Sacrificial Template-Directed Fabrication of Superparamagnetic Polymer Microcontainers for pH-Activated Controlled Release of Daunorubicin

Magnetic pH-sensitive microcontainers were produced by a four-step process. The first step involves the synthesis of citrate-modified magnetic nanoparticles via the coprecipitation method. The second step consists of the encapsulation of magnetic nanoparticles in non-cross-linked poly(methacrylic acid) (PMAA) microspheres through distillation precipitation polymerization, resulting in a core/shell structure. The third step concerns the formation of a poly(N,N'-methylenebis(acrylamide)-co-mathacrylic acid) (P(MBAAm-co-MAA)) layer on the surface of magnetic PMAA microspheres by second distillation precipitation polymerization in order to produce a trilayer hybrid microsphere. The last step deals with the removal of PMAA layer in ethanol and formation of a stable P(MBAAm-co-MAA) microcontainer with magnetic nanoparticles entrapped inside the formed cavity. This process is simple and leads to the formation of superparamagnetic pH-sensitive microcontainers. The structure and properties of the magnetic microcontainers were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), vibrating sample magnetometry (VSM), and dynamic light scattering (DLS) to determine the functionalities of the hybrid structure. The magnetic pH-sensitive microcontainers were loaded with Daunorubicin and tested with respect to release rate at different pH values in order to evaluate their functionality as controlled release system.