Poly(lactic-co-glycolic acid) Encapsulated Gadolinium Oxide Nanoparticles for MRI-Based Cell Tracking

Superparamagnetic iron oxide particles have proven useful for cell tracking applications by monitoring cell transplantation and migration in living organisms. However, one perceived drawback is that these particles cause dark contrast in MRI, sometimes yielding confusion with other biological phenomena, which also yield dark contrast. To that end, researchers have investigated the use of gadolinium oxide (Gd2O3) based contrast agents for MRI-based cell tracking, as Gd2O3 has favorable r(1) molar relaxivity. We synthesized Gd2O3 nanocrystals and encapsulated them within PLGA matrices to form similar to 150 nm nanoparticles. r(1) was 1.9 mM(-1) sec(-1) and r(2) was 8.4 mM(-1) sec(-1). Cell labeling with particles was well tolerated by cells except at very high doses. MRI of labeled cells showed that labeled cells could achieve both R-1 and R-2 enhancements due to the internalized particles. R-2 enhancements were similar to twice that of R-1 enhancements suggesting the use of very short echo times when using Gd2O3 based contrast agents for MRI-based cell tracking.