Dual reactive polymer brush coated magnetic nanoparticles

In recent years, iron oxide nanoparticle based systems have attracted attention for biomedical applications due to their nanoscale size and unique magnetic properties. For many applications they are coated with polymers, which provide them desired dispersibility, as well impart desired properties for enabling biomedical applications. In this study, we synthesized dual reactive polymer brush coated iron oxide nanoparticles. Nanoparticles were synthesized via the thermal decomposition method to obtain near monodisperse size distribution. Dopamine terminated polymers were synthesized for use in grafting-to method. Also, nanoparticles with chain transfer agent (CTA) anchored to their surface using dopamine were synthesized to obtain polymer brushes using the graft-from approach. Reversible addition fragmentation chain transfer (RAFT) polymerization was utilized to obtain polymers using both grafting-to and grafting from approach. Polymers containing the thiolactone unit could be synthesized with good control over composition and molecular weight using the dopamine-containing CTAs. For the grafting-from approach, CTA was anchored onto nanoparticles, and surface-initiated RAFT polymerization was used. The thiolactone unit was used as a reactive group to impart the system with dual reactivity. The thiolactone ring reacts with amine-containing molecules, and in the process releases a free thiol as a second reactive unit. In our work, we used an azide-containing amine for the thiolactone ring-opening, followed by trapping of the newly formed thiol group as a pyridyl disulfide unit which is known to undergo exchange reactions with thiolated molecules. As a model cargo, thiolated hydrophobic fluorescent dye, BODIPY thiol, was conjugated to the system via thiol-disulfide exchange reaction. As a result, we obtained magnetic nanoparticles bearing a clickable azide and a thiol-exchangeable PDS group to attach any desired cargo for intended applications.