(A-35) Improving the Flexibility of Polycaprolactone-based Small Diameter Vascular Grafts through Plasticizer Incorporation

Introduction:: Small diameter vascular grafts (SDVGs, < 6 mm) often present a high incidence of failure due to their tendency to develop thrombosis and obstruction. Polycaprolactone (PCL) has been extensively studied as a material for vascular graft fabrication due to its biocompatibility and biodegradability. However, PCL's high Young's modulus and stiffness can cause mechanical mismatch with the native vascular tissue. In addition, PCL's high Young's modulus and stiffness also makes it a difficult material to suture or shape into complex geometries, which is necessary in the fabrication of vascular grafts. Therefore, while PCL shows promise as a vascular graft material, further research is needed to address these limitations and customize its mechanical and biological properties for use in clinical applications.


Materials and Methods::
To improve the flexibility of 3D printed SDVGs, different concentrations of plasticizer have been added to PCL (Mw 80000) solution in tetrahydrofuran and stirred for 30 minutes. The resulting solutions were casted into glass petri dishes and allowed to dry under the hood for 48h. The mechanical properties of the prepared films were evaluated using a SANTAM STM-20 testing machine fitted with a load cell of 100 N. The samples (n=6, 20 mm x 10 mm x 1 mm) were tested at a constant strain speed of 50 mm/min to determine the ultimate tensile strength, elongation, and Young's modulus based on the stress-strain curves and the initial linear slope.




Results, Conclusions, and Discussions:: The addition of different concentrations of plasticizer to PCL significantly reduced its Young's modulus (282 ± 49.49 MPa). The PCL film containing 40 wt% plasticizer gave the best Young's modulus (160.5 ± 13.435 MPa) being similar to vascular tissue, which is within the optimum range for SDVGs' fabrication. The reduction in Young's modulus of PCL films with the addition of plasticizer is attributed to the plasticizer molecules that increase the distance between PCL chains and decrease the intermolecular forces and interchain interactions. The resulting decrease in stiffness and increased flexibility of the PCL films with plasticizer is advantageous for the fabrication of vascular grafts with improved mechanical properties comparable to native tissues. Moreover, the films with reduced Young's modulus can be easily shaped into complex geometries and sutured in large animal models. The reduced Young's modulus achieved with this plasticizer-based PCL represents a step forward in the development of biodegradable scaffolds with tissue regeneration capacities. The principle is applicable to the cardiovascular field and engineering of other tissues, providing a promising avenue for the development of medical devices.




Acknowledgements (Optional): : This work was sponsored by the Flemish Research Foundation (FWO) awarding a postdoctoral grant to FK (1291021N) and a fundamental clinical research mandate to RH (1881820N). This work was also supported by the Internal Research Fund KU Leuven (STG/19/009) and the Clinical Research Fund UZ Leuven.

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