Bi-/multi-modal pore formation of PLGA/hydroxyapatite composite scaffolds by heterogeneous nucleation in supercritical CO2 foaming

Scaffolds with multimodal pore structure are essential to cells differentiation and proliferation in bone tissue engineering.Bi-/multi-modal porous PLGA/hydroxyapatite composite scaffolds were prepared by supercritical CO2 foaming in which hydroxyapatite acted as heterogeneous nucleation agent.Bimodal porous scaffolds were prepared under certain conditions,i.e.hydroxyapatite addition of 5％,depressurization rate of 0.3 MPa· min-1,soaking temperature of 55 ℃,and pressure of 9 MPa.And scaffolds presented specific structure of small pores (122 μm+ 66 μm) in the cellular walls of large pores (552 μm ± 127 μm).Furthermore,multimodal porous PLGA scaffolds with micro-pores (37 μm± 11 μm) were obtained at low soaking pressure of 7.5 MPa.The interconnected porosity of scaffolds ranged from (52.53 ± 2.69)％ to (83.08 ± 2.42)％ by adjusting depressurization rate,while compression modulus satisfied the requirement of bone tissue engineering.Solvent-free CO2 foaming method is promising to fabricate bi-/multi-modal porous scaffolds in one step,and bioactive particles for osteogenesis could serve as nucleation agents.