X-ray photoelectron spectroscopy studies on adsorption of amino acids from aqueous solutions onto oxidised titanium surfaces

Osseointegration is concerned with processes at the cellular level. However, the titanium surface is also capable of interactions with organic structures at the molecular level. These properties of titanium are presented from a physicochemical viewpoint. Adsorption experiments are described that should simulate molecular processes in the organism. The selected model substances, amino acids, were adsorbed from aqueous saline solutions with various pH values onto evaporated titanium layers. The evidence of adsorbates was determined by photoelectron spectroscopy. The pH values at which adsorption occurred, the binding energies and signal intensities according to curve fit allow conclusions to be drawn from the adsorption reactions. Thus, the titanium surface preferentially forms a surface complex with the carboxyl groups of the amino acids in an acidic solution. The resulting positions of the adsorbed molecules can be confirmed through evaluation of the line intensities. The results show clearly that there is chemical bonding between the titanium surface and the organic substances. Assuming that a comparable situation occurs in the organism, such processes or similar ones can be viewed as preliminary stages of osseointegration.