There are several ways to produce magnetic iron oxide nanoparticles, described in several publications and patents. Historically, ferrofluids have been produced by long-term grinding of bulk magnetite in the presence of stabilizing surfactant. The most common way to synthesize super paramagnetic iron oxide nanoparticles (SPION) for biomedical applications is the coprecipitation method, although numerous other approaches are becoming more prevalent as the synthesis of SPIONs with uniform core diameters becomes more desirable.

The most common method for the synthesis of magnetic nanoparticles is the synthesis via the coprecipitation of ferrous and ferric salts in an alkaline medium. As complexing agent we use dextran carboxymethyldextran or polyethylene glycol. Surface complexing agents are often used to provide colloid stability and biocompatibility. Our dextran coated SPIOs are created by the addition of a base (NH3) to a di- and trivalent ferrous salt solution in the presence of the polymers. The suspension is treated with a permanent magnet and centrifuged. These magnetite nanoparticles are polydisperse with a mean hydrodynamic diameter of approximately 100 nm and are roughly spherical in shape.