Positive MRI contrast enhancement in THP-1 cells with Gd2O3 nanoparticles

There is a demand for more efficient and tissue‐specific MRI contrast agents and recent developments involve the design of substances useful as molecular markers and magnetic tracers. In this study, nanoparticles of gadolinium oxide (Gd2O3) have been investigated for cell labeling and capacity to generate a positive contrast. THP‐1, a monocytic cell line that is phagocytic, was used and results were compared with relaxivity of particles in cell culture medium (RPMI 1640). The results showed that Gd2O3‐labeled cells have shorter T1 and T2 relaxation times compared with untreated cells. A prominent difference in signal intensity was observed, indicating that Gd2O3 nanoparticles can be used as a positive contrast agent for cell labeling. The r1 for cell samples was 4.1 and 3.6 s−1 mm−1 for cell culture medium. The r2 was 17.4 and 12.9 s−1 mm−1, respectively. For r1, there was no significant difference in relaxivity between particles in cells compared to particles in cell culture medium, (pr1 = 0.36), but r2 was significantly different for the two different series (pr2 = 0.02). Viability results indicate that THP‐1 cells endure treatment with Gd2O3 nanoparticles for an extended period of time and it is therefore concluded that results in this study are based on viable cells. Copyright © 2008 John Wiley & Sons, Ltd. Relaxivity measurements of phagocytic THP‐1 cells labeled with gadolinium oxide nanoparticles, Gd2O3, showed an r1 of 4.1 and r2 of 17.4 s−1 mm−1. Corresponding results for particles in RPMI 1640 cell culture medium were 3.6 and 12.9 s−1 mm−1. Gd2O3 produced prominent positive contrast when internalized in cells with maximum intensity in samples with a concentration of 0.56 mm Gd2O3. Image of two sets of THP‐1 cell samples with increasing concentrations of gadolinium from left to right. Incubation concentrations ranged from 0.5 to 2.5 mm (TR = 1000 ms, TE = 20 ms). Signal intensity is high in samples with a final concentration of 0.56 mm Gd2O3 (top row, middle sample, incubation concentration 1.5 mm).