Effects of hydroxyapatite content on cytotoxicity, bioactivity and strength of metakaolin/hydroxyapatite composites

Abstract

The development of new materials is a critical challenge in advancing bone repair technology. Nowadays, the use of high strength geopolymers is extended to various fields, including biomedical research. This study investigates the influence of hydroxyapatite (HAp) content on the in vitro properties and characteristics of the metakaolin/HAp (MK/HAp) composites for potential application as bone substitutes. The MK/HAp composites with varying HAp contents were fabricated and subjected to cytotoxicity, bioactivity, physical and mechanical testing. PrestoBlue assay results confirmed acceptable osteoblast cell compatibility for all composites, with cell viability increases with increasing HAp content. Simulated body fluid (SBF) immersion demonstrated enhanced bioactivity and bone-like apatite formation on the composite surfaces with increasing HAp content. The compressive strength of the composite decreased mainly due to the reduced amount of silica and alumina contents and the increased porosity with higher HAp. Based on the present results, the relationship between bioactivity and strength with variations in HAp content indicates a promising composite. The HAp content of the MK/HAp composites for a bone substitute material should be 50% or higher to match the apatite formation and strength of specific human bones.

Keywords

• Cell viability
• Apatite formation
• Compressive strength
• Geopolymer composite
• Bone substitute material