Electrospun scaffolds for spinal cord explant cultures

Spinal cord injury (SCI) affects thousands of patients worldwide every year, and leads to numerous lifelong medical difficulties for these patients. Ex vivo research into strategies for improving neural interfaces is a key area of development for neural prosthetics, a method for restoring function after SCI. Such improved neural interfaces are also important for the ex vivo study of neuronal biology, for example the formation of neuromuscular junction synapses, neuronal survival and axonal outgrowth. This is especially true as in vivo studies are challenging due to technical limitations and a high level of complexity, and in vitro studies do not adequately model native cell populations and architecture. Electrospun fibers are an excellent interface material, as they can not only serve as a topographically tunable culture substrate, but can also be used for controlled delivery of neuroprotective molecules ex vivo. In this thesis, the formulation of electrospun nanofibers for enhanced ex vivo neuronal outgrowth is explored. Firstly, the incorporation of cationic polymer polyethylenimine (PEI) into electrospun gelatin was achieved, using both linear and branched PEI of various molecular weights (Chapter 3). The resulting branched PEI/gelatin scaffolds were demonstrated to increase the outgrowth of neurites from spinal cord explants. Secondly, polyacrylonitrile (PAN) was electrospun with PEI to determine if the addition of PEI could make non-biocompatible hydrophobic PAN into a biocompatible material (Chapter 4). The mats containing 600 MW branched PEI allowed for increased numbers of dissociated spinal cord explant to attach. The mats containing 600 and 10,000 MW branched PEI also demonstrated increased hydrophilicity. This indicates that other electrospun polymers may be made permissible for spinal cord explant growth with the addition of PEI. Thirdly, uric acid (UA) was incorporated into electrospun gelatin nanofibers and released under physiological conditions (Chapter 7). UA is a powerful neuroprotective biomolecule that acts as an antioxidant in vivo, however excess systemic UA can lead to gout and/or kidney stones. This indicates that UA is an ideal candidate for controlled localized release. The UA release achieved was ~ 80 [mu]g, more than the ~21 [mu]g needed for beneficial effect in neuronal cultures with induced peroxynitrite- or glutamate-induced toxicity