Modification of 3-D Porous Hydroxyapatite/Thermoplastic Polyurethane Composite Scaffolds for Reinforcing Interfacial Adhesion by Polydopamine Surface Coating

Composite tissue engineering scaffolds show good comprehensive properties, but improving their interfacial binding force is still a challenge. In this study, polydopamine (PDA) was used as a glue-like layer to solve the interface problem in three-dimensional (3-D) porous hydroxyapatite (HA)/thermoplastic polyurethane (TPU) composite scaffolds and to improve their comprehensive properties. The morphology, water absorption, porosity, hydrophilicity, mechanical properties, and cell viability of HA/TPU and PDA/HA/TPU scaffolds were systematically studied. The scanning electron microscopy and X-ray photoelectron spectroscopy results showed that a uniform PDA coating layer successfully formed on the surface of 3-D porous HA/TPU composite scaffolds by dopamine self-polymerization. Moreover, the conjugation effect occurred between the PDA and HA/TPU matrix, resulting in an increase in the interfacial binding force of the 3-D PDA/HA/TPU scaffold. The hydrophilicity of the PDA/HA/TPU scaffolds was significantly higher than those of the TPU scaffolds. Both static and dynamic mechanical property tests revealed that the PDA/HA/TPU scaffold possessed excellent comprehensive mechanical properties, such as high strength, high stiffness, and good flexibility, due to the enhancement of the interfacial binding force. Compared with TPU and HA/TPU scaffolds, the addition of a PDA coating could effectively improve the attachment and viability of mouse embryonic osteoblasts cells (MC3T3-E1) incubated on PDA/HA/TPU scaffolds. These results indicate that the PDA/HA/TPU scaffolds possess great potential to be used as tissue engineering scaffolds, and that the PDA coating could be a simple, practical, effective, and universal approach to modify composite scaffolds.