Degradation modeling of poly-l-lactide acid (PLLA) bioresorbable vascular scaffold within a coronary artery

Abstract

In this work, a strain-based degradation model was implemented and validated to better understand the dynamic interactions between the bioresorbable vascular scaffold (BVS) and the artery during the degradation process. Integrating the strain-modulated degradation equation into commercial finite element codes allows a better control and visualization of local mechanical parameters. Both strut thinning and discontinuity of the stent struts within an artery were captured and visualized. The predicted results in terms of mass loss and fracture locations were validated by the documented experimental observations. In addition, results suggested that the heterogeneous degradation of the stent depends on its strain distribution following deployment. Degradation is faster at the locations with higher strains and resulted in the strut thinning and discontinuity, which contributes to the continuous mass loss, and the reduced contact force between the BVS and artery. A nonlinear relationship between the maximum principal strain of the stent and the fracture time was obtained, which could be transformed to predict the degradation process of the BVS in different mechanical environments. The developed computational model provided more insights into the degradation process, which could complement the discrete experimental data for improving the design and clinical management of the BVS.

Application of in silico Platform for the Development and Optimization of Fully Bioresorbable Vascular Scaffold Designs

“…In Szymonowicz et al (15), the authors presented an advanced Bergstrom-Eswaran material model, based on hyperelasticity and viscoplastic effects. A similar study was described in Lin et al (29), but this approach requires a significant number of material constants. Another approach was provided by Schiavone et al (30), where material stiffening was implemented as a function of plastic strain.…”

Poly-l-Lactic Acid (PLLA)-Based Biomaterials for Regenerative Medicine: A Review on Processing and Applications

“…The optimal degradation rate of a 3D support should match that of the ECM deposition of a specific tissue [ 6 ]. The kinetics of PLLA degradation depends on its crystallinity, strain, and microstructure that follows its deployment [ 10 ]. Lower crystallinity and higher strains lead to a faster degradation rate.…”

“…Among the biodegradable polymers used for tissue engineering, poly- l -lactic acid (PLLA) has been widely studied because of its interesting mechanical properties and tailorable biodegradability [ 9 ]. As a result, it can maintain mechanical and structural integrity during in vitro and in vivo applications while supporting tissue formation [ 10 , 11 , 12 ]. PLLA belongs to the PLA family, and, compared to PDLA (created through the polymerization of D-lactide), it exhibits higher crystallinity, chemical stability, and degradation resistance to enzymes and, as a consequence, a much longer resorption time [ 1 , 13 , 14 , 15 ].…”

“…For these therapeutic applications, a low rate of biodegradation is required [ 30 , 37 ], as observed for PLLA. Hence, it is a suitable candidate for a prolonged drug delivery system [ 10 , 38 , 39 ].…”

The Development of Design and Manufacture Techniques for Bioresorbable Coronary Artery Stents

“…Lin et al developed a strain-based degradation model to estimate the dynamic interactions between the stent and the artery. The model obtained a nonlinear relationship between the maximum principal strain of the stent and the fracture time that can predict the degradation process under different mechanical conditions [ 76 ].…”