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New publication on bioinert hydrogel coatings

Any artificial surface that is brought into the blood stream may cause thrombus formation. We have developed surface coatings that may minimize this risk. Now we have reported some of the mechanisms that may prevent such dangerous complications and we are now in a better position to predict the behavior of many materials in this regard.

In a comprehensive study we looked at the behavior of a homologous series of poly(alkylacryl amides) in contact with bloodproteins, various cells or platelets rich plasmas. All coatings of polar poly(alkylacryl amides) that showed significant swelling in aqueous environments repelled all relevant proteins, and subsequently also any cell and blood platelets. These surfaces proved to be rather bioinert.

All coatings, however, from hydrophobic materials showed the exact opposite behavior and were clearly prone to thrombus formation.

It was found that the swelling behavior was the parameter that was suitable to predict the behavior of the surfaces in contact to biological media.

Further analysis has revealed that the proteins are repelled from the surface by two different mechanisms. Larger proteins did not adsorb because diffusion into the swollen networks was excluded because the mesh size of the network was too small. However, also rather small proteins did not enter the swollen networks. For theses cases, we assume that thermodynamic reasons are responsible and the proteins are kept out by a mechanism called entropic shielding.

The paper is a result of a collaborativ effort on Ventricular Assist Devices (in German). It is available from the journal's webpage via DOI: 10.1002/mabi.201200445.

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