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Abstract

A non-radioactive metallic stent is coated with a biodegradable thin coating of less than about 100 microns in thickness selected to avoid provoking any foreign body reaction. The biodegradable material in the coating disintegrates over time in the presence of body fluid. The coating contains a radioactive source of, for example, a beta radiation emitter for irradiation of tissue when the stent is implanted in a blood vessel treated by angioplasty, to inhibit proliferation of smooth muscle cells in response to trauma to the wall of the blood vessel from the angioplasty, and thereby to prevent rapid tissue growth and consequent restenosis of the vessel. The stent coating incorporating the radioactive source constitutes a first layer adherent to and overlying the surface of the stent. The coating may further include a second layer atop the first layer, incorporating an anti-coagulant substance to inhibit thrombus formation on the stent. The radioactive source has an activity level of, for example, approximately one microcurie, and a half life which is shorter than the time interval required for the biodegradable coating to completely disintegrate. Thus, by the time the coating disappears, the effective level of radioactivity of the radioactive substance has dissipated to an extent which avoids any lingering systemic effect.

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First Claim