Surface characteristics, properties and in vitro biological assessment of a NiTi shape memory alloy after high temperature heat treatment or surface H2O2-oxidation: A comparative study

► A titania gel layer was prepared on NiTi SMA by a low temperature H2O2-oxidiation. ► Abundant Ti-OH functional groups were detected on the titania gel layer. ► The titania gel layer was more chemically stable than the oxide layer on heat treated NiTi SMA. ► The titania gel layer on NiTi SMA facilitated cell attachment, spread and proliferation. ► Properties of oxide layers formed by two methods were systematically investigated and compared.