Polymer encapsulation of raw ferrofluids was carried out by free radical emulsion polymerization using macro-RAFT copolymers as stabilizers. The iron oxide cores with positively charged surface at the pH of encapsulation were dispersed in a solution of negatively charged random macro-RAFT copolymer by ultrasonication. Uniform polymer encapsulated super paramagnetic iron oxide nanoparticles (SPIONs) were produced by feeding the mixture of methyl methacrylate (MMA) and n-butyl acrylate (BA) monomers into the dispersion containing water soluble initiator 4,4'-azobis (4-cyanopentanoic acid) (V501). Shell thickness could be controlled by adjusting the amount of coating monomer added. Polymer encapsulation of SPIONs aligned in a magnetic field produced polymer encapsulated SPION rods. Monodispersed sterically stabilized crosslinked polymer encapsulated SPIONs were synthesized using diblock and random macro-RAFT copolymers as stabilizers. Rhodamine labeled SPIONs were found to be non-cytotoxic and suitable for cell labeling. (C) 2016 Elsevier Ltd. All rights reserved.