Preparation and characterization of chondroitin‐sulfate‐A‐coated magnetite nanoparticles for biomedical applications

• Novel CSA-coated core–shell magnetite nanoparticles were prepared successfully.
• The aggregation range of MNPs was shifted gradually to the lower pHs by CSA-loading.
• CSA stabilizes electrosterically the MNPs over wide pH-range relevant to biosystems.
• The salt tolerance of CSA@MNP enables them to use under physiological condition.

Polysaccharides are promising candidates for manufacturing biocompatible core–shell nanoparticles with potential in vivo use. Superparamagnetic magnetite nanoparticles (MNPs) have prospective application in both diagnosis and therapy, and so developing a novel polysaccharide shell on MNP core is of great challenge. MNPs were prepared by co-precipitation, then the surface of purified MNPs was coated with chondroitin-sulfate-A (CSA) to obtain core–shell structured magnetite nanoparticles (CSA@MNP). The effect of the added amount of CSA on the surface charging and the aggregation state of MNPs at various pHs and 10 mM NaCl was measured by electrophoresis and dynamic light scattering. The amphoteric behavior of MNPs was fundamentally modified by adsorption of CSA polyanions. A very low CSA-loading induces the aggregation of MNPs, while four times more stabilizes the dispersions over the whole pH-range studied. The coagulation kinetics experiments measured at pH=6.3±0.3 showed that salt tolerance of CSA@MNPs rises up to ~150 mM NaCl.