A mechanistic analysis of delamination of elastic coatings from the surface of plastically deformed stents

Abstract

Several medical papers have reported delamination of the coating from the stent-substrate following intravascular deployment leading to adverse outcomes for patients. However, the mechanisms of delamination of such polymer coatings from the surface of a stent due to large deformations during device deployment has not been studied. In this paper, a novel and indepth investigation of the mechanisms and parameters that govern stent-coating delamination is performed, using a cohesive zone formulation to simulation the evolution of traction at the stent-coating interface. The study firstly analyses the behaviour of elastic coatings on idealised elastic stent substrates. Simulations reveal that the mode mixity of delamination is strongly dependent on the level of stent deployment at initiation. In general, peak normal tractions exceed peak shear tractions at low levels of stent deployment whereas the reverse trend is computed at high levels of stent deployment. Interface tractions increase with both increasing stent thickness and coating thickness suggesting that thinner stents and thinner coatings should be utilised for the delivery of antiproliferative drugs in order to reduce the risk of coating delamination. Next, the influence of stent plasticity on interface tractions and coating delamination is investigated. Even at low levels of deployment, plastic yielding occurs in the stent hinge region and the patterns of normal and shear tractions are found to be significantly more complex than those computed for elastic stents, with both tensile and compressive regions of normal traction occurring in the stent arch. At a high level of stent deployment shear tractions at the stent-coating interface are computed to increase with decreasing strain hardening modulus. The findings of this paper provide a new insight into the stress-state at the stentcoating interface as a function of the stent design parameters and large deformation elasticity and plasticity during deployment, allowing for a more reliable assessment of the limits relating to safe implantation of coated stents.

Incorporation of Controlled Release Systems Improves the Functionality of Biodegradable 3D Printed Cardiovascular Implants

“…93 The finite element method (FEM) can predict the structural integrity, the coating delamination, and the degradation rate which influences the controlled release systems. 94 For example, a 3D quantitative finite element model predicted the polymeric coating delamination and stress−concentration of biodegradable magnesium stents. Based on the obtained results, the design of the stent was optimized and showed an improved stress and strain distribution of the coating and no coating delamination.…”

“…Computational modeling is an innovative design strategy which can optimize the implant performance and functionality . The finite element method (FEM) can predict the structural integrity, the coating delamination, and the degradation rate which influences the controlled release systems . For example, a 3D quantitative finite element model predicted the polymeric coating delamination and stress–concentration of biodegradable magnesium stents.…”

Endothelialization strategy of implant materials surface: The newest research in recent 5 years

“…The complete remodeling of vascular wall structure is affected by many factors, such as the mechanical properties of materials, hemodynamics, plasma protein adhesion, and drug effects. 98,[201][202][203] Therefore, it is determined that the endothelialization design strategy should be a holistic consideration of the post-implantation pathological environment rather than surface modification under the influence of a single factor. This means that not only the effectiveness, feasibility, and time-sequence of the modification method need to be considered, but also the impact of the material surface on the entire vascular microenvironment, including cells, blood, and tissues (Figure 3): Implant material-Blood: After implantation, the material first faces the blood environment.…”