1) The researchers tested two methods of adding sodium chloride to electrospun polyurethane scaffolds to create pores large enough for cell infiltration but did not achieve the target pore size of 50-100 μm. 2) Method 1, directly applying sodium chloride granules, produced larger pores when larger granules were used but did not reach the target. Method 2, electrospinning a polyurethane-sodium chloride solution, did not effectively introduce pores. 3) Future work may use larger sodium chloride granules or an alternative vertical electrospinning approach to help granules reach the collector and create larger pores.

1. © 2015 Mayo Foundation for Medical Education and Research
Erik Wennberg1, Brandon J. Tefft, Ph.D1,2, Susheil Uthamaraj2, Dan Dragomir-Daescu, Ph.D2,3,Gurpreet S. Sandhu M.D., Ph.D1
1Division of Cardiovascular Diseases, 2Division of Engineering, and 3Mayo Clinic School of Medicine
Mayo Clinic, Rochester, MN
• The electrospun PU scaffolds from both methods do
not show results of the target pore size of 50-100 µm.
Figures E and H when compared to figures C and G
show that nanofiber quality increases when a size of
NaCl larger than 63 µm is salt leached out. Overall,
larger salt size tended to increase pore size. The
method 1 of applying 0.50g NaCl showed larger pore
sizes than applying 0.25g NaCl. This may be due to
the larger amount of NaCl available to stick to the
scaffold between each spinning. Method 1 using
0.50g NaCl was comparable to method 2. These
methods may have failed to produce the target pore
size due to method 1 using too small NaCl granules
and method 2 not having NaCl granules make it to
the collector plate.
• In the future, researchers may incorporate larger
NaCl granules (>100 µm) or electrospin vertically so
the NaCl granules use gravity to make it to collector.
Discussion
• Our current methods created micron- scale pores,
but did not reach our target goal of 50-100 µm to
introduced cells for infiltration. Future alterations
should produce larger pores able to succeed this
goal.
Conclusions
1. Wang, Kai, Meifeng Zhu, Ting Li, Wenting Zheng, Li Li, Mian Xu,
Qiang Zhao, Deling Kong, and Lianyong Wang. "Improvement of Cell
Infiltration in Electrospun Polycaprolactone Scaffolds for the
Construction of Vascular Grafts." Biomedical Nanotechnology 10
(2014): 1588-598. NCBI. Web. 10 July 2015.
2. Sanaz Khademolqorani, Ali Zeinal Hamadani, and Hossein Tavanai,
“Response Surface Modelling of Electrosprayed Polyacrylonitrile
Nanoparticle Size,” Journal of Nanoparticles, vol. 2014, Article ID
146218, 7 pages, 2014. doi:10.1155/2014/146218
3. B. Wulkersdorfer, K. K. Kao, V. G. Agopian, et al., “Bimodal Porous
Scaffolds by Sequential Electrospinning of Poly(glycolic acid) with
Sucrose Particles,” International Journal of Polymer Science, vol. 2010,
Article ID 436178, 9 pages, 2010. doi:10.1155/2010/436178
References
Many vascular grafts are electrospun from synthetic
or natural substances into a nanofiber scaffold.
However, a major limitation of electrospinning is the
lack large pore sizes. Large pore sizes allow
interstitial cells to pass through. Small pore size can
result in generating the graft prone to intimal
hyperplasia and thrombosis. Researchers have tried
many different approaches to create large pores,
such as using sacrificial poly(ethylene oxide) fibers
with polycaprolactone1, electrospraying
polyacrylonitrile2 and the use of other poragens such
as sucrose particles3. However, these methods have
all been accomplished with a biodegradable polymer.
Background
• Find an effective method of introducing sodium
chloride to electrospun PU nanofibers
• To create a porous PU scaffold that allows
interstitial cell infiltration and integration with the
surrounding tissue
Objectives
Control
• Fig. A: Electrospun PU nanofibers control show pore sizes
of 1-2 µm with dense fibers under 1µm.
Method 1: 0.25g NaCl applied to scaffolds
• Fig. B: Non- salt leached fibers show NaCl granules ~300-
750 µm. Nanofibers just under 1 µm thick.
• Fig. F: High quality, dense nanofibers with smaller pore sizes
• Fig. D: Nanofiber pore size 1-3 µm. Nanofiber thickness
below 1 µm.
• Fig. E: Nanofibers shows blobs of polyurethane in some
areas of the scaffold.
Results
• To create micropores (50-100 µm) in a non-
biodegradable polyurethane scaffold
• Seed interstitial cells in vitro on a porous scaffold
and assess migration into the scaffold
Study Aim
Methods
SEM Images
Electrospun Polyurethane Graft Porosity for Cellular
Infiltration: Current Methods and Future Directions
Hypothesis
The addition of sodium chloride to an electrospun
non-biodegradable polyurethane (PU) vascular graft
will create large micropores in an electrospun
scaffold, allowing interstitial cells to migrate through.
SEM Images: A) Control nanofibers. B) Method 1: 38-75µm NaCl+
nanofibers. C) Method 1: 0.50g of 63-75 µm NaCl salt leached nanofibers.
D) Method 1: 0.25g of >75 µm NaCl salt leached nanofibers. E) Method 1:
0.25g of 53-63 µm NaCl salt leached nanofibers. F) Method 1: 0.25g of 63-
75 µm NaCl salt leached nanofibers. G) Method 1: 0.50g of 63-75 µm
NaCl salt leached nanofibers. H) Method 1: 0.5g 53-63 µm salt leached
nanofibers. I) Method 2: PU+NaCl salt leached solution nanofibers. J)
Method 2: PU+ NaCl non- salt leached solution nanofibers.
Acknowledgements
A thank you to the Mayo Clinic undergraduate
research employment program, the summer
undergraduate research fellowship program and the
European Regional Development Fund – FNUSA-
ICRC (no. CZ.1.05/ 1.1.00/ 02.0123).
Method 1 Method 2
Method 1: 0.50g NaCl applied to scaffolds
• Fig. C: Few larger nanofibers. Some white debris on a few
fibers. Nanofiber thickness ranges from below 1- 2 µm.
• Fig G: Nanofibers look dense, small pore sizes.
• Fig. H: Nanofibers shows blobs of polyurethane in some
areas and the nanofibers overall were dense.
Method 2: 15%PU + 4g NaCl solution
• Fig. I: Pore sizes 1-3 µm. Few very small fiber pieces on
some of the larger fibers. Regular fibers under 1 µm thick.
• Fig. J: Fibers do not appear present. Few pores in the
scaffold of 1-5 µm varying sizes.
Results
A
B F
D
E
C G
H
I
J