Calcium phosphate cement incorporated with N-acetylcysteine-loaded silk fibroin microspheres：preparation and characterization / 中国组织工程研究

ABSTRACT

BACKGROUND:Calcium phosphate bone cement has been applied to clinical surgery because of its good biocompatibility and osteoconduction. However poor mechanical properties and lack of osteoinductivity limit its wide application. OBJECTIVE:To develop calcium phosphate cement incorporated with N-acetylcysteine (NAC) loaded silk fibroin microspheres (SFM), which is a kind of new injectable bone graft material with slow-release function, and evaluate its physical and chemical properties and cel compatibility. METHODS: Empty SFMs were prepared with emulsion solvent evaporation to absorb NAC solution of different concentrations by NAC-SFM and the concentration of NAC at the maximum drug loading ratio was determined. Then, NAC-SFM was loaded into calcium phosphate bone cement to test the drug release propertiesin vitro. MC3T3-E1 osteoblasts were cultured on the surface of NAC-SFM calcium phosphate bone cement and cel attachment and growth were observed by scanning electron microscope. Additionaly, MC3T3-E1 cels were cultured with three kinds of bone cement extracts (calcium phosphate cement, SFM-calcium phosphate cement, NAC-SFM-calcium phosphate cement, as wel as cultured in theα-minimum essential medium containing a volume fraction of 10% fetal bovine serum and 1% penicilin-streptomycin double antibody as the control. MTS assay was used to evaluate cel proliferation. RESULTS AND CONCLUSION:Microspheres in the composite bone cement presented with smooth surface, same size, diffused distribution and no obvious destroy. Thus, the SFM could remain stable in the reaction process of the composite bone cement. The double slow release system which contained silk fibroin microspheres and calcium phosphate bone cement showed a significant decrease in the cumulative release percentage of NAC within the first 24 hours compared with the control group (P < 0.05). In the next 28 days, the release speed of NAC was significantly lower in the NAC-SFM-calcium phosphate cement group than the calcium phosphate cement group (P< 0.05). In addition, different extracts had no significant cytotoxicity to the growth of MC3TC-E1 cels. Thus, the NAC-SFM-calcium phosphate cement has good cytocompatibility, which provide a new insight into the development of bone repair biomaterials.