The applications of the cold atmospheric plasma jet (CAPJ) in cancer treatment have been investigated for over a decade, focused on the effect that the CAPJ creates on cancer cells. Here we report for the first time on the impact that cells have on the CAPJ during treatment. To better understand these CAPJ-cell interactions, we analyzed the CAPJ behaviors in the presence of several normal and cancer cell lines and investigated the CAPJ selectivity. A more in-depth study of plasma self-organization patterns utilizing a model which contains a combination of normal and cancer cells reveals that the cells' capacitance can be an important predictor of plasma jet behavior. Cancer cells can direct the jet either toward or away from normal cells, which depends on the boundary condition behind the cell colony. Both experimental and theoretical results show that a grounded copper board beneath the cell-culture dish leads to opposite CPAJ behaviors compared with a floating boundary condition. In conclusion, our findings indicate that plasma can be self-adaptive toward cancer cells, and such a feature can be manipulated. Therefore, using the permittivity difference among cell lines may help us focus plasmas upon cancer cells at the vicinity of normal tissues and maximize the selectivity of plasma treatments.
Keywords: capacitance imaging; cell feedback; cold atmospheric plasma; plasma medicine; selective treatment; self-organization pattern.