Polyetheretherketone‐hydroxyapatite composite filament: A comparative analysis of the effect of micro and nano hydroxyapatite particles on extrusion and performance

Abstract The performance of polyether‐ether‐ketone (PEEK) as an orthopedic biomaterial can be improved by bulk modification of PEEK through hydroxyapatite (HA) incorporation. In this context, we have studied the size effect of HA particles (from micro to nano) on the high‐temperature extrusion, physicochemical and biological properties of the extruded PEEK‐HA filaments. Our study showed that incorporation of HA into PEEK up to 5% w/w allows filament formation through single screw extrusion. However, a more significant temperature gradient between the hopper end and nozzle was necessary for the extrusion of nano‐HA incorporated PEEK compared to micro‐HA incorporated PEEK. The micro‐CT revealed a homogeneous dispersion of HA particles within the extruded filaments. The inclusion of nano HA powder (<200 nm) in PEEK (5%w/w) did not alter the mechanical properties of PEEK. When checked in vitro using MG‐63 cells, PnHA exhibited better cytocompatibility, as evidenced by calcein‐AM staining and MTT assay. Cellular expression of vascular endothelial growth factor and alkaline phosphatase was also found to be 2–3 fold higher for PnHA. Further, PnHA was found to be a promoter of angiogenesis when checked by tube formation assay. The results together implied that nano‐HA is more suitable than micro‐HA for improving the essential qualities of PEEK for orthopedic applications. Highlights Incorporation of HA in PEEK improves the performance of PEEK as a biomaterial. PEEK with 5% micro/nano HA can be extruded as PEEK‐HA composite filament. Variation in HA particle size (micro/nano) impacts the performance of composite. PEEK‐HA composite filament has improved angiogenic and osteoconductive properties.