Effect of Fe-Mg co-incorporation on the mechanical properties, biodegradation, osteogenesis and immunoregulation in vitro of 3D printed biphasic calcium phosphate bioceramics

Introducing functional elements to biomaterials is a widely recognized effective strategy to enhance their biological properties. In this study, iron (Fe) and magnesium oxide (MgO) were co-incorporated into biphasic calcium phosphate (BCP) bioceramics fabricated by vat polymerization (VPP) technique to regulate the microstructure, mechanical properties, biodegradation, biocompatibility and bioactivity. Our results showed the decrease of curing depth of BCP slurries was mainly owing to the addition of Fe. The incorporation of Fe increased the grain size, but co-incorporation of MgO decreased the grain size again. The co-incorporation of Fe and MgO increased the porosity of BCP scaffolds, and decreased their compressive strength. However, the single addition of Fe increased the compressive strength. The introducing of Fe suppressed the degradation of BCP, but Fe-Mg co-doped BCP showed faster degradation than BCP with Fe alone. However, the addition of MgO diminished the formation of bioactive apatite. In vitro, Fe-Mg co-doped BCP showed good biocompatibility, and 0.5Fe2Mg-BCP showed the best capacity on promoting osteogenic differentiation of MC3T3-E1. Fe-Mg co-doped BCP obviously regulated the RAW 264.7 polarization, inflammatory and anti-inflammatory activities which are favor of osteogenesis. This work demonstrated that the co-doping of Fe²⁺ and Mg²⁺ was favor of promoting osteogenic differentiation and Fe-Mg co-doped BCP was a promising biomaterial for bone regeneration.