THE POTENTIAL OF ELECTRICAL HETEROGENEITY IN MODULATING FIBROBLAST VIABILITY IN Co-Cr-Ta ALLOYS

Cobalt-chromium (Co-Cr) alloys are widely used as biomaterials due to their mechanical and corrosion resistance properties. In orthopedic applications, their bioinercity is a limitation. Variations in chemical composition and surface modification processes are efficient strategies to enhance alloys. In this sense, this work aimed to investigate the role of composition, through the addition of tantalum (Ta), and anodization on the structure, topography, wettability, surface potential/work function, and cytocompatibility in Co_72-xCr₂₈Ta_x alloys (x = 0, 3, 6, and 9% w/w). The alloys were synthesized by melting in an arc furnace, sliced, polished, and anodized (2V for 20s in H₂SO₄ and HF). The samples were characterized by X-ray Diffraction (XRD), Raman Spectroscopy, Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS), Kelvin Probe Force Microscopy (KPFM), and wettability. Cytocompatibility was evaluated with L929 fibroblasts (ISO 10993-528) after 24 and 48 hours. XRD identified the formation of Co allotropes and the extra TaCo₂ phase in the polished samples, and did not reveal crystalline oxides in the anodized samples, correlating with SEM/EDS data showing a localized distribution of the elements. Meanwhile, Raman spectra confirmed the formation of Co, Cr, and Ta oxides in the anodized samples. Anodization generated complex topographies according to KPFM measurements: micrometric pores and spherical nanoparticles (diameter of ~27-50 nm), with increased surface area and roughness. The wettability of the polished samples increased with Ta content (hydrophilicity), while in the anodized samples it decreased, becoming hydrophobic at 9% w/w Ta (θ ~ 94º). The central finding was that cell viability (up to 165% of the control in 48h) correlated strongly with the heterogeneity of the surface potential/work function) induced by TaCo₂ phase segregation. Polished samples with heterogeneous potential (3 and 9% Ta) stimulated greater cell proliferation than those with homogeneous potential (0 and 6% Ta), presumably by mimicking the natural microenvironment of the extracellular membrane. All samples were non-cytotoxic. Thus, electronic heterogeneity emerges as a key parameter for modulating the cellular response of fibroblasts in Co-Cr-Ta alloys, overcoming the influence of topographic and wettability factors.