ev3 Protege GPS Self-Expanding Nitinol Stent Biliary System--- Sterilization with Ethylene Oxide Gas. ev3, 4600 Nathan Lane North, Plymouth, MN 55442-2920 USA. The self-expanding stent is made of nickel titanium alloy (Nitinol) and comes pre-mounted on an over-the-wire delivery system. The stent is cut from a nitinol tube into an open lattice design and is designed with tantalum radiopaque markers at the proximal and distal ends of the stent. Upon deployment, the stent achieves its predetermined diameter and exerts a constant, gentle outward force to establish patency in the biliary ducts.