Cell Responses to Surface and Architecture of Tissue Engineering Scaffolds

Abstract

Cell responses on surface chemistry of tissue engineering scaffoldsWhen cells adhere to surface of a scaffold, a sequence of physico -chemical reactions will happen between cells and the scaffold.Immediately after a tissue engineering scaffold is implanted into an organism or comes into contact with cell culture environments, protein adsorption to its surface occurs and which mediates the cell adhesion, and also provides signals to the cell through the cell adhesion receptors, mainly integrins.Cells can adhere on the surfaces of tissue engineering scaffolds and release active compounds for signaling, extra-cellular matrix deposition, cell proliferation and differentiation.The interaction www.intechopen.comRegenerative Medicine and Tissue Engineering -Cells and Biomaterials 570 between cells and biomaterial scaffolds is called focal adhesion.To understand the factors that influence cell adhesive ability is a key in the development and application of new tissue engineering scaffold.Cell attachment is a complex process, affected by numerous aspects, such as cell behavior, material surface properties, and environmental factors.Material surface properties comprise the hydrophobicity, charge, roughness, softness and chemical composition of the biomaterial surface itself. Surface hydrophobicityBiomaterial development has been focusing on surface modifications of biomaterials over years in order to promote a greater understanding and control of the material characteristics for regulating biocompatibility.The surface hydrophobicity is well known as a key factor to govern cell response.The surface hydrophobicity can be assessed by measuring contact angle through water spread of a droplet on a surface.The lower the contact angle, the more hydrophilic the surface is.Previous studies showed the more hydrophilic surface of material films is the much more cell adhesion on the surface (Goddard & Hotchkiss, 2007;Xu, 2007).For example, osteoblast adhesion was reported decrease when the contact angle of surface increased from 0° to 106°.Fibroblasts were found to have maximum adhesion when contact angles were between 60° and 80° (Tamada & Ikada, 1993;Wei et al., 2009).Interestingly, Vogler mentioned that the hydrophilic surface were suitable for the attachment of Madin-Darby Canine Kidney (MDCK) cells but more hydrophilic surfaces (contact angel θ< 65°) did not yield progressively high level of attachment efficiency (Vogler, 1999).Furthermore, surface hydrophobicity is related to the rate of cell spreading and differentiation.On hydrophilic surfaces, cells generally showed good spreading, proliferation and differentiation.Mouse osteoblast-like cell line MC3T3-E1 showed more fractal morphology on hydrophilic surface (contact angel θ= 0°) (Wei et al., 2009).7F2 mouse osteoblasts on hydrophilic surface (contact angel θ= 24-31°) demonstrated accelerated metabolic activity and osteodifferentiation compared to their unmodified counterparts (contact angel θ= 72°) (Yildirim et al., 2010).The same phenomenon was observed in neuronal spreading and neurite outgrowth when the material surfaces reduced their hydrophobicity (Khorasani & Irani, 2008;Lee et al., 2003). Protein adsorptionSince cell adhesion to material surface requires a series of cytoplasmic, transmembranal and extracellular proteins that assemble into stable contact sites (Geiger & Bendori, 1987), cell adhesion and behaviors is likely involved the adsorption onto the material surface of serum and ECM proteins (Brynda & Andrade, 1990;Hattori et al., 1985).Many proteins, including immunoglobulins, vitronectin, fibrinogen, and fibronectin (Fn), adsorb onto implant surfaces immediately upon contact with physiological fluids and modulate subsequent inflammatory responses.For example, adsorbed adhesive proteins mediate the attachment and activation of neutrophils, macrophages, and other inflammatory cells.Many literature studies mentioned that different cell behaviors, related to different hydrophobicities, may be mediated by protein absorption, because surface wettability modified the sort and the quantity of adsorbed cell adhesion molecules.Hydrophobic surfaces tend to adsorb more proteins, while hydrophilic surfaces tend to resist protein adsorption (Xu, 2007).Tamada et al. used bovine serum albumin (BSA), bovine γ-globulin and plasma Fn to study the protein www.intechopen.com