Size effect of platinum nanoparticles in simulated anticancer photothermal therapy

Platinum nanoparticles (Pt NPs) with properties including damage of DNA, enzmatic activity and possibility of light absorption in the biological range could find application as effective photosensitizers in photothermal anticancer therapy (PTT). The photothermal properties of Pt NPs depend on their shape, size and crystalline structure. Therefore, in this paper the effect of Pt NPs size on photothermal efficiency is determined. For this purpose, spherical, crystalline 80 nm PtI NPs and 2 nm PtII NPs were synthesized and characterized by transmission electron microscopy (TEM), selected area diffraction patterns (SAED) and X-ray diffraction (XRD). The possibilities of using Pt NPs in PTT were investigated using two colon cancer cell lines: SW480 and SW620, which were cultured with both Pt NPs and irradiated by two, 650 nm and 808 nm lasers. Microscopy images of cells and MTS assay showed, that the PTT is the most effective when 2 nm nanoparticles and the 650 nm laser were used. The mortality of cells was around 62% for SW480 and 70% for SW620. Furthermore, higher temperatures after irradiation of Pt NPs by lasers were observed for the 2 nm Pt NPs for both wavelengths. Consequently, the values of photothermal efficiency are higher by approximately 5% and 6% for 2 nm Pt NPs, than for 80 nm ones, which were irradiated by 650 and 808 nm lasers, respectively. Moreover, the results obtained from experimental data corresponded with Mie theory.