Freeze casting of porous biomaterial scaffolds for bone tissue engineering

This paper firstly reviews the current trends in fabrication techniques to produce porous inorganic biomaterial constructs for hard tissue augmentation. Of these, simple and cost effective freeze casting method has been employed over the last few years to process mainly bioceramics but has often met with difficulty in controlling variously oriented pore structures. The present work also compares two novel freeze casting methods using camphene and a mixture of water and glycerol in fabricating excellent networked 3-D porous structures of Bioglass and hydroxyapatite. It was possible to control the development of dendritic pore microstructure by the control and optimization of the process parameters such as mould temperature (0 to -196 degrees C), temperature of freezing vehicle, glycerol concentration (5-40wt%) and temperature gradient driving the solidification and/or sublimation. DTA-TGA, XRD, density, and SEM analysis of bioscaffolds, air sintered up to 1100 degrees C, showed monotonic correlations between porosity, pore size, orientation and solid loading (10-70%). A maximum porosity of 90% was achieved for stnictures with micro and macropores of 2-120 mu m, a clinically viable range that is amenable for bone in-growth and revascularization