ABSTRACT
BACKGROUND: High molecular materials have been proved to enhance the mechanical properties of calcium phosphate bone cement, as well as attenuate the injectability of composite materials. It thereby influences the clinical application of composite materials.OBJECTIVE: To observe the compressive strength and injectability of silk fihroin compound calcium phosphate bone cement, to evaluate the effect of silk fibroin on calcium phosphate, and to investigate the feasibility of applying silk fibroin as an injectable hone substitute to repair hone defects.DESIGN, TIME AND SETTING: Controlled study was performed in the central laboratory of Analysis and Testing Center, Soochow University from September to December in 2007.MATERIALS: Calcium phosphate cement was purchased from Shanghai Rebone Biomaterials Co., Ltd; silk fibroin was offered by Institute of Material & Engineering, Soochow University.METHODS: Six groups were set with different mass fractions (0.5%, 1%, 1.5%, 2%, 2.5%, 3%) of silk fibroin, which were mixed with bone cement at a certain liquid/solid ratio of 0.4 mL/g to prepare the calcium phosphate composite. The calcium phosphate cement without silk fibroin was served as control group.MAIN OUTCOME MEASURES: The compressive strength and injectability were determined. The characteristic microstructure was observed using scanning electron microscope.RESULTS: The compressive strength increased firstly and then decreased with the addition of silk fibroin. The compressive strength of the experimental groups was remarkably higher than the control group when the silk fibroin content was 1%-2.5% (P<0.05). The injectability of the paste diminished with the addition of silk fibroin, which was statistically different when the silk fibroin content was 1.5%-3% (P<0.05). Scanning electron microscope result revealed that the silk fihroin penetrated throughout calcium phosphate crystals, which were tightly connected.CONCLUSION: Silk fibroin can improve the compressive strength of silk fibroin/calcium phosphate cement composites without significant influence of manipulation, and can widen the application field of calcium phosphate bone substitute.