RESUMO
BACKGROUND: Gold nanoparticles (GNPs) are among the most promising radiosensitive materials in radiotherapy. Studying the effective sensitizing factors such as nanoparticle size, concentration, surface features, radiation energy and cell type can help to optimize the effect and possible clinical application of GNPs in radiation therapy. In this study, the radiation sensitive polymer gel was used to investigate the dosimetric effect of GNP size in megavoltage (MV) photon beam radiotherapy. MATERIAL AND METHODS: GNPs with the size of 30nm, 50nm and 100nm in diameter were used. Transmission electron microscope (TEM) and dynamic light scattering (DLS) were applied to analyze the size of nanoparticles. The MAGICA polymer gel was synthesized and impregnated with different sizes of GNPs. The samples were irradiated with 6MV photon beam and 24 hours after irradiation, they were read using a Magnetic Resonance Imaging (MRI) scanner. Macroscopic Dose Enhancement Factor (DEF) was measured to compare the effect of GNP size. The MAGICA response of the 6MV x-ray beam was verified comparing Percentage Depth Dose (PDD) curve extracted from polymer gel dosimetry and Treatment Planning System (TPS). RESULTS: MAGICA polymer gel dose response curve was linear in the range of 0 to 10 Gy. DEFs by adding 30nm, 50nm and 100nm GNPs were 1.1, 1.17 and 1.12, respectively. PDD curves of polymer gel dosimeter and treatment planning system were in good agreement. CONCLUSION: The results indicated a substantial increase in DEF uses a MV photon beam in combination with GNPs of different sizes and it was inconsistent with previous radiobiological studies. The maximum DEF was achieved for 50nm GNPs in comparison with 30nm and 100nm leading to the assumption of self-absorption effect by larger diameters. According to the outcomes of this work, MAGICA polymer gel can be recommended as a reliable dosimeter to investigate the dosimetric effect of GNP size and also a useful method to validate the current radiobiological and simulation studies.
RESUMO
Recently, it has been showed that gadolinium oxide nanoparticles can provide high-contrast enhancement in magnetic resonance imaging (MRI). Moreover, liposomes due to high biocompatibility have shown unique model systems, with the most successful application being the drug delivery system. As a suitable cell-tracking contrast agent (CA) in molecular MRI (mMRI), the synthesis and optimisation characteristic of a novel paramagnetic liposomes (PMLs) based on gadolinium nanoparticles, essentially composed of a new complex of gadolinium oxide-diethylene glycol (Gd2O3-DEG) loaded in liposomes have been determined in this research. Gd2O3-DEG was prepared by a new supervised polyol method and was encapsulated with liposome by the film hydration method. The paramagnetic liposome nanoparticle (PMLN) sizes ranged from 65 to 170 nm. The r1 of PMLNs and Gd2O3-DEG were much higher than that of Gd-diethylenetriamine penta-acetic acid (Gd-DTPA). In MC/9 cell lines, the experiments showed similar results as in water. PMLNs with lower T1 than Gd-DTPA are sensitive, positive MRI CA that could be attractive candidates for cellular and molecular lipid content targets such as diagnostic applications.
