Unveiling the main factors triggering the coagulation at the SiC ‐blood interface

Hemocompatibility is the most significant criterion for blood-contacting materials in successful in vivo applications. Prior to the clinical tests, in vitro analyses must be performed on the biomaterial surfaces in accordance with the ISO 10993-4 standards. Designing a bio-functional material requires engineering the surface structure and chemistry, which significantly influence the blood cell activity according to earlier studies. In this study, we elucidate the role of surface terminations and polymorphs of SiC single crystals in the initial stage of the contact coagulation. We present a detailed analysis of phase, roughness, surface potential, wettability, consequently, reveal their effect on cytotoxicity and hemocompatibility by employing live/dead stainings, live cell imaging, ELISA and Micro BCA protein assay. Our results showed that the surface potential and the wettability strongly depend on the crystallographic polymorph as well as the surface termination. We show, for the first time, the key role of SiC surface termination on platelet activation. This dependency is in good agreement with the results of our in vitro analysis and points out the prominence of cellular anisotropy. We anticipate that our experimental findings bridge the surface properties to the cellular activities, and therefore, pave the way for tailoring advanced hemocompatible surfaces

Revealing bactericidal events on graphene oxide nano films deposited on metal implant surfaces

At a time when pathogens are developing strong resistance to antibiotics, ,the demand for microbe-killing surfaces on implants has increased significantly. To achieve this goal, profound understanding of the underlying mechanisms is crucial. We show that graphene oxide (GO) nano-films deposited on stainless steel (SS316L) exhibit superior antibacterial features. The physicochemical properties of GO itself have a crucial impact on the biological events and their diversity may account for the contradictory results reported elsewhere. However, essential properties of GO coatings, such as oxygen content and resulting electrical conductivity, have been overlooked so far. We hypothesized that the surface potential and electrical resistance of the oxygen content in the GO-nano films may induce bacteria-killing events on the conductive metallic substrates. In our study, GO applied contains 52 wt.% of oxygen, thus exhibits insulating properties. Deposited as nano-film on an electrical conducting steel substrate, GO flakes induce a Schottky-barrier in the interface, which, in consequence, inhibits the transfer of electrons to the conducting, underlying substrate. Deposited as nano-film on an electrical conducting steel substrate, GO flakes can induce Schottky-barrier in the interface, which, in consequence, inhibits the transfer of electrons to the conducting, underlying substrate. Consequently, this generates reactive oxygen species (ROS), resulting in bacteria-death. We confirmed the presence of GO coatings and their hydrolytic stability by using X-ray photoelectron spectroscopy (XPS) XPS, μRaman spectroscopy, scanning electron microscopy (SEM), and Kelvin probe force microscope (KPFM) measurements. The biological evaluation was performed on the MG63 osteoblast-like cell line and two elected bacteria species: S. aureus and P. aeruginosa, demonstrating both, cytocompatibility and antibacterial behavior of GO-coated SS316L substrates. We propose a two-step bactericidal mechanism: electron transfer from the bacteria membrane to the substrate, followed by ROS generation. This mechanism is supported by changes in contact angle, surface potential, and work function, identified as decisive factors