Novel porous hydroxyapatite prepared by combining H₂O₂ foaming with PU sponge and modified with PLGA and bioactive glass

Porous hydroxyapatite (HA) scaffolds have been intensively studied and developed for bone tissue engineering, but their mechanical properties remain to be improved. The aim of this study is to prepare HA-based composite scaffolds that have a unique macroporous structure and special struts of a polymer/ceramic interpenetrating composite and a bioactive coating. A novel combination of a polyurethane (PU) foam method and a hydrogen peroxide (H₂O₂) foaming method is used to fabricate the macroporous HA scaffolds. Micropores are present in the resulting porous HA ceramics after the unusual sintering of a common calcium phosphate cement and are infiltrated with the poly(D,L-lactic-co-glycolic acid) (PLGA) polymer. The internal surfaces of the macropores are further coated with a PLGA-bioactive glass composite coating. The porous composite scaffolds are characterized in terms of microstructure, mechanical properties, and bioactivity. It is found that the HA scaffolds fabricated by the combined method show high porosities of 61-65% and proper macropore sizes of 200-600 μm. The PLGA infiltration improved the compressive strengths of the scaffolds from 1.5-1.8 to 4.0-5.8 MPa. Furthermore, the bioactive glass-PLGA coating rendered a good bioactivity to the composites, evidenced by the formation of an apatite layer on the sample surfaces immersed in the simulated body fluid (SBF) for 5 days. The porous HA-based composites obtained from this study have suitable porous structures, proper mechanical properties, and a high bioactivity, and thus finds potential application as scaffolds for bone tissue engineering.