Measurements of nanoparticle-enhanced heating from 1MHz ultrasound in solution and in mice bearing CT26 colon tumors.

Hyperthermia is considered as a new approach for cancer therapy. Non-selectivity of tissue heating in conventional hyperthermia methods results in collateral damages to healthy tissues and this is the greatest obstacle against hyperthermia in clinic. Herein, to promote the efficiency of conventional hyperthermia methods, nanoparticle-enhanced heating from 1MHz ultrasound was investigated in vitro and in vivo. The experiments were conducted on two mediums; (1) various colloidal nano-solutions (in vitro section) and (2) CT26 mouse colon carcinoma tumor loaded by various nanoparticles (in vivo section). Experiments in this study were designed to evaluate and compare the sonosensitizing potentials of gold nanoparticles (AuNPs), iron oxide nanoparticles (IONPs), and nano-graphene oxide (NGO) in enhancement of ultrasound-induced heat generation. The temperature profile of the solutions and the animal tumors containing nanoparticles were recorded during sonication. An increased heating rate during sonication was observed for both in vitro and in vivo mediums when the nanoparticles were present. Our in vitro experiments revealed that percentages of increases in temperature elevation rates were 12.5%, 20.4%, and 37.5% for IONPs, NGO, and AuNPs, respectively. Compared to the nanoparticles-free tumors, direct injection of AuNPs, NGO and IONPs into the tumors and subsequent sonication for 10min caused an increased temperature elevation rate of 37.5%, 24.1% and 16.1%, respectively. AuNPs, IONPs and NGO are proposed as ultrasound responsive nanomaterials with the potential of focusing the energy of acoustic waves on the tumor and inducing localized hyperthermia.