Ultrasonically controlled release and targeted delivery of diclofenac sodium via gelatin magnetic microspheres

In the present work, an attempt was made to target diclofenac sodium to its site of action through magnetic gelatin microspheres. The gelatin magnetic microspheres loaded with 8.9% w/w of diclofenac sodium and 28.7% w/w of magnetite were formulated by emulsification/cross-linking with glutaraldehyde. The formulated microspheres were characterized by particle size distribution, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), X-ray diffraction and in vitro release studies. The in vivo distribution and targetability of gelatin magnetic microspheres after i.v. administration were studied in rabbits. The formulated microspheres were below 5 microm and spherical in nature as evidenced by the SEM photographs. DSC and X-ray diffraction studies revealed the absence of drug-polymer interaction. Encapsulated diclofenac sodium was released slowly more than 18 days. Application of sonication, as external stimuli to enhance drug release, during release study, has slightly increased the release rate. The formulated microspheres were injected intravenously after keeping a suitable magnet near the target area. The quantity of drug available at the target and non-target area was determined by HPLC. About 5.5% of injected dose localized near the target organ. Majority of injected dose was recovered from lungs, spleen and liver indicating localization of microspheres in these organs. Further studies are required to improve the targeting efficiency of gelatin microspheres by modifying surface properties to overcome phagocytosis and by selecting suitable particle size to avoid the entrapment of microspheres in non-target organs.