Traction Stresses and Morphology of 3T3 Fibroblast Cells on Fibronectin-versus RGD- Modified Elastic Substrata
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Traction Stresses and Morphology of 3T3 Fibroblast Cells on Fibronectinversus RGD- Modified Elastic Substrata Padmavathy Rajagopalan, William A. Marganski, Micah Dembo, Joyce Wong Department of Biomedical Engineering Boston University, Boston, MA 02215, USA ABSTRACT We report a study on cellular traction forces and morphology on fibronectin (FN)- and Arg-Gly-Asp (RGD) modified substrata. We have focused on fibronectin- and RGD- modified substrata because RGD is a primary cell-binding site on fibronectin. In this study we report the traction stresses exerted by NIH (National Institutes of Health) 3T3 fibroblasts on model polyacrylamide hydrogel substrates using the elastic substrata technique. At equal values of input concentration of fibronectin and RGD we find that the values for projected cell area are similar. However, a significant difference is observed in the traction forces exerted by fibroblasts on fibronectin- compared to RGD-modified surfaces. At equal values of input concentration, the average force exerted by NIH 3T3 fibroblasts is approximately ten fold higher on fibronectin-modified surfaces in comparison to RGD-modified surfaces. INTRODUCTION Surfaces of biomaterials that can elicit a desired cell response are extremely important for the development of future medical implant devices and tissue engineering. Determining the effect that chemical and mechanical properties of the biomaterial substrata exert upon on cellsubstrata interactions is of particular importance for understanding biological processes such as morphogenesis and wound healing. Previous studies [1-3] have shown that the chemical and mechanical properties of biomaterial substrates significantly impact cell-substratum interactions such as cell migration, morphology, and cellular traction stresses. Immobilizing extracellular matrix proteins or short peptide sequences on the surfaces of biomaterials leads to enhanced cell adhesion as well as specific cell-substratum interactions. Fibronectin, a multifunctional protein promotes cell adhesion through its multiple binding sites e.g. heparin, RGD, collagen, (Figure 1). Among these binding sites, the RGD sequence on fibronectin III domain 10 is recognized by several known [4,5] integrins. Thus, there have been numerous studies modifying a wide range of biomaterials with RGD [6]. Although RGDmodified surfaces promote cell adhesion and proliferation, previous studies [7] have reported differences in cell spreading and focal contact for surfaces modified by fibronectin and RGD. However, the effect on cellular traction forces has not been addressed. In our studies, the primary focus is to study the effect of RGD alone and fibronectin on cellular traction forces. Traction forces are the forces exerted by a cell tangential to its substratum [8]. Such forces occur due to specific cell-substratum adhesion as well as non-specific frictional interactions. The quantification of cellular contractile strength is important in understanding wound-healing mechanisms. Furthermore, attaining a thorough understand
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