A new thermogelling chitosan-glycerophosphate system has been recently proposed for biomedical applications such as drug and cell delivery. The objectives 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 filtration-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 weight, 3-5-fold decrease in dynamic viscosity, and substantial loss of mechanical properties of the resulting gel. However, sterilization did not impair the ability of the system to form a gel at 37 degrees C. The antimicrobial activity of chitosan against several microorganisms was evaluated after inoculation of chitosan solutions and removal of the cells by filtration. It was found that, although chitosan was bacteriostatic against the heat sterilization bioindicator Bacillus stearothermophilus, the bacteria could rapidly grow after separation from the chitosan solution by filtration. This indicated 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 autoclaving time.

No abstract

No abstract

No abstract

The primary purpose of this study was to characterize the main features of a BCP-loaded chitosan-GP composite. The two-syringe design improves the storage conditions, facilitates the sterilization procedure and provides an easy-to-use injectable biomaterial, ensuring reproducible properties with minimal manipulation. Rheological measurements confirm that the chitosan- GP/BCP composite retains the thermosensitive properties already described for chitosan-GP hydrogels. At 37°C, the system gels within 10 minutes and reaches sufficient consistency after 30 minutes to prevent the mineral granules from migration into the surrounding tissues in vivo. The compressive force needed for the injection of chitosan-GP/BCP before gelation is approximately 6.6 N, only about 6 times that required for water and much lower than the average force that the majority of adults can exert. Morphology was investigated by environmental scanning electron microscopy (ESEM), which revealed 3-D dispersion of BCP granules embedded in chitosan-GP hydrogel. This open, porous structure affords complete access for body fluids and cells to each mineral granule immediately following implantation. The design using disposable syringes equipped with 16G hypodermic needles described here allows easy in vivo delivery of a fully injectable biomaterial containing porous scaffold that naturally enhances the osteogenic activity recognized for both chitosan and BCP.