Bovine serum albumin (BSA) and cleaved-BSA conjugated ultrasmall Gd2O3 nanoparticles: Synthesis, characterization, and application to MRI contrast agents

Abstract

Bovine serum albumin (BSA) (Mn=66.5kD, size=14×4×4nm) is an attractive biological molecule for biomedical applications because of its water-solubility and bio-compatibility. It can also bind many ultrasmall nanoparticles (NPs) as confirmed in this study. We synthesized polyethylene glycol diacid (PEGD) coated ultrasmall Gd2O3 nanoparticles (PEGD-GNPs, the core davg=2.0nm), which were then conjugated to BSA and cleaved-BSA (C-BSA) (i.e. BSA-PEGD-GNPs and C-BSA-PEGD-GNPs) through amide bonding. Large relaxivities were observed in both aqueous sample solutions (r1=6.0s−1mM−1 and r2=28.0s−1mM−1 for BSA-PEGD-GNPs and r1=7.6s−1mM−1 and r2=22.0s−1mM−1 for C-BSA-PEGD-GNPs). Three tesla T2 magnetic resonance imaging (MRI) in a mouse after the injection of an aqueous sample solution of BSA-PEGD-GNPs into a mouse tail vein revealed significant negative contrast enhancements. Large relaxivities and in vivo MR images prove that BSA-PEGD-GNPs and C-BSA-PEGD-GNPs are potential MRI contrast agents.