Preparation of the SM-345431 silicone DDS and in vitro release study. (A) Analysis of the inhibitory activity of SM-345431 in the growth cone collapse assay using E8 chick and E14 rat DRGs. (B) Collagen co-culture assay using E8 chick DRGs and semaphorin3A-expressing COS7 cell aggregates. (C) Pictures showing the effects of SM-345431-silicone or control-silicone in the collagen gel. (D) Schematic illustration of drug release from the matrix silicone preparation; the drug is dissolved in water, permeates into the preparation and is then released. The rate of water permeation into the silicone matrix is controlled by various additives, and the proportions of these additives included in the DDS control the variations in the drug release profile. The preparation used here contained the water-soluble additives listed in the table (D). Stable and linear release of SM-345431 was observed for up to 2 months as shown in (E) and (F). (E, F) SM-345431 release curve for the preparation. The linear cumulative percent release curve at 2 months (E) and the stable release dosage per day (F) are shown for the administration of SM-345431 using this novel DDS. (G) Exposed intact spinal cord. (H) Transected spinal cord. (I) The novel DDS we employed. A silicone sheet containing SM-345431 was placed onto the transected site of the spinal cord. The system allowed for stable and continuous release of the semaphorin3A inhibitor throughout the experimental period.