Effects of polymer amount and processing conditions on the in vitro behaviour of hybrid titanium dioxide/polycaprolactone composites

Titanium dioxide (TiO2) and TiO2 glasses containing poly(e-caprolactone) (PCL) up to 24% by weight were obtained by the sol-gel process. Powder compaction was achieved providing heat and pressure. Properties were evaluated through compression and bending tests assisted by X-ray micro-computed tomography imaging. The effects of compaction conditions (i.e. temperature, pressure and duration) on mechanical properties of inorganic/organic composites were investigated. Biocompatibility tests on organic/inorganic composites were carried out using human cells and the MTT assay to determine viability. Results indicated that the mechanical properties (i.e. Young's modulus and maximum strength), in both compression and bending, were a function of the compression moulding conditions. Highest mechanical properties were measured using a compaction pressure of 1500 MPa acting for 90 min at a die temperature of 100 degrees C. The results, however, also suggest that mechanical properties can be tailored by varying the amount of PCL to TiO2. Strength and stiffness spanned between the properties of spongy and cortical bone. Young's modulus in both compression and bending were higher for PCL amounts of 6%. Instead, higher bending strength values were measured for PCL amounts of 12%. These weight amounts of PCL also provide higher average density values, thus suggesting that the polymeric phase is effective in toughening TiO2-based materials. The investigated materials also showed a very good cytocompatibility as indicated by the MTT assay results. (C) 2007 Elsevier Ltd. All rights reserved.