| AVS 55th International Symposium & Exhibition | |
| Surface Science | Friday Sessions |
| Session SS+AS+NC-FrM |
| Session: | Environmental Surfaces and Water Interaction with Oxide Surfaces |
| Presenter: | I. Van De Keere, Vrije Univ. Brussel, Belgium |
| Authors: | I. Van De Keere, Vrije Univ. Brussel, Belgium S. Svedhem, Chalmers Univ. of Tech., Sweden A. Kunze, Chalmers Univ. of Tech., Sweden J. Vereecken, Vrije Univ. Brussel, Belgium B. Kasemo, Chalmers Univ. of Tech., Sweden A. Hubin, Vrije Univ. Brussel, Belgium |
| Correspondent: | Click to Email |
Titanium is frequently used as a biomaterial in orthopaedics and cardiovascular devices. The metal is covered with a native oxide layer of a few nm, which contributes to the high biocompatibility of Ti implants. One of the surface properties of a biomaterial, which plays an important role in the interaction with biomolecules is electrostatic interaction at the surface. By varying the potential of Ti, the surface charge of Ti changes, and electrostatic interactions are likely to be influenced. The goal of the present study is to investigate the influence of an electric field on the adsorption of biomolecules, such as proteins and lipids, onto Ti surfaces and their conformational changes with electrochemical quartz crystal microbalance with dissipation (ECQCMD). QCMD is a well-established technique for monitoring mass and film thickness (through the frequency shift) and to obtain information about the viscoelastic properties of the adsorbed layers (through the dissipation shift). It has recently become possible to carry out combined QCMD and electrochemical measurements using a specially designed flow cell. This combination is valuable for adsorption studies under the influence of external fields and/or where one wants to in situ change the oxide layer thickness. A difficulty arises upon using Ti compared to other model substrates as gold since the surface of Ti is always covered with a native oxide layer, which may grow upon application of an external potential to the Ti surface. Firstly, the oxidation of Ti in buffer under the influence of an electric field was investigated, because a stable oxide layer was desired before investigating the interaction of biomolecules with Ti under applied external potential. With ECQCMD, quantitative information on the growth behaviour and the thickness of the Ti oxide layer was obtained. The calculated thickness from ECQCMD was correlated with the depth profiles obtained from X-ray Photoelectron Spectroscopy (XPS). Secondly, the adsorption of biomolecules on Ti was studied. The influence of an external potential applied to the Ti-surface on the formation of supported lipid bilayers of DOEPC (positively charged phospholipid) is pronounced. The moment of vesicle rupture, which precedes the formation of bilayers, is delayed significantly upon application of a potential of 0 V vs SHE, compared to open circuit potential and 0.6 V vs SHE. For these two potentials, the rupture of vesicles occurs faster and at the same moment.