Atmospheric Non-Equilibrium Plasma on Bactericidal Effect

In this study, the relationship between plasma gas temperature and the bactericidal effects on five of bacteria (Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, Enterococcus faecalis and Bacillus cereus (spore)) in liquid was investigated using a temperature-controllable plasma source. We determined that the bactericidal ability improved as the plasma gas temperature increased. Specifically, the bactericidal ability on E. coli of 80-℃ plasma was enhanced by as much as 6.3 times compared to that of 10-℃ plasma. The relationship between plasma gas temperature and the amount of hydroxyl radical, singlet oxygen, hydrogen peroxide, and ozone introduced into the solution was investigated. Our results also showed that each reactive species production increased by 2.1, 9.0, 1.6, and 17 times, respectively, with 80-℃ compared to 10-℃ plasma. The relationship between the bactericidal ability and amount of reactive species indicated that singlet oxygen and ozone introduced to the solution mostly influenced the bactericidal ability as the plasma gas temperature increased. We conclude that the plasma gas temperature is the crucial parameter for plasma sterilization.

Direct protein introduction into plant cells using a multi-gas plasma jet

Protein introduction into cells is more difficult in plants than in mammalian cells, although it was reported that protein introduction was successful in shoot apical meristem and leaves only together with a cell-penetrating peptide. In this study, we tried to introduce superfolder green fluorescent protein (sGFP)-fused to adenylate cyclase as a reporter protein without a cell-penetrating peptide into the cells of tobacco leaves by treatment with atmospheric non-thermal plasmas. For this purpose, CO2 or N2 plasma was generated using a multi-gas plasma jet. Confocal microscopy indicated that sGFP signals were observed inside of leaf cells after treatment with CO2 or N2 plasma without substantial damage. In addition, the amount of cyclic adenosine monophosphate (cAMP) formed by the catalytic enzyme adenylate cyclase, which requires cellular calmodulin for its activity, was significantly increased in leaves treated with CO2 or N2 plasma, also indicating the introduction of sGFP-fused adenylate cyclase into the cells. These results suggested that treatment with CO2 or N2 plasma could be a useful technique for protein introduction into plant tissues.