Mechanical properties of laser cut poly(L-lactide) micro-specimens: implications for stent design, manufacture, and sterilization.
BACKGROUND
The development of endoluminal stents from polymeric materials requires an understanding of the basic mechanical properties of the polymer and the effects of manufacturing and sterilization on those properties.


METHODS
Pure poly(L-lactide) (PLLA) and PLLA containing varying amounts of triethylcitrate (TEC) as a plasticizer (5-10-15%) were studied. The specimens were solution-cast and CO2 laser-cut. Specimen dimensions were adapted to the strut size of polymeric vascular stents. The properties of the PLLA micro-specimens were assessed before and after sterilization (EtO cold gas, H2O2-plasma, beta- and gamma-irradiation). Tensile tests, and creep and recovery tests were carried out at 37 degrees C. Additionally the thermal and thermo-mechanical characteristics were investigated using dynamic-mechanical analysis (DMA) and differential scanning calorimetry (DSC).


RESULTS
The results showed the dramatic influence of the plasticizer content and sterilization procedure on the mechanical properties of the material. Laser cutting had a lesser effect. Hence the effects of processing and sterilization must not be overlooked in the material selection and design phases of the development process leading to clinical use. Altogether, the results of these studies provide a clearer understanding of the complex interaction between the laser machining process and terminal sterilization on the primary mechanical properties of PLLA and PLLA plasticized with TEC.
Grabow
Niels
N
University of Rostock, Institute for Biomedical Engineering, Ernst-Heydemann-Str 6, D-18057 Rostock, Germany. niels.grabow@medizin.uni-rostock.de
Schlun
Martin
M
Sternberg
Katrin
K
Hakansson
Nico
N
Kramer
Sven
S
Schmitz
Klaus-Peter
KP
D001672:Biocompatible Materials / Q000032:analysis / Q000737:chemistry* / Q000528:radiation effects; D001807:Blood Vessel Prosthesis; D002951:Citrates / Q000032:analysis / Q000737:chemistry; D004548:Elasticity; D019544:Equipment Failure Analysis / Q000379:methods; D007834:Lasers; D008422:Materials Testing; D008970:Molecular Weight; D010968:Plasticizers / Q000032:analysis / Q000737:chemistry; D011091:Polyesters / Q000032:analysis / Q000737:chemistry* / Q000528:radiation effects; D011474:Prosthesis Design / Q000379:methods; D015607:Stents; D013242:Sterilization / Q000379:methods*; D013696:Temperature; D013718:Tensile Strength; D044366:Transition Temperature; D014783:Viscosity
D001672:Biocompatible Materials; D002951:Citrates; D010968:Plasticizers; D011091:Polyesters; C033616:poly(lactide)