In this study, the behavior of neural stem cells from the newborn rat spinal cord was compared at neurosphere level after the addition of neurotrophin-3 (NT-3) once or daily, blank chitosan carriers, or NT-3-chitosan carriers respectively. We found that NT-3 enhanced the viability and differentiation of neural stem cells, but as NT-3 has an extremely short half-life at 37 degrees C, in order to maintain the NT-3-mediated proliferation and differentiation effects on neural stem cells, NT-3 needed to be added to the medium every 24 h. However, NT-3-chitosan carriers dramatically increase the differentiation percentage of neural stem cells into neurons, which includes GABAergic and as cholinergic neurons. Although blank chitosan carriers also showed good biocompatibility to the neural stem cells, they induced the differentiation of these cells into neurons at a much lower percentage than the daily addition of NT-3 or the NT-3-chitosan carriers. Our results suggest that NT-3-chitosan carriers may not only maintain the viability of neural stem cells and increase their differentiation percentage into neurons, but also reduce the amount of NT-3 required for the survival and differentiation of these cells. These results may provide an experimental basis for maximum replacement of dead neurons by neural stem cell transplant after spinal cord injury (SCI). (C) 2009 Elsevier Ltd. All rights reserved.