No abstract

Due to their magneto‐mechanical coupling and biocompatibility, Fe‐Pd based ferromagnetic shape memory alloys are a highly promising materials class for application as contact‐less magneto‐mechanical transducers in biomedical environments. For use in cell and tissue actuators or strain sensors, sufficient adhesion to mediate strains clearly constitutes a prerequisite. As the RGD sequence is the most important binding motif for mammalian cells, which they express to facilitate adhesion, the potential of RGD coatings to achieve this goal is explored. Employing large‐scale density functional theory calculations the physics of bonding between RGD and Fe‐Pd surfaces, which is characterized by coordinate bonds of O and N atoms to Fe, accompanied by electrostatic contributions, is clarified. Theoretical predictions on adhesion, that are confirmed experimentally, suggest RGD as suitable strain mediator to Fe‐Pd surfaces. On the cell side, favorable adhesion properties of RGD‐coated Fe‐Pd are manifested in cell morphology and spreading behavior. Demonstrating that the adhesion forces between RGD and Fe‐Pd exceed those exerted by cells to the RGD coating, as well as traction forces acting onto integrin bonds, the findings pave the way for novel type of applications as cell and tissue actuator or sensor within the areas of tissue engineering and regenerative medicine.

Durable, mechanically robust osseointegration of metal implants poses one of the largest challenges in contemporary orthopedics. The application of biomimetic hydroxyapatite (HAp) coatings as mediators for enhanced mechanical coupling to natural bone constitutes a promising approach. Motivated by recent advances in the field of smart metals that might open the venue for alternate therapeutic concepts, we explore their mechanical coupling to sputter-deposited HAp layers in a combined experimental-theoretical study. While experimental delamination tests and comprehensive structural characterization, including high-resolution transmission electron microscopy, are utilized to establish structure-property relationships, density functional theory based total energy calculations unravel the underlying physics and chemistry of bonding and confirm the experimental findings. Experiments and modeling indicate that sputter-deposited HAp coatings are strongly adherent to the exemplary ferromagnetic shape-memory alloys, Ni-Mn-Ga and Fe-Pd, with delamination stresses and interface bonding strength exceeding the physiological scales by orders of magnitude.