Assessment of Irinotecan Loading and Releasing Profiles of a Novel Drug-Eluting Microsphere (CalliSpheres) In Vitro.

Background: This study investigated irinotecan loading efficiency and release profiles of CalliSpheres in vitro. Materials and Methods: CalliSpheres with size of 50-150, 100-300, and 300-500 μm and irinotecan at different amounts (20, 40, 80, and 100 mg) and concentrations (5 and 10 mg/mL) were prepared for experiments. Dynamic light scattering and Agilent 1260 high-performance liquid chromatography system were used to quantify bead diameters and the efficiency of irinotecan loading and releasing properties, respectively. Results: The diameters of CalliSpheres with all sizes were reduced after being loaded with irinotecan compared with unloaded ones with shrinkage rate ranging from 8.5% to 16.2%. Above 80% irinotecan was incorporated with CalliSpheres with all sizes when being loaded with irinotecan 20, 40, and 80 mg, while loading efficiencies were 70%-80% when being loaded with irinotecan 100 mg. Besides, elevated loading efficiency was observed at a higher concentration of irinotecan solutions (10 mg/mL) compared with a lower concentration (5 mg/mL) for CalliSpheres with all sizes. As to release profiles, irinotecan was released from CalliSpheres very quickly, and irinotecan release rate was elevated in CalliSpheres with smaller size than CalliSpheres with larger size within the first 12 h, whereas it was similar among CalliSpheres with different sizes at 24 and 48 h with maximum release rate ∼100%. In addition, fetal bovine serum seemed to have an effect on the accelerating irinotecan release. Conclusion: CalliSpheres exhibits good physical characteristics, satisfied irinotecan loading efficiency, and acceptable releasing profiles.