Method to minimize chain scission and monomer generation in processing of poly(l-lactide) stent

Abstract

Methods of fabricating an implantable medical devices such as stents made from biodegradable polymers are disclosed that reduce or minimize chain scission and monomer generation during processing steps. The method includes processing a poly(L-lactide) resin having an number average molecular weight between 150 to 200 kD in an extruder in a molten state. A poly(L-lactide) tube is formed from the processed resin and a stent is fabricated from the tube. The number average molecular weight of the poly(L-lactide) of the stent after sterilization is 70 to 100 kD.

1 - 14 . (canceled) 
     
     
         15 . A stent scaffolding crimped over a delivery balloon within a package,
 wherein the stent scaffolding is made of a lactide-based polymer, and   wherein a number average molecular weight (Mn) of the stent scaffolding prior to sterilizing with e-beam radiation is 100 to 150 kD and the Mn of the stent scaffolding after sterilizing with e-beam radiation is 70 to 110 kD.   
     
     
         16 . The method of  claim 15 , wherein a dose of the e-beam exposure is between 20 and 35 kGy. 
     
     
         17 . The method of  claim 15 , wherein the polymer comprises poly(L-lactide). 
     
     
         18 . The method of  claim 15 , wherein the polymer comprises poly(L-lactide-co-caprolactone). 
     
     
         19 . A stent comprising:
 a stent scaffolding comprising a bioresorbable aliphatic polyester polymer having a number average molecular weight of 70 to 110 kD, wherein the stent scaffolding is made by steps comprising:   processing a resin of the polymer in a molten state, the polymer having an Mn between 150 to 200 kD prior to the processing step;   forming a tube from the processed resin;   fabricating a stent scaffolding from the tube; and   sterilizing the stent scaffolding through exposure to e-beam radiation, wherein the Mn of the stent scaffolding prior to sterilizing is 100 to 150 kD.   
     
     
         20 . The method of  claim 19 , wherein the polymer comprises poly(L-lactide). 
     
     
         21 . The method of  claim 19 , wherein the polymer comprises poly(L-lactide-co-caprolactone). 
     
     
         22 . The method of  claim 19 , wherein the stent scaffolding is crimped over a delivery balloon within a package.