Engineering Pro‐Osteogenic Poly( l ‐Lactide‐ co ‐ε‐caprolactone) Sponges Through Carbonate Apatite Integration

ABSTRACT

Flexible and porous sponges with high osteoconductivity have a wide range of bone healing applications. Although polymer/ceramic composite materials can serve as soft bone grafts, osteogenesis can be compromised when the ceramic surface is covered by the polymer. This study aimed to fabricate a bone‐graft sponge with high elasticity and osteoconductivity by integrating carbonate apatite (CAp) particles inside and on the surface of poly(

‐lactide‐ co ‐ε‐caprolactone) (PLCL). A slurry comprising PLCL and a calcium carbonate (CaCO ₃ ) precursor was freeze‐dried to obtain a PLCL/CaCO ₃ sponge, which was then phosphatized into a PLCL/CAp sponge using a mildly alkaline sodium phosphate solution. This sodium phosphate solution not only converted CaCO ₃ into CAp but also partially degraded the PLCL matrix to expose CAp on the surface, which improved the hydrophilicity of the surface. Interconnected macropores with diameters of 500–600 μm were also introduced by embedding and subsequently leaching sodium chloride (NaCl) crystals from the PLCL/CaCO ₃ sponge. In vitro cell experiments demonstrated that CAp and the macroporous structure significantly enhanced osteoblast adhesion and differentiation. In vivo evaluations using a rabbit femoral defect model revealed that CAp endowed the PLCL sponge with osteoconductivity, facilitating bone ingrowth from the defect margins in 4 weeks. The macroporous structure enabled bone regeneration throughout the sponge. These findings suggest that the developed PLCL/CAp sponge is a promising biomaterial for bone regenerative applications.