Elution of adsorbed fibrinogen from a silica surface by anionic surfactants. 2. Effect of the hydrocarbon chain lengths

The chain length effect of 8, 10, and 14 carbon homologous sodium alkyl sulfate surfactants on the elution of fibrinogen molecules adsorbed onto a silica surface has been studied. Previously, it has been shown (Zembala et al. Langmuir 1998, 14, 2167) that the release mechanism of fibrinogen by sodium dodecyl sulfate (SDS) is the result of a competition between the elution and anchoring of the adsorbed proteins. All of the removal kinetics, followed by a radioactive labeling technique, could be described by a single-exponential decay function. The apparent release rate constant k and the amount of released proteins increase with the surfactant concentration c(s) and attain plateau values for c(s) close to the critical micelle concentration (cmc). By means of two-step elution experiments (first, low-concentration surfactant injection, followed by the injection of surfactants above cmc), it was shown that all surfactants were able to anchor fibrinogen molecules onto the solid surface and that surfactants with a smaller chain length possess a higher ability to anchor proteins than surfactants with longer chains. On the contrary, for a given surfactant concentration, elution increases with the chain length.