Plasma is the fourth phase of matter consisting of charged particles, such as ions and electrons, which interact via electrostatic forces. Plasmas are also known to contain chemically active free radicals. Biological interactions have shown plasmas to result in killing known dental pathogens as well as inducing cell-to-cell detachment and apoptosis. In order to investigate cell growth, the direct (plasma-cell contact) and indirect (plasma-treated medium contact) effects of plasma on human oral cell growth were performed at varying plasma operation parameters.
Method:
The device, a small handheld probe, was built around a central tungsten wire. High voltage current was used to generate atmospheric plasma at the tip of the wire. During indirect plasma treatment of cells, aliquots of cell culture medium were treated with the device at high (0.72 l/min) and mid- (0.58 l/min) helium gas flow rates and durations of exposure ranging from 10-300 s. Following incubation of human osteoblasts (MG63) and gingival fibroblasts (HGF) with plasma treated medium, AlamarBlue™ assay was performed. The effects of plasma helium flow rate and duration of exposure on the cells were compared using two-way analysis of variance (ANOVA). Both cell types were grown on Thermanox™ coverslips and subjected to direct and indirect plasma treatment for qualitative SEM assessment.
Result:
Indirect exposure to plasma led to some cell death but not total elimination. SEM images indicated direct plasma exposure led to total cell death. The types of cells were affected differently by the operational parameters investigated during indirect plasma exposure. MG63 cells were significantly affected by duration of exposure whilst HGF cells were significantly affected by plasma gas flow rate.
Conclusion:
These early studies have revealed interesting data and the device requires further calibration and optimization to characterize the mode of action of helium plasma with oral cells.