Optimization of iron oxide nanoparticles encapsulation within poly(d,l-lactide-co-glycolide) sub-micron particles

This work describes a method for preparation of sub-micron poly(d,l-lactide-co-glycolide) (PLGA) particles loaded with magnetite/maghemite nanoparticles to be used as magnetically-controlled drug delivery systems. The methodology of simple emulsion/evaporation technique has been optimized to provide greater iron oxide loading rates. The surface of iron oxide nanoparticles was coated with oleic acid (OA) for better compatibility with organic phase containing the polymer. To increase their loading into polymeric sub-micron particles, we added dried iron oxide nanoparticles in variable ferrite/polymer ratio of 1:1; 1:1.5 and 1:2 w/w. Composition and surface properties of obtained composite sub-micron particles have been studied in comparison with those of ferrite-free PLGA sub-micron particles. Presence of magnetite/maghemite was qualitatively confirmed by characteristic bands in the FT-IR spectra of composite sub-micron particles. Quantification of the incorporated iron was achieved by AAS. The highest incorporation rates of ferrite (up to 13.5% w/w) were observed with initial ferrite/polymer ratio of 1:1 w/w. TEM images indicate that the composite sub-micron particles are nearly spherical. According to laser granulometry data, average hydrodynamic diameter of the composite sub-micron particles is close to 280 nm, independently of ferrite presence. Electrophoretic properties (zeta potential) were very similar for both composite and ferrite-free PLGA sub-micron particles, thus indicating that the polymeric coating should mask the surface of ferrite nanoparticles buried inside. Finally, composite sub-micron particles exhibit superparamagnetic property.