(80b) Structured Particles for Controlled Release

The ability to store active substances within the internal structure of particles with the ability of releasing the subtance upon an external stimulus is a key factor for many applications including targeted drug delivery.

A thermo-sensitive crosslinked hydrogel based on poly(N-isopropylacrylamide (PNIPAM) was used as a building block of these particles. Such hydrogel can exhibit volume transition from swollen to shrunken state at lower critical solution temperature LCST of approximately 32 °C. In order to effectuate ?remote control? of the hydrogel volume change, magnetic nanoparticles (like Fe3O4) were incorporated into its structure to create a composite particle. Upon exposing such composite particle to the alternating electromagnetic field, the temperature of particles will increase locally, and consequently induce transition from expanded to the collapsed state of the polymer.

External magnetic field was used for the release of active substances stored within the pores of composite particles. The rate of release was investigated with respect to the magnetically-induced heating of the comoposite particle. The particle internal structure was investigated by scanning electron microscopy and confocal laser scanning microscopy.