POLYIONIC INSOLUBLE HYDROGELS COMPRISING XANTHAN

摘要

A method for the preparation of insoluble hydrogels from the complexation of polycations and xanthan is reported. Stable hydrogels capable of retaining between 65 and 95% weight water were prepared particularly with chitosan and xanthan. The water retention and properties of the hydrogels were studied as a function of the degree of acetylation of chitosan and the ratio chitosan/xanthan used in the preparation of the gel. The chitosan-xanthan complex was used to immobilize biological material. Hydrogels containing enzymes (for example endo-1,4-.beta.-xylanase and protease) either as single enzymes or as a binary system have been prepared. Immobilization varied between 85 and 98%. The immobilized xylanase activity was significantly greater with respect to the free enzyme while the binary enzyme system promoted protease activity. Other hydrogels prepared with polybasic drugs complexed to xanthan with or without chitosan have been prepared. These complexes slowly dissociate in acidic media and provide for sustained release of compounds in near neutral pHs. Gels containing chitosan are stable in all physiological pHs and the immobilized molecules are released therefrom by diffusion.