Deposition of hydroxyapatite onto shape memory NiTi wire

This study investigates the deposition of hydroxyapatite (HA, Ca10(PO4)6(OH)2) onto shape memory NiTi wire using an ambient temperature blast process. Hydroxyapatite is a potential alternative to polymeric coatings as a drug delivery system. Polymer coatings used as the drug delivery systems can result in an inflammatory response and late stage thrombosis. The shape memory properties of NiTi are sensitive to stress and temperature. The aim of this study is to assess what impact the process has on the bulk shape memory properties of the wire. The coating was characterised using light microscopy, backscattered scanning electron microscopy and X-ray diffraction. The shape memory properties of the wire after coating were compared to the as-supplied wire. The process can be used to produce a highly adherent coating on the surface of the NiTi wire. There was no significant difference in the shape memory properties after coating compared to the as-supplied NiTi wire. The work indicates that the process may be used to deposit hydroxyapatite onto the surface of a stent to act as a drug-delivery system, without impairing the shape memory properties of the stent.