Biomaterial surface chemistry

Brodbeck WG, Nakayama Y, Matsuda T, Colton E, Ziats NP, Anderson JM. Biomaterial surface chemistry dictates adherent monocyte/macrophage cytokine expression in vitro. Cytokine 2002, 18, 311-319. 

Both XPS and TOF-SIMS are nowadays standard analytical tools for the determination of biomaterials surface chemistry. Examples of the use of XPS or TOF-SIMS for the analysis of biomimetic polymers include the investigation of different protein " ° and phosphate group modified polymeric surfaces. 

Keselowsky, B.G., Collard, D.M., Garcia, A.J. Integrin binding specificity regulates biomaterial surface chemistry effects on cell differentiation. Proc. Natl. Acad. Sci. U.S.A. 102, 5953-5957 (2005)... 

Brodbeck, W.G. et al. Influence of biomaterials surface chemistry on apoptosis of adherent cells, /. Biomed. Mater. Res., 55, 661, 2001. 

Fig. 3 Biomaterial surface chemistry modulates cellular responses. A SAMs presenting different chemistries differentially modulate integrin receptor binding in osteoblasts. B Substrate-dependent differences in osteoblast-specific gene expression correlate with integrin binding specificity. C Matrix mineralization is dependent on integrin binding specificity. Surfaces that support specific binding of asfii integrin exhibit high levels of mineralization. Adapted from [46,48]...

The increasing demand for synthetic biomaterials, especially polymers, is mainly due to their availability in a wide variety of chemical compositions and physical properties, their ease of fabrication into complex shapes and structures, and their easily tailored surface chemistries. Although the physical and mechanical performance of most synthetic biomaterials can meet or even exceed that of natural tissue (see Table 5.15), they are often rejected by a number of adverse effects, including the promotion of thrombosis, inflammation, and infection. As described in Section 5.5, biocompatibility is believed to be strongly influenced, if not dictated, by a layer of host proteins and cells spontaneously adsorbed to the surfaces upon their implantation. Thus, surface properties of biomaterials, such as chemistry, wettability, domain structure, and morphology, play an important role in the success of their applications. 

Brodbeck WG, Voskerician G, Ziats NP, Nakayama Y, Matsuda T, Anderson JM. In vivo leukocyte cytokine mRNA responses to biomaterials are dependent on surface chemistry. Journal ofBiomedicalMaterials Research A 2003, 64, 320-329. 

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). 

Brown, X. Q., Ookawa, K., Wong, J. Y. Evaluation of polydimethylsiloxane scaffolds with physiologically-relev ant elastic moduli interplay of substrate mechanics and surface chemistry effects on vascular smooth muscle cell response. Biomaterials 2005, 26, 3123-3129. 

As discussed in Section I, the surface chemistry of any biomaterial has a central role in determining in vivo responses. If a copolymer is designed with two monomers with differing surface energies, surface chemistry can deviate significantly from bulk chemistry. Therefore a large number of investigations with XPS and SSIMS have been devoted to the analysis of surface enrichment of copolymer constituents. 

New experimental results on specific polymer material problems are presented in the last nine chapters. Several cases involve the study of polymers from commercial sources. The topics include (1) surface chemistry as induced by (a) outdoor weathering, (b) chemical reactions, and (c) plasma exposure (2) chemical bond formation at the polymer -metal interface and (3)biomaterials characterization and relationship to blood compatibility. 

This book contains papers from the Fourth International Conference on Computational Methods and Experiments in Materials Characterisation which brought researchers who use computational methods, those who perform experiments, and of course those who do both, in all areas of materials characterisation, to discuss their recent results and ideas, in order to foster the multidisciplinary approach that has become necessary for the study of complex phenomena. The papers in the book cover the follow topics Advances in Composites Ceramics and Advanced Materials Alloys Cements Biomaterials Thin Films and Coatings Imaging and Image Analysis Thermal Analysis New Methods Surface Chemistry Nano Materials Damage Mechanics Fatigue and Fracture Innovative Computational Techniques Computational Models and Experiments Mechanical Characterisation and Testing. 

Tan J, Saltzman WM. Topographical control of human neutrophil motihty on micropatterned materials with various surface chemistry. Biomaterials 2002 23 3215-25. 

The development of new methods for studying surfaces is progressing rapidly, precipitated by the phenomenal growth and interest in surface physics and chemistry which was stimulated, in part, by the need for clean, well-characterized surfaces for microelectronic and other high-technology applications. The biomaterials field should be able to capitalize upon this plethora of new methods which have appeared primarily in the past 15 years. In particular, many of the new techniques measure surface chemistry directly, in contrast to older methods which often required indirect or thermodynamic data. At the present stage of development in the field of surface analysis, a picture of a surface must be built up by using a variety of methods. Combinations of the classic surface analysis methods (e.g., con-... 

As documented in the previous sections, tools now exist to detect contamination to very low levels and to characterize many of the parameters that define surface chemistry and structure. Both of these aspects of characterization are essential to insure surface reproducibility in biomaterials investigations and for commercial medical devices. The most work remains to be done in the area of correlation between surface structure and biocom-patibilitv. 

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. 

The studies of protein adsorption to biomaterials undertaken so far have shown that the process is understandable in terms of the principles of surface activity, mass action, surface chemistry, and transitions in the structure of proteins. Furthermore, cells with receptors for certain of the adsorbed proteins are likely to respond to surfaces in proportion to the amount of this protein on the surface, although other processes involving... 

Protein diffusivity, however, is not always the main determinant in the composition of adsorbed protein layers. If this were the case, the composition of the adsorbed protein layer would be the same on different materials exposed to the same solution. This condition is not usually observed (Horbett, 1999), indicating that the affinity of each protein is influenced by the surface chemistry of the biomaterial (Horbett and Brash, 1995). Because proteins differ in affinity for various surface chemistries, the competitive protein adsorption process will also differ, leading to unique protein layer compositions upon different materials. Furthermore, the vast majority of protein adsorption studies have been carried out in vitro, assuming that this accurately mimics the in vivo environment. However, differences in implant site (i.e., blood-contacting devices vs solid tissue... 

---