Interactions of Proteins with Polyelectrolytes at Solid/Liquid Interfaces: Sequential Adsorption of Albumin and Heparin
✍ Scribed by Milan Houska; Eduard Brynda
- Publisher
- Elsevier Science
- Year
- 1997
- Tongue
- English
- Weight
- 129 KB
- Volume
- 188
- Category
- Article
- ISSN
- 0021-9797
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✦ Synopsis
components and disturb hemostatic and immune balance of
The association of heparin with the surface-immobilized albublood. Surface-induced thrombosis is a major cause of min exhibits a strong pH dependence governed by the protonizafailure of small-diameter vascular implants and the use of tion of albumin. At neutral pH the interaction is quite weak but standard extracorporeal devices like blood oxygenators and at acidic pH and especially below the isoelectric point of albumin dialyzers requires systemic anticoagulation of patients to the interaction becomes pronounced: about 0.42 g of heparin is prevent thrombosis and maintain hemostasis. However, sysbound per 1 g of albumin at pH 3. The stoichiometry of the comtemic anticoagulation brings about a serious danger of bleedplex at saturation corresponds to the state of charge equivalence.
ing and other adverse effects (1-3).
The dependence of heparin binding on the ionic strength shows
To improve biocompatibility and decrease or avoid necesan inexpressive maximum in ca. 0.2 M NaCl (pH 4.0), apparently due to a less extended conformation of heparin. The primary albu-sity of systemic anticoagulation, various methods of surface min monolayer adsorbed on a solid support by hydrophobic intertreatment of medical devices have been devised. It has been action can serve as an anchor for the sequential adsorption of observed that a surface passivation with albumin adsorbed alternating monolayers of heparin and albumin and thus multiple from a priming solution decreases adhesion and activation layers with a sandwich-like architecture are deposited on the surof platelets and activation of the coagulation system and of face. The adsorption in each step reaches saturation determined the complement (4-9). Albumin adsorbs on most surfaces by the charge equivalence and the composition of the bilayers but a simple adsorption does not yield a compact and durable tends to be the same regardless of their distance from the surface. coverage of the surface. In the blood environment the pread-
The approach described makes it possible to cover surfaces with sorbed albumin is gradually replaced by other constituents a regular multilayer of a required and uniform thickness. ᭧ 1997 and, in general, its protective effect is rather short-term.