Hydrophobically-modified Chitosan Microspheres for Release of Diosgenin

Chitosan microspheres (CS) prepared by water-in-oil emulsion/glutaraldehyde cross-linking-evaporation and simple coacervation/cross-linking with sodium tripolyphosphate were covalently linked to diosgenin hemiesters. The diosgenin content found using elemental analysis was ca. 6 to 42 wt-% and it showed dependence on the type of diosgenin hemiesters and on the method of preparation of the CS microspheres. Fourier transform infrared spectroscopy confirmed the hydrophobic functionalization of CS with the diosgenin hemiesters by amide bond formation. The effect of CS modification with diosgenin on the thermal properties was also studied using differential scanning calorimetry. Microsphere sizes determined using optical microscopy ranged from 60 to 700 um, while scanning electron microscopy depicted morphology dependent on the selected method to obtain CS microspheres. In vitro release studies performed in aqueous medium indicated a drug release dependence on the diosgenin hemiester linkers, the steroid content and the acidity of the solution. Sustained diosgenin release in acidic aqueous solution (pH 6.0) reached from 34 to 81% after 48 h.