(625x) Chitosan Scaffold Morphology Optimized for Ultrasonically Mediated Articular Cartilage Synthesis

Cell seeded scaffolds provide the platform for effective tissue engineering.  These scaffolds must be designed to optimize the environment for increased cell proliferation and viability.  Our research group uses porous chitosan scaffolds for the ultrasonically mediated synthesis of articular cartilage.  Chitosan is obtained from the deacetylation of chitosan, the second most abundant natural polymer.  It is non-toxic and biodegradable, allowing for the direct implantation in patients and the high concentration of primary amine groups on chitosan makes it ideal for surface functionalization to enhance cell growth.

Chitosan scaffolds are prepared through a two-step freezing, lyophilizing process.  Dissolved chitosan exposed to subzero temperatures experience phase separation during the solidification of the solvent.  The solvent is then selectively removed through freeze drying.  Scanning electron microscopy reveals a spatial variation in pore diameter.  Our central hypothesis is that the pore size is dependent on the spatial and temporal temperature profile during the freezing process.  We have developed and validated a simple yet accurate finite difference model to predict the internal energy of the chitosan solution, including non-linearities due to temperature dependent material properties.  We then correlate the model results with the scaffold morphology as determined by scanning electron microscopy. 

Furthermore, the use of ultrasound to enhance the physiological properties of the synthetic tissue must be investigated.  We investigate the propagation of the acoustic wave through the porous scaffold and propose an engineered structure to maximize the beneficial effects of ultrasound.