The induction of cell alignment by covalently immobilized gradients of the 6th Ig-like domain of cell adhesion molecule L1 in 3D-fibrin matrices.

Concentration gradients of matrix-bound guidance cues in the extracellular matrix direct cell growth in native tissues and are of great interest for the design of biomedical scaffolds and on implant surfaces. This study describes effects of covalently immobilized gradients of the 6th Ig-like domain of cell adhesion molecule L1 (TG-L1Ig6) within 3D-fibrin matrices on cell alignment. Linear gradients of TG-L1Ig6 were established and shown to be stable for at least 24 h whereas soluble gradients disappeared completely. Fibroblast alignment along the gradients was observed when cultured on top and within TG-L1Ig6-gradient matrices. Fibroblasts responded to an increase of 0.2 microg TG-L1Ig6/ml per mm matrix, corresponding to a concentration change of <1% per cell. Significant differences were observed when fibroblasts were cultured within the TG-L1Ig6-gradient matrices as the number of aligned cells decreased by 20-30% in the middle of the gradient when compared to cells cultivated on top of the gradient. This finding might be explained by approximately 13% reduction in the average cell length of fibroblasts within compared to fibroblasts cultured on top of the gradient matrix. In contrast to fibroblasts endothelial cells did not show any alignment with TG-L1Ig6-gradient matrices. The study indicates that cells exposed to gradients of matrix-bound TG-L1Ig6 are able to respond differentially to 2D- or 3D-environments suggesting the use of gradients for cell guidance within 3D-scaffolds and on implant surfaces to improve their biomedical functions.