Cationic Hyperbranched Polymers with Biocompatible Shells for siRNA Delivery

Cationic hyperbranched polymers (HBP) were prepared by self-condensing vinyl polymerization of an atom transfer radical polymerization (ATRP) inimer containing a quaternary ammonium group. Two types of biocompatible shells, poly(oligoethylene glycol) methacrylate (polyOEGMA) and poly(2-(methylsulfinyl) ethyl methacrylate) (polyDMSO), were grafted respectively from HBP core to form core-shell structures with low molecular weight dispersity and high biocompatibility, polyOEGMA-HBP and polyDMSO-HBP. Both of the structures showed low cytotoxicity and good siRNA complexing ability. The efficacy of gene silencing against Runt-related transcription factor 2 ( Runx2) expression and the long-term assessment of mineralized nodule formation in osteoblast cultures were evaluated. The biocompatible core-shell structures were crucial to minimizing undesired cytotoxicity and nonspecific gene suppression. polyDMSO-HBP showed higher efficacy of forming polyplexes than polyOEGMA-HBP due to shell with lower steric hindrance. Overall, the gene silencing efficiency of both core-shell structures was comparable to commercial agent Lipofectamine, indicating long-term potential for gene silencing to treat heterotopic ossification (HO).

Iron Oxide Nanoparticles with Grafted Polymeric Analogue of Dimethyl Sulfoxide as Potential Magnetic Resonance Imaging Contrast Agents

Novel water-dispersible hybrid iron oxide nanoparticles grafted with a polymeric analogue of dimethyl sulfoxide (DMSO) were prepared. Superparamagnetic iron oxide nanoparticles with immobilized atom-transfer radical polymerization (ATRP) initiators were prepared via an in situ method using 12-(2-bromoisobutyramido)dodecanoic acid as a surface ligand/initiator. The initiator-functionalized particles were employed in a surface-initiated initiator for continuous activator regeneration ATRP to graft poly(2-(methylsulfinyl)ethyl acrylate) (a polyacrylate analogue of DMSO) from the surface. The resulting hybrid nanoparticles showed a high magnetic relaxivity ratio ( r₂/ r₁) of 600 at 7 T in fetal bovine serum, and a good biocompatibility up to 1000 mg L^-1.