Advanced manufacturing of coil-reinforced multilayer vascular grafts to optimize biomechanical performance

Abstract

Small diameter vascular grafts require a complex balance of biomechanical properties to achieve target burst pressure, arterial compliance-matching, and kink resistance to prevent failure. Iterative design of our multilayer vascular grafts was previously used to achieve high compliance while retaining the requisite burst pressure and suture retention strength for clinical use. To impart kink resistance, a custom 3D solution printer was used to add a polymeric coil to the electrospun polyurethane graft to support the graft during bending. The addition of this reinforcing coil increased kink resistance but reduced compliance. A matrix of grafts were fabricated and tested to establish key structure-property relationships between coil parameters (spacing, diameter, modulus) and biomechanical properties (compliance, kink radius). A successful graft design was identified with a compliance similar to saphenous vein grafts (4.1 ± 0.4 %/mmHgx10⁻²) while maintaining a kink resistance comparable to clinically used synthetic grafts. To explore graft combinations that could increase graft compliance to match arterial values while retaining this kink resistance, finite element (FE) models of compliance and kink radius that simulated experiment testing were used. The FE-predicted graft compliance agreed well with experimental values. Although the kink model over-predicted the experimental kink radius values, key trends between graft parameters and kink resistance were reproduced. As an initial proof-of-concept, the validated models were then utilized to parse through a targeted graft design space. Although this initial parameter range tested did not yield a graft that improved upon the previous balance of graft properties, this combination of advanced manufacturing and computational framework paves the way for future model-driven design to further optimize graft performance.

Statement of Significance

The development of a small-diameter vascular graft requires a balance of key biomechanical properties to prevent failure. To impart kink resistance, a polymeric coil was applied. A matrix of grafts was tested to establish structure-property relationships between coil parameters and biomechanical properties. A successful graft design was identified with a compliance similar to saphenous vein grafts and kink resistance within range of clinically grafts. Finite element models for compliance and kink resistance were developed to optimize graft performance. The validated models were utilized to parse a targeted design space. Although this initial range did not yield a graft that improved upon the previous graft properties, this combination of advanced manufacturing and computational framework paves the way for future model-driven design.