The present study was designed to improve the mechanical performance of a small-diameter vascular prosthesis made from a flexible membrane of poly(
Atherosclerotic vascular disease is one of the most common causes of death and disability worldwide [
PET monofilaments and multifilaments (30D) were purchased from Shaoxing Fangxin Chemical Fibre Company (Zhejiang, China) and used for the weft-knitted tubular fabric. The properties of PET monofilaments and multifilaments are shown in Table
Properties of polyester yarns.
Yarn code* | Yarn count (diner) | Tenacity (cN/dtex) | Elongation at break (%) | Density (g/cm3) |
---|---|---|---|---|
Mono | 30 D |
|
|
1.39 |
Multi | 30 D/22 f |
|
|
1.39 |
A PCL tubular freeze-dried graft was fabricated by dissolving PCL in acetic acid to prepare a 15wt.% solution. This solution was coated on the exterior of a 6 mm diameter PTFE rod, which served as the mould controlling the inside diameter of the tubular scaffold. Additional layers of coating were added to control the wall thickness within
Fabric densities of PET weft-knitted tube fabrics.
NO | 1 | 2 | 3 | 4 | 5 | 6 |
---|---|---|---|---|---|---|
Sample code | Mono(1) | Mono(2) | Mono(3) | Multi(1) | Multi(2) | Multi(3) |
The density | High | Medium | Low | High | Medium | Low |
The PCL solution was coated on both sides of the tubular knitted structure prior to mounting on the 6 mm diameter PTFE rod. After coating, the PCL composite scaffolds were cooled and held at –10°C for 12 h. Afterwards, the scaffolds were freeze-dried at –60°C under less than 10 Pa pressure for 5 h using an FD-1A-50 freeze drying machine. The scaffolds were subsequently immersed in a series of three distilled water baths, with each immersion lasting for 12 h, to remove residual solvents, as shown in Figure
(a) Schematic representation of new prototype vascular graft. (b) and (c) Optical images of new prototype vascular grafts.
Tensile measurements were performed on a YG061 electronic single yarn strength tester with an initial gauge length of 300 mm according to the Chinese standard GB/T 3916-1997.
The knitted structure was assessed using a Stereo Microscope PXS8-T (Nikon Co., Ltd.). Photos were taken by inserting glass (diameter of 6 mm) into the weft-knitted tubular fabric under 2x magnification.
Geometrical characteristics were determined according to ISO Standard 7198 : 1998 [
The porosities of the composite prototype vascular grafts were calculated from the density of composite using the following:
SEM experiments were performed to analyse the surface morphologies and cross sections of the PCL vascular grafts reinforced with weft-knitted tube fabric. A Jeol JSM-5600LV instrument was used. Before examination, samples were gold-sputtered under nitrogen at an excitation voltage of 15 kv.
The tensile strength of the samples (along the longitudinal and radial directions) was tested using a YG-B026H universal mechanical tester (Wenzhou Darong Textile Instrument Co., Ltd., China) according to ISO Standard 7198: 1998 [
A water reservoir was connected to a polyethylene tube. The 2.65 cm long graft (surface area of 1 cm2) was connected to two conductors, and the group was connected to the device. The water reservoir was placed in a location elevated by about 165 cm. The pressure transducer was used to verify that the distal end of the graft was constantly exposed to 120 mmHg pressure. The water (mL) permeating through the wall of the grafts (cm2) over time (min) was collected in a graduated cylinder to calculate the water permeability in mL/cm2 min. Water permeability can be expressed using (
Radial compression was tested using a YG061 radial compressive apparatus (Laizhou Electronic Instrument Co., Ltd., China). The testing method for the elastic recovery was based on the principles found in [
Calculation of the elastic recovery of prototype vascular grafts.
The suture retention strength was tested using a YG-B026H universal textile strength tester (Wenzhou Darong Textile Instrument Co., Ltd., China) according to ISO Standard 7198: 1998 [
Figure
Elongation-strength curves of polyester yarns.
Figure
Optical microscopic images of the structures of weft-knitted fabric (X2): (a)–(c) monofilament yarns and (d)–(f) multifilament yarns.
Table
Density of PET monofilament and multifilament weft-knitted tube fabrics.
Number | Sample code | Wale/(50 mm) | Course/(50 mm) | Density/fabric (2500 mm2) | Length of loop (mm) |
---|---|---|---|---|---|
A | Mono(1) | 32.0 | 67.3 | 2153.0 | 1.6 |
B | Mono(2) | 29.2 | 71.4 | 2086.5 | 1.8 |
C | Mono(3) | 19.3 | 72.7 | 1401.5 | 2.6 |
D | Multi(1) | 31.1 | 63.0 | 1959.0 | 1.6 |
E | Multi(2) | 25.1 | 68.6 | 1723.2 | 2.1 |
F | Multi(3) | 15.8 | 69.6 | 1098.5 | 2.9 |
Table
Characteristics of new composite prototype and ePTFE commercial vascular grafts.
Sample |
Fabric density (loop/2500 mm2) | Thickness |
Weight |
PCL content |
Porosity |
---|---|---|---|---|---|
Mono(1) | 2153.0 |
|
|
|
|
Mono(2) | 2086.5 |
|
|
|
|
Mono(3) | 1401.5 |
|
|
|
|
Multi(1) | 1959.0 |
|
|
|
|
Multi(2) | 1723.2 |
|
|
|
|
Multi(3) | 1098.5 |
|
|
|
|
ePTFE | — | 0.458 | 338 | — | 45.63 |
Microporous structures of PCL were fabricated using the freeze-drying method. Figure
SEM images of microstructures of (a) surface section, (b) cross section of PCL composite prototype vascular graft, and (c) surface section of ePTFE vascular graft.
Composite vascular grafts with the strength and stability of a knitted structure combine the elasticity and blood-proof properties of PCL. Table
Effect of fabric density on breaking strength and elongation at break.
Sample code | Longitudinal | Circumferential | ||
---|---|---|---|---|
Elongation at break (%) | Breaking stress (MPa) | Elongation at break (%) | Breaking stress (MPa) | |
Mono(1) |
|
|
|
|
Mono(2) |
|
|
|
|
Mono(3) |
|
|
|
|
Multi(1) |
|
|
|
|
Multi(2) |
|
|
|
|
Multi(3) |
|
|
|
|
ePTFE |
|
|
— | 4.67 |
The water permeability of the PCL/PET composite prototype small-diameter vascular graft is zero (Table
Water performance of PCL/PET composite prototype and commercial ePTFE vascular grafts.
Sample code | All our samples | Woven | Knitted | ePTFE |
---|---|---|---|---|
Manufactures | Our work | Vascutek | ||
Water permeability (mL/cm2/min) | 0 | 75.73 | 1126.3 | 0 |
General analysis of Figure
Compressive strength and elastic recovery of PCL/PET composite prototype vascular grafts.
Sample code | Fabric density (loop/2500 mm2) | Compressive strength |
Elastic recovery |
|
|||
Mono(1) | 2153.0 | 96.01 | 93.54 |
Mono(2) | 2086.5 | 94.25 | 94.16 |
Mono(3) | 1401.5 | 90.51 | 98.64 |
Multi(1) | 1959.0 | 120.9 | 92.19 |
Multi(2) | 1723.2 | 114.7 | 94.87 |
Multi(3) | 1098.5 | 105.3 | 95.90 |
Elastic recovery curves of PCL/PET composite prototype vascular grafts: (a) monofilament and (b) multifilament.
Figure
Suture strengths at break of PCL/PET composite prototype and ePTFE commercial vascular grafts.
Sample code | Mono(1) | Mono(2) | Mono(3) | Multi(1) | Multi(2) | Multi(3) | ePTFE |
---|---|---|---|---|---|---|---|
Suture strength at break (g) |
|
|
|
|
|
|
|
Suture strength at break (N) | 0.413 | 0.404 | 0.378 | 0.394 | 0.386 | 0.364 | 0.818 |
Suture retention strength curves of prototype vascular grafts with different fabric densities: (a) monofilament and (b) multifilament.
Figure
In summary, a new composite prototype vascular graft was successfully fabricated. This vascular graft features excellent pore sizes, tensile strength, water permeability, elastic recovery, and suture retention strength. The graft shows promising potential for composite scaffold development in vascular graft applications and tissue engineering.
Fabric density showed significant effects on the mechanical properties of the graft. As the loop density was increased, increases in compressive strength and suture retention strength were observed; decreases in elastic recovery, however, were further noted. Meanwhile the mechanical properties are close to or better than the commercial ePTFE graft, which indicated that the composite PCL graft is promising in potential application for small-diameter vascular graft.
The authors declare that there is no conflict of interests regarding the publication of this paper.
This work was supported by the Fundamental Research Funds for the Central Universities (Donghua University NS2013), the National Nature Science Foundation (31100682), the 111 Project “Biomedical Textile Materials Science and Technology” (B07024), and the Engineering Research Center of Technical Textiles Ministry of Education in China.