# Surface Engineering of Non-Equiatomic TiZrNbTaMo HEA by MAO Treatment in a Cu-Rich Electrolyte for Biomedical Applications

## TL;DR

This paper shows how treating a special metal alloy with a Cu-rich solution can create a surface suitable for biomedical implants by improving its structure and compatibility with bone cells.

## Contribution

The study introduces a novel MAO treatment in Cu-rich electrolyte to create bioactive and cytocompatible coatings on a non-equiatomic HEA for biomedical use.

## Key findings

- MAO treatment produced porous, bioactive oxide coatings with Cu2O and stable metal oxides.
- The treated surfaces showed improved hydrophilicity and surface roughness, beneficial for osseointegration.
- In vitro tests confirmed the cytocompatibility of Cu-incorporated coatings with MC3T3-E1 cells.

## Abstract

This study evaluated the surface functionalization of a non-equiatomic TiZrNbTaMo high-entropy alloy (HEA) by micro-arc oxidation (MAO) in Cu-rich electrolytes to tailor its performance for biomedical implants. The Cu content was varied, and the resulting coatings were investigated for their morphology, phase constitution, chemical structure, wettability, and cytocompatibility. X-ray diffraction (XRD) measurements of the substrate indicated a body-centered cubic (BCC) matrix with minor HCP features, while the MAO-treated samples depicted amorphous halo with sparse reflections assignable to CaCO3, CaO, and CaPO4. Chemical spectroscopic analyses identified the presence of stable oxides (TiO2, ZrO2, Nb2O5, Ta2O5, MoO3) and the successful incorporation of bioactive elements (Ca, P, Mg) together with traces of Cu, mainly as Cu2O. MAO treatment increased surface roughness and rendered a hydrophilic behavior, which are features typically favorable to osseointegration process. In vitro cytotoxic assays with MC3T3-E1 cells (24 h) showed that Cu addition did not induce harmful effects, maintaining or improving cell viability and adhesion compared to the controls. Collectively, MAO in Cu-rich electrolyte yielded porous, bioactive, and Cu-incorporated oxide coatings on TiZrNbTaMo HEA, preserving cytocompatibility and supporting their potential for biomedical applications like orthopedic implants and bone-fixation devices.