Reduced temperature sterilization of stents
Methods and systems for reduced temperature radiation sterilization of stents are disclosed.
1. A method of sterilizing a stent comprising:
providing a stent-catheter assembly including a polymer stent crimped to a balloon of a balloon catheter, the stent having a stent strut and a crimped diameter;
selecting a sterilization temperature for the stent, wherein the sterilization temperature is selected by criteria including reducing a number of cracks in the stent strut after the stent is made sterile and expanded from the crimped diameter to a deployed diameter by the balloon, the sterilization temperature being below ambient temperature;
cooling the stent to the sterilization temperature; and
exposing the cooled stent to a dose of radiation.
2. The method of claim 1 , wherein the dose of radiation is sufficient to sterilize the stent.
3. The method of claim 1 , wherein the sterilization temperature is less than 0.degree. C.
4. The method of claim 1 , wherein the stent comprises a biostable polymer, biodegradable polymer, or a combination thereof.
5. The method of claim 1 , wherein the stent comprises a coating including a biostable polymer, biodegradable polymer, drug, or a combination thereof.
6. The method of claim 1 , wherein the radiation is selected from the group consisting of e-beam, gamma ray, ultraviolet, infra-red, ion beam, x-ray, and laser.
7. The method of claim 1 , wherein the exposing is repeated one or more times.
8. The method of claim 1 , wherein the cooling step occurs before and after the exposing the step, wherein the cooling step slows down a rate of modification of a polymer material of the polymer stent that is induced following the exposing step.
9. The method of claim 8 , wherein the exposing step includes exposing the stent to a plurality of doses of radiation and wherein the cooling step occurs only prior to a first of the plurality of doses of radiation and after a last of the plurality of doses of radiation.
10. The method of claim 1 , wherein the exposing step includes exposing the stent to a plurality of doses of radiation, and wherein the cooling step occurs at least during the exposing step.
11. The method of claim 1 , further including the step of placing the stent-catheter assembly in a sterile packaging before or after the exposing step.
12. The method of claim 11 , wherein the sterile packaging includes a cold medium pocket for receiving a cold medium.
13. The method of claim 12 , further including the step of placing a cold medium in the pocket before, during or after the exposing step to assist with attaining or maintaining a temperature near the sterilization temperature.
14. The method of claim 1 , further including the step of placing the stent-catheter assembly on a cold slab for lowering or maintaining the stent-catheter assembly temperature to near the sterilization temperature.
15. The method of claim 1 , wherein the polymer for the stent is poly(L-lactide), the stent further including a poly(DL-lactide)-drug coating.
16. The method of claim 1 , wherein the stent is a poly(L-lactide) stent.
17. The method of claim 1 ,
further including providing a radiation barrier adjacent to the stent;
wherein the radiation barrier is arranged such that an uniformity of dose received by the stent is increased over a dose received by the stent in the absence of the barrier.
18. The method of claim 17 , wherein the radiation barrier is arranged such that the uniformity of dose received by the stent is increased over a portion of the balloon catheter portion of the stent-catheter assembly.
19. The method of claim 17 , wherein the cooling step takes place before and after the exposing step.
20. The method of claim 17 , wherein the radiation barrier is made of a foam material.
21. The method of claim 17 , further providing a container comprising the radiation barrier.
22. A method of sterilizing a medical device, comprising:
providing a stent-catheter assembly including a poly(L-lactide) stent crimped to a balloon of a balloon catheter, the stent having a stent strut;
selecting a pre-sterilization temperature for reducing a number of cracks in the stent strut after the stent is made sterile;
cooling the stent-catheter assembly to the pre-sterilization temperature;
exposing the stent-catheter assembly to a dose of radiation sufficient to sterilize the stent-catheter assembly; and
cooling the stent-catheter assembly to a post-sterilization temperature below ambient temperature after exposing the stent-catheter assembly to the dose of radiation, wherein the post-sterilization temperature slows down a rate of modification of the poly(L-lactide) that is induced following the exposing step.
23. The method of claim 22 , wherein the step of exposing the stent-catheter assembly to a dose of radiation includes exposing the stent-catheter assembly to a plurality of doses of radiation, wherein the cooling the stent-catheter assembly to the pre-sterilization temperature occurs only prior to a first of the plurality of doses of radiation.
24. The method of claim 22 , wherein the pre-sterilization temperature is selected to reduce the number of cracks having a length that is over 25% of the width of stent struts after the stent has been deployed by the balloon.