Fabrication of hydroxyapatite/PLA composite nanofibers and effects of surface treatment of hydroxyapatite on their mechanical properties and dispersion

Abstract

In recent years, bone tissue engineering, whose basic elements are an appropriate cell source, optimal culture conditions and a biodegradable scaffold, has been getting attention. The scaffold is used as space filling material to work as an extra cellular matrix to organize cells into three dimensional structures. Nanofibers are expected to be used as the scaffold because their small size is close to the structural dimension of the extra cellular matrix of native tissues. Thermoplastic polymers have been spun to nanofibers by the electrospinning method, which applies a high voltage to a polymer solution. Among many thermoplastic polymers, polylactic acid (PLA) is expected to be used for a scaffold because of its biocompatibility, bioabsorbability and mechanical properties. To obtain better affinity properties of a PLA nanofiber scaffold with the bone, compounding with hydroxyapatite nanoparticles (HA), which have the same composition formula with the human bone, had been conducted. HA/PLA composite nanofiber is expected as the scaffold for bone tissue engineering. However, the strength of HA/PLA composite nanofiber is weak because of its low interfacial strength between HA and PLA and the easy aggregation property of HA. In this study, the surface treatment of HA by hot water and silane coupling agent was conducted (HW+HTS). HA/PLA composite nanofibers were fabricated by electrospinning, and the mechanical properties of its nonwoven fabrics, aligned fabrics and single fibers were evaluated. HW+HTS treated HA showed high dispersion condition in PLA. While the tensile strength of untreated HA/PLA composite nanofibers was smaller than that of pure PLA nanofibers, HW+HTS treated HA/PLA composite nanofibers showed almost the same strength of pure PLA nanofibers. By dispersing HA in PLA nanofiber by HW+HTS treatment, HA/PLA composite nanofiber showed uniform mineralization behavior, which was evaluated using Hanks' Balanced Salt Solution (HBSS).