Preparation and Characterization of Collagen Microspheres for Sustained Release of Steroidal Saponins

Steroidal saponins are the major pharmacological constituents of ophiopogon japonicus which have been used to treat bone and joint diseases, nerve damage, and hematischesis for hundreds of years in China. The objective of this study was to investigate the therapeutic potential of collagen microspheres loaded with steroidal saponins as an inducer factor for skeletal defects using an in vitro model. The collagen-steroidal saponins composite microspheres were prepared using a water-in-oil-in- water emulsion/solvent evaporation technique. SEM micrographs showed that spherical particles with diameters of tens micrometers were successfully produced. Release kinetics was characterized by an initial burst release reducing to a linear release over the first 8 days. MTT assay showed that the cells attached on composite microspheres were more in comparison with pure collagen microspheres and stimulated significantly higher level of alkaline phosphatase than the counterpart. Moreover, composite microspheres possess osteoinductive activities as demonstrated by the ability to induce cells to commit to crystals in contact coculture. The present finding suggests that sustained delivery of steroidal saponins may be very effective in improving the osteogenic potential of collagen microspheres and the composite microspheres are useful for tissue-engineering applications.