Lysine adsorption on the silanized SiO₂-surface for immobilization of the estrogen receptor hER(alpha)

We investigated the adsorption of the L-Lysine (200 mmol) molecule to a silanized SiO₂ surface as a function of the pH value. The SSC (spraying spin coating)-method [Cherkouk et al, J. of Col. and Int. Sci., 337(2009)] was applied to functionalize the SiO₂ surface by using the (3-Aminopropyl)trimethoxysilane (APMS) as coupling agent with a NH2 functional group. We adsorbed lysine molecules for the pH-values of 2.5, 7.5, 8.7, 9.5 and 13 to the silane film. The infrared spectroscopy is not suitable to investigate the system because the NH3+ signal at 1600 cm-1 originating from the silane film overlaps with the infrared signal of the deprotonated carboxyl group of the lysine molecule. X-ray photoelectron spectroscopy (XPS) was used to measure the binding energies C1s and N1s as function of the pH value. This pH change affects the charge state which was fitted in the XPS spectra to obtain the optimal adsorption conditions at pH= 7.5 via carboxyl groups of the lysine to the functionalized SiO₂ surface.