Proteins at Titanium Interfaces
Proteins in solutions accumulate spontaneously at interfaces. Exceptions to this rule may be charge neutral surfaces with high water retention and/or high mobility. In the human body, cell membranes in general, albumin associating cell surfaces, and mucos
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Pentti Tengvall
Linkoping University, Laboratory of Applied Physics, Linkoping, Sweden
Introduction .•..••.....•.....•................................. Adsorption from Single- and Multi- Protein Solutions In Vitro ......... Serum Albumin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ovalbumin, Lysozyme and a-Lactalbumin ......................... Fibrinogen .................................................. Fibronectin .................................................. Multi-Protein Solutions ........................................ Others . .............................. '" .................... Adsorption from Serum and Saliva ..••....••........•...•....••••• Activation of Humoral Cascade Systems In Vitro ..••....••...•.•.... The Intrinsic Pathway of Coagulation ............................. Complement ................................................. Accumulation of Proteins at the Titanium Interface In Vivo ........... Interactions with Endothelial Cells, Platelets and PMNGs Ex Vivo ...••. Interactions with Osteoblast-like Cells in Culture .....•.....••....•.. Final Remarks .........................•........•.....•.....•.. Abbreviations and Symbols ...................................... References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
D. M. Brunette et al., Titanium in Medicine © Springer-Verlag Berlin Heidelberg 2001
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14 Proteins at Titanium Interfaces
14.1 Introduction Proteins in solutions accumulate spontaneously at interfaces. Exceptions to this rule may be charge neutral surfaces with high water retention and/or high mobility. In the human body, cell membranes in general, albumin associating cell surfaces, and mucosas with high oligosaccharide content behave in this manner. In vitro, artificial surfaces, such as the charge-neutral poly(ethyleneoxide/-glycols) type of surfaces are protein repellent in one or a few protein systems. However, rigid surfaces like oxide-covered titanium adsorb proteins within seconds of exposure to e.g. blood plasma. Properties that determine adsorption Titanium surface properties
Protein properties
Free energy Charge Ion binding Redox/corrosion potential Hydrogen bonding capacity Surface water structure/ binding strength Acidlbase properties (pcz) Surface impurities Surface topography Oxide (thickness, growth, dielectric constant, water and ion sorption) Interactions with small (organic) molecules
Overall hydrophobicity Charge Prosthetic groups Ion binding Hydrogen bonding residues Water binding pI Specific interacting residues Quarternary, tertiary and secondary structure Number of disulphide bridges Size
The electrochemical potential of titanium v.s. the H2/Pt electrode is -1.63 V. Hence, metallic titanium reacts rapidly with oxygen and water becoming passivated with an invisible n-type semiconducting Ti0 2 layer with thickness 3-5 nm at room conditions (Fig. 14.1; see also C
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