Stability studies of collagen-based microspheres with Calendula officinalis flower extract

Controlled drug delivery technology represents the more rapidly advancing area in recent years. Gelatin and collagen-gelatin microspheres were produced by emulsion technique using distilled water and paraffin oil containing 1% Span 85. Then microspheres were cross-linked by ethyl-3(3-dimethylaminopropyl) carbodiimide (EDC) and N-hydroxysuccinimide (NHS) mixture. Microspheres have been also cross-linked using dehydrothermaltreatment (DHT) to compare chemical cross-linking with physical cross-linking. Collected microspheres were loaded with Calendula officinalis flower extract, as drug model. Morphological analysis revealed homogeneous microspheres characterized by an average diameter 21 μm and 26 μm for gelatin and collagen-gelatin microspheres, respectively. The largest amount of Calendula officinalis flower extract was entrapped in DHT cross-linked microspheres. Active substance contained in collagen-gelatin microspheres was released much faster than that released from gelatin microspheres. Finally, after incubation of microspheres in acetate buffer, their sizes were 9.77- and 5.76-fold smaller reduced in the case of gelatin and collagen-gelatin samples, respectively.