Tri-layered Electrospinning to Mimic Native Arterial Architecture using Polycaprolactone, Elastin, and Collagen: A Preliminary Study

Summary

The aim of this study was to mimic the native three layered architecture of the arterial wall. To accomplish this, electrospinning was employed with the use of a 3-1 (input-output) nozzle and blends of polycaprolactone, elastin, and collagen.

Abstract

Throughout native artery, collagen and elastin play an important role, providing a mechanical backbone, preventing vessel rupture, and promoting recovery under pulsatile deformations. The goal of this study was to mimic the structure of native artery by fabricating a multi-layered electrospun conduit composed of poly(caprolactone) (PCL) with the addition of elastin and collagen with blends of 45-45-10, 55-35-10, and 65-25-10 PCL-ELAS-COL to demonstrate mechanical properties indicative of native arterial tissue, while remaining conducive to tissue regeneration. Whole grafts and individual layers were analyzed using uniaxial tensile testing, dynamic compliance, suture retention, and burst strength. Compliance results revealed that changes to the middle/medial layer changed overall graft behavior with whole graft compliance values ranging from 0.8 - 2.8 % / 100 mmHg, while uniaxial results demonstrated an average modulus range of 2.0 - 11.8 MPa. Both modulus and compliance data displayed values within the range of native artery. Mathematical modeling was implemented to show how changes in layer stiffness affect the overall circumferential wall stress, and as a design aid to achieve the best mechanical combination of materials. Overall, the results indicated that a graft can be designed to mimic a tri-layered structure by altering layer properties.

Protocol

1. Prior to electrospinning, collagen, from 6 month bovine corium, must be extracted using an acetic acid based process. This extracted collagen is then purified through a subsequent series of dissolutions, precipitations, and dialyses. Once collagen is lyophilized, the electrospinning process can begin.
2. Three materials are massed: polycaprolactone (PCL), elastin (ELAS), and collagen (COL). These materials will be separately dissolved in 1,1,1,3,3,3 hexafluoro-2-propanol (HFP, TCI America) at concentrations of 100 mg/ml, 200 mg/ml, and 70 mg/ml, respectively.
3. The materials are blended in five different scintillation vials at volumetric ratios of 98-2-0 PCL-EL....

Discussion

The most critical portion of this study is the electrospinning process. When using a 3-1 input-output nozzle, arching and charge loss may occur. If this does occur, the voltage associated with the polymer that is spinning will decrease causing welded, "wet" fibers and creating delamination between each of the three layers. Therefore, consistent electric potentials are essential to obtain an ideal multi-layered tube.

Compliance mismatch is one of the main causes of graft occlusion at the sm.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Polycaprolactone	Sigma-Aldrich
Elastin	Elastin Products Company
Collagen
Acetic Acid	Fisher Scientific
Sodium Chloride	Fisher Scientific
TRIS	Fisher Scientific
6 L Avanti J-HC Centrifuge	Beckman Coulter Inc.
1,1,1,3,3,3 hexafluoro-2-propanol	TCI America
3 ml Becton Dickinson Syringe
CZE1000R Rack Mount Power Supply	Spellman
High-Pressure Syringe Pump	Cole-Parmer
1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide	Pierce, Thermo Scientific
70 % ethanol	Sigma-Aldrich
ImageTool 3.0 software	Shareware provided by UTHSCSA
Scanning Electron Microscope	Carl Zeiss, Inc.
MTS Bionix 200 testing system	MTS Systems Corp.
TestWorks version 4
Intelligent Tissue Engineering via Mechanical Stimulation (ITEMS) Bioreactor	Tissue Growth Technologies