Rare Earth Oxide-Based Nanoparticles with Application in Photodynamic Therapy for Cancer

Photodynamic therapy is a non-invasive technique approved for the treatment of cancer. A photosensitizer (in this case, methylene blue) is activated by absorption of light of a specific wavelength to generate reactive oxygen species, which are toxic to cells1. Therefore, our aim is to synthesize and optimize doped rare earth oxide-based nanoparticles that, when excited by X-ray radiation, emit in the visible region, activating the photosensitizer. Nanoparticles were synthesized by PVA-assisted sol-gel route2, preparing a solution of 0,2 mol/L GdCl3·6H2O and mixing it with another solution of 0,2 mol/L LnCl3·6H2O, adding PVA 10% (w/v), where Ln = Eu, Sm, Tb and Tm. After 30 min of stirring, solution was dried at 100 °C for 24 h, kept at 200 °C for 5 h, and calcined at 1000 °C for 5 h. Structural and luminescence properties were determined. DLS showed that Gd2O3:Eu3+ systems have hydrodynamic radius between 140-200 nm. SEM images confirmed that Gd2O3 NPs doped with Sm3+ and Eu3+ have different size and shape distributions. Total excitation showed that NPs have a bandgap of 5.25 eV. Figure 1 shows excitation and emission spectra of Gd2O3:Ln3+. It was observed that Eu3+ and Sm3+ are the most suitable emitters for the use with photosensitizer. It is concluded that it is necessary to optimize size and shape distribution of these NPs.