Implant Surface Modification by Biological Multi-layer Systems
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B8.6.1
Implant Surface Modification by Biological Multi-layer Systems Regine Willumeit, Helmut Kamusewitz, Michael Schossig, Jens Schröder, and Helmut Clemens GKSS Research Center Max-Planck-Str.1, 21502 Geesthacht, Germany
ABSTRACT The current design of implants or implant materials is under the pressure of an increasing demand. In our society we find more and more active older people with an increasing life time. On the other hand it can be observed that also for younger people implants become more and more necessary due to sport or accidents. As a consequence the development of new surgery strategies as well as new materials systems is needed. In this work we present the idea of creating a metal implant surface which mimics a cell membrane or at least parts of it. Scanning electron and atomic force microscopy investigations show that a multilamellar closed lipid layer can be prepared and that this layer resembles the same contact angle observed for the membrane of an osteoblast.
INTRODUCTION In living organisms like eucaryotes the contact areas between cells are their cell membranes. These plasma membranes not only separate the individual cells but they have specific functions: certain components play an important role in cell-cell identification and signal transduction and the selective permeability allows transport of substances in and out of the cells. These different functions result from the great variety of membrane components, such as lipids (about 40%) and proteins (about 60%). In terms of implant development the next neighbors to the cells are materials, which do not belong to the normal cell surroundings. Thus, a necessary biocompatibility must be achieved by either the correct choice of material and surface roughness or by means of surface functionalization. Another approach is the use of protein layers (mainly cell adhesion proteins) or the construction of materials that can be used as drug delivery systems. So far, little is known of the role lipids play in this context. However, it is known from literature that phospholipids can cause calcification [1,2] and that phosphorylcholine modified polymers (MPC polymers) are used to decrease cell adhesion and to improve blood compatibility [3-5]. In the last few years it has been found that the lipid function in the membrane is not only important in supporting proteins, but also influences the function of proteins. Furthermore, lipids themselves can be a target for drug design [6]. Therefore, we have focused our interest on this class of amphiphilic molecules. In this paper we present initial results on the modification of metallic implant surfaces of Ti-6Al-7Nb alloy substrates with different roughness by phospholipids multi-layers using contact angle measurements and surface sensitive characterization techniques, such as scanning electron microscopy (SEM) and scanning force microscopy (SFM).
B8.6.2
EXPERIMENTAL DETAILS Ti-6Al-7Nb (composition in mass percent) represents a so-called two-phase (α + β) alloy used for implant applications because of its
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