Biocompatibility of Single Crystalline Ferromagnetic Shape Memory Films for Cell Actuation

Abstract

Ferromagnetic shape memory alloys (FSMAs) have received great attention recently as an exciting class of smart functional materials. They exhibit large reversible strains of several percent at moderate stresses due to an external magnetic field induced reorientation of twin variants in the martensitic phase. External controllability at constant temperatures and sufficiently high strains thus make them excellent candidates for biomedical actuation devices, such as surgical implant materials, applying for bone prostheses or drug delivery systems. In comparison to conventional shape memory alloys, FSMA bears the significant potential for miniaturized devices for single cell actuation which is capable of yielding magnetically controllable shear strains and/or volume dilations of several percent, thus perfectly matching the requirements of cell investigations. However, the biocompatibility of this material must first be well confirmed as it has not been done yet. Thus, our work focuses on the interaction of fibroblast cells with single crystalline Fe70Pd30 FSMA films on MgO substrates. Additionally, corrosion resistance of the films was obtained employing simulated body fluid (SBF) tests. Calcium-phosphate aggregates with granular microstructure were detected on the film surface after soaking in SBF. Cell viability and biocompatibility tests with NIH 3T3 cells revealed that the cells adhered and proliferated on the surface of the FSMA, whereas cells were smaller compared to cells on culture dish surfaces. Biocompatible polymer coatings on the Fe70Pd30 film can be employed to improve cell proliferation and cell-substrate interactions.