Despite its good resolution, magnetic resonance imaging intrinsically has low sensitivity. Recently, contrast agent nanoparticles have been used as sensitivity and contrast enhancer. The aim of this study was to investigate a new controlled synthesis method for gadolinium oxide-based nanoparticle preparation. For this purpose, diethyleneglycol coating of gadolinium oxide (Gd2O3-DEG) was performed using new supervised polyol route, and small particulate gadolinium oxide (SPGO) PEGylation was obtained with methoxy-polyethylene-glycol-silane (550 and 2,000 Da) coatings as SPGO-mPEG-silane550 and 2,000, respectively. Physicochemical characterization and magnetic properties of these three contrast agents in comparison with conventional Gd-DTPA were verified by dynamic light scattering transmission electron microscopy, Fourier transform infrared spectroscopy, inductively coupled plasma, X-ray diffraction, vibrating sample magnetometer, and the signal intensity and relaxivity measurements were performed using 1.5-T MRI scanner.As a result, the nanoparticle sizes of Gd2O3-DEG, SPGO-mPEG-silane550, and SPGO-mPEG-silane2000 could be reached to 5.9, 51.3, 194.2 nm, respectively. The image signal intensity and longitudinal (r1) and transverse relaxivity (r2) measurements in different concentrations (0.3 to approximately 2.5 mM), revealed the r2/r1 ratios of 1.13, 0.89, 33.34, and 33.72 for Gd-DTPA, Gd2O3-DEG, SPGO-mPEG-silane550, and SPGO-mPEG-silane2000, respectively.The achievement of new synthesis route of Gd2O3-DEG resulted in lower r2/r1 ratio for Gd2O3-DEG than Gd-DTPA and other previous synthesized methods by this and other groups. The smaller r2/r1 ratios of two PEGylated-SPGO contrast agents in our study in comparison with r2/r1 ratio of previous PEGylation (r2/r1 = 81.9 for mPEG-silane 6,000 MW) showed that these new three introduced contrast agents could potentially be proper contrast enhancers for cellular and molecular MR imaging.

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.

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