Preparation And Characterization Of Silk Fibroin/Mesoporous Bioactive Glass Ceramics Composite Materials For Bone Repair

The treatment of bone defects, especially large bony defects resulting from trauma,infections, tumors, or congenital malformations, represents a challenging problem for cliniciansto reconstructive surgery. Bone grafting materials such as autografts, allografts, metallic screws,and prosthesis are applied to reconstruct bones. However, these treatment modalities havewell-known drawbacks. Thus, it is clinically important to develop a novel promosing bonerepairs materials in bone regeneration.Currently, progress in new bone matrix synthesis has fueled interest in producingbiocompatible organic/inorganic biphasic scaffolds. By biomimetic strategy, a novelorganic-inorganic nanofibrous biocomposites was developed by introducing mesoporousbioactive glass ceramics into SF matrix. Taking this composite as research object, the propertiesof this composite material including mesoporous bioactive glass ceramics were prepared andinvestigated. The obtained results were described as follows:(1) Preparation and characterization of the novel mesoporous bioactive glass ceramicsincluding HA nanocrystals. Considering that HA was the inorganic constituents of natural bone,the new mesoporous bioactive glass ceramics including HA nanocrystals was firstly prepared tomimic natural bone extracellular matrix. This mesoporous bioactive glass ceramics wasconducted through sol-gel method followed by in situ carbonization, with non-ionic blockco-polymer as mesoporous template and carbon sphere as co-template. Here the influence ofdifferent carbon spheres contents and carbonization temperature into the glassy network on thestructural, morphological, textural and bioactive properties of MGHAs were investigated. TheMGHA0.5sample with high surface area and large pore volume possessed a faster apatite phaseformation in SBF. These findings suggested that increasing carbon sphere contents and carbonization temperature were conducive to the crystalline HA nanocrystals in the glassnetwork. Meanwhile, the agglomerated HA nanoparticles lead to the collapse of glassy networkand the destruction of mesoporous.Owing to the long experiment period and large quantity of carbon spheres used in abovemethod, this MGHA material was fabricated via one-step synthesis under glucose-assistedconditions using P123as a mesoporous template. The schematic illustration of the MGHAformation process was further discussed. In the study, glucose was added to form hydrophiliccarbon spheres, which served as the co-template for the joint presence of Ca2+and PO43-. In vitrobioactive assays showed a faster apatite-like phase formation on the surface of the MGHA thanthat on the surface of the MG sample.(2) Fabrication of organic–inorganic nanofbrous biocomposites with novelbioceramics. The bioactive nanofibrous scaffolds by blending MGHA into silk fibroin matrix(referred as SF/MGHA) was fabricated to mimic native tissue via using electronspinningtechnique. When treated with ethanol solution, the fiber diameters for SF/MGHA matrices werebetween1.1and1.3μm. And the pore size of the composite metrices was about2–3μm. Theappropriate MGHA additive also modified the material bioactivity, degradation kinetics, andmorphological changes of the matrix materials. However, the tensile strength of compositematerial decreased when adding high MGHA content. Compared with SF sample, the excellentapatite-formation ability of MGHA-introduced nanocomposite also improved the bioactivity ofthe matrix materials. The biphasic composite increasingly degraded in PBS or enzyme solutionin vitro compared with pure SF. After the additive of MGHA particles, high silicon content inthe system can improve its degradation rate, affecting the weight variation of the composites.(3) In vitro biocompatibility of nanofbrous SF/MGHA biocomposites. In vitroco-culture with MG-63osteoblasts and primary cultured human bone marrow mesenchymal stemcells (hMSCs) found that the cells distributed evenly on all the scaffolds. In the series ofSF/MGHA scaffolds, the addition of MGHA into SF could improve the bone bonding abilitybetween cells and scaffolds, which resulted in composite scaffolds with better cytocompatibility as compared with the pure SF scaffolds. The results showed that cells in composite nanofibergroup with5wt%MGHA exhibited highest ALP activity, indicating higher content ofincorporated MGHA enhanced higher ability of osteogenic differentiation of osteoblasts andpreosteoblasts. This phenomenon was related to the presence of MGHA in the composite system,which improved its surface roughness and hydrophilicity. Moreover, Si and Ca ions playedimportant role in the stimulation of cell proliferation. Therefore, composite scaffolds withappropriate MGHA amount may be an excellent candidate for potential application in thebiomedical field.(4) SF/MGHA nanofibrous membrane for guided bone regeneration. On the basis of invitro studies, pure SF nanofibrous membranes and composite nanofibrous membranes with5wt%MGHA were further implanted into rat calvarial defect model respectively, using the blankas a control. At4and8weeks post-operation, micro-CT detection revealed that remarkable boneformation and defect regeneration in the bone defect, in which the SF/MGHA5composite hadbeen implanted, was found as compared with the SF group and the blank group. Histologicalanalysis also confirmed that in vivo the new bone formation area in the SF/MGHA5group washigher than that in the pure SF group. Immunohistochemical analysis showed that SF/MGHA5composite nanofibrous membranes had better bone repair quality, and formed good boneintergration with host bone at8weeks post-operation. The results suggested the SF/MGHA5composite nanofibrous membranes had well guided bone regeneration effects.In summary, nanofibrous SF/MGHA scaffolds possessed excellent bioactivity, degradability,and cell compatibility. In vivo evaluation of bone formation confirmed that SF/MGHA was moreadvantageous in bone reconstruction than the SF group, suggesting the suitability of theSF/MGHA composite system in bone defects. All these findings indicate that SF/MGHAcomposite materials are potential bioactive materials for bone repair and treatment, whichprovide the feasible and theoretical guidance for further bone regeneration research.