Effects of steam sterilization on thermogelling chitosan-based gels

A new thermogelling chitosan-glycerophosphate system has been recently prop osed for biomedical applications such as drug and cell delivery, The object ives of this work were to characterize the effect of steam sterilization on the in vitro and in vivo end performances of the gel and to develop a filt ration-based method to assess its sterility. Autoclaving 2% (w/v) chitosan solutions for as short as 10 min resulted in a 30% decrease in molecular we ight, 3-5-fold decrease in dynamic viscosity, and substantial loss of mecha nical properties of the resulting gel. However, sterilization did not impai r the ability of the system to form a gel at 37 degreesC. The antimicrobial activity of chitosan against several microorganisms was evaluated after in oculation of chitosan solutions and removal of the cells by filtration. It was found that, although chitosan was bacteriostatic against the heat steri lization bioindicator Bacillus stearothermophilus, the bacteria could rapid ly grow after separation from the chitosan solution by filtration. This ind icated that B. stearothermophilus is an adequate strain to validate a heat sterilization method on chitosan preparations, and accordingly this strain was used to assess the sterility of chitosan solution following a 10 min au toclaving time. (C) 2001 John Wiley & Sons, Inc.