| gelatin |
co-electrospinning with TPU |
HUVECs formed a monolayer that almost reached confluence similar
to physiological morphology of endothelial cells, with a cobblestone-like
arrangement after 6 days. Cells on TPU only were unable to undergo
appropriate spreading and proliferation and a rounded morphology. |
|
(146) |
| core–shell structure electrospinning |
The highest human pulmonary artery EC growth rate
reached confluence on PCL-gelatin. With human pulmonary artery SMCs,
the highest cell growth rate was on PCL-gelatin. |
PCL-gelatin 29.7%/100 mmHg, PLA-gelatin 27.7%/100 mmHg, PU-gelatin 7.9%, umbilical vein ∼3.7%/100 mmHg |
(88) |
| PCL-gelatin |
| PLA-gelatin |
| PU-gelatin |
| electrospinning |
At 2 weeks PCL and PCL-gelatin groups showed a
thick layer of cells that might have been ECs or platelets. PCL-gelatin-heparin
grafts had a thin cell layer similar to that of the native endothelium.
After 4 weeks, the endothelial cell layer of the PCL group was discontinuous
in comparison with the regenerated endothelium of the PCL-gelatin-heparin.
After 2 weeks, the coverage thickness of SMCs in PCL and PCL-gelatin
grafts was slightly higher than that of PCL-gelatin-heparin grafts
and after 4 weeks growth in PCL-gelatin-heparin was no longer evident. |
After 2 and 4 weeks, luminal surfaces of PCL and
PCL-gelatin-heparin grafts were smooth at both time points, whereas
macroscopic thrombus had occurred within the lumen surface of PCL-gelatin
graft implants at week 4. |
(147) |
| PCL-gelatin-heparin |
| electrospinning and
coating |
In vitro rat aortic EC number on PGH grafts
was much higher
than those of PCL grafts and PH grafts at 48 and 72 h, and rat aortic
SMC number on PGH grafts was higher than that on PH grafts at 24 h,
but at 48 and 72 h, the number on PCL was much higher than PH and
PGH grafts. |
Compliance of PGH graft was 7.52 ± 0.93%/100 mmHg and for the PH graft was 9.48 ± 0.93% /100 mmHg |
(148) |
| PCL-gelatin-heparin (PGH) |
In vivo,
flat polygonal ECs were found on the
PGH grafts after 1 week, with no ECs on the PH graft. After 4 weeks,
PGH grafts were fully covered by a continuous layer of ECs, and a
smooth endothelium can be observed. ECs covered most parts of the
PH grafts, but the endothelium was rough and discontinuous. |
No thrombus observed on the internal surface of
PH and PGH grafts. PH and PGH grafts were patent, and no significant
stenosis was found. |
| PCL-heparin (PH) |
| collagen elastin |
electrospinning and hydrogel PU-PEG collagen-mimetic
(Scl2-1 and Scl2-2) protein hydrogel, PU-PEG collagen hydrogel |
The average bovine aortic EC spreading on PEG-Scl2-2
hydrogels was lower than that on the PEG-collagen controls. |
The levels of platelet adhesion on the PEG, PEG-Scl2-1, and
PEG-Scl2-2 hydrogels were statistically similar and were each significantly
lower than the values for the TCPS and collagen-coated TCPS positive
controls. |
(149) |
| In a pulsatile bioreactor,
PEG, PEG-Scl2-1, and PEG-Scl2-2
hydrogels remained patent during the testing time, while the ePTFE
(GORE-TEX) vascular graft occluded due to thrombosis within 1 h. Compliance of was 2.7 ± 0.3%/100 mmHg. |
| electrospinning |
In vivo at 14 days, staining of the luminal surface
was positive for collagen, mononuclear cells, entrapped red blood
cells, and vWF+ cells, suggestive of an endothelial-cell-containing
neointima. |
Glass had the largest number of adherent
platelets (2.42 ± 0.10 × 105 platelets mm–2), followed by collagen (2.04 ± 0.09 × 105 platelets mm–2), ePTFE (1.62 ± 0.05 × 105 platelets mm–2), elastin protein polymer (6.62 ± 0.36 × 104 platelets
mm–2), and the luminal surface of protein composite
conduits (6.78 ± 0.05 × 105 platelets mm–2). |
(81) |
| collagen, elastin |
In vivo, at 14 days, grafts appeared
patent with a minimal
adhesive response to the abluminal surface. Visual observation of
graft luminal surface showed no thrombus or visible intimal hyperplasia. |
| electrospinning and knitting |
More human umbilical vein ECs were spindle-shaped
and well-attached to the collagen substrates compared to those on
the PLA substrate. The Col-K scaffolds showed significantly superior
initial cell attachment and overall cell growth compared to the Col-KE
and PLA-K grafts. |
Between 80 and 120 mmHg,
Col-K had a compliance
of 2.81 ± 0.28%/100 mmHg, and
Col-KE had 3.06 ± 0.96%/100 mmHg. The PLA grafts (PLA-K) showed significantly higher compliance of 5.42 ± 0.17%/100 mmHg, which was similar to
that of a human artery (4.7–17.0%/100 mmHg). |
(80) |
| collagen knitted (Col-K) |
| collagen knitted and electrospun (Col-KE) |
| control PLA knitted (PLA-K) |
| electrospinning |
Human umbilical vein EC
attachment and proliferation
was compared to BSA, fibronectin and uncoated tissue culture plastic
(TCP). Cell attachment to elastin was greater than BSA at all time
points and not significantly different to fibronectin but was higher
than on BSA and TCP. A substantial covering of HUVECs on elastin and
PCL/elastin scaffolds was observed on day 1, increasing out to day 3. HUVECs attached
to and spread on PCL, PCL/elastin and elastin scaffold surfaces by day 3. |
The elastin coating reduced
platelet attachment compared to
BSA by 53 ± 1.9% and collagen
by 61 ± 7.1%. |
(83) |
| PCL/elastin |
Platelet attachment to
elastin scaffolds was strikingly reduced
by 88 ± 1.6% compared to ePTFE (P < 0.001), and importantly
by 80 ± 8.4% compared to PCL alone |
| freeze-drying |
Results
showed that both the developed graft (elastin/collagen)
and the control (ePTFE) were patent 1 week after surgery. However, 4 weeks post-implantation,
all four of the elastin/collagen grafts and only one of the ePTFE
were occluded. Fibrin infiltrated the surrounding tissue in both the
natural and synthetic graft and in the developed graft. Elastin fibers
in the luminal layer were dislodged. |
(82) |
| lumina layer-elastin/outer collagen |
| hyaluronic acid |
electrospinning
and plasma coating PCL-HA |
Immobilization of HA increased
the number of adherent mesenchymal
stem cells (MMSCs) cells on the surface by more than 65% compared
to the surface of the untreated sample (PCL). |
|
(150) |
| film |
At 5 h post-seeding,
cells on all surfaces possessed
a highly rounded morphology of bovine aortic ECs. At 5 days, a significant increase in cell number at was achieved on HA and heparin conjugated
grafts. Only HA conjugated grafts exhibited a cobblestone pattern
typical of ECs and reached confluency by day 5, with more cells adhered than any other condition followed by the
PPH grafts. |
Only HA-grafted surfaces permitted
significantly
less protein adsorption than that found on the unmodified PU-PEI control. |
(151) |
| PU/polyethylenimine (PEI)-HA (PPHA) |
| PU/PEI-heparin (PPH) |
| PU/PEI–PEG
(PPP) |
| electrospinning |
At 5 h post-seeding, similar numbers of bovine
aortic ECs had adhered to both the PU and PU-HA grafts. At day 5, a significant increase in EC number was achieved across PU-HA grafts. However,
PU alone had the highest number of ECs. |
There was a 50–70% reduction
in protein adsorption with PU-HA compared to that with
unmodified PU. Incorporation of HA into the PU backbone resulted in
significantly decreased platelet adhesion relative to the PU. |
(152) |
| PU-HA |
| |
electrospinning and coating |
Combining
collagen IV and laminin together resulted in the
highest number of adhered HUVECs after 6 hrs and the highest proliferation
rate after 6 days of culture. There was no significant different between
the collagen and laminin coated membranes however cell adhesion and
proliferation were higher compared to just PCL fibers. |
Collagen IV and laminin immobilization had limited
influences on BSA adsorption. The surface modified PCL before conjugating
with collagen or laminin had the largest platelet adhesion value and
showed a dendritic morphology with many extruding filopodia showing
a potential to recruit other platelets. On the laminin and collagen
modified nanofibers numbers of adhered platelets were significantly
lower with some platelets showing a round shape with less filopodia. |
(153) |
| PCL-collagen/laminin |
Biomolecule
immobilization also resulted in increased NO and
PGI2 release capability from the HUVECs and this was significantly
higher in the laminin coated and laminin and collagen combination
fibers than collagen only coated samples. |
| electrospinning |
Endothelialization coverage
value of PCL/fibrin
grafts were higher than that of PCL grafts at 1, 3, and 9 months. At 9 months in vivo, compared with PCL grafts, PCL/fibrin grafts showed more
cobblestone-like cells covering the surface, slightly less than the
native artery. HE staining results showed that PCL grafts showed fewer
SMCs and thinner graft wall. The wall thickness and cell number of
the PCL/fibrin grafts were close to those of native artery. Results
of immunofluorescence experiments showed that the α-SMA expression
quantity in PCL/fibrin vascular grafts group was similar to native
artery group. |
After 9 months in
vivo, the luminal surface of the samples was very smooth and clean,
and no thrombosis and platelet aggregation were found. However, PCL
grafts had significantly more calcification than PCL/fibrin grafts
located near the lumen. At 1 month, macrophages oriented with microfibers of PCL/fibrin grafts were
observed, and there were many CD68 positive markers. However, as the
transplantation time prolonged, the CD68+ macrophages gradually decreased,
and by 9 months, their number was close
to the native arteries. |
(154) |
| PCL/fibrin |
| electrospinning |
From the hUASMCs seeded, the native umbilical
cord artery exhibited organized ECM cells and expressed both α-SMA
and calponin, highlighting a functional contractile apparatus. However,
the PCL/fibrinogen scaffolds developed a collagenous ECM. There was
a limited expression of α-SMA and no positive calponin expression
was detected. After 4 weeks in culture,
the cells in the PCL only scaffold revealed no distinct organization
or orientation, and cellular infiltration was highly heterogeneous.
With the PCL/fibrinogen graft, DAPI staining of scaffold cross sections
revealed excellent cellularization across the entire thickness of
the graft wall with a a circumferential orientation. |
After 4 weeks in
culture, the appearance and handling properties of the composite scaffold
were tissue-like, with smooth union of the layered sheets and excellent
patency |
(155) |
| PCL/fibrinogen |
| bacterial nanocellulose (BNC) with
human albumin,
fibronectin, and heparin–chitosan coating |
In
static conditions, for vascular ECs, only fibronectin-coated
patches showed multiple large and partially coherent colonized areas
but also nonpopulated spots and areas. All other coatings only showed
smaller cell islets or singular cells. For endothelial progenitor
cells, densely populated areas of EPCs were found for all coatings
and also uncoated BNC patches after seeding the cells under static
conditions. |
|
(156) |
| Under dynamic conditions, the most confluent coverage and highest
density was in the fibronectin group, partially confluent areas of
VECs were found for the albumin group, while the uncoated group showed
a lower density of VECs. The heparin group showed only scattered signals
at much lower density. For EPCs, there was very high overage for the
fibronectin group. The heparin group was also colonized, but at lower
cell densities. The albumin and uncoated groups remained mostly unpopulated,
and only scattered cells were found. |
| chitosan |
electrospinning |
Using RBSMCs, PCL-PEGME, and PCL-chitosan membranes
showed similar proliferation rates at 7 days. Different types of SMC markers were highly expressed in RBMSCs cultured
on PCL-chitosan electrospun mats than on PCL-PEGME mats. |
|
(157) |
| PCL, PCL-PEGME (polyethylene
glycol methyl ether), and PCL-chitosan |
| electrospinning/hydrogel
layer |
On day 1, all the
samples showed
the same proliferation intensity. With time, the least cell adhesion
and proliferation was observed on the TPU only grafts. As heparin
increased the wettability of the grafts, it promoted better adherence.
When SF was added, these samples showed enhanced cell viability and
attachment; however, with time (1 week), there was a decreased proliferation rate. The combination of SF
and heparin resulted in the highest HUVECs growth and proliferation. |
With platelet adhesion, the inclusion of heparin
into the samples significantly reduced the number of adhered platelets
on the surface. Both the TPU only and TPU/SF samples showed an increased
amount of platelet adhesion to the extend forming aggregates on the
surfaces of the samples. |
(158) |
| TPU-heparin/SF (core/shell structure)-inner layer, chitosan/gelatin-hydrogel
(C/G) outer layer |
For the outer layer, using SMCs, the 1/1 and 3/1 hydrogel
ratios showed almost
the same cell growth compared with the blank sample at 1, 3, and 7 days after cell seeding. Sample 2/1 had the least cell adhesion and proliferation,
even compared to the control cell with no bioactive polymer. |
| electrospinning |
Results
with human skin fibroblast cells showed
that the electrospun PU/chitosan membranes showed enhanced cell attachment
and proliferation than the pristine PU membrane. The cell attachment
and proliferation percent of pure PU was observed to be 141.9 ± 2.264 and for PU/chitosan nanofibers
electrospun at ratio 8:2 (v/v) and 7:3 (v/v) were found to be 181.8 ± 2.611 and 180.8 ± 3.846, respectively. |
|
(159) |
| PCL/chitosan nanoparticles |
| electrospinning |
Vascular remodeling was found to still be occurring
at the time of explantation, in the neointima. A cellular monolayer
stained positively for vWF, indicating endothelial cell layer formation.
Some mature and functional smooth muscle cells were detected in the
media of the developed graft. Both types of cells were mature and
well-organized, which reflected the native carotid artery in area,
distribution, and density. |
Results showed
that after 6 months in vivo, the compliance
of the developed graft decreased significantly
(from 14.04 ± 1.50 to 6.58 ± 1.76%). The patency rate of the developed
grafts was found to be ∼66% (4 out 6 grafts). The decrease in compliance was attributed to an increased presence
of collagen in the developed graft. The luminal surfaces of patent
grafts displayed no evidence of microthrombosis. The TEVG’s
wall thickness was however significantly higher than the native carotid
artery, resulting from a significant macrophage infiltration into the scaffold. |
(160) |
| PCL/chitosan |
| silk fibroin |
knitted and sponge |
After implanting (in beagles), mild bleeding was observed in
the grafts and anastomotic sites. The grafts adhered to the surrounding
muscles by thin fibrous tissue. After 1 year in vivo, a layered structure mainly composed of smooth muscle cells,
elastic fibers, and collagen fibers was identified. |
Occlusion due to thrombus formation was observed 4 weeks post-implantation in 1 out of 6 grafts. In the remaining 5 grafts, there was also no intimal hyperplasia or aneurysms at 3 months, 5 months, and 1 year. Inflammatory cells, such
as neutrophils, lymphocytes, and macrophages, were concentrated around
the graft but could not be found around the base of the graft or in
the lumen at 3 months post-implantation
and these decreased with increasing time points. |
(161) |
| electrospinning inner and outer layer, braiding-middle layer |
Endothelial cells, smooth muscle cells, and adventitial fibroblasts
were used for the cell study, and after 3 h of cell seeding, all cell types covered approximately 61 ± 5% of the surface. The polystyrene control
had 2.1× less cells than on the SF surfaces. After 20 days, the
fibroblast cells seeded onto SF graft increased their number 4-fold,
endothelial cells 3-fold, and SMCs 6.5-fold. Contrary to the theory
where proliferation is greater on natural bioactive polymers, the
polystyrene surface had a 7.5× increase in fibroblast cells,
5× increase in endothelial cells and a 7× increase in SMCs. |
To assess the patency of the grafts, ultrasound and angiographic
analysis were used at days 13 and 24 post-implantation. The results
showed patent grafts with no signs of aneurysm, dilation, dissection,
blood collection or signs of infection. The graft implanted in the
sheep showed no stenosis, whereas in the minipig, a slight stenosis
near the proximal anastomosis was identified. A thin layer of soft tissue was found in the external surface of the graft
explanted from the sheep, however that from the minipig had a thicker
layer. Signs of an ongoing foreign body response in the stenosis of
the graft explanted from the minipig were identified by the presence
of collagen fibers, fibroblasts, macrophages, and multinucleated giant
cells together with a lesser number of lymphocytes, plasma cells,
and neutrophils filling the voids of the middle layer. |
(162) |
