Effects of annealing temperature on both radial supporting performance and axial flexibility of poly(L-lactic acid) braided stents

In this paper, the effects of annealing temperature on both radial supporting performance and axial flexibility of poly(L-lactic acid) (PLLA) braided stents are studied. Stents are annealed at a series of temperatures ranging from 80 to 160 degrees C for 1 h, then indicators of shaping effect, radial supporting performance, and axial flexibility are compared. Stents not annealed and annealed at 80 degrees C cannot be completely shaped. In contrast, stents annealed at 100 to 160 degrees C are well shaped showing radial shrinkage rate of 1.0 +/- 0.2% and almost no axial elongation. The radial compressive force and axial force are gradually increased by 51.2% and 89.2%, respectively with the annealing temperature gradually increasing from 80 to 160 degrees C, indicating that the radial supporting performance is improved but axial flexibility is weakened by a higher annealing temperature. Taken together, PLLA braided stents can be annealed at 100 to 120 degrees C to obtain sufficient radial force and lower axial force simultaneously for clinical applications. Moreover, tensile test, X-ray diffraction, and differential scanning calorimetry are performed for monofilaments annealed at different temperatures to further explore the effect mechanism of annealing temperature on the mechanical properties of stents. This study may provide helpful suggestions for the manufacture of biodegradable braided stents.

Automated summary

The study shows that PLLA braided stents annealed at 100 to 120 degrees Celsius can achieve sufficient radial force and lower axial force simultaneously, providing better support for clinical applications.