Evaluation of important treatment parameters in supraphysiological thermal therapy of human liver cancer HepG2 cells.

This study was aimed at simulating the effect of various treatment parameters like heating rate (HR), peak temperature (PT) and hold/total treatment time on the viability of human liver cancer HepG2 cells subjected to different thermal therapy conditions. The problem was approached by investigating the injury kinetics obtained using experimentally measured viability of the cells, heated to temperatures of 50-70 degrees C for 0-9 min at HRs of 100, 200, 300 and 525 degrees C min(-1). An empirical expression obtained between the activation energy (E) and HR was extended to obtain the E values over a broad range of HRs from 5 to 600 degrees C min(-1) that mimic the actual conditions encountered in a typical thermal therapy protocol. Further, the effect of the HR (5-600 degrees C min(-1)) and PT (50-85 degrees C) on the cell survival was studied over a range of hold times. A significant drop in survival from 90% to 0% with the simultaneous increase in HR and PT was observed as the hold time increased from 0 to 5 min. For complete cell death, the hold time increased with the increase in the HR for a given PT, while the total time showed presence of minima for 60, 65 and 70 degrees C at HRs of 50, 100 and 200 degrees C min(-1), respectively.