Acrylated epoxidized soybean oil/hydroxyapatite-based nanocomposite scaffolds prepared by additive manufacturing for bone tissue engineering

The mechanical properties and biocompatibility of nanocomposites composed of Acrylated Epoxidized Soybean Oil (AESO), nano-Hydroxyapatite (nHA) rods and either 2-Hydroxyethyl Acrylate (HEA) or Polyethylene Glycol Diacrylate (PEGDA) and 3D printed using extrusion-based additive manufacturing methods were investigated. The effects of addition of HEA or PEGDA on the rheological, mechanical properties and cell-biomaterial interactions were studied. AESO, PEGDA (or HEA), and nHA were composited using an ultrasonic homogenizer and scaffolds were 3D printed using a metal syringe on an extrusion-based 3D printer while simultaneously UV cured during layer-by-layer deposition. Nanocomposite inks were characterized for their viscosity before curing, and dispersion of the nHA particles and tensile mechanical properties after curing. Proliferation and differentiation of human bone marrow-derived mesenchymal stem cells (BM-MSCs) were studied by seeding cells onto the scaffolds and culturing in osteogenic differentiation medium for 7, 14 and 21 days. Overall, each of the scaffolds types demonstrated controlled morphology resulting from the printability of nanocomposite inks, well-dispersed nHA particles within the polymer matrices, and were shown to support cell proliferation and osteogenic differentiation after 14 and 21 days of culture. However, the nature of the functional groups present in each ink detectably affected the mechanical properties and cytocompatibility of the scaffolds. For example, while the incorporation of HEA reduced nHA dispersion and tensile strength of the final nanocomposite, it successfully enhanced shear yield strength, and printability, as well as cell adhesion, proliferation and osteogenic differentiation, establishing a positive effect perhaps due to additional hydrogen bonding.