Enhanced in vitro biocompatibility of ultrafine-grained biomedical NiTi alloy with microporous surface

► Irregularly rough, microporous and hierarchical porous surfaces were produced by sandblasting, acid etching and alkali treatment. ► Sandblasting with acid etching followed by alkaline treatment severely impaired the corrosion resistance. ► Sandblasting plus HF/HNO3 solution etching increased the apatite forming ability. ► Sandblasting enhanced cell attachment and acid etching increased cell proliferation.