Towards compliant small-diameter vascular grafts: Predictive analytical model and experiments

Area of Science:

• Biomaterials Science
• Vascular Engineering
• Mechanical Engineering

Background:

• The development of compliant vascular grafts is crucial for blood vessel replacement.
• Predictive tools are needed to identify optimal biomaterials for graft design.
• Existing synthetic grafts often lack the compliance of native arteries.

Purpose of the Study:

• To develop a simple analytical model for predicting the mechanical properties of vascular graft materials.
• To fabricate and evaluate random electrospun Polyurethane/Polycaprolactone (PU/PCL) tubular scaffolds.
• To compare the mechanical properties of PU/PCL grafts with commercial expanded polytetrafluoroethylene (ePTFE) prostheses.

Main Methods:

• An analytical model was created to calculate the ratio of ultimate stress to elastic modulus (σult/E).
• Random electrospun PU/PCL tubular scaffolds were fabricated.
• Mechanical properties (elastic modulus, compliance, burst pressure) and impermeability were experimentally tested and compared to the model and ePTFE grafts.

Main Results:

• The model predicted a minimum σult/E ratio of 1.78 for desired graft compliance and burst pressure.
• PU/PCL grafts exhibited significantly higher compliance (0.036%/mmHg) than ePTFE (0.0034%/mmHg).
• The fabricated PU/PCL scaffolds had a σult/E ratio of 1.54, below the model's threshold, and the model overestimated experimental results by 13-34%.

Conclusions:

• The analytical model serves as a useful tool for selecting materials with appropriate mechanical properties for small-diameter vascular grafts.
• Electrospun PU/PCL tubular scaffolds demonstrate superior compliance compared to commercial ePTFE grafts.
• Further refinement of the model is needed to account for material anisotropy and non-linear behavior in electrospun scaffolds.