Simultaneous delivery of an active protein and neutralizing antibody: creation of separated regions of biological activity

Spatial control over the biological activity of nerve growth factor (NGF) v ia a novel type of controlled-release device was demonstrated in an in vitr o system. Two-layer polymer matrices that simultaneously released NGF and a neutralizing antibody (anti-NGF) from opposite faces were placed in PC12 c ell-populated collagen gels. Biological activity in the gels was assessed o ver the course of 10 days by direct observation of the cells, which extend neuronal processes in the presence of NGF in a dose-dependent manner. The c oncentrations of both proteins in the gels were determined by ELISA as a fu nction of distance from the polymer matrices at various time points. A boun dary in biological activity was established within a few days of the initia tion of the cultures; this boundary persisted and became more pronounced th roughout the duration of the experiment. ELISA analysis revealed regions of high concentration of both NGF and anti-NGF on their respective sides of t he polymer matrix early in the experiment. The theoretical amount of active NGF in the gel sections was calculated on the basis of these ELISA results ; the concentration of active NGF in the region adjacent to the polymer cor related with the observed degree of biological response. These experiments suggest that spatial control over the biological activity of a potent agent can be obtained by an appropriately designed controlled-release device. (C ) 2001 Elsevier Science B.V. All rights reserved.