AbstractBiodegradable Mg-based alloys have attracted increasing attention from orthopedic surgeons and biomaterials scientists since their Young’s modulus is close to that of bone. However, control of the degradation rate is still a challenge. Sputtered TiO2 coatings were deposited on Mg-Zn-Ca alloys aiming to reduce the initial strong reactivity of Mg with biological fluids. However, the degradation tests indicated that the coated samples induced a larger variation in the pH, greater H2 production and formation of degradation products in comparison to the bare alloys. Consequently, an enhanced cytotoxicity of the coated samples was observed.