LIGAS À BASE DE COBALTO, CROMO E TÂNTALO PARA POTENCIAL APLICAÇÃO BIOMÉDICA: Da concepção ao estudo in vivo

Abstract

Cobalt-chromium (Co-Cr) alloys are widely recognized in the medical field for their bioinertness, corrosion resistance, and excellent mechanical properties. However, the continuous demand for materials with superior properties has driven investigations into novel compositions. One promising way involves the addition of tantalum (Ta), a material known for its bioactivity and ability to promote cell proliferation. This work developed and characterized a new series of Co(72-x)Cr(28)Ta(x) (x = 0, 3, 6, and 9 % w/w) for biomedical applications. The alloys were synthesized by arc-melting and analyzed by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS), Vickers Microhardness, Atomic Force Microscopy (AFM), Potentiodynamic Polarization (PDP) and Electrochemical Impedance Spectroscopy (EIS). Furthermore, the samples underwent surface modification via anodization, followed by wettability measurements, immersion in simulated body fluid, and in vivo testing to assess their biological response. The results revealed that the addition of Ta promoted: formation of Co allotropes (εCo and αCo) and an extra TaCo2 phase (from 3 % w/w); dendritic microstructure; increase in microhardness by ~ 77% in the sample with 9 % w/w (466 HV0.5); increase in the local potential difference between the Co-Cr matrix (εCo and αCo) and the extra phase (TaCo2) by ~ 1500% in the sample with 9 % w/w (687 mV); and, increase in hydrophilicity by ~ 7% in the sample with 9 % w/w (71 °). The combination of AFM, PDP and EIS techniques revealed the matrix with an anodic nature and the extra phase with a cathodic nature (higher nobility). Anodization generated nanostructures (~40-50 nm), pores (~0.8 µm), and cellular viability (> 100%). The 6 % w/w alloy excelled in spontaneous calcium phosphate nucleation (~ 1.3 µm), indicating high bone-contact potential, while the anodized 9 % w/w exhibited hydrophobicity (θ ~ 94 °), ideal for non-adherent applications. At the macroscopic level, the 9% w/w alloy exhibited a corrosion resistance profile similar to samples commonly used in the biomedical field (corrosion rate ~10-4 mm/year), in addition to presenting in vivo biocompatibility without adverse effects. Our findings indicate that Ta modulates the properties of Co-Cr alloys, with the 6 and 9% w/w compositions being the most promising for specific applications, combining bioactivity, mechanical strength, and biocompatibility.