Photothermal therapy (PTT) is a nanotechnology-assisted cancer hyperthermia approach in which the interaction between laser light and plasmonic nanoparticles (NPs) generates localized heating. The exploitation of plasmonic NPs in association with active targeting moieties causes the preferential accumulation of NPs inside cancer cells, thereby providing targeted PTT. Herein, we evaluate the effect of folic acid (FA) as an active targeting agent in enhancing the photothermal efficiency of multifunctional Iron (III) Oxide (Fe2O3)@Au core- shell NPs. Fe2O3@Au NPs were synthesized, modified with FA and then characterized. Human nasopharyngeal (KB) cancer cells were treated with different concentrations of Fe2O3@Au, with and without FA modification and the temperature rise profiles of the cells were measured upon administration of the near-infrared (NIR) laser (808 nm, 6 W/cm2, 10 min). The recorded temperature profiles of the cells were used for thermal dose calculation. Finally, the level of induced apoptosis was determined by flow cytometry using an annexin V-fluorescein isothiocyanate/propidium iodide apoptosis detection kit. The characterization data showed that the Fe2O3@Au NPs are spherical, with a hydrodynamic size of 33 nm. The data corroborated the successful conjugation of the NPs with FA. The thermometry results indicated the superior temperature elevation rate of the cells in the presence of the NPs upon NIR irradiation. Meanwhile, the higher heating rate and the higher thermal dose were obtained for the cells exposed to FA-targeted Fe2O3@Au rather than the non-targeted nanocomplex. Flow cytometry studies revealed that FA-targeted Fe2O3@Au induced higher level of apoptosis than non-targeted Fe2O3@Au NPs. In conclusion, our findings suggest that the synthesized FA-targeted Fe2O3@Au NP has high potentials to be considered as an efficient thermosensitizer in the process of targeted cancer hyperthermia.
Keywords: Nanotechnology; apoptosis; cancer targeting; folic acid; hyperthermia; thermal dose.