Phosphonic Acid Coupling Agent Modification of HAP Nanoparticles: Interfacial Effects in PLLA/HAP Bone Scaffold

• Main Authors: Cijun Shuai, Li Yu, Wenjing Yang, Shuping Peng, Yancheng Zhong, Pei Feng
• Format: Article
• Language: English
• Published: MDPI AG 2020-01-01
• Series: Polymers
• Subjects: interfacial bonding; coupling agent; hap; scaffold
• Online Access: https://www.mdpi.com/2073-4360/12/1/199
• ISSN: 2073-4360

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 PO₃^2− of CEPA formed an electrovalent bond with the Ca²⁺ 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 Ca²⁺ in simulated body fluid (SBF) solution by the phosphonic acid group to induce apatite layer formation and also release Ca²⁺ and PO₄^3− by degradation to facilitate cell attachment, growth and proliferation.