(385a) Magnetic Block Ionomer Complexes for Imaging and Therapeutics

Multifunctional nanocarriers comprising a combination of therapeutic and imaging agents are of great interest for delivering drugs and tracking their biodistribution. With an aim to develop nanocarriers with high drug loadings that integrate magnetic nanoparticles for imaging into one system, we report antibiotic-laden magnetic block ionomer complexes (MBICs) based on assembly of block ionomers with nanomagnetite and cationic drugs. The magnetite core was synthesized via reduction of an Fe(III) organometallic precursor. Nonionic-ionic block copolymers were synthesized through controlled free-radical polymerization (ATRP). The polymer was bound to the magnetic nanoparticle surfaces via ligand adsorption of the PAA, thereby creating a double corona structure with a nonionic PEO shell and an ionic layer of PAA. The portion of carboxylates that were not attached to the magnetite provided binding sites for drug loading via ionic complexation. The multi-cationic drugs, gentamicin and streptomycin, were employed as models for encapsulation. Results suggest that the MBICs are sufficiently stable in physiological conditions to be suitable as drug carriers. Dispersions of the MBICs were stable in PBS containing 0.14 M NaCl for up to 10 days, and were stable in PBS containing fetal bovine serum (FBS). Physicochemical properties of the MBICs were significantly altered upon gentamicin encapsulation (31 wt % drug). A near zero-order release of gentamicin (pH 7.4 in PBS) that reached ~35 wt% of the initial gentamicin within 10 h was observed, and this was followed by slower release of another 7% by 18 h. We will show how the transverse relaxivities (r₂) of the complexes correlate with cluster size as it is affected by drug complexation.