| Spinal cord injury leads to a non-permissive environment for axonal regeneration. Nerve growth factor (NGF) promotes regeneration because of its action through tyrosine kinase receptors, which results in targeted innervation. We previously demonstrated that in vitro (1) a soluble NGF concentration gradient of 133 ng/ml/mm guides primary dorsal root ganglion axons and (2) a surface immobilized NGF concentration gradient of 357 ng/ml/mm guides pheochromocytoma (PC-12) cell neurites, yet neither of these provide a cell-invasive matrix.; Concentration gradients of NGF were synthesized within a 3-D poly(2-hydroxyethyl methacrylate) [p(HEMA)] scaffold that promoted cell-adhesion and cell invasion. Using a direct ELISA technique, we were able to prove that the gradients inside of the p(HEMA) gel were stable, predictable, and reproducible. The neurites of both PC-12 and DRG cells were guided by NGF concentration gradients. This was at a concentration of 350 ng/ml/mm NGF and 298 ng/ml/mm and 350 ng/ml/mm NGF, respectively. |
