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Effect of Blending Chitosan and Gelatin on Cell Adhesion

Yan Huang and Sundararajan V. Madihally. School of Chemical Engineering, Oklahoma State University, 423 Engineering North, Stillwater, OK 74078

Chitosan, a biodegradable positively polysaccharide has shown promise for use in various biomedical applications including tissue engineering. Although chitosan has no specific binding domain for integrin-mediated adhesion, it supports biological activity of diverse cell types. Recently, blending gelatin to chitosan as a way to improve biological activity has gained much attention. However, the influence of blending gelatin with chitosan on cell adhesive properties is not clearly understood. In this study, we evaluated the alteration in cell spreading characteristics, cytoskeletal actin distribution, focal adhesion kinase (FAK) distribution and PECAM-1 expression of HUVECs under static and 4.5, 8.5, 13 and 18 dyn/cm2 shear stress conditions. Addition of gelatin greatly affected the stiffness of 2D and 3D scaffolds, facilitated the degradation rate and maintained the dimension in the presence of lysozyme. Evaluation of cell adhesive interactions showed decreased cell spreading area on chitosan membranes, accumulated actin and localized FAK inside HUVECs in static culture. Exposure to shear stress showed weak cell adhesion on chitosan surfaces since the lowest shear stress tested (4.5 dyne/cm2) for 3h washed away majority of the cells. On chitosan-gelatin membranes, human umbilical vein endothelial cells (HUVECs) exhibited morphology similar to gelatin in static culture. However, at higher shear stresses (8.5, 13 and 18 dyn/cm2) and longer exposure time (48 hr), presence of chitosan inhibited shear-induced alterations in cell alignment. This could be due to weak binding-strength, conforming that the presence of cell-binding ligands play crucial role in maintaining cell adhesion under forces in 2D culture. However, no significant differences were observed in PECAM-1 expression.