Biomaterials, adsorption from protein

Protein adsorption from protein mixtures can be complex. For example, when plasma proteins from whole blood bind to biomaterials, albumin often binds initially and is later displaced by fibrinogen. Fibrinogen can then be displaced by other blood proteins (5). This is the Vroman Effect. Although the Vroman Effect was discovered for blood proteins, it may take place in other situations in which multiple components can bind. 

Chen et al. utUized a direct chemical reaction with a given solution (wet treatment) to modify the surface of the silicone rubber. The presence of a layer of PEO on a biomaterial surface is accompanied by reductions in protein adsorption, and cell and bacterial adhesion. In order to obtain a PEO layer on top of the silicone rabber surface, the surface was firstly modihed by incorporating an Si-H bond using (MeHSiO) , and followed by PEO grafting to the surface using a platinum-catalyzed hydrosilylation reaction. These PEO-modified surfaces were demonstrated by fibrinogen adsorption both from buffer and plasma, as well as albumin adsorption from buffer. Reductions in protein adsorption of as much as 90% were noted on these surfaces. 

Fortunately, highly purified HEMA became available (from Hydro Med Sciences) about this time, and other monomers were readily purified by vacuum distillation. The poly (HEMA) hydrogels made with the purified HEMA showed far lower protein adsorption from either water or buffered saline than hydrogels made with the commercially available HEMA as experiment C, Table I shows. These results emphasize the biological importance of hydrogel composition in particular and biomaterial composition and purity in general. 

Protein adsorption from relatively complex mixtures is involved in many different applications of biomaterials. A summary of all studies involving protein adsorption that were done in the author s laboratory is given largely in the form of an annotated table. Certain aspects of the methods results and conclusions of studies that pertain especially to adsorption from mixtures are also discussed. 

In all these applications of biomaterials, adsorption occurs from relatively complex solutions containing many different proteins. For this reason, much of the effort in my laboratories has focused on the behavior of protein adsorption as it occurs from protein mixtures. In this paper, a summary of these studies is provided with the... 

The results of studies in the author s laboratory summarized in Table 1 constitute a relatively large amount of information about how adsorption occurs from the protein mixtures typically encountered by biomaterials. Overall, the most important observations made are that variations in surface chemistry, time of adsorption, and protein type are major factors in determining the composition of the adsorbed layer. The adsorbed layer formed from mixtures thus contains a rather complex and changeable combination of proteins. 

HORBETT Adsorption to Biomaterials from Protein Mixtures... 

Figure 1.12 Schematics illustrating interfacial interactions between bone tissne or cell and implanted biomaterials viewed from the host tissne perspective (a) protein adsorption from blood and tissue fluids, (b) protein desorption, (c) substrate surface changes and material release, (d) inflammatory and connective tissue cells approach the implant, (e) possible targeted release of matrix proteins and selected adsorption of proteins, (f) formation of lamina limitans and adhesion of osteogenic cells, (g) bone deposition on both the exposed bone and implant surfaces, and (h) remodeling of newly formed bone.

Unsworth, L.D., Sheardown, H., and Brash, J.L. 2005. Polyethylene oxide surfaces of variable chain density by chemisorption of PEO-thiol on gold Adsorption of proteins from plasma studied by radiolabelhng and immunoblotting. Biomaterials 26 5927-5933. 

Tan, J., Brash, J. L. (2009). Nonfouling biomaterials based on polyethylene oxide-containing amphiphilic triblock copolymers as surface modifying additives adsorption of proteins from human plasma to copolymer/polyurethane blends. Journal of Biomedical Materials Research Part A, 90A, 196-204. http //dx.doi.Org/10.1002/jbm.a.32074. 

---