Enhanced encapsulation of superparamagnetic Fe3O4 in acidic core-containing micelles for magnetic resonance imaging

Abstract

We report the synthesis of a well-controlled amphiphilic block copolymer having pendant carboxylic acid groups in the hydrophobic block (BCP-HY) by a combination of controlled radical polymerization and partial hydrolysis. Aqueous micellization of the block copolymer in the presence of hydrophobic superparamagnetic iron oxide nanoparticles (SNPs) results in the formation of magnetic nanoassembled structures with acidic cores. Compared with the counterparts having neutral cores, the resulting SNP/BCP-HY micelles retain a greater loading level of SNPs due to the ability of the acidic cores to anchor to SNP surfaces, thus providing dark magnetic resonance imaging (MRI) contrast enhancement. Further, they exhibit good colloidal stability in physiological conditions and in the presence of proteins, as well as promisingly show acidic pH-responsive enhanced release of encapsulated doxorubicin (an anticancer drug). These results suggest that the SNP/BCP-HY micelles having acidic cores have great potential for theranostics with treatment (anticancer drug delivery) and diagnosis based on MRI.