Alumina Foam (AF) Fabrication Optimization and SBF Immersion Studies for AF, Hydroxyapatite (HA) Coated AF (HACAF) and HA-bentonite Coated AF (HABCAF) Bone Tissue Scaffolds

Abstract

The aim of this study was to evaluate the bioactivity response of alumina (Al2O3) coated scaffold for bone tissue engineering (BTE) applications. The porous alumina (alumina foam, AF) was coated with hydroxyapatite (HA), with bentonite (Al2O3.4(SiO2).H2O) as an intermediate layer between HA and alumina. Bentonite acted as binding agent to improve the alumina-HA coating, with hope that excellent coating with HA will have a positive effect on subsequent cellular efforts, with alumina responsible for just the scaffold strength. In brief, AF has been fabricated with acceptable properties (i.e., porosity >80%, compressive strength >3 MPa, average pore size of 900-1000 μm) through polymer foam replication (PFR). After AF fabrication, initially, the AF was dipped into HA slurry and sintered at 1300°C to make HA coated AF (HACAF) scaffold. Due to poor uniformity of HA coating on the AF, the alumina foam was first dipped into bentonite slurry and sintered at 800°C before coated with HA, creating HA-bentonite coated AF (HABCAF). It was shown that with an inner-coat of bentonite (on AF), the HA coating was smoother, more uniform and more complete/thorough. The in-vitro degradability was conducted using simulated body fluid (SBF) as a preliminary study to evaluate bioactivity response for each sample (i.e., AF (as control), HACAF, HABCAF). The weight loss of the HACAF is quicker compared to HABCAF and are seen increased with longer soaking time. The ions particle precipitations were found on surface layer after 7 days for coated alumina compared to alumina skeleton. The result suggested that HABCAF offers an attractive option for fabrication of BTE scaffolds.