Photocurable high internal phase emulsions (HIPEs) containing hydroxyapatite for additive manufacture of tissue engineering scaffolds with multi-scale porosity

Porous composites containing hydroxyapatite (HA) were templated from high internal phase emulsions (HIPEs) and were further structured using direct-write UV stereolithography to produce composite scaffolds with multi-scale porosity. FTIR, TGA and SEM analyses confirmed that HA was retained after photocuring and subsequent treatments and was incorporated within the polymerised HIPE (polyHIPE). The addition of HA particles to the polyHIPE caused changes in the mechanical properties of the material. An increase in both the Young's modulus and maximum stress at yield was observed compared with the pure polyHIPE from 1.544 ± 0.231 to 4.614 ± 0.775 and 0.177 ± 0.009 to 0.267 ± 0.034 MPa, respectively. Except at very high concentrations, adding HA did not adversely cause the phase separation of the HIPE or the porous microstructure of the resulting polyHIPE. In combination with a photoinitiator, the HIPE emulsion containing HA was investigated as a photocurable resin for stereolithography-based additive manufacturing. The material was readily processable into "woodpile" structures via direct-write UV stereolithography, producing scaffolds with multi-scale porosity which may be useful for medical applications such as tissue engineering. In conclusion, HA was successfully added into polyHIPEs, producing a similar porous structure to that of the pure polyHIPE whilst improving the mechanical performance.