Vitronectin adsorption

Select proteins that mediate adhesion of specific anchorage-dependent cells (such as osteoblasts, fibroblasts, and endothelial cells) on substrate surfaces have been identified (Underwood and Bennett, 1989 Thomas et al., 1997 Ayad et al, 1994). For example, adsorption of fibronectin and vitronectin on tissue-culture polystryene subsequently enhanced osteoblast, fibroblast, and endothelial cell adhesion (Underwood and Bennett, 1989). More importantly, fibronectin and vitronectin adsorption on borosilicate glass, in a competitive environment, maximized fibroblast and osteoblast adhesion, respectively (Thomas et al., 1997). Ayad et al. (1994) reported that enhanced adsorption of laminin on tissue-culture polystyrene promoted subsequent endothelial cell adhesion. These studies provided evidence that adsorption of specific protein(s) can, subsequently, control select cell adhesion on material surfaces. 

Many studies so far have demonstrated a proportional relationship between surface energy of nanomaterials and the adsorption of hydrophilic cell adhesive proteins (e.g., fibronectin and vitronectin). For example, maximum vitronectin adsorption was noted on hydrophilic surfaces compared to hydrophobic ones [65]. Therefore, it is speculated that hydrophilic (i.e., high surface energy) nanomaterials have a higher affinity for cell adhesive proteins and, subsequently, promote cell functions and tissue responses better than hydrophobic nanomaterials. The verifications and debates on this hypothesis will be further discussed in the following chapters. 

Chrysotile Rabbit pleural Coating of fi- Vitronectin adsorption to fibres in- Wu et al. ... 

Protein adsorption is the first event that takes place on material surfaces when blood or other body fluids are brought into contact with any material. Therefore, cell - material interactions must be discussed by taking into consideration the species and the nature of the protein adsorbed on the material surfaces. For instance, a series of cell-attachment and spreading experiments [11] of fibroblasts on the surface of modified polystyrene (TCP and Primaria) carried out in the presence of fetal calf serum (FCS) showed that FCS contains components which tend to decrease the attachment and spreading of fibroblast cells. The effect of these nonadhesive components was only evident when the FCS was depleted of vitronectin, showing that vitronectin overcomes the effect of these nonadhesive components and promotes cell-attachment and spreading on the polystyrene surface. Fibronectin, on the other hand, does not play a principal role in this fibroroblast adhesive process (Fig. 2). 

Cooper et al. [21, 22] reported in detail the results of their laborious work on the adsorption of four proteins human serum albumin (HSA), fibrinogen (FGN), fibronectin (FN), and vitronectin (VN), on five biomaterials polyethylene (PE), silicone rubber (SR), Teflon-FEP (FEP), poly(tetramethylene oxide)-poly-urethane (PTMO-PU), and polyethylene oxide)-polyurethane(PEO-PU). Hard segments of these polyurethanes are composed of a methylene-bis(p-phenylisocyanate) (MDI) chain extended wih 1,4-butanediol. 

If we consider that cell adhesion under biological circumstances is mainly brought about with the aid of preadsorbed protein on the material s surface, we may explain the unique behavior of amino-containing materials against the cell-adhesion process in terms of the reduced residence-time of protein molecules at the interface. Actually, a recent study [129] revealed that the surface of polyamine-gra/t-polystyrene copolymer (SA) containing 6 wt.% polyamine portion exhibited a minimal adsorptive property against bovine plasma fibronectin (FN) and vitronectin (VN), both of which are known to mediate cell-adhesion processes. 

Indirect patterning A protein repellent background is locally opened, rendering areas of the surface prone to protein adsorption. The patterning of cell-attractive areas is indirectly achieved by a subsequent deposition of proteins either by preincubation with a solution of proteins (most prominent are fi-bronectin, vitronectin, and laminin) or by adsorption from serum-supplemented cell culture media during cell seeding. 

Fabriziushoman DJ, Cooper SL (1991) Competitive adsorption of vitronectin with albumin, fibrinogen, and fibronectin on polymeric biomaterials. J Biomed Mater Res 25(8) 953-971... 

Specific domains of proteins (for example, those mentioned in the section Organic Phase ) adsorbed to biomaterial surfaces interact with select cell membrane receptors (Fig. 8) accessibility of adhesive domains (such as specific amino acid sequences) of select adsorbed proteins may either enhance or inhibit subsequent cell (such as osteoblast) attachment (Schakenraad, 1996). Several studies have provided evidence that properties (such as chemistry, charge, and topography) of biomaterial surfaces dictate select interactions (such as type, concentration, and conformation or bioactivity) of plasma proteins (Sinha and Tuan, 1996 Horbett, 1993 Horbett, 1996 Brunette, 1988 Davies, 1988 Luck et al., 1998 Curtis and Wilkinson, 1997). Albumin has been the protein of choice in protein-adsorption investigations because of availability, low cost (compared to other proteins contained in serum), and, most importantly, well-documented conformation or bioactive structure (Horbett, 1993) recently, however, a number of research groups have started to examine protein (such as fibronectin and vitronectin) interactions with material surfaces that are more pertinent to subsequent cell adhesion (Luck et al., 1998 Degasne et al., 1999 Dalton et al., 1995 Lopes et al., 1999). 

Investigations of the underlying mechanism(s) revealed that the concentration, conformation, and bioactivity of vitronectin (a protein contained in serum that is known to mediate osteoblast adhesion ((Thomas et al., 1997) see the section Vitronectin ) was responsible for the select, enhanced adhesion (a crucial prerequisite for subsequent, anchorage-dependent-cell function) of osteoblasts on these novel nanoceramic formulations. Specifically, of the proteins (such as albumin, laminin, fibronectin, collagen, and vitronectin) tested, vitronectin adsorbed in the highest concentration on nanophase alumina after 4 hr moreover, competitive adsorption of vitronectin was 10% greater on nanophase compared to conventional alumina (Webster et al.,... 

Fibronectin, vitronectin, and type 1 collagen are some of the most representative ECM proteins involved in cell adhesion processes, therefore adsorption studies with these proteins and the PLA/G5 composite material have been performed. Preliminary studies have shown that all proteins adhere better to the G5 (the most hydrophilic material) than to the other materials. Vitronectin presented the best adhesion with PLA (the most hydrophobic material), and the PLA/glass composite presented an intermediate behavior. Further experiments are being conducted to evaluate the direct impHcation of the main proteins present in ECM to regulate cell proliferation and differentiation in the studied materials, and to obtain information on how the quality of the surface (physicochemical and topographical) influences the adsorbed protein layer. 

However, the mechanisms behind nanotopographically mediated tissue responses are still not clear. The increased adsorption of cell adhesive proteins (such as fibronec-tin, vitronectin, etc.) on nanoscale rough surfaces, due to either uneven surface landscapes or inaeased specific surface area, is a plausible mechanism. However, this mechanism is not enough to explain aU the nanoscale roughness (or nanotopography) related tissue responses. For example, there is a lack of evidence to explain the fact the many different types of cells see the same roughness but their responses are different from cell type to cell type [64]. These questions will be further examined in Chapter 8. 

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