Polydopamine chelating strontium on graphene oxide enhances the mechanical and osteogenic induction properties of PLLA/PGA bone scaffold

Poly (lactic acid)/poly (glycolic acid) (LG) bone scaffold exhibits good biocompatibility for bone defect regeneration but lacks satisfactory mechanical and osteogenic induction properties. Here, graphene oxide (GO) was encapsulated by polydopamine (PDA) via self-polymerization of dopamine, and strontium (Sr) was loaded onto GO by the chelation of PDA. The modified GO was added to the LG scaffold prepared via selective laser sintering as a reinforcing phase to improve the mechanical properties and osteogenic induction properties. The results indicated that the tensile and compressive strengths of the scaffold with 1.5 wt% modified GO were 9.49 MPa and 19.22 MPa, respectively, representing 67.08% and 95.33% improvement compared to the LG scaffold. The enhancement mechanisms of the modified GO in the scaffold included crack branching, crack deflection, crack pinning, crack bridging, and pulling out. More importantly, the scaffold with modified GO exhibited superior bioactivity and osteogenic induction properties compared to the LG scaffold, because PDA could chelate calcium ions derived from the surrounding physiological environment, and the calcium ions attracted phosphate ions through electrostatic interactions to promote the apatite layer deposition. Additionally, the presence of Sr in the scaffold promoted the proliferation and differentiation of osteoblasts, thereby improving osteogenic induction properties.