Preparation and properties of calcium sulfate bone cement incorporated with silk fibroin and Sema3A-Ioaded chitosan microspheres

To search for new bioactive materials which can be used as the substitute of bone repairing and drug carriers, Sema3A-Ioaded chitosan microspheres （SLCM） and silk fibroin （SF） were mixed with calcium sulfate cement （CSC）. SEM, particle size analysis and swelling rate determination were performed to study properties of the microspheres. The drug loading, encapsulation efficiency and drug release rate were determined by ELISA. Microspheres with different SLCM weight contents （0.5%, 1% and 5%） were prepared to determine which one has the strongest mechanical properties and the appropriate setting time. It was revealed that CSC/SF/0.5SLCM has satisfactory mechanical properties, and its in vitro biocompatibility was assessed by MTS. Chitosan microspheres （5-18 μm） were globular, the surface was smooth, and the swelling rate is （77.02 ± 5.57）%. With this formula, the setting time was increased with the addition of SLCM in CSCISF, and the cumulative drug release rate is 44.62% in 28 d. XRD results demonstrate that the main component is calcium sulfate. Also it was found that CSCiSFI 0.5SLCM supports the growth of MC3T3 cells. Thus the preparation of CSCISFIO.5SLCM was reliable, and the products had good structures, physical properties and biocompatibility, appearing to be a promising bone substitute material.