Adsorption of lysozyme on Silica Surfaces and Specific ion effects

Abstract: Biomedical application of nanoparticles is largely associated to their fate in biological media which, in fact, is related to their surface properties. Surface functionalitzation plays a key role in determining biodegradation, cytotoxicity and biodistribution through interactions which may be meditated by the macromolecules occurring in biological media. This project is focused on the effect of different buffers on lysozyme adsorption on flat silica surfaces and hydrophobized silica surfaces as well as mesoporous silica nanoparticles functionalized with amino groups (MSN-NH2). In order to know the adsorption amount of lysozyme we used ellipsometry, where each buffer has been studied independently at two different buffer concentrations at the same pH. The effect of different buffers can be related to specific ion effect described interaction of buffers and salts induces relevant effects on the charged interfaces (Hofmeister effect), and thus lysozyme loading. Lysozyme adsorption on silica and hydrophobized silica as well mesoporous silica at pH 7.15 was found to be buffer specific. The BES buffer seems to present a unique characteristic behavior which does not allow desorption. TRIS buffer shows the highest lysozyme adsorption amounts, while citrate and phosphate buffer usually show quite similar results. The sequential addition of MSN-NH2 causes more extensive desorption of lysozyme from the flat surface as observed with ellipsometry. Large effects of the buffer are also observed. The competitive adsorption to the particles, i. e. lysozyme protein corona formation, is likely to promote detachment from the silica surface