Abstract
Axons are guided to their targets by a combination of haptotactic and chemotactic cues. We previously demonstrated that soluble neurotrophic factor concentration gradients guide axons in a model system. In an attempt to translate this model system to a device for implantation, our goal was to immobilize a stable neurotrophic concentration gradient for axonal (or neurite) guidance. Nerve growth factor (NGF) was immobilized within poly(2โhydroxyethylmethacrylate) [p(HEMA)] microporous gels using a gradient maker. The NGF was stably immobilized, with only โผ0.05% of the amount originally incorporated into the gel released over an 8โday period. Immobilized NGF was bioactive: the percent of PC12 cells extending neurites on NGFโimmobilized p(HEMA) gels was 16 ยฑ 2%, which was statistically the same as those exposed to soluble NGF (22 ยฑ 6%). We were able to predict and reproducibly create stable NGF concentration gradients in the gel. At an NGF concentration gradient of 357 ng/mL/mm, PC12 cell neurites were guided up the gradient. The facile, flexible, and reproducible nature of this method allowed us to translate soluble growth factor gradient models to stable growth factor gradient devices that may ultimately enhance axonal guidance and regeneration in vivo. ยฉ 2003 Wiley Periodicals, Inc. J Biomed Mater Res 68A: 235โ243, 2004