Bioactive polymers. 70. The kinetics of controlled release of neomycin in an alkaline medium.

Neomycin is coupled on xanthan--a polysaccharide of microbial biosynthesis produced by Xanthomona campestris--through ionic complexation. The kinetics of neomycin release, in vitro, at pH = 8.2 is studied. A release of neomycin, following a zero order kinetics, is observed, regardless of the eluent flow-rate. The neomycin-xanthan complex, protected by a cellulosic membrane, behaves like a monolithic-type device. Diffusion coefficients--increasing with increasing the eluent flow-rate--are also calculated.

[Scaffolds based on collagen and chitosan for post-burn tissue engineering]. / Membrane poroase pe baza de colagen si chitosan pentru ingineria tisulara post-arsura.

UNLABELLED: Porous scaffolds based on collagen and chitosan have been obtained from mixed bio-polymeric solutions and mixture freeze-drying method in the purpose of using them as materials for post-burns tissue regeneration. MATERIAL AND METHOD: Soluble collagen from bovine leather was obtained by acid-base extraction (isoelectric pH = 4.82). Two types of chitosan (CS I, M(w) = 755.900, de-acetylating degree of 79.2% and CS II, M(w) = 309.900, de-acetylating degree of 79.7%), were provided by Vascon Co., Canada. Various compositions were prepared and then structurally and morphologically characterized. In vitro degradation studies were performed in buffered collagenase or chitosan solutions, respectively, and the kinetic data were analysed. Materials effect on the tissue regeneration was tested on heat-induced burns in Wistar rats by covering the damaged tissue with collagen-chitosan scaffolds for a period of 28 days. Materials were changed every 7 days. At the end of the follow-up period skin tissue samples were harvested for histological investigation. RESULTS: By freeze-drying of collagen-chitosan solutions porous scaffolds were obtained with a lamellar morphology and porosity closer to chitosan than to collagen. In vitro degradation tests in simulated body fluid with collagenase revealed a decrease of the degradation rate of the collagen by mixing with chitosan. By using chitosan with lower molecular weight the degradation rate of the materials was decreased too, and the influence of the proportion of chitosan in composition diminished; stronger interactions between polymers hinder the enzyme diffusion to the following amino-acids groups: glycine - leucine (Gly-Leu), glycine - isoleucine (Gly-Ile), alanine-proline-glycine/leucine (-Ala-Pro-Gly-/-Leu-). In vivo tests and histological examination revealed a differentiated repair process of the post-combustion wounds in accordance with the scaffold-type influence. CONCLUSION: Scaffolds based on collagen and chitosan are biocompatible materials with promising results for tissue regeneration of the wounds.