Simultaneous formation and mineralization of star-P(EO-stat-PO) hydrogels

Natural bone is an organic-inorganic composite of highly ordered collagen fibrils and ~60-70% nanocrystalline hydroxyapatite (HA) crystals resulting in a high fracture resistance for various mechanical loading situations. This study aimed to synthesize highly mineralized hydrogels to mimic the mechanical properties of cancellous bone. A six armed star molecule functionalized with isocyanate groups as reactive termini (NCO-sP(EO-stat-PO)) was used to build up a hydrogel matrix, which was then subsequently mineralized with hydroxyapatite nanocrystals following the hydrolysis of incorporated α-tricalcium phosphate particles. The advantage of this dual setting approach in comparison to simply adding unreactive filler particles to the hydrogel was demonstrated to be a strength improvement by the factor of 30. After 1-28d setting, the mechanical properties of a composite with 30wt% NCO-sP(EO-stat-PO) such as elasticity (5.3-1.4%), compression strength (11-23MPa) and E-modulus (211-811MPa) were found to be similar to the properties of cancellous bone.