Novel hybrid PET/DFA–TiO2 nanocomposites by in situ polycondensation

Multiblock poly(aliphatic/aromatic-ester)s containing phthalic acid sequences (as in poly(ethylene terephthalate) (PET) or poly(butylene terephthalate) (PBT)) and a dimmer fatty acid (DFA) represent novel biocompatible materials offering the processability of thermoplastics combined with the good elasticity of rubber (thermoplastic elastomers, TPE). In the present investigation TiO2 nanoparticles were incorporated into PET/DFA copolymer with the aim of increasing mechanical properties and bioactivity, for use of the composites in tissue engineering and other biomedical applications. It was found that a relatively low concentration of TiO2 nanoparticles (0.13 vol.%) led to an impressive improvement of fracture strength (100%) and elongation at fracture (300%). As expected, the surface roughness increased with the addition of TiO2 nanoparticles. However upon immersion in simulated body fluid for up to 21 days, the composites did not exhibit formation of hydroxyapatite crystals on their surfaces, confirming the “bioinert” character of the composite constituents. This indicates that the possible bioactive behavior of the composites in in vitro or in vivo conditions may be related to the improved nanotopography imparted by TiO2 nanoparticle additions rather than due to chemistry related effects at the cell/biomaterial interface.