Magnetic-sensitive behavior of intelligent ferrogels for controlled release of drug.

An intelligent magnetic hydrogel (ferrogel) was fabricated by mixing poly(vinyl alcohol) (PVA) hydrogels and Fe3O4 magnetic particles through freezing-thawing cycles. Although the external direct current magnetic field was applied to the ferrogel, the drug was accumulated around the ferrogel, but the accumulated drug was spurt to the environment instantly when the magnetic fields instantly switched "off". Furthermore, rapid to slow drug release can be tunable while the magnetic field was switched from "off" to "on" mode. The drug release behavior from the ferrogel is strongly dominated by the particle size of Fe3O4 under a given magnetic field. The best "magnetic-sensitive effects" are observed for the ferrogels with larger Fe3O4 particles due to its stronger saturation magnetization and smaller coercive force. Furthermore, the amount of drug release can be controlled by fine-tuning of the switching duration time (SDT) through an externally controllable on-off operation in a given magnetic field. It was demonstrated that the highest burst drug amounts and best "close" configuration of the ferrogel were observed for the SDT of 10 and 5 min, respectively. By taking these peculiar magnetic-sensitive characteristics of the novel ferrogels currently synthesized, it is highly expected to have a controllable or programmable drug release profile that can be designed for practical clinical needs.