Removal of lysozyme from methylated silicon oxide surfaces by a non-ionic surfactant, pentaethylene glycol mono n-dodecyl ether (C(12)E(5))

The removal of lysozyme adsorbed to a hydrophobic surface by a non-ionic surfactant, C(12)E(5) was investigated using in situ ellipsometry. Both the adsorption and removal of protein were studied at different protein and surfactant concentrations. The surfaces used were methylated silica surfaces and the experiments were carried out at pH 5.6 in 0.01 M NaCl solution. The adsorption isotherm of lysozyme did not reach a plateau level within the concentration range investigated and judging from the adsorbed amount at high protein concentrations the protein adsorbs at least in a bilayer. The adsorbed protein was only to a minor extent removed upon rinsing with buffer and addition of surfactant gave partial removal which was dependent on surfactant concentration and the amount of protein adsorbed. An increase in the surface concentration of protein led to a decrease in the fraction of the adsorbate that was removed due to surfactants. However, the absolute amount removed did not decrease but levelled off at 1.3 mg m(-2). The removal of adsorbed lysozyme started at about the same surfactant concentration as that required for the surfactant to adsorb at the interface and the amount removed by surfactant increased with surfactant concentration up to half its cmc.