Preparation, Characterization And Biological Properties Of Organic/inorganic Xerogel Composites

We prepared organic/inorganic xerogel composites through thesol-gel process. Polymer molecule was introduced into the system whenthe hydrolysis and condensation reaction of tetraethyl orthosilicate occurs.It is referred that the one-dimensional polymer chain would penetrate intothe three-dimensional SiO2network, so the resulted semi-IPN structurewould highly improve the homogeneity of the composite. The inorganiccomposition we selected in this paper were ternary SiO2-CaO-P2O5bioactive glasses,78mol%SiO2-20mol%CaO-2mol%P2O5(denoted as78S) and60mol%Si-36mol%CaO-4mol%P2O5(denoted as60S),respectively, which had been demonstrated to be bioactive in manyresearches. Due to the excellent biocompatibility and outstandingmechanical properties of silk fibroin (SF), it was chosen as the organicphase of the composite. Another polymer that was acted as the organicadditive was poly (ethylene glycol)(PEG) because of goodbiodegradability and flexibility.The structure, composition and morphology of the xerogel compositewere analyzed by the Fourier Transform Infrared (FT-IR)Spectrophotometer, X-Ray Diffraction instrument (XRD), and ScanningElectrical Microscope (SEM) respectively. The pore structure, bioactivity,mechanical property and the cell compatibility of the material were alsotested. The results showed that the78S xerogel had large BET surfacearea and pore diameter, and the pore distribution of the sample is kind ofwide. This type of pore structure is very fit to be the scaffold for theadhesion and growth of the cells. However, the mechanical properties of78S xerogel were not as good as we expected, and when the xerogel wasimmersed in the simulated body fluid (SBF), the hydroxyapatite-likecrystals did not precipitate on its surface. Though the addition of polymerindeed optimizes the pore structure of the composite, they do not haveany effect on the material’s bioactivity. As to the60S xerogels, it isdemonstrated to be cell compatible and bioactive in our research, and the introduction of SF and PEG could ameliorate the pore structure of thecomposite. Though the polymer had some negative influence with themechanical property of the material, the bioactivity and cell compatibilityof the composite were highly improved compared to the pure60S xerogel.In comparation with other organic/inorganic composite prepared in thispaper, the60S-PEG xerogel is the most potential candidate for the bonerepair application.