Chitosan sponges as sustained release drug carriers

Chitosan sponges as sustained release drug carriers were prepared by freeze-drying partially N-acetylated chitosan gels and crosslinked chitosan solutions. Micronized triamcinolone acetonide was used as a model drug. N-acetylchitosan sponges were prepared from 2.5% chitosan solutions acetylated with 10.58 mmol of acetic anhydride per gram of chitosan. Crosslinked chitosan sponges were prepared from 2.5% chitosan solution crosslinked with 1.33% glutaraldehyde in respect to chitosan mass. Drug content in both N-acetylated and crosslinked chitosan sponges were uniform. Scanning electron microscopy (SEM) photos show a leaflet-or a platelet-like structure of both chitosan sponges. The incorporated drug was found in a crystalline form. The water uptake ability of both chitosan sponges was more than 20 times of their weight. The pH of dissolution media and the drug content of the sponges affected the release rate of the drug. The drug release at pH 1.2 was faster than at pH 7.4. The drug release al pH 7.4 was a function of square root of time over 52 h from the N-acetylchitosan sponges and over 36 h from the crosslinked chitosan sponges. With increasing the drug content a slower drug release was found. The delayed drug release was due to the decreased chitosan solubility by either N-acetylation or crosslinking. (C) 1997 Elsevier Science B.V.