Effect of hydroxyapatite and β-tricalcium phosphate on the properties of Thai silk fibroin/gelatin scaffold

Abstract

This research aimed to investigate the effects of hydroxyapatite (HA) and β-tricalcium phosphate (β-TCP) on the properties of Thai silk fibroin/gelatin scaffolds. The Thai silk fibroin/gelatin solution incorporated with both inorganic compounds, β-TCP and HA, were homogenized and fabricated via freeze drying technique. The effect of different weight percentages of each inorganic compound incorporated was examined. It was found that all Thai silk fibroin/gelatin based scaffolds incorporated with β-TCP and HA possessed porous structure with uniform distribution of β-TCP and HA. The Thai silk fibroin/gelatin based scaffold incorporated with both inorganic compounds, β-TCP and HA, showed lower water absorption (%) because of the hydrophobic part of inorganic compounds and lower porosity than that of pure protein scaffolds. The incorporation of β-TCP and HA could enhance compressive strength of scaffolds compared to the pure protein scaffold in dry and wet condition. In addition, the compressive modulus of Thai silk fibroin/gelatin based scaffolds incorporated with β-TCP was slightly higher than that with HA incorporation. This could be due to the smaller pore size of scaffold incorporated with β-TCP. The scaffold with smaller pore size can give more paths for distributing to applied stress, resulting in the greater compressive modulus. The results on in vitro biodegradability in collagenase solution revealed that the Thai silk fibroin/gelatin based scaffolds without inorganic compounds was completely degraded within 7 days. The remaining weight (%) of scaffold incorporated with both β-TCP and HA were decreased and remained at the weight percentage of incorporated inorganic compounds after 7 days. All samples clearly presented low cytotoxic effect. The results on in vitro cell culture using periosteum derived cells indicated that the incorporation of both inorganic compounds could enhance osteoconductive potential of the Thai silk fibroin/gelatin based scaffolds, particularly the scaffolds containing 50-70% of β-TCP and 50% HA. When compared among the four types of scaffolds, the scaffold with 30-70% of β-TCP tended to be slightly better osteoconductive than the scaffold with 50% of HA. The results on the physical and biological properties of Thai silk fibroin/gelatin based scaffolds incorporated with β-TCP and HA markedly indicated that the scaffolds had a high potential to be applied in bone tissue engineering.