Workshop proceeding - final.pdf - Faculty of Information and ...

new tissue[10]. Most of these human organs deposited on fibrous structures with the fibril/fiber size
realigning from nanometer realigning from nanometer to millimeter scale. So nanofibers have now
been extensively used to mimic these natural tissue matrixes. At present, electrospinning is the most
prevalent process that can creates nanofibers through an electrically charged jet of polymer solution
or polymer melt. Different processing parameters such as kind of polymer, viscosity, surface tension,
jet charge density, temperature and humidity control the electrospinning process, especially the
diameter and morphology of the resulting fibers[11]. Recently, researchers have found that the
nanofibrous structure formed by electrospinning method will improve the function in vitro tissue
regeneration and decrease the formation of scar tissue[12]. So the scaffolds prepared from
electrospinning method can be considered to mimic the native extracellular matrix (ECM).
Representative polymers including synthetic ones such as poly(lactic-acid)(PLA)[13,
14],poly(glycolic-acid)(PGA)[15], poly(lactic-co-glycolic acid)(PLGA)[16], poly(ε-caprolactone)
(PCL)[17, 18]and natural ones such as collagen[19], chitosan[20], gelatin[21] and silk[22]have been
electrospun into nanofibers.
Native ECM is the complex of polyprotein and polysaccharide with nanofibrous structure.
Among the natual biopolymers, collagen as polyprotein has been widely used in TE for its excellent
biocompatibility and nonimmunogenicity, but the mechanical property can’t achieve the request of
native ECM. Thermoplastic polyurethanes (TPUs) are a widely used class of polymer with excellent
mechanical properties and good biocompatibility, and have been evaluated for a variety of
biomedical applications such as coating materials for brest implants, catheters, and prosthetic heart
valve leaflets[23]. Conventional TPU are among biomaterials not intended to degrade but are
susceptible to hydrolytic, oxidative and enzymatic degradation in vivo. While the susceptibility of
TPU to such degradation is a problem for long lasting biomedical implants, it can be deliberately
exploited to design biodegradable polyurethane[24]. The TPU used in this research one kind of
medical-grade, aliphatic, polyether-based TPUs. It can biodegrade and the biostability is better than
poly(ester urethane).
As candidate materials, pure TPU and collagen have already been electrospun into nanofibers
as biomaterials respectively[19, 25]. And they all have biological benefits used as TE scaffolds. The
promising study of electrospun TPU and collagen complex has not been well understood. Especially,
the relationship between processing parameters and microstructures in the electrospun nanofbers has
not been reported.
In this study, collagen and and TPU were co-electrospun to produce collagen/TPU composite
nanofibrous scaffolds. We created these electrospun hybrid scaffolds that combined synthetic
material with natural proteins to overcome limitations seen with scaffolds constructed with either
one alone. We characterized the properties of these novel scaffolds and optimized for porosity,
strength, cell seeding. Collagen/TPU hybrid fibrous scaffolds were determined to provide optimal
fiber diameter, pore size and mechanical strength, leading to enhance the seeding of the electrospun
scaffolds with cells. The object of this project is to study the electrospinning of TPU/collagen
complex and to develop the biomimetic extracellular matrix for TE application.
2 Materials and methods
2.1 Materials
The polymer of TPU (Tecoflex EG-80A) was purchased from Noveon, Inc.(USA) and collagen
(mol.wt, 0.8-1×105Da) was purchased from Sichuan Ming-rang Bio-Tech Co. Ltd (China). The two
materials all used 1,1,1,3,3,3,-hexafluoro-2-propanol (HFP) as solvent, which was brought from
Daikin Industries Ltd( Japan). Pig iliac endothelial cells (PIECs) were obtained from institute of
biochemistry and cell biology (Chinese Academy of Sciences, China). Except specially explained, all
culture media and reagents were purchased from Gibco Life Technologies CO, USA.
2.2 Scaffold fabrication
The polymers of TPU and Collagen solutions were dissolved in HFP separately. When they were
prepared already, the two solutions were blended at different weight ratios and volume ratios with
sufficient stirring at room temperature before electrospinning.
The pure and blend polymer solutions were placed into a 2.5 ml plastic syringe with a bluntended
needle with an inner diameter of 0.21mm. The needle was located at a distance of 130~150mm
from the grounded collector. A syringe pump (789100C, cole-pamer, America) was employed to feed
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