Molecular mechanism of thermal sensitization effect of potential materials for microwave hyperthermia

The materials susceptible to microwave irradiation has the potential to improve the heating efficiency of microwave tumour ablation. A molecular dynamics simulation was performed to investigate the mechanisms of thermal sensitisation of the potential susceptible materials including pure water, normal saline, hydrogel, sodium alginate and calcium alginate under microwave heating conditions. The comparison result of the temperature rises of these materials indicated that calcium alginate gels was the highest and that of pure water was lowest. The reasons were analysed by calculating the variations in translational and rotational kinetic energies, dielectric constant and energy contribution of the components of the materials in the presence of an external electromagnetic field of 2.45 GHz. It is found that the rapid translational molecular motion of salt ions leads to higher temperature rise of normal saline compared with pure water. The polymeric network structure of hydrogel can trap the water molecules in a small space and pack the surrounding water molecules more closely, and the temperature rise increases nonlinearly with the increase of the density of the water molecules. A combination of the heating mechanisms of normal saline and hydrogel induces the highest temperature rise of the alginates among all of the investigated materials.