Synthesis and encapsulation of magnetite nanoparticles in PLGA: effect of amount of PLGA on characteristics of encapsulated nanoparticles

Oleic acid-coated superparamagnetic iron oxide nanoparticles (Fe₃O₄) encapsulated within poly(d,l-lactide-co-glycolide) (PLGA) particles were prepared by the w/o/w emulsion technique using poly(vinyl alcohol) as a dispersant. The concentration of PLGA in the oil phase was varied (5, 15, 30, 45, and 60 mg/ml) at constant magnetite concentration in the oil phase (5 mg/ml) to study the properties of composite Fe₃O₄–PLGA nanoparticles. Even though PLGA concentration varied widely in the oil phase, the weight percent of 7–16 nm diameter magnetite in the particles varied only from 56 to 62 % (23–28 vol.%). The obtained composite nanoparticles were essentially spherical with magnetite spatially uniformly dispersed in individual PLGA particles, as measured by transmission electron microscopy (TEM). Also, the magnetite concentration in each particle did not vary widely as determined qualitatively via microscopy. Hydrodynamic diameters of the composite nanoparticles as measured by dynamic light scattering increased by approximately 10 % with added magnetite, with a smaller relative increase in diameter measured by TEM. The zeta potential of the particles was about −26 mV, independent of Fe₃O₄ loading. Relatively high saturation magnetizations (36–45 emu/g) were measured for these highly loaded particles, with the latter value only 7 emu/g lower than the value measured for the oleic acid-coated particles alone.