Killing adherent and nonadherent cancer cells with the plasma pencil
Summary (2 min read)
I. INTRODUCTION
- Plasma Medicine is a field of research that deals with the biomedical applications of low temperature plasmas (LTPs) and most specifically plasmas generated at atmospheric pressure and at biologically tolerable temperatures.
- The plasma can be tuned to achieve various effects ranging from killing pathogens, to stimulating the proliferation of healthy cells, to destroying cancer cells. [1] [2] [3].
- Tuning the plasma to achieve desired effects involves judicious selection of the operating gas mixture, the type of waveform of the applied voltage (DC, pulsed DC, RF, pulsed RF, microwave, etc.), and careful adjustment of the amount of applied power to influence the electrons energy distribution function and to control the fluxes of the reactive species.
- This comes as no surprise as it is well known from cell biology investigations that ROS and RNS are involved in various biochemical events that occur on the cellular and subcellular levels.
- Some of these include lipids peroxidation, DNA damage, and the triggering of cellular signals. [1] [2] [3] [4].
II. MECHANISMS OF ACTION OF LTP AGAINST CANCER CELLS
- Therefore, the reactive species generated by the plasma in the gaseous state have to go through a gas-liquid interface and then diffuse into the bulk of the liquid.
- Hence, the authors concluded that plasma reaction byproducts in the medium are responsible for killing the cells, but as their concentrations decrease with PAM storage/aging time most cells would be able to cope and survive.
- Hence, exposure of cancer cells to LTP leads to an even higher intracellular oxidative stress, therefore causing their death.
- Caspases are proteins that play a crucial role in apoptosis or programmed cell death.
- 9 Ishaq et al. suggested that because tumor cells are defective in several regulatory signaling pathways they exhibit metabolic imbalance, which leads to a lack of cell growth regulation.
III. PLASMA PENCIL
- The application of LTP in biology and medicine relies on the availability of various sources that can produce plasmas with gas temperatures less than about 40 C, and at atmospheric pressure ($760 Torr).
- Various types of plasma jets have therefore been developed with designs tailored for specific needs.
- One such device, the plasma pencil, a handheld plasma jet generator developed in their laboratory, is presented here in some detail.
- The length of the plume depends on the gas flow rate, the magnitude of the applied voltage pulses, their widths, and the frequency.
- The plasma plume exhibits low temperature and can be touched by bare hands without causing any harm.
IV. EFFECTS OF THE PLASMA PENCIL ON CANCER CELLS
- To investigate the efficacy of the plasma pencil against cancer both adherent and nonadherent cancerous cells were tested.
- As a representative of nonadherent cell lines leukemia cells were selected.
- The reader is hereby notified that the following is not a review of the field but rather a review of their own results.
- These results were originally published elsewhere, in various scientific journals.
- The remainder of this paper mainly summarizes their work of the last few years on cancer application using their low temperature plasma generator, the plasma pencil.
A. Case of nonadherent cells
- T-cell line (ATCC No. CCL-119; aka CCRF-CEM) originally isolated from the blood of a patient with acute lymphoblastic leukemia was used.
- The growth media consisted of buffered RPMI-1640 media supplemented with 10% fetal bovine serum, 1% antibiotics (penicillin/streptomycin), and 1% glutamine.
- The delayed response of cell death may be attributed to cell signaling cascades that may result in apoptosis.
- Figure 7 shows images of the control DU 145 cells and that of cells treated for 10 min.
- The delayed killing of cells (24 h and longer post-treatment) indicates that the destruction of the cells is not achieved by brute force at the time of plasma exposure.
2. Squamous cell carcinoma
- The human bladder cancer cell line SCaBER (ATCCV R HTB3 TM ), originating from a patient with squamous cell carcinoma, was used (see image in Fig. 8 ).
- The plasma exposure times were 2, 3.5, and 5 min, and the untreated cells were kept as control for the cell viability assays.
- 1 of the trypan blue dye (0.4% trypan blue solution) to cells in MEM solution was used, also known as A ratio of 1.
- To test if cell signaling plays a role in leading to apoptosis caspase-3 activation assay was used.
- The cells detachment/reattachment function was also examined.
V. CONCLUSIONS
- This paper reviewed their experiments which used one of their plasma jet generators, the plasma pencil, to evaluate the effects of LTPs on various cancer cell lines.
- These include selectivity, works as well in vivo, minimal side effects, etc.
- Since the cells were always in a suspension within a growth medium, it is reasonable to assume that the plasma interacts more directly with the medium than the cells themselves.
- Since the observed effects only appear several hours/days later, the authors hypothesize that these species trigger biochemical events within the cells that follow slow progressing cascades in cell signaling pathways.
- As possible evidence, caspase activation, which can lead to apoptosis, was measured:.
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Cites background from "Killing adherent and nonadherent ca..."
...XXIII), les cellules tumorales traitées au plasma montrent des modifications morphologiques proches de ce que nous observons en laboratoire [14,25,45]....
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...Parmi les techniques générant un jet de plasma et utilisé dans le traitement des tissus/cellules tumorales, on rapporte (i) le ‘plasma pencil’ composé d’un tube diélectrique cylindrique, de 2 disques diélectriques de diamètres identiques au tube et placés à l’intérieur du tube [25]; (ii) le ‘plasma needle’ pouvant être utilisé dans le détachement cellulaire sélectif correspond à une décharge couronne créée au bout d’une pointe en imposant une onde électromagnétique RF (∼13MHz) pour exciter le gaz (Fig....
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...4) puisque les cellules sont alors dans un stade critique très avancé : on note une diminution de la taille, certaines semblent s’être désagrégées (‘fondues’ sur elle-même sans trace de milieu intracellulaire dans l’environnement) et le focus devient alors plus difficile à régler pour pouvoir visualiser simultanément une zone traitée et une zone non traitée : ce phénomène a été observé dans certaines études [14,25,45]....
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Frequently Asked Questions (18)
Q2. What is the length of the plume?
The length of the plume depends on the gas flow rate, the magnitude of the applied voltage pulses, their widths, and the frequency.
Q3. What is the role of caspase-3 in cell death?
Caspase-3 is a protein involved in the apoptotic pathway that interacts with caspase-8 and caspase-9 through a sequential process that activates cell apoptosis.
Q4. Why are plasma bullets used in biological applications?
14Because plasma bullets are launched in air, they produce very interesting reactive chemistry that can be exploited in biological and medical applications.
Q5. What are the common reactive chemistry in the plasma pencil?
Reactive oxygen species, such as O, OH, O2 , and reactive nitrogen species, such as NO, NO2, which are known to have biological implications, are abundantly generated by the plasma bullets.
Q6. What is the role of caspases in cancer cell death?
In general, cancer cells have much higher metabolic rate than healthy cells and therefore exhibit higher levels of intracellular concentrations of ROS and RNS.
Q7. What is the effect of LTP on cells?
6,7 Keidar and coworkers reported that LTP causes an increase in the expression of the oxidative stress reporter cH2A.X (pSer 139) and a decrease in DNA replication in the S-phase of the cell cycle.
Q8. How long can a plasma plume reach?
Plasma plumes reaching lengths up to 5 cm can be launched through the hole of the outer electrode and in the surrounding room air.
Q9. How long did the cells survive in the humidified atmosphere?
They were grown in complete growth media in a vented tissue culture flask and were incubated at 37 C in a humidified atmosphere containing 5% CO2.
Q10. How many cells survived after plasma treatment?
For 5 min plasma treatment, only about 25% of cells remained viable at 24 h postplasma exposure, indicating that the higher the dose of the plasma the lower the number of the cells that survived.
Q11. How long did the cells survive after plasma treatment?
18 The results from this study indicate that there is a dose dependent response in the induction of cell death of leukemia cells and single doses of plasma treatment continue killing cells up to 2.5 days post treatment.
Q12. How long does plasma kill leukemia cells?
Initial experiments revealed that plasma kills the leukemia cells and that the effects of a single dose of plasma continue for up to few days.
Q13. What is the name of the cell line used in this study?
In this study, T-cell line (ATCC No. CCL-119; aka CCRF-CEM) originally isolated from the blood of a patient with acute lymphoblastic leukemia was used.
Q14. What is the role of caspases in cancer cell growth?
Laroussi and co-workers studied caspase-3 activation in the case of squamous cell carcinoma and found higher level of caspase-3 activation in cells treated by LTP than in control samples (untreated cells), indicating that LTP induces apoptosis in these cells.9 Ishaq et al. suggested that because tumor cells are defective in several regulatory signaling pathways they exhibit metabolic imbalance, which leads to a lack of cell growth regulation.
Q15. What is the process of releasing reactive species from the plasma?
the reactive species generated by the plasma in the gaseous state have to go through a gas–liquid interface and then diffuse into the bulk of the liquid.
Q16. How long did plasma exposure cause cell death?
starting with 24 h post-treatment, a slow but steady trend of cell death for plasma exposure times longer than 5 min was observed.
Q17. How long did the cells survive after plasma exposure?
The results revealed that the cell viability did not differ dramatically at time 0 h postplasma treatment even at the highest dose of treatment which was a plasma exposure of 10 min.
Q18. how many cells were killed after plasma pencil treatment?
The counts immediately after plasma pencil treatment at time 0 h029401-5 Laroussi, Mohades, and Barekzi: Killing adherent and nonadherent cancer cells 029401-5Biointerphases, Vol. 10, No. 2, June 2015reveal no dead cells, suggesting that there were no immediate physical effects.