Development of biodegradable 3d matrices for the repair of spinal cord injury by a tissue engineering approach

Spinal cord injury could occur after a trauma caused by a traffic accident, sports injuries, work accident or by a non-traumatic reason, such as tumor removal, infection, soft tissue disease. This kind of injury is a critical health problem which not only limits lives of the patients but also effects their family and even entire population. Various methods have been proposed for the quick and effective solution for the damage, such as cell-based treatments, biomaterials, and the usage of several biological factors that increase neurotic regeneration, alone or by drug delivery systems. However, mentioned treatments contain only one active ingredient in repairing a very complex tissue injury, thus they are insufficient. Considering these disadvantages, for this thesis, it is aimed to produce a bilayered matrix that consisting both the morphological and biochemical structure to provide axonal orientation and the release of biomolecules in order to stimulate regeneration. In the first part of the study, a collagen layer that was loaded both the neuronal growth factor Neurotrophin-3 that promotes axonal regeneration and Chondroitinase ABC (ChABC) enzyme which is capable of degrading the glial scar, was prepared by the plastic compression method. Then, in vitro release profiles of the biomolecules, contained in the prepared collagen layer, were examined. While NT-3 had been released into the damaged area in certain amounts over time, the release profile of the chABC molecule could not be determined despite different methods. Then, the nanofibrous membrane that forms the top layer of the bilayered matrix was constructed from the polymer solution prepared from different concentrations of collagen/poly (lactate-co-glycollate (PLGA) with the electrospinning method. This top layer also contained laminin proteins that promote neuronal regeneration. While the nanofiber top layer had an aligned nanofiber structure that provides adipose-derived stem cells (ASCs) and axonal extensions of the dorsal root ganglia (DRGs) to grow in same directions, the collagen substrate had a smooth and patternless structure. It was determined that the nanofiber top layers, which were analyzed morphologically, had different orientation degrees and fiber diameters according to the collagen / PLGA content they contained. On top of that, according to the amount of collagen / PLGA they contained, for both wet and dry state biomechanical behavior differences were also observed. Water uptake capacities, which are important for cell adhesion, were measured and it was clear that all membranes had the ability to absorb almost equal amounts of water due to bearing same collagen bottom layer. While all matrices provided sufficient cell adhesion and development, it was seen that in comparison with control membranes, biomolecule-containing matrices were more effective in the development of ASCs and DRGs and had positive affect on axonal branching and development.