Investigation of the injury behavior in thermal therapy of human renal cell carcinoma cells using a non-isothermal method

In this study, the thermal injury behavior of both suspended and attached human renal cell carcinoma (RCC) SN12 cells under thermal therapy conditions (i.e., heating cells to elevated temperature for seconds to minutes) was investigated using a non-isothermal method. This non-isothermal method entailed heating the cells using a programmable heating stage from room temperature at 130°C min^-1 to various peak temperatures from 45 to 70°C, held for 0 to 10 minutes, and then cooled down to room temperature at 65°C min^-1. It was found that the suspended SN12 cells are more heat susceptible than attached ones. The non-isothermal portions (i.e., the heat-up and cool-down portions) of the thermal histories were found to be able to cause significant injury (>10%) in both suspended and attached SN12 cells when the peak temperature is above 60°C. Therefore, a new non-isothermal method, which accounts for both the isothermal and non-isothermal portions of the thermal histories, was used to extract the kinetic parameters (i.e., the activation energy and frequency factor) in the Arrhenius injury model for SN12 cells. Furthermore, these results suggest that this non-isothermal method can be used to extract kinetic parameters from in vivo heating studies using minimally invasive surgical probes, where it is very difficult to get a thermal history in tissue with a dominant isothermal portion.