Manufacturing and Characterization of Highly Porous Bioactive Glass Composite Scaffolds Using Unidirectional Freeze Casting

The aim of this work is the fabrication of bioactive and degradable scaffolds for bone tissue engineering. Freeze casting is used to obtain macropores. Alongside, highly bioactive 45S5 Bioglass, gelatin and chitosan are used as biocompatible binder and stabilizing agent, respectively. By varying the cooling rate between 2 and 4 K min(-1) and whether the slurry is allowed to form a gelled network at 7 degrees C before freeze casting or not, samples with a porosity of 75% are achieved. X-ray tomography analysis shows smallest pore sizes between 73 and 77 mu m and a rather lamellar structure parallel to the freezing direction for the non-gelled samples, whereas the gelled samples have smallest pores between 96 and 120 mu m and show a rather cellular structure. Compression tests reveal compressive strengths from 2 (non-gelled) to 3 MPa (gelled), while the quasielastic moduli of the gelled samples (44-46 MPa) clearly exceed values of the non-gelled (20-23 MPa). Thus, it is concluded that the modified pore structure caused by the gelling process markedly improves the mechanical properties of the samples. After seven days in SBF under physiological conditions, a calcium phosphate rich layer is detected on the samples surface, revealing the bioactivity of the scaffolds.