Magnetite Nanoparticles Coated with Biodegradable Zwitterionic Polymers as Multifunctional Nanocomposites for Drug Delivery and Cancer Treatment

Tailor-made materials for biomedical applications can be constructed with different building blocks to confer multiple functions on one platform. Here, we demonstrate the facile synthesis of magnetite-biodegradable polymer nanocomposites combining superparamagnetism with the possibility of loading and controlling the release of a lipophilic drug. The magnetite nanoparticles were synthesized by reduction–precipitation and used as nuclei to grow a biodegradable zwitterionic shell. The copolymer used for this scope comprises a hydrophobic block made of a biodegradable ε-caprolactone-based macromonomer (CLn) with three different degrees of polymerization (DPn, n = 3, 5, and 7) obtained by ring-opening polymerization (ROP). Dopamine molecules were attached to the end of this CLn oligomer (CLnDopa), conferring a specific affinity for the magnetite surface. A hydrophilic zwitterionic poly(2-methacryloyloxyethyl phosphorylcholine) block (PMPC) was included by reversible addition–fragmentation chain transfer (RAFT) polymerization to add colloidal stability and water dispersibility to the copolymer. This PMPC was chain-extended with CLnDopa via RAFT polymerization targeting four different DPm (m = 10, 20, 30, and 40), resulting in a library of 12 copolymers. A facile nanoprecipitation process produced copolymer nanoparticles and copolymer-coated magnetite nanostructures. Physicochemical characterization confirmed the inorganic–organic composite nature. The copolymer-coated magnetic materials showed water stability, superparamagnetic behavior, and appropriate hyperthermic ability under an alternate magnetic field. Biological assays using HeLa cells showed high biocompatibility and efficient nanoparticle uptake. In addition, a sustained release of dexamethasone, used as a model drug encapsulated in the polymer shell, and local heating as a dual functional material could be accessed.