Cisplatin-conjugated degradable gelatin microspheres: fundamental study in vitro

The object of this study was to generate cisplatin-conjugated gelatin microspheres (GMSs) and to confirm the subsequent release of cisplatin in vitro. The GMSs (1 mg) were immersed in 50 microl of a cisplatin solution (0.06, 0.15, 0.27, 0.30 or 0.54 mg ml(-1)) at 38 degrees C to allow conjugation. The cisplatin-conjugated GMSs were then extensively washed in double-distilled water and freeze-dried. The platinum concentration in the GMSs samples was investigated as a function of the concentration of cisplatin solution used in their preparation, the number of immersions in cisplatin (1, 2, 3, 4 or 5) and the period of immersion (1, 6 or 11 h). In vitro release tests were performed at different time intervals (1, 3, 6, 12 or 24 h) to allow the rate of cisplatin release to be calculated. The platinum concentration of the GMSs increased in proportion to the concentration of cisplatin solution and the length or number of immersions in cisplatin. In vitro release tests demonstrate that the release rate (%) from GMSs after 1, 3, 6, 12 or 24 h was 4.8, 5.5, 7.6, 10.0 and 12.4, respectively. We demonstrated the ability of GMSs to bind cisplatin forming cisplatin-conjugated GMSs. Moreover, we showed that cisplatin continued to bind GMSs strongly during the in vitro release test.