In Vivo Positive Magnetic Resonance Imaging Applications of Poly(methyl vinyl ether-alt-maleic acid)-coated Ultra-small Paramagnetic Gadolinium Oxide Nanoparticles

Abstract

The study of ultra-small paramagnetic gadolinium oxide (Gd₂O₃) nanoparticles (NPs) as in vivo positive (T₁) magnetic resonance imaging (MRI) contrast agents is one of the most attractive fields in nanomedicine. The performance of the Gd₂O₃ NP imaging agents depends on the surface-coating materials. In this study, poly(methyl vinyl ether-alt-maleic acid) (PMVEMA) was used as a surface-coating polymer. The PMVEMA-coated paramagnetic ultra-small Gd₂O₃ NPs with an average particle diameter of 1.9 nm were synthesized using the one-pot polyol method. They exhibited excellent colloidal stability in water and good biocompatibility. They also showed a very high longitudinal water proton spin relaxivity (r₁) value of 36.2 s^-1mM^-1 (r₂/r₁ = 2.0; r₂ = transverse water proton spin relaxivity) under a 3.0 tesla MR field which is approximately 10 times higher than the r₁ values of commercial molecular contrast agents. High positive contrast enhancements were observed in in vivo T₁ MR images after intravenous administration of the NP solution sample, demonstrating its potential as a T₁ MRI contrast agent.