Preparation And Characterization Of Calcium Phosphate Cement Incorporated With N-acetylcysteine-loaded Silk Fibroin Microspheres

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 cell compatibility.Methods:The empty SFM were prepared by emulsion solvent evaporation method, and the particle size was determined by granulometer,scanning electron microscope to observe the characteristics of the microspheres. NAC-SFM was prepared by absorbingdifferent concentrations of NAC solution, and the maximum drug loading ratio was determined. Then, NAC-SFM was loaded into calcium phosphate bone cement to test the drug release properties in vitro. MC3T3-E1 osteoblasts were cultured on the surface of NAC-SFM calcium phosphate bone cement and cell attachment and growth were observed by scanning electron microscope. Additionally, MC3T3-E1 cells were co-cultured with three kinds of bone cement extracts(calcium phosphate cement, SFM-calcium phosphate cement, NAC-SFM-calcium phosphate cement, as well as co-cultured with the α-minimum essential medium containing a volume fraction of 10% fetal bovine serum and 1% penicillin-streptomycin double antibody as the control. MTS assay was used to evaluate cell proliferation.Results:(1)Particle size analysis showed that fibroin microspheres concentrated within 2 to 10μm, and the average particle size is 3.20μm.Microspheres in the composite bone cement presented with smooth surface, same size, diffused distribution and no obvious destroy.(2)The initial and final setting time of calcium phosphate cement which was solidified by fibroin solution was significantly shortened(P<0.05)(3) The double slow-release system which contained SFM and CPCs released 5.35±2.19% totally in the first 24 h,which was obviously less than the control group(13.45±1.04%),and the cumulative released quantity was 18.99±0.92% with 37.64±1.73%(control)(4)Different extracts had no significant cytotoxicity to the growth of MC3TC-E1 cells in the MTS assay, and the SEM pictures showed that the cells on the cement form a spindle shaped,growed well.Conclusion:1.The addition of SFM improved the drug slow release performance of calcium phosphate bone cement.2.Silk fibroin solution can shorten the coagulation time of calcium phosphate bone cement,hence the application of the surgery could bebroaden.3.The composite bone cement material has good biocompatibility, which provide a new insight into the development of bone repair biomaterials.