Synthesis of gelatin microspheres containing interferon.

Gelatin microspheres with a diameter less than 2 microns were synthesized by means of cross-linking with glutaraldehyde. When the microspheres were subjected to degradation in phosphate-buffered saline solution containing collagenase, the digestion of microspheres was found to decrease with increasing cross-linking. Interferon was incorporated in the microspheres at a high trapping efficiency, and the rate of interferon release from the microspheres was regulated by the extent of cross-linking with glutaraldehyde. Gelatin microspheres incorporating interferon-alpha were readily phagocytosed by macrophages, regardless of the extent of cross-linking, and the phagocytosed microspheres were observed to be degraded gradually in the interior of macrophages, resulting in the slow release of the incorporated interferon in the cells.