Low Power Argon Laser-Induced Thermal Therapy for Subcutaneous Ehrlich Carcinoma in Mice Using Spherical Gold Nanoparticles

Abstract

The present study examines the feasibility of a low power argon laser-induced thermal therapy to Ehrlich carcinoma, employing a direct administration of spherical gold nanoparticles (GNPs). This modality utilizes the advantage of strong surface plasmon resonance exhibited by spherical GNPs in the visible range. Ehrlich tumors were grown in female balb mice by subcutaneous injection of Ehrlich ascites carcinoma cells. GNPs with an average diameter 13 +/- 1.2 nm and optical density (ODlambda:518 nm = 3) were directly injected within the tumor interstitium. Tumors were then illuminated with a continuous-wave (CW) argon ion laser with irradiance 55 mW cm-2 for 45 min. All laser-GNPs treated tumors exhibited a significant suppression in tumor growth throughout 15 days. On the contrary, sham-treated group (laser treatment without GNPs injection) and control group (neither laser nor GNPs treatment) showed a progressive increase in tumor growth during the same period. Histopathological examination demonstrated extensive necrotic percentage in laser-GNPs treated group (90%) in comparison with sham (35%) or control group (3-7%). A wide-angle X-ray scattering also revealed detectable changes in tumor protein structure exposed to both laser and GNPs. It can be concluded from this study that the intense surface plasmon resonance exhibited by spherical GNPs in the visible range could be very useful as a noninvasive technique for photothermal therapy of skin or near-surface type tumors that need much less laser energy and lower concentrations of GNPs.