Research Papers

Formation of Highly Aligned Grooves on Inner Surface of Semipermeable Hollow Fiber Membrane for Directional Axonal Outgrowth

[+] Author and Article Information
Yu Long, Yong Huang

Department of Mechanical Engineering, Clemson University, Clemson, SC 29634

Ning Zhang, Xuejun Wen

Clemson-MUSC Bioengineering Program, Clemson University, Charleston, SC 29425

J. Manuf. Sci. Eng 130(2), 021011 (Mar 28, 2008) (8 pages) doi:10.1115/1.2896111 History: Received April 16, 2007; Revised February 03, 2008; Published March 28, 2008

It is generally believed that organized neural architecture is essential for nervous system development, function, and regeneration. In the absence of guidance cues, regenerating axons may lose their directions and become misaligned, resulting in the formation of neuromas and/or misappropriate connections. To help regenerate axons across damaged regions and guide them to appropriate targets, some bridging devices such as microgrooves are being intensively researched to achieve a better directional axonal growth. This paper reports a novel fabrication process to generate a highly aligned groove texture on the inner surface of semipermeable hollow fiber membranes (HFMs). HFMs have demonstrated promising results in guiding axonal regeneration. The fabrication process utilized a wet phase-inversion procedure with polyurethane (PU) as model polymer, dimethyl sulfoxide (DMSO) as solvent, and water as nonsolvent. Data indicated that highly aligned groove texture could be formed on the HFM inner surface by carefully controlling phase-inversion conditions such as the polymer solution flow rate, and/or nonsolvent flow rate, and/or polymer solution concentration ratio. The texture forming mechanism is qualitatively explained using a PU-DMSO-water ternary phase diagram and the dynamics of fluid instability. Axonal outgrowth on the HFM with aligned grooves showed the highly aligned orientation and improved axonal outgrowth length. This study may eventually lead to a new and effective way to fabricate nerve grafts for the spinal cord injury and nerve damage treatment based on this highly aligned three dimensional scaffold.

Copyright © 2008 by American Society of Mechanical Engineers
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Figure 1

Schematic of the phase-inversion setup

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Figure 2

Spinneret design (S: solvent DMSO, NS: nonsolvent water, PU: polymer polyurethane)

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Figure 3

Typical HFM morphology with a smooth inner surface

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Figure 4

Typical HFM morphology with an aligned groove texture on the inner surface

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Figure 5

Approximated ternary phase diagram of the PU/DMSO/water system

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Figure 10

Directionality of regenerated neurites on two types of HFMs. (a) Pattern of regenerated neurites on the HFMs with smooth inner surface. Neurites in most regions were not well aligned with the longitudinal axis of HFMs. (b) Neurite outgrowth pattern on the HFMs with highly aligned textures.

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Figure 6

Schematic of a wet phase-inversion process

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Figure 7

Fluctuations in the solution

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Figure 8

The match between sinusoidal wave and groove shape

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Figure 9

HFM morphologies when polymer solution flow rates (part of Scenario 1 in the experiment design) were (a) 1.2ml∕min, (b) 1.6ml∕min, and (c) 1.8ml∕min with a constant water flow rate of 4ml∕min



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