Development of porous scaffolds for bone tissue engineering

In bone tissue engineering, biodegradable scaffolds are used as a temporary biological and mechanical support for new tissue growth. A scaffold must have good biocompatibility, controllable degradation rate, and enough mechanical strength to support bone cell attachment, differentiation, and proliferation as it gradually degrades and finally is completely replaced by new bone tissues.; Biological studies and clinical practices have established that a three-dimensional interconnected porous structure is necessary to allow cell attachment, proliferation, and differentiation, and to provide pathways for biofluids. However, the mechanical strength of a material generally decreases as increasing porosity. The conflicting interests between biological and mechanical requirements thus pose a challenge in developing porous scaffolds for load-bearing bone tissue engineering.; Two types of ceramic scaffolds, (1) Hydroxaypatite and (2) Hydroxaypatite/tricalcium phosphate, are prepared in this study utilizing a novel technique that combines the gel casting and polymer sponge methods. This technique provides better control over material microstructure and can produce scaffolds with enhanced mechanical toughness and strength.; The hydroxyapatite scaffolds prepared by this technique have an open, uniform and interconnected porous structure (∼porosity = 76%) with compressive modulus of 7 GPa, comparable to that of cortical bone, and compressive strength of 5 MPa, comparable to that of cancellous bone. The second type of ceramic scaffold is a biphasic nano composite with tricalcium phosphate as the main matrix reinforced with hydroxyapatite (HA) nano-fibers. The porous scaffold attained a compressive strength of 9.6 MPa (∼porosity = 73%), comparable to the high-end value of cancellous bone. The toughness of the scaffold increased from 1.00 to 1.72 kN/m (∼porosity = 73%), as the addition of HA nano-fibers increased up to 5 wt.%.; Polymer scaffolds are prepared using a solid-liquid phase separation technique with a polyelectrolyte complex of chitosan and alginate as scaffolding material. These scaffolds were used to study sustained delivery of a model protein. The effect of size of ceramic in polymer matrix on mechanical and biological properties of scaffold is also examined by using both nano- and micron-sized ceramic particles.