Proteins, adsorption

Proteins react with silicon-containing materials in a variety of ways. ° For example, peptides in a phage library were exposed to the surface of 

In many applications it is important to have surfaces that repel proteins. Hydrophilic poly(ethylene oxide) segments are effective in this regard. Such segments make polyoxide surfaces protein-repellant when either incorporated in the bulk material or covalently bonded to its surface. - 

Proteins play a critical role in regulating cell interactions with both biological and synthetic surfaces. The type and density of proteins presented on a surface are major determinants in cell function. Because proteins are present in all bodily fluids and most cell culture media, it is important to understand the dynamics of protein adsorption to biomaterials. Additionally, protein adsorption to materials impacts the overall performance of biomaterials in several manners, including regulation or inhibition of cell adhesion. 

Proteins may adopt an altered conformation upon adsorption to a surface. In solution, hydrophobic sequences within proteins are folded such 

The irreversibility of adsorption of some proteins also emphasizes the importance of understanding the kinetics of the adsorption process. Given a situation where transport of the protein to the material surface is diffusion controlled, Eq. (2) can be used during initial stages of adsorption, where the amount of protein on the surface (A) is proportional to the product of the protein concentration in solution (C) and the square roots of protein diffusion coefficient ( )) and time (t)  

This relationship allows one to estimate the relative flux of proteins within a multicomponent solution to the material surface. In the case of irreversible protein adsorption, the first protein to arrive stays on the surface permanently, illustrating the importance of understanding the properties of the proteins in solution. 

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 

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SAMs are generating attention for numerous potential uses ranging from chromatography [SO] to substrates for liquid crystal alignment [SI]. Most attention has been focused on future application as nonlinear optical devices [49] however, their use to control electron transfer at electrochemical surfaces has already been realized [S2], In addition, they provide ideal model surfaces for studies of protein adsorption [S3]. 

Protein adsorption has been studied with a variety of techniques such as ellipsome-try [107,108], ESCA [109], surface forces measurements [102], total internal reflection fluorescence (TIRE) [103,110], electron microscopy [111], and electrokinetic measurement of latex particles [112,113] and capillaries [114], The TIRE technique has recently been adapted to observe surface diffusion [106] and orientation [IIS] in adsorbed layers. These experiments point toward the significant influence of the protein-surface interaction on the adsorption characteristics [105,108,110]. A very important interaction is due to the hydrophobic interaction between parts of the protein and polymeric surfaces [18], although often electrostatic interactions are also influential [ 116]. Protein desorption can be affected by altering the pH [117] or by the introduction of a complexing agent [118]. 

J. D. Andrade, Surface and Interfacial Aspects of Biomedical Polymers, Vol. 2, Protein Adsorption, Plenum, 1985. 

Norde W and Lykiema J 1979 Thermodynamios of protein adsorption J. Colloid Interface Sol. 71 350-66... 

Golander C G, Lin Y S, Fllady V and Andrade J D 1990 Wetting and plasma-protein adsorption studies using surfaoes with a hydrophobieity gradient Colloids Surf. 49 289-302... 

Harder P, Grunze M, Dahint R, Whitesides G M and Laibinis P E 1998 Molecular conformation in oligo(ethylene glycol)-terminated self-assembled monolayers on gold and silver surfaces determines their ability to resist protein adsorption J. Rhys. Chem. B 102 426-36... 

Feldman K, Hahner G, Spencer N D, Harder P, and Grunze M 1999 Probing resistance to protein adsorption of oligo(ethylene glycol)-terminated self-assembled monolayers by scanning force microscopy J. Am. Chem. Soc. at press... 

DiMilla P A, Folkers J P, Biebuyck H A, Harter R, Lopez G P and Whitesides G M 1994 Wetting and protein adsorption of the self-assembled monolayers of alkanethiolates which are supported on transparent films of gold J. Am. Chem. Soc. 116 2225-6... 

Ramsden J J 1994 Experimental methods for investigating protein adsorption kinetics at surfaces Q. Rev. Blophys. 27 41-105... 

Ramsden J J 1998 Kinetios of protein adsorption Biopolymers at Interfaces ed M Malmsten (New York ... 

Kurrat R, Wallvaara B, Marti A, Textor M, Tengvall P, Ramsden J J and Spencer N D 1998 Plasma protein adsorption on titanium Colloids Surf. B 11 187-201... 

Van Tassel P R, Guemourl L, Ramsden J J, Tar]us G, VIot P and Talbot J 1998 A model for the Influence of conformational change on protein adsorption kinetics J. Colloid Interfaoe Sc/. 207 317-23... 

Biomaterials with Low Thrombogenicity. Poly(ethylene oxide) exhibits extraordinary inertness toward most proteins and biological macromolecules. The polymer is therefore used in bulk and surface modification of biomaterials to develop antithrombogenic surfaces for blood contacting materials. Such modified surfaces result in reduced concentrations of ceU adhesion and protein adsorption when compared to the nonmodifted surfaces. 

A good example of a surface-modified lens is the Sola/Bames-Hind Hydrocurve Flite lens, introduced in 1986. The material for the commercial Hydrocurve lens, bufilcon A [56030-52-5] contains methacrylic acid and has a high affinity for protein and subsequent deposition. The surface of the Flite lens was chemically modified with the addition of diazomethane (190) to reduce the surface charge. In vitro testing demonstrated a decrease in protein adsorption (191). 

The major problems in assay of protein by CE are the low efficiency and reproducibility by presents of protein adsorption on the inner surface of a capillary, and poor concentration sensitivity UV-detection. 

RAIRS is routinely used for the analysis of chemically modified surfaces - surface systems in electrochemistry [4.277], polymer research [4.266, 4.278], catalysis [4.265, 4.271], selfassembling monolayers [4.267, 4.268], and protein adsorption [4.268, 4.279] have been investigated. 

The most possible reason may be in the higher free energy of the protein adsorption on PolyPROPYL A materials. Chemisorbed neutral poly(succinimide) of molecular weight 13000 apparently forms a diffuse interface as predicted by theory (see Sect. 2.2). Controversially, a short polyethyleneimine exists on a surface in a more flat conformation exhibiting almost no excluded volume and producing... 

Owing to the weak hydrophobicity of the PEO stationary phases and reversibility of the protein adsorption, some advantages of these columns could be expected for the isolation of labile and high-molecular weight biopolymers. Miller et al. [61] found that labile mitochondrial matrix enzymes — ornitine trans-carbomoylase and carbomoyl phosphate synthetase (M = 165 kDa) could be efficiently isolated by means of hydrophobic interaction chromatography from the crude extract. 

Andrade, J. D-, Hlady, V. Protein Adsorption and Materials Biocompability A. Tutorial Review and Suggested Hypothesis. Vol. 79, pp. 1-63. 

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. 

Ishihara K, Shibata N, Tanaka S, Iwasaki Y, Kurosaki T, and Nakabayashi N. Improved blood compatibility of segmented polyurethane by polymeric additives having phospholipids polar group. U. Dispersion state of polymeric additive and protein adsorption on the surface. J Biomed Mater Res, 1996, 32(3), 401 18. 

VandeVondele S, Voros J, Hubbell JA (2003) Rgd-grafted poly-l-lysine-graft- (polyethylene glycol) copolymers block non-specific protein adsorption while promoting cell adhesion. Biotechnol Bioeng 82 784—790... 

To conclude, a strong correlation was found to exist between the net charge of the proteins in solution, the net charge of the SUM surface, and the extent of protein adsorption, which was expressed in terms of flux losses measured after filtration of the different protein solutions. Moreover, in the case of charge-neutral SUMs, flux losses increased with the hydrophobicity of the nucleophiles bound to the S-layer lattice. All proteins caused higher flux losses on SUMs modified with HDA than on those modified with GME or... 

Roth, CM Lenhoff, AM, Electrostatic and van der Waals Contributions to Protein Adsorption Comparison of Theory and Experiment, Langmuir 11, 3500, 1995. 

Abramson, S., Hofistein, S.T. and Weissmann, G. (1982). Superoxide anion generation by human neutrophils exposed to monosodium urate. Effect of protein adsorption and complement activation. Arth. Rheum. 25, 174-180. 

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