Formation and characterization of biobased magnetic nanoparticles double coated with dextran and chitosan by layer-by-layer deposition

Magnetic nanoparticles double coated with different concentrations of dextran sulfate or reduced dextran and chitosan solutions were formed by layer-by-layer deposition and characterized by physicochemical techniques. Magnetic particles based on iron oxides presented superparamagnetic behavior, which indicates that they could be used in the future in magnetic driven therapies. The first layer of dextran sulfate on magnetic nanoparticles gave spherical nanoparticles with hydrodynamic diameters ranging from 45 nm to 88 nm and ζ-potential ranging from −45 mV to −52 mV depending on the concentration of dextran sulfate, and with hydrodynamic diameters of 77 nm and ζ-potential around 42 mV when the polymer coating was reduced dextran. The second layer was of chitosan and gave nanoparticles with hydrodynamic diameters ranging from 230 nm to 250 nm. The coating with this polymer at concentrations between 5 mg/mL and 10 mg/mL shifted the ζ-potential from negative to high positive values. The resulting colloidal systems were stable over time for a period 60 days. The content of iron, dextran sulfate and chitosan in the final double coated colloidal system were estimated in 47%, 9% and 34% using termogravimetric analysis. Dextran sulfate and chitosan layers could be visualized by microscopic techniques.