The effect of pore size, crosslinking and collagen content on mechanical properties of collagen-GAG scaffolds

Tissue-engineered bone provides an alternative source of bone grafts. Collagen-GAG scaffolds (porosity 99.5%) have shown great potential as a construct on which to culture bone cells [1], but the mechanical properties of the scaffold are currently not suitable for use as a bone graft. Therefore, the goal of this study was to investigate the effects of pore size, dehydrothermal (DHT) crosslinking and collagen content on the mechanical properties of collagen-GAG scaffolds. Scaffolds were produced via a freeze-drying process, using two compositions of collagen-GAG slurry (0.5% and 1% collagen). Pore size was altered by varying the final freezing temperature of the freeze-drying process (pore size range: 69-96~tm). DHT crosslinking was then carried out at a pressure of 0.05 bar. DHT duration and temperature were varied between 24 and 96 hours and 105°C and 120°C, respectively. Compression testing was carried out on dry samples to determine elastic modulus. Pore size did not have a significant effect on modulus (p > 0.05), which agrees with previous work [3]. For DHT crosslinking, prolonged exposure did not produce an increase in modulus at 105°C, but at 120°C there was s 50% increase in modulus after three days of crosslinking (p<0.05). Increasing the temperature from 105°C to 120°C produced a 2to 5-fold increase in modulus (p <0.001). Doubling the collagen content produced a 10-fold increase in modulus (p<0.001). Results show that the modulus can be substantially increased both by using DHT treatment and by increasing the collagen content in the scaffold. The combined effects of increasing DHT temperature and doubling the collagen content are being investigated to further increase scaffold modulus. Acknowledgements: Science Foundation Ireland, Integra Life Sciences.