Multidentate Block Copolymer Stabilization: A Versatile Strategy for Colloidal Superparamagnetic Iron Oxide Nanoparticles Exhibiting Excellent Colloidal Stability and Enhanced Positive MRI Visualization

Colloidal superparamagnetic iron oxide nanoparticles (SNPs) have been a preferred choice for biocompatible contrast agents in magnetic resonance imaging (MRI) in vivo. One remaining critical challenge is the control over surface chemistry of colloidal SNPs to retain biocompatibility and colloidal stability under harsh physiological conditions. This chapter describes the versatility of a multidentate block copolymer (MDBC) strategy to develop aqueous SNP colloids coated with a single layer of strongly bound MDBCs. The robust strategy centers on the synthesis of well-defined block copolymers utilizing controlled radical polymerization techniques and post-modification methods. Well-defined MDBCs with narrow molecular weight distributions consist of an anchoring block of pendant carboxylate or catechol groups, strongly bound to SNP surfaces, and a hydrophilic block, endowing the colloids with biocompatibility and water -solubility. The resultant aqueous MDBC/SNP colloids exhibit excellent colloidal stability in biological environments, increased bright MRI contrast enhancement at lower concentration of Fe, and prolonged blood circulation time. Further, this chapter introduces the development of magnetic nanoassemblies with ionic cores for enhanced encapsulation of SNPs.