Biocompatibility of an additively manufactured zirconium-based bulk metallic glass: Effect of surface roughness on osteoblastic cell response

Jithin James Marattukalam, Lisa Larsson, Björgvin Hjörvarsson, Natalia Ferraz, Cecilia Persson

Uppsala University, Sweden

Zirconium-based bulk metallic glasses (BMGs) have demonstrated a combination of excellent 
mechanical and chemical properties which would make them suitable for bone implant 
applications. New manufacturing techniques of BMGs, such as laser additive manufacturing, 
provides an effective way to bypass critical casting thickness constraints associated with 
conventional manufacturing techniques, thereby allowing fabrication of components with 
desired size and geometry. Few studies have however explored the biocompatibility of additively manufactured zirconium-based BMGs. The present work therefore investigated the biocompatibility of a selectively laser melted (SLM) Zr-based BMG with composition Zr59.3Cu28.8Al10.4Nb1.5 (AMZ4) for its potential application as bone implant material.

By changing the laser power during the SLM process, the average surface roughness (Sa) of the samples was varied (11 µm to 4 µm), and its influence on cell behaviour and ion release was examined. The response of the MC3T3-E1 pre-osteoblastic cell line to the different surface roughnesses on the material was systematically investigated. Cell proliferation and differentiation studies revealed that cells cultured on AMZ4 substrates demonstrated excellent cell proliferation and high alkaline phosphatase activity, indicating promising cell response irrespective of differences in surface roughness between the samples. Ion release experiments were performed in cell culture medium under physiological and inflammatory test conditions and the ion release for different samples was quantified using inductively coupled plasma - optical emission spectrometry. A large increase in ion release was found under inflammatory conditions (with reactive oxygen species and acidic pH) as compared to physiological conditions (pH 7.5), demonstrating the importance of simulated physiological conditions when studying the ion release profile of implant materials. The findings in this work reveal the promising biocompatibility of the AMZ4 alloy towards orthopedic applications, and establishes SLM as a manufacturing technique for fabrication of Zr-based BMGs for a wide range of biomedical applications in the future.