Effectiveness of various sintering aids on the densification and in vitro properties of carbonated hydroxyapatite porous scaffolds produced by foam replication technique

Abstract

Synthetic carbonated hydroxyapatite (CHA) ceramics are considered as future materials for bone substitutes due to their good bioactivity, biocompatibility and similarity to the inorganic mineralized phase of bone. However, limited thermal stability of CHA-based materials due to carbonate content at elevated temperature remains a critical challenge particularly in producing three-dimensional (3D) porous scaffolds. To address the aforementioned limitation, this paper presents a new approach by incorporating several types of sintering aids, namely Mg(OH)2, Ca(OH)2, NaOH, KOH and K2CO3 into the CHA slurry composition to identify the most effective aid in producing 3D CHA scaffolds in terms of architecture, mechanical and biological properties. This approach focused on physico-chemical, mechanical and biological characteristics that can be helpful in designing scaffolds for bone tissue engineering. Five compositions of scaffolds with different sintering aid were prepared by replication technique, sintered at 800 °C and eventually cooled down in wet CO2 atmosphere. Scaffolds prepared with K2CO3 (CHAKC) as sintering aid exhibited optimum interconnected pores with densified struts and the highest compressive strength. Biologically, CHAKC provides the most favorable environment in supporting apatite formation as well as encouraging better cell attachment and activities. Our findings highlight that the use of K2CO3 had effectively enhanced the architecture and compressive strength of the CHA scaffolds without any toxicity evidence.