Design and characterisation of PEI/HA filaments for fused filament fabrication (FFF) in biomedical applications

Polyetherimide (PEI) has recently been used in additive manufacturing as it possesses excellent mechanical and thermal properties. These properties have led to its applications across industries including aerospace, automotive, and medical industries. The use of high-performance polymers (HPP) possess attractive properties in relation to medical devices; however, concerns remain with respect to bioactivity. Addition of bioactive fillers to mitigate against this has been considered, such as hydroxyapatite (HA), the main mineral component of human bone. This study considers the preparation and characterisation of PEI-based filaments containing 10, 20, and 30 wt.% of HA and then subsequently printed using fused filament fabrication (FFF). Mechanical, thermal, and morphological analysis was performed. Bioactivity was investigated via immersion in simulated body fluid (SBF) and cell studies conducted using mesenchymal stem cells (MSC). Results revealed a significant decrease in ultimate tensile strength (UTS) compared to neat PEI. Young’s modulus peaked at 1683 MPa for PEIHA-20%. Scanning electron microscopy (SEM) and SEM-energy dispersion X-rays (EDX) confirmed apatite-like precipitates through the detection of calcium and phosphorus elements on the top surface of the samples after 7 days of immersion. Cell metabolic activity increased from day 1 to 3 and plateaued at day 7. The results demonstrate that the addition of hydroxyapatite to PEI is a promising material candidate for further biomedical evaluation.