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Hyaluronic Acid Scaffolds for Neural Tissue Engineering. Shalu Suri April 2009. Department of Biomedical Engineering The University of Texas at Austin. Hyaluronic acid. Ubiquitous ECM component Cartilage and synovial fluid Non-immunogenic Multiple sites for modification hydroxyl
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Hyaluronic Acid Scaffolds for Neural Tissue Engineering Shalu Suri April 2009 Department of Biomedical Engineering The University of Texas at Austin
Hyaluronic acid • Ubiquitous ECM component • Cartilage and synovial fluid • Non-immunogenic • Multiple sites for modification • hydroxyl • carboxyl • acetamido • Enzymaticallydegradable Hyaloid (vitreous) +Uronic acid Isolated first in 1934
Role in Wound Repair and angiogenesis • Plays an important role in wound repair • Inflammation, granulation, repair, remodeling • Participates in angiogenesis when degraded in small fragments • 500 – 8000 Da
Nerve Structure www.backpain-guide.com/.../10-1_Nerve_Struct.jpg
Current Clinical Treatments End to End reconnection causesTension Autologous nerve graft Schmidt and Leach, Ann Rev BME, 2003
Design of Nerve Guidance Conduit Channels Bellamkonda, Biomaterials, 2007
Digital Micromirror Device (DMD) Lu et al., JBMR, 2006 Developed by Yi Lu and Dr. ShaoChen Chen
Fabrication using Digital Micromirror Device (DMD) Han et al, 2008 Lu et al, JBMR-A, 2006
HA scaffolds of DMD a) b) c) d)
3D Scaffold ?? • HA scaffolds are soft • Water absorption • Difficult to create long 3D scaffolds using layer by layer fabrication • Addition of acrylated salts • Zinc acrylate
“Designer Scaffolds” • Scaffolds with structures mimicking native architecture • Branched Scaffolds • Multi lumen conduits • Growth factors gradient • Nerve growth factor gradient ? • Multiple gradients running in opposite directions • Permissive cues • Inhibitory cues
Growth factors • Support the regeneration of axons • NGF,BDNF, neurotropin-3, neurotrophin-4/5, GDNF, FGF, PDGF, VEGF, CNF, and IGF-I • Agarose scaffolds with laminin gradient – enhanced neurite extension from DRGs • NGF gradient – guide neurite growth Cao et al, Neuroscience 2003
Branched conduit Scale bars 500 µm
XPS analysis Unwashed washed in PBS (pH 4)
Hyaluronan retains bioactivity top middle bottom negative Scaffold was incubated with biotinylated HA-binding protein and stained for PE-streptavidin
Summary • Optimization of the fabrication technique to create HA scaffold • Successfully created 3D scaffold with defined architecture • “Designer scaffolds” • Multi lumen • Gradient
What Next ?? • Create NGF gradient • Study the feasibility of gradient with DRGs • Create other designer architectures • Multiple gradients with in single scaffolds
SEM 10 µm
Final goal Bioactive scaffold composed of Native ECM components and cells with neural architecture for Neural tissue engineering