This work is funded in part by the USDA National Institute for Food and Agriculture, National Competitive Grants Program, National Research Initiative Program 71.1 FY 2007 as Grant No. 2007-35503-18392, and National Institutes of Health, Institute for Allergy and Infectious Disease, R33AI94514-03.

1. Spinning Dope Preparation
<ol>
	<li>Prepare a range of biopolymer concentrations to be investigated (0.1% to 30%, w/v) and be sure to consider moisture content of the biopolymer powder in these calculations. For each concentration, weigh the biopolymer (starch or pullulan) powder into a 50 ml test tube. Add aqueous dimethyl sulfoxide (DMSO) solution and a stir bar.</li>
	<li>Place the tube into boiling water with constant stirring on a magnetic stirrer hotplate.</li>
	<li>After about 1 hr, turn off heat and allow th...

<ol>
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The authors declare that they have nothing to disclose.

Rheology is an essential tool to study the processing of polymers, including conventional fiber spinning and electrospinning13. From the steady shear rheological studies, polymer conformation and their interactions in different solvents can be resolved (Figures 2&#160;and&#160;3). At concentrations not high enough for biopolymer molecules to overlap with one another, their concentration dependence was around 1.4 (Figure 3), which was in good agreement with rep...

Electrospinning is a technique that is capable of producing continuous micro- to nano-scale fibers from a wide variety of materials. It has gained increasing academic and industrial interest1. Though the setup and practice of electrospinning seem straightforward, the ability to predict electrospinnability and control fiber properties remains a challenge. The reason may lie in the fact that there are many factors influencing the electrospinning process2 and the process, especially the path travelled by the fiber, is chaotic1. Often an empirical &#8220;cook-and-look&#8221; approach is used for screening potential electrospinnable materials. However, to gain better control over the electrospinning process and resultant fiber properties, a more complete understanding of the mechanisms that govern electrospinnability is required. Several researchers have found that molecular entanglement of polymers in the spinning dope is an essential prerequisite for successful electrospinning3-5.
Rheology is a powerful tool to probe molecular conformation and interaction in polymer dispersions. For instance, McKee et al. investigated the molecular conformation of linear and branched poly(ethylene terephthalate-co-ethylene isophthalate) copolymers in a solvent containing chloroform/dimethyl terephthalate (7/3, v/v), and determined that the polymer concentration had to be 2-2.5x&#160;the entanglement concentration for successful electrospinning4.
There is currently renewed interest in fibers from biopolymers because of their advantages in biodegradability, biocompatibility, and renewability vis-&#224;-vis their synthetic counterparts. Yet practitioners confront many challenges arising generally from their structural complexity, difficulty in thermal processing and inferior mechanical properties. Starch, found in plant tissues, is among the most abundant and inexpensive biopolymers on earth. Pure starch fibers fabricated using an electro-wet-spinning apparatus were recently described6. Pullulan is a linear polysaccharide produced extracellularly by certain bacteria. The regular alternation of (1&#8594;4) and (1&#8594;6) glucosidic bonds are believed to be responsible for several distinctive properties of pullulan, including excellent fiber/film forming capability7,8. Electrospinning of pullulan fibers from aqueous dispersion has been reported by a number of researchers9,10. In our previous publications, the electrospinnability of two biopolymers, starch11 and pullulan12, has been discussed. This report focuses on demonstrating the protocol for utilizing rheological principles in the investigation of the electrospinnability of these two biopolymers.

<table border="0" cellpadding="0" cellspacing="0" width="762">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Name of Reagent/ Equipment</td>
			<td style="width:253px;">Company</td>
			<td style="width:119px;">Catalog Number</td>
			<td style="width:175px;">Comments/Description</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Gelose 80 starch</td>
			<td style="width:253px;">Ingredion</td>
			<td style="width:119px;"></td>
			<td>Used as it is</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Pullulan</td>
			<td style="width:253px;">Hayashibara Co. Ltd</td>
			<td style="width:119px;"></td>
			<td>Used as it is</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Dimethyl Sulfoxide</td>
			<td style="width:253px;">BDH Chemicals</td>
			<td style="width:119px;">BDH1115-4LP</td>
			<td></td>
		</tr>
		<tr height="23">
			<td height="23" style="height:23px;width:216px;">Ethanol</td>
			<td style="width:253px;">VWR International</td>
			<td style="width:119px;">89125-172</td>
			<td>200 proof</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;"></td>
			<td style="width:253px;"></td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Rheometer</td>
			<td style="width:253px;">TA Instruments</td>
			<td style="width:119px;">ARES&#160;</td>
			<td>50 mm cone and plate geometry</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Syringe (10 mL)</td>
			<td style="width:253px;">Becton, Dickinson and Company</td>
			<td style="width:119px;">309604</td>
			<td>Syringe with Luer-Lok&#174; Tip</td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:216px;">High voltage generator</td>
			<td style="width:253px;">Gamma High Voltage Research, Inc.</td>
			<td style="width:119px;">ES40P</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Syringe pump</td>
			<td style="width:253px;">Hamilton Company</td>
			<td style="width:119px;">81620</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Environmental scanning electron microscope</td>
			<td style="width:253px;">FEI Company</td>
			<td style="width:119px;">Quanta 200</td>
			<td>for starch fibers</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Environmental scanning electron microscope</td>
			<td style="width:253px;">Phenom-World</td>
			<td style="width:119px;">Phenom G2 Pro</td>
			<td>for pullulan fibers</td>
		</tr>
	</tbody>
</table>

molecular entanglement and electrospinnability of biopolymers

Electrospinning is a fascinating technique to fabricate micro- to nano-scale fibers from a wide variety of materials. For biopolymers, molecular entanglement of the constituent polymers in the spinning dope was found to be an essential prerequisite for successful electrospinning. Rheology is a powerful tool to probe the molecular conformation and interaction of biopolymers. In this report, we demonstrate the protocol for utilizing rheology to evaluate the electrospinnability of two biopolymers, starch and pullulan, from their dimethyl sulfoxide (DMSO)/water dispersions. Well-formed starch and pullulan fibers with average diameters in the submicron to micron range were obtained. Electrospinnability was evaluated by visual and microscopic observation of the fibers formed. By correlating the rheological properties of the dispersions to their electrospinnability, we demonstrate that molecular conformation, molecular entanglement, and shear viscosity all affect electrospinning. Rheology is not only useful in solvent system selection and process optimization, but also in understanding the mechanism of fiber formation on a molecular level.

Flow curves of the biopolymer dispersions as a function of biopolymer concentration and DMSO concentration in solvent were obtained. Two representative figures show the flow curves of starch (Figure 2A) and pullulan (Figure 2B) as a function of their concentration in pure DMSO solvent. The specific viscosities were plotted against biopolymer concentration (Figure 3A&#160;for starch and Figure 3B&#160;for pullulan). From these plots, entanglement concentr...

Watch this Scientific Journal Video about Molecular Entanglement and Electrospinnability of Biopolymers at JoVE.com

Molecular Entanglement and Electrospinnability of Biopolymers

Electrospinning is a fascinating technique used to fabricate micro- to nano-scale fibers from a wide variety of materials. Molecular entanglement of the constituent polymers in the spinning dope is essential for successful electrospinning. We present a protocol for utilizing rheology to evaluate the electrospinnability of two biopolymers, starch and pullulan.

Electrospinning is a fascinating technique to fabricate micro- to nano-scale fibers from a wide variety of materials. For biopolymers, molecular ...

molecular-entanglement-and-electrospinnability-of-biopolymers

Research

JoVE Journal

Bioengineering

13.6K Görüntüleme.  Pennsylvania State University.  Elektro malzemeler çok çeşitli nano-ölçekli liflere mikroskopik olarak imal etmek için kullanılan bir ilginç bir tekniktir. Eğirme dop içindeki kurucu polimerlerin moleküler dolanması başarılı bir şekilde üretebilmektedir için gereklidir. Biz iki Biyopolimerlerin, nişasta ve pullulan bir electrospinnability değerlendirmek reolojisini kullanan bir protokol mevcut. 