Biomaterials surface interaction

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). 

Fig. 8. Schematic representation of protein-mediated cell adhesion on biomaterial surfaces. Biomaterial surface properties (such as hydrophilicity/hydrophobicity, topography, energy, and charge) affect subsequent interactions of adsorbed proteins these interactions include but are not limited to adsorbed protein type, concentration, and conformation. Changes in protein-surface interactions may alter accessibility of adhesive domains (such as the peptide sequence arginine-glycine-aspartic acid) to cells (such as osteoblasts, fibroblasts, or endothelial cells) and thus modulate cellular adhesion. (Adapted and redrawn from Schakenraad, 1996.)...

Upon approach, organisms will be attracted or repelled by the biomaterial surface, depending on the resultant of the various interaction forces. Thus, the physico-chemical surface properties of the biomaterial, with or without conditioning film, and those of the microorganisms play a decisive role in this process. Because the size of microorganisms is in the im range, adhesion can be described in terms of colloid science. Indeed, for several strains and species physico-chemical models like the Deijaguin-... 

Dr. Thomas Chandy is a research associate in the Division of Chemical Engineering Material Sciences, Biomedical Engineering Institute and Interventional Cardiology Laboratories at the University of Minnesota. He has over two decades research experience at Sri Chlia Tvunal Institute for Medical Sciences Technology, Trivandrum, India, in the area of biomaterial surface engineering and blood biomaterial interactions. More recently. Dr. Chandy and Dr. Rao have focused their research on platelet biomaterial interactiorrs and development of assist devices for cardiovascular applications. They continue to be active in this newly evolving area of research. 

Red cell-surface interactions may play a role in the dynamics of protein adsorption. We have been investigating the turnover of protein between solution and surface for several years (27-29), and have established that turnover occurs on a variety of surfaces. The rate and extent of turnover depend strongly on the surface character, with hydrophilic materials, for example, showing much more rapid turnover than hydrophobic materials. If red cells have the ability to strip protein off a biomaterial surface, then clearly this effect could influence the characteristics of the turnover process, particularly from a rate point of view. This process, in turn, could affect the development of the protein layer over a period of time. 

There are a number of other important factors which influence the biological interaction and ultimate fate of a biomaterial in the body. Biomaterial properties, such as purity, tendency to absorb water and degrade are clearly important. Also, the design of the device or implant, the flow of biological fluids by the foreign surfaces or movement of the implant within a tissue space, the test techniques selected to assay biomaterial responses iri vitro or i vivo (in different animal species), and the implantation itself can all contribute to the ultimate fate of the implant device. Table V lists these factors and Table VI details important biomaterial surface properties. 

Figure 8. The importance of the scale and intensity of biomaterial surface "roughness" will depend upon the relative size and interaction of cells on that surface (schematic).

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