Creation of highly aligned electrospun poly-L-lactic acid fibers for nerve regeneration applications. J Neural Eng 6(1):016001

Department of Chemical Engineering, Michigan Technological University, Houghton, MI 49931, USA.
Journal of Neural Engineering (Impact Factor: 3.3). 02/2009; 6(1):016001. DOI: 10.1088/1741-2560/6/1/016001
Source: PubMed


Aligned, electrospun polymer fibers have shown considerable promise in directing regenerating axons in vitro and in vivo. However, in several studies, final electrospinning parameters are presented for producing aligned fiber scaffolds, and alignment where minimal fiber crossing occurs is not achieved. Highly aligned species are necessary for neural tissue engineering applications to ensure that axonal extension occurs through a regenerating environment efficiently. Axonal outgrowth on fibers that deviate from the natural axis of growth may delay axonal extension from one end of a scaffold to the other. Therefore, producing aligned fiber scaffolds with little fiber crossing is essential. In this study, the contributions of four electrospinning parameters (collection disk rotation speed, needle size, needle tip shape and syringe pump flow rate) were investigated thoroughly with the goal of finding parameters to obtain highly aligned electrospun fibers made from poly-L-lactic acid (PLLA). Using an 8 wt% PLLA solution in chloroform, a collection disk rotation speed of 1000 revolutions per minute (rpm), a 22 gauge, sharp-tip needle and a syringe pump rate of 2 ml h(-1) produced highly aligned fiber (1.2-1.6 microm in diameter) scaffolds verified using a fast Fourier transform and a fiber alignment quantification technique. Additionally, the application of an insulating sheath around the needle tip improved the rate of fiber deposition (electrospinning efficiency). Optimized scaffolds were then evaluated in vitro using embryonic stage nine (E9) chick dorsal root ganglia (DRGs) and rat Schwann cells (SCs). To demonstrate the importance of creating highly aligned scaffolds to direct neurite outgrowth, scaffolds were created that contained crossing fibers. Neurites on these scaffolds were directed down the axis of the aligned fibers, but neurites also grew along the crossed fibers. At times, these crossed fibers even stopped further axonal extension. Highly aligned PLLA fibers generated under optimized electrospinning conditions guided neurite and SC growth along the aligned fibers. Schwann cells demonstrated the bipolar phenotype seen along the fibers. Using a novel technique to determine fiber density, an increase in fiber density correlated to an increase in the number of neurites, but average neurite length was not statistically different between the two different fiber densities. Together, this work presents methods by which to produce highly aligned fiber scaffolds efficiently and techniques for assessing neurite outgrowth on different fiber scaffolds, while suggesting that crossing fibers may be detrimental in fostering efficient, directed axonal outgrowth.

44 Reads
  • Source
    • "Yang , Wang , & Wang , 2010 ; Wang , Gao , Wei , & Wang , 2009 ; Wang , Liu , Song , & Wang , 2007 ; Wang , Song , Liu , & Wang , 2007 ; Yang , Qin , Li , Zhu , & Wang , 2009 "
    [Show abstract] [Hide abstract]
    ABSTRACT: Polyvinylidene fluoride (PVDF) is one of the most studied polymer systems that exhibits piezoelectric, pyroelectric, and ferroelectric properties. It is well known that PVDF is able to crystallize in four different forms that involve three different chain conformations, namely α, β, γ, and δ phases. Among the four polymorphs, the β-phase has the largest spontaneous polarization per unit cell and thus exhibits the highest electro active properties. In the past few decades, many researches have been done to increase the β-phase content in PVDF using various processing techniques and additives. One of these processing methods is electrospinning/electrospray with organic/inorganic additives, nanoparticles or carbon nanotubes. Material and structural analyses on fabricated nanofibers using instruments such as X-ray diffraction, Fourier transform infrared, Differential Scanning Calorimetry, and Scanning Electron Microscope as the characterizations of piezoelectric nanofibers are carried out. This article attempts to have an overview on the electrospinning process of PVDF as a piezoelectric polymer, method of characterization of its β-phase and its application as a nanogenerator.
    Journal of the Textile Institute 09/2015; DOI:10.1080/00405000.2015.1083300 · 0.72 Impact Factor
  • Source
    • "), a fiber diameter of ∼2 μm was selected as smaller diameter fibers (<1.3 μm) did not promote greater and longer outgrowth. A specific density of ∼0.15 fibers/μm was selected for this study to minimize fiber crossing and neurite crossings between adjacent fibers, which would likely impact the anisotropic growth and possibly branching (Wang et al 2009). Fibers were highly aligned with 95% of the fibers oriented ± 10 • parallel or perpendicular to the long axis (supplementary figure 1, available from "
    [Show abstract] [Hide abstract]
    ABSTRACT: Objective: Both electrical stimuli (endogenous and exogenous) and topographical cues are instructive to axonal extension. This report, for the first time, investigated the relative dominance of directional topographical guidance cues and directional electrical cues to enhance and/or direct primary neurite extension. We hypothesized the combination of electrical stimulation with electrospun fiber topography would induce longer neurite extension from dorsal root ganglia neurons than the presence of electrical stimulation or aligned topography alone. Approach: To test the hypothesis, neurite outgrowth was examined on laminin-coated poly-L-lactide films or electrospun fibers (2 µm in diameter) in the presence or absence of electrical stimulation. Immunostained neurons were semi-automatically traced using Neurolucida software and morphology was evaluated. Main results: Neurite extension increased 74% on the aligned fibers compared to film controls. Stimulation alone increased outgrowth by 32% on films or fibers relative to unstimulated film controls. The co-presentation of topographical (fibers) with biophysical (electrical stimulation) cues resulted in a synergistic 126% increase in outgrowth relative to unstimulated film controls. Field polarity had no influence on the directionality of neurites, indicating topographical cues are responsible for guiding neurite extension. Significance: Both cues (electrical stimulation and fiber geometry) are modular in nature and can be synergistically applied in conjunction with other common methods in regenerative medicine such as controlled release of growth factors to further influence axonal growth in vivo. The combined application of electrical and aligned fiber topographical guidance cues described herein, if translated in vivo, could provide a more supportive environment for directed and robust axonal regeneration following peripheral nerve injury.
    Journal of Neural Engineering 06/2014; 11(4):046002. DOI:10.1088/1741-2560/11/4/046002 · 3.30 Impact Factor
  • Source
    • "Electrospinning is a nanotechnology process by which polymer fibers with micro- to nanometer diameters can be obtained from an electrostatically driven jet of electrostatic polymer solution.10,11 These fibers have a high surface area-to-volume ratio, which improves the surface properties of biomedical implants.11 "
    [Show abstract] [Hide abstract]
    ABSTRACT: Ideal implant-cement or implant-bone interfaces are required for implant fixation and the filling of tissue defects created by disease. Micron- to nanosize osseointegrated features, such as surface roughness, fibers, porosity, and particles, have been fused with implants for improving the osseointegration of an implant with the host tissue in orthopedics and dentistry. The effects of fibers and loading angles on the interface fracture toughness of implant-cement specimens with and without fibers at the interface are not yet known. Such studies are important for the design of a long-lasting implant for orthopedic applications. The goal of this study was to improve the fracture toughness of an implant-cement interface by deposition of micron- to nanosize fibers on an implant surface. There were two objectives in the study: 1) to evaluate the influence of fibers on the fracture toughness of implant-cement interfaces with and without fibers at the interfaces, and 2) to evaluate the influence of loading angles on implant-cement interfaces with and without fibers at the interfaces. This study used titanium as the implant, poly(methyl methacrylate) (PMMA) as cement, and polycaprolactone (PCL) as fiber materials. An electrospinning unit was fabricated for the deposition of PCL unidirectional fibers on titanium (Ti) plates. The Evex tensile test stage was used to determine the interface fracture toughness (KC) of Ti-PMMA with and without PCL fibers at 0°, 45°, and 90° loading angles, referred to in this article as tension, mixed, and shear tests. The study did not find any significant interaction between fiber and loading angles (P>0.05), although there was a significant difference in the KC means of Ti-PMMA samples for the loading angles (P<0.05). The study also found a significant difference in the KC means of Ti-PMMA samples with and without fibers (P<0.05). The results showed that the addition of the micron- to nanosize PCL fibers on Ti improved the quality of the Ti-PMMA union. The results of the study are essential for fatigue testing and finite-element analysis of implant-cement interfaces to evaluate the performance of orthopedic and orthodontic implants.
    International Journal of Nanomedicine 04/2014; 9(1):1689-97. DOI:10.2147/IJN.S59253 · 4.38 Impact Factor
Show more


44 Reads
Available from