Novel sustained-release implant of herb extract using chitosan.

Chitosan (CS), a naturally occurring high-molecule polymer, which is stable in vivo, has proved to be a useful biomaterial. The extract of danshen (Radix Salviae miltiorrhizae), a medicinal herbal, was developed with CS-gelatin as an implant for the promotion of anastomosing and healing on muscles and tissues at the organic incision site in abdominal cavities. Measurements were made of the sustained release of tanshinone IIa, a marker component, from the material in vitro. The dissolution medium was assayed with an high-performance liquid chromatography method. Biodegradation studies of the material were also conducted both in vitro and in vivo. The film made of this material exhibited a sustained release effect. The release profile confirms to the Higuchi equation. At most about 20% of the incorporated drug were released over 15 days in a CS-gelatin (1:2) matrix. Drug release was found to be effectively controlled by the drug-amount loaded in the matrix. The improved film (CS/gelatin ratio: 1:16) can be hydrolyzed by lysozymes in vitro in 4 days. This film of 0.5 cm2 was implanted and degraded completely in rats over 28 days and the animals' wounds of abdominal incision healed well.