Optimization of the structure of polyurethanes for bone tissue engineering applications

Polyurethanes containing 22–70 wt.% hard segments were developed and evaluated for bone tissue engineering applications. Aliphatic poly(ester-urethanes) were synthesised from poly(ε-caprolactone) diol with different molecular masses (M = ∼530, 1250 and 2000 Da), cycloaliphatic diisocyanate 4,4′-methylenebis(cyclohexyl isocyanate) and ethylene glycol as a chain extender. Changes in macromolecule order with increasing hard segment content were observed via modulated differential scanning calorimetry. Depending on the hard segment content, a gradual variation in polyurethane surface properties was revealed by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and static contact angle measurements. As the hard segments content increased the polyurethane surface exhibited more phase separation, a higher content of urethane moieties and higher hydrophilicity. The biocompatibility results indicated that proliferation of human bone-derived cells (HBDC) cultured in vitro improved with increasing hard segment content while the osteogenic potential of HBDC decreased with increasing hard segment content.