Abstract

Viability, Adhesion, and Morphology of Bone Marrow Stromal Cells on Four Magnesium-Zinc-Calcium Alloys

Aaron Cipriano, Student, University of California-Riverside

Magnesium (Mg) alloy-based implants hold great promise for orthopedic implant applications. Commercially available alloys (designed for industrial applications) contain possible toxic elements, which calls for development of new Mg alloys specifically designed for biomedical applications. From both biological and materials science points of view, Zinc (Zn) and Calcium (Ca) have been studied as promising alloying elements for Mg. The objective of this study was to investigate the degradation and cytocompatibility of four Mg-xZn-0.5Ca (x = 0.5, 1, 2, 4; weight %) alloys and their effects on adhesion and growth of bone marrow stromal cells (BMSCs) in vitro during 72 hr of cell culture. BMSCs were used due to their important role of supplying progenitor cells needed for bone remodeling and repair. The degradation of the alloys was characterized through electrochemical polarization tests and analysis of solubilized degradation products in the media. BMSC adhesion and morphology was evaluated through fluorescence and scanning electron microscopy. Our results showed that the degradation of the Mg-xZn-0.5Ca alloys throughout the 72 hr culture had no statistically significant effect on the viability of BMSCs cultured on the surface of the samples; however, a statistically significant effect was observed at 48 hr on the viability of BMSCs cultured on the plates surrounding the samples. In contrast, the cellular F-actin-area per BMSC on the sample surface was modulated by the degradation of the alloys resulting in a change of BMSC diameter; however, the cellular F-actin-area per BMSC surrounding the samples showed no statistically significant differences. Despite a change in BMSC size, the aspect ratio of the max/min diameters of the cells (both on the sample and on the plate) remained unchanged for all groups. The surface morphology of the samples was distinct for all groups and time points evaluated, suggesting a correlation between surface degradation and cell behavior.