oa Hybrid Nanocomposite Polymers For Tissue Engineering

The purpose of this project was to further investigate the characteristic properties of an inorganic-organic hybrid material with respect to its potential application in the field of tissue engineering. The organic component chosen for this project was a co-polymer 2-hydroxyethyl methacrylate (HEMA) and 3-trimethoxysilyl propylmethacrylate (TMSPMA), able to crosslink the polymer to the silica network via hydrolysis and condensation of the alkoxysilane functional group. Copolymers of HEMA-TMSPMA were made by the process of free radical polymerization (FRP), using azobisisobutyronitrile (AIBN) as a thermal initiator. Hybrid monoliths were then produced by the sol-gel process with hydrolysed tetraethyl orthosilicate (TEOS) and HCL solution as the inorganic precursor. The HEMA:TMSPMA ratios used for this study were 200:1, 100:1, 50:1, 20:1 and pure HEMA, at a concentration of 60wt% organic, to allow for comparison on the effect of crosslinking on the hybrids properties. Characterization of the copolymer and hybrid monoliths determined their chemical and physical properties. Characterisation techniques included Proton Nuclear Magnetic Resonance (HNMR), Gel Permeation Chromatography (GPC), Fourier Infrared Spectroscopy (FTIR), dissolution study in TRIS solution and which was analysed using Inductively Coupled Plasma (ICP), Thermo-Gravimetric Analysis (TGA), X-Ray Diffraction (XRD), compressive strength testing and Scanning Electron Microscopy (SEM). These methods were used to determine the molecular composition, mechanical properties and characteristic degradation of the copolymers and monoliths. HNMR showed that the FRP process produced highly polymerised copolymers. The sol-gel process produced successful crack-free monoliths with an average gelation/drying period of 3weeks and average of 4 crack free monoliths from samples of 10 for the optimised sol-gel process. The 3 week dissolution study showed a reduction in silica ions release rate and plateaued at a lower concentration with increasing TMSPMA content and hence a higher degree of cross-linking, with a plateau of Si release between week 2 and 3. XRD shows that no crystalline structures formed on the surface of the hybrids, which is expected as TRIS doesn't contain phosphorus or calcium meaning that no precipitates are expected. Mechanical testing shows that the 200:1 HEMA-TMSPMA monoliths have the highest compressive strength, and Pure HEMA monoliths are the most brittle as expected by the materials natural character, with values of 134.6 ± 19.80 MPa and 42.6 ± 17.39 MPa respectively.