Iron oxide nanoparticles encapsulated (II) with poly(d,l-lactide-co-glycolide) (PLGA) having high magnetic susceptibility were prepared
by an emulsification–diffusion method. The preparation method consists of emulsifying an aqueous solution of PLGA in ethylacetate and
extracting the organic solvent into a water phase. After mutual saturation of the organic and the continuous phases, PLGA precipitated to
encapsulate nanoparticles (I) by adding excess water. As the homogenization strength in the emulsification step and the agitation speed in the
solvent diffusion step increased, the mean size of IONE (iron oxide nanoparticles encapsulated) was reduced to a limiting size. The images
under SEM and TEM showed that IONE has almost a spherical shape with 90–180 nm and that iron oxide nanoparticles with 8–20 nm were
embedded in the PLGA matrix. The magnetization of IONE was measured with vibrating sample magnetometer (VSM), varying the size
from 120 to 180 nm. It is observed that the small IONEs have a high magnetic susceptibility. It is attributed that the packing densities of iron
oxide nanoparticles and IONE increased as their sizes decreased.