Silk scaffolds for neural tissue engineering.
Hopkins, Amy.
2017-04-24T15:10:53.118Z
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Abstract: There is a critical need for therapies that promote neural regeneration and target disease mechanisms of the nervous system. Neural tissue engineering (TE) is in the early stages of development with research focusing on several aspects of therapeutics including peripheral nerve repair, image processing analysis techniques, and in vitro tissue systems. TE functional neural systems present... read moreunique challenges including low tissue stiffness, high cell density, and complex neural network functions still being elucidated in vivo. Silk biomaterials are attractive candidates for TE applications due to their biocompatibility, aqueous-based processing, and robust and tunable mechanical and degradation properties. The present work evaluated two silk scaffold platforms for neural TE applications: (1) silk hydrogels, and (2) silk sponges. Mechanical stiffness and biochemical functionalization of silk hydrogels were examined for promotion of neurite extension for peripheral nerve guidance. One to 8% silk hydrogels exhibited low stiffness of 4-33kPa as measured by atomic force microscopy. The structural integrity of the silk gels was maintained throughout cell culture whereas fibrin and collagen gels decreased in mass over time. Neurite extension was greatest on 2 and 4% silk hydrogels as compared to softer or stiffer gels and gels loaded with neurotrophin-3 exhibited low release of <5% and remained bioactive over 2 weeks. Functionalization of silk hydrogels with fibronectin and laminin led to observations of differences in axonal bundling. Due to the lack of quantitative image processing methods for analysis of fasciculation events, silk hydrogels were employed for development of a semi-automated neurite directional distribution analysis (NDDA) program, which quantifies fasciculation based on tortuosity of neurite extension. Finally, a compartmentalized silk sponge scaffold with arrays of hollow channels was characterized for development of 3D neuron cell culture systems. The silk sponge scaffold allowed for localized, long-term co-cultures of vascular and neuronal cells and resembled the 3D architecture of the neurovascular unit (NVU). The 3D NVU culture system has potential for supplementing 2D cultures and animal models for CNS therapeutic development. Collectively, this work exemplifies several neural TE applications with silk biomaterial scaffolds offering promising in vitro systems for understanding nervous system mechanisms and therapeutic development.
Thesis (Ph.D.)--Tufts University, 2013.
Submitted to the Dept. of Biomedical Engineering.
Advisor: David Kaplan.
Committee: Fiorenzo Omenetto, Barry Trimmer, Michael Whalen, and Cristian Staii.
Keyword: Biomedical engineering.read less - ID:
- js956s618
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