Selective inhibition effects on cancer cells and bacteria of Ni–Ti–O nanoporous layers grown on biomedical NiTi alloy by anodization

Stents made of nearly equiatomic NiTi alloy are used to treat malignant obstruction caused by cancer, but prevention of re-obstruction after surgery is still a challenge because the bare stents possess poor anticancer and antibacterial properties to inhibit cancer/bacteria invasion. The present work aims at endowing the NiTi alloy with anticancer and antibacterial abilities by surface modification. Ni–Ti–O nanoporous layers with different thicknesses were prepared on NiTi by anodization, and biological experiments were conducted to evaluate the effects on gram-positive Staphylococcus aureus, human lung epithelial cancer cells (A549), as well as human endothelial cells (EA. hy926). The nanoporous layer with a thickness of 10.1 μm inhibits growth of cancer cells and kill bacteria but shows little adverse effects on normal cells. Such selectivity is related to the larger amount of Ni ions leached from the sample in the acidic microenvironment of cancer cells in comparison with normal cells. The Ni–Ti–O nanoporous layers are promising as coatings on NiTi stents to prevent re-obstruction after surgery.