Medical devices, particularly stents, and methods for their manufacture

Abstract

A medical device which includes a component formed from an alloy which contains at least about 40% Ni by weight. The alloy in a 10 nm deep surface region of the component contains not more than about 10% Ni by weight. The Ni content in that surface region can be reduced by polishing and oxidizing treatment such as (a) exposure to superheated steam, or (b) immersion in a chemical solution, or (c) an electrochemical treatment, using the device as the anode in a solution bath with a current running therethrough.

What is claimed is:  
     
         1 . A medical device which includes a component formed from an alloy which contains at least about 40% Ni by weight, the device having a 10 nm deep surface region of containing not more than about 5% Ni by weight.  
     
     
         2 . A device as claimed in  claim 1 , in which the alloy in the said surface region contains not more than about 3% Ni.  
     
     
         3 . A device as claimed in  claim 1 , in which the alloy has been subjected to polishing and oxidizing treatment on said surface region.  
     
     
         4 . A device as claimed in  claim 3 , in which the said polishing treatment comprises an electrochemical or mechanical treatment.  
     
     
         5 . A device as claimed in  claim 3 , in which the said oxidizing treatment comprises at the steps of exposure to superheated steam, a chemical treatment and an electrochemical treatment.  
     
     
         6 . A device as claimed in  claim 1 , in which the alloy is a Ni—Ti based alloy.  
     
     
         7 . The device of  claim 5 , in which the said electrochemical oxidizing treatment comprises anodizing in a acidic, neutral or basic solution.  
     
     
         8 . A device as claimed in  claim 1 , in which the device has been treated so that it exhibits superelastic properties.  
     
     
         9 . A device as claimed in  claim 1 , in which the alloy contains at least about 48% Ni by weight.  
     
     
         10 . A device as claimed in  claim 9 , in which the alloy contains at least about 50% Ni by weight.  
     
     
         11 . A device as claimed in  claim 1 , in the form of a stent.  
     
     
         12 . A method of making a medical device comprising a component formed from an alloy which contains nickel, which includes the step of exposing the component in a surface region thereof to a treatment which causes the Ni content of the alloy in that region to be reduced compared with that in the remainder of the component.  
     
     
         13 . The method of  claim 12  wherein said device is a stent.  
     
     
         14 . A method as claimed in  claim 12 , in which the component is exposed to superheated steam.  
     
     
         15 . A method as claimed in  claim 14 , in which the component is exposed to steam for at least about 3 hours.  
     
     
         16 . A method as claimed in  claim 14 , in which the steam is heated to at least about 120° C.  
     
     
         17 . A method as claimed in  claim 13 , in which the said treatment comprises a chemical treatment, in which the device is immersed in an acidic, neutral or basic chemical solution bath.  
     
     
         18 . A method as claimed in  claim 17 , in which the said treatment comprises a chemical treatment, in which the device is immersed for at least about 0.5 hour.  
     
     
         19 . A method as claimed in  claim 12 , in which the said treatment comprises an electrochemical treatment, in which the device is included in an electrochemical system as an anode in a solution bath with current running therethrough.