Preparation of porous hollow polyaniline microspheres and study on their in vitro release behavior

We report the synthesis of porous hollow polyaniline (PANI) microspheres loaded with Acid Red 8 dye (200-600 nm diameters under different reaction conditions) by using spherically mesoporous aggregates of Fe3O4 particles as soft templates and ammonium persulfate (APS) as the oxidant at 2.5 degrees C. Since the as-prepared spherical aggregates of Fe3O4 particles are readily dissolved in acidic aqueous solution, these spherical aggregates can be treated as soft template for the fabrication of hollow spheres. This process is therefore more convenient than other reported methods which require the post-treatment to remove the templates under strict conditions. The influence of the synthetic conditions on the formation and size of PANI microspheres was investigated. The morphology was confirmed by transmission electron microscopy (TEM). The chemical and electronic structures of the PANI microspheres were also studied by FTIR and UV-Vis spectrometry, respectively. The experimental in vitro release showed that these porous hollow PANI microspheres provided a controlled release of the entrapped dye, which was regulated by pH. Furthermore, the releasing behavior was qualitatively explained based on effective dissociation constant as a function of the pH.