Post electron beam conditioning of polymeric medical devices

Abstract

Methods are disclosed for conditioning a polymeric stent after sterilization, and/or after crimping and before packaging, such that the properties of the polymeric stent fall within a narrower range of values. The stent is exposed to a controlled temperature at or above ambient for a period of time after radiation sterilization and/or after crimping and before sterilization. As a result, the polymeric stent properties, particularly radial strength and number-average molecular weight of the polymer of the polymeric stent, fall within a narrower range.

1 . (canceled) 
     
     
         2 . A method for conditioning a polymeric stent, the method comprising:
 selecting a specified value of a radial strength of a polymeric stent including a polymeric scaffolding to result from exposing the polymeric stent to a controlled temperature for a duration of time, wherein the specified value is a 10% to 40% decrease from an initial value of the radial strength of the polymeric stent;   exposing the polymeric stent to the controlled temperature greater than 28 deg C. for the duration of time of at least 30 minutes sufficient to reduce the radial strength of the polymeric stent to the specified value;   wherein the polymeric scaffolding is made of a polymer derived from reaction of monomers including L-lactide, and   wherein the polymeric stent has been crimped onto a delivery device, packaged, and sterilized prior to the exposure.   
     
     
         3 . The method of  claim 2 , wherein the polymeric scaffolding is formed from a polymeric tube that has been deformed by the application of stress, the deformation comprising radial expansion of the polymeric tube at a temperature greater than that of the glass transition temperature of the polymeric tube. 
     
     
         4 . The method of  claim 2 , wherein the polymeric scaffolding comprises a polymer selected from the group consisting of poly(L-lactide), poly(DL-lactide), poly(L-lactide-co-glycolide), and all combinations thereof in all proportions. 
     
     
         5 . The method of  claim 2 , wherein the scaffolding is made of a random, alternating, or block copolymer of two or more of the group of  claim 4 . 
     
     
         6 . The method of  claim 2 , wherein the exposure temperature is not higher than 20° C. below the glass transition temperature of the polymeric scaffolding. 
     
     
         7 . The method of  claim 2 , wherein the exposure temperature is 30° C. to 40° C. and the duration of exposure is 1 day to 20 days. 
     
     
         8 . The method of  claim 2 , wherein the specified value is a 10% to 20% decrease from the initial value of the radial strength. 
     
     
         9 . The method of  claim 2 , wherein the exposure temperature is controlled to within ±3° C. 
     
     
         10 . The method of  claim 2 , wherein the specified value is a pseudo-steady state or plateau value. 
     
     
         11 . The method of  claim 2 , wherein the specified value is a 30% to 40% decrease from the initial value of the radial strength. 
     
     
         12 . The method of  claim 2 , further comprising determining the specified value of the radial strength of the polymeric stent. 
     
     
         13 . A method for conditioning a polymeric stent, the method comprising:
 selecting a specified value of a number average molecular weight (Mn) of a polymeric stent including a polymeric scaffolding to result from exposing the polymeric stent to a controlled temperature for a duration of time, wherein the specified value is a 10% to 60% increase from an initial value of the Mn of the polymeric stent;   exposing the polymeric stent to the controlled temperature greater than 28 deg C. for the duration of time of at least 30 minutes sufficient to increase the Mn of the polymeric stent to the specified value;   wherein the polymeric scaffolding is made of a polymer derived from reaction of monomers including L-lactide, and   wherein the polymeric stent has been crimped onto a delivery device, packaged, and sterilized prior to the exposure.   
     
     
         14 . The method of  claim 13 , wherein the polymeric scaffolding is formed from a polymeric tube that has been deformed by the application of stress, the deformation comprising radial expansion of the polymeric tube at a temperature greater than that of the glass transition temperature of the polymeric tube. 
     
     
         15 . The method of  claim 13 , wherein the polymeric scaffolding comprises a polymer selected from the group consisting of poly(L-lactide), poly(DL-lactide), poly(L-lactide-co-glycolide), and all combinations thereof in all proportions. 
     
     
         16 . The method of  claim 13 , wherein the exposure temperature is not higher than 20° C. below the glass transition temperature of the polymeric scaffolding. 
     
     
         17 . The method of  claim 13 , wherein the duration of exposure is from about 2 days to about 6 days. 
     
     
         18 . The method of  claim 13 , wherein the exposure temperature is 30° C. to 40° C. and the duration of exposure is 1 day to 20 days. 
     
     
         19 . The method of  claim 13 , wherein the exposure temperature is controlled to within ±3° C. 
     
     
         20 . The method of  claim 13 , wherein the specified value is a pseudo-steady state or plateau value. 
     
     
         21 . The method of  claim 13 , wherein the specified value is a 10% to 40% increase from the initial value of the Mn. 
     
     
         22 . The method of  claim 13 , further comprising determining the specified value of the Mn of the polymeric stent.