Oleic acid

To enhance the magnetic properties of the SPION-loaded micelles, cobalt-doped superparamagnetic iron oxide nanoparticles (SPIONs) were synthesized, as previously described.^{58 (link)} The 10 nm cobalt-doped SPIONs could be readily synthesized in one step (i.e., vs. sequential seed growth) and efficiently loaded into the micelles. Briefly, 1 mmol cobalt chloride (Alfa Aesar), 2 mmol iron (III) acetylacetonate (Sigma), 2 mmol oleic acid (Chem-Impex International), 6 mmol oleylamine (Sigma), and 5 mmol 1, 2-hexadecanediol (Sigma) were reacted in 20 mL benzyl ether (Sigma) in a two-neck flask while stirred under nitrogen. The reaction was heated to 200°C for 30 minutes, followed by heating to reflux for 75 minutes. The product was cooled to room temperature and washed with 100% ethanol by centrifugation at 5,500 g × 15 minutes. The pellet was resuspended in toluene and large aggregates were removed by centrifugation at 3,000 g × 15 minutes.