Introduction: Photothermal therapy using gold nanoshells is one of cancer therapy methods. Gold nanoshells generally consist of a silica core and a thin gold shell. Fe3O4@Au core-shell can be used for magnetic targeted therapy. The objective of this study was investigation of the photothermal effects of magnetically targeted Fe3O4@Au NPs and NIR laser irradiation on model of melanoma cancer. The effective parameters in photothermal therapy include nanoparticles concentration, laser power density, and laser exposure time. In this research the effects of these parameters on produced heat and its spatial distribution in tissue equivalent phantom during photothermal therapy was evaluated.
Materials and Methods: At the first, the thermal distribution in tissue equivalent phantom have been simulated. The optimum laser power density and exposure time determined and simulation result verified in tissue equivalent phantom using thermocouple thermometer model ST 8891E. Invivo studies was performed on 100 C57BL/6 mice. Fe3O4@Au NPs was injected veinously to tumor inoculated mice, and accumulated in tumor using an external magnet. Then the tumor region was irradiated by laser (808 nm, 2.5 W/cm2, 6 minutes). For evaluation of treatment efficiency, we used pathologic studies and tumor growth measurement. Moreover, the temperature of tumor region was measured using IR camera model 875-1i.
Results: Simulation predicted a maximum temperature elevation of 12.5 ºC for nanoparticles concentration of 7 × 109 NP/ml and laser power density of 3.5 W/cm2 and irradiation time 6 min. The maximum discrepancy between simulations and phantom measurements was 8.6%. on the basis of simulation results the optimum parameters for treatment was nanoparticles dose 1.5 mg/kg, laser power density 3.5 W/cm2 and irradiation time 6 min. 2 weeks after treatment the average tumor volume multiplication in control relative to treatment group, was 10 and this was significant (one-way ANOVA, p < 0/001). The difference in average percentages of necrosis in control and treatment group was significant too (Mann-Whitney, p = 0.029).
Conclusion: In this study melanoma tumor inoculated in mice was treated using magnetically targeted Fe3O4@Au nanoparticles (dose of 1.5 mg/kg) and laser exposure (power density = 2.5 W/cm2 and exposure time 6 min). The results showed that simulation can be a reliable technique for photothermal therapy treatment planning.