Effect of nanoparticle concentration on thermal damage in nanoparticle-assisted thermal therapy

Abstract

Photothermal therapy involving nanoparticles is evolving as a promising targeted treatment for cancer. This paper presents the results for the effect of nanoparticle concentration, within a tumor, to control the thermal damage during nanoparticle assisted thermal therapy. A surface tumor embedded with gold nanoparticles (distributed uniformly) is considered. The thermal damage is evaluated for various nanoparticle concentrations (within the tumor) to identify an optimal concentration of the nanoparticles so as to achieve spatial confinement of the damage to the tumor region. Optical interaction is coupled to the biological heat transfer through Pennes' bioheat model and Beer's law. Spatiotemporal thermal damage is simulated through the Arrhenius method. The finite difference implicit method is used to solve the coupled phenomenon. Results show that there is a specific value of nanoparticle concentration at which it is possible to confine thermal damage to the tumor within a spatial scale of less than 1 mm. This way the healthy tissues surrounding a tumor are safe. This optimum value of nanoparticle concentration (irrespective of tumor diameters) is 0.00001%. This concentration along with irradiation intensity of 1 W/cm2 for irradiation duration of 110 seconds is sufficient to thermally ablate the considered tumors. Novelty of this study is that it presents a combination of the controlling parameters for achieving a high (<1 mm) spatial confinement of the thermal damage. This finding is very much significant from clinical point of view. Clinically it is always desired to attain the therapeutic efficacy with minimal delivery of external agents (nanoparticles in this case) to a patient.