Summary: | In order to improve the interfacial bonding between hydroxyapatite (HAP) and poly-l-lactic acid (PLLA), 2-Carboxyethylphosphonic acid (CEPA), a phosphonic acid coupling agent, was introduced to modify HAP nanoparticles. After this. the PLLA scaffold containing CEPA-modified HAP (C-HAP) was fabricated by selective laser sintering (frittage). The specific mechanism of interfacial bonding was that the PO<sub>3</sub><sup>2−</sup> of CEPA formed an electrovalent bond with the Ca<sup>2+</sup> of HAP on one hand, and on the other hand, the −COOH of CEPA formed an ester bond with the −OH of PLLA via an esterification reaction. The results showed that C-HAP was homogeneously dispersed in the PLLA matrix and that it exhibited interconnected morphology pulled out from the PLLA matrix due to the enhanced interfacial bonding. As a result, the tensile strength and modulus of the scaffold with 20% C-HAP increased by 1.40 and 2.79 times compared to that of the scaffold with HAP, respectively. In addition, the scaffold could attract Ca<sup>2+</sup> in simulated body fluid (SBF) solution by the phosphonic acid group to induce apatite layer formation and also release Ca<sup>2+</sup> and PO<sub>4</sub><sup>3−</sup> by degradation to facilitate cell attachment, growth and proliferation.
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