Regensburg 2007 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 7: POSTER: INTERNAL SYMPOSIUM Scattering Experiments

CPP 7.15: Poster

Montag, 26. März 2007, 16:00–18:00, Poster B

Investigation of lubrication in natural joints by neutron reflectometry — •Thomas Kaltofen¹, Thomas Gutberlet², Maximilian Wolff³, Roland Steitz⁴, and Reiner Dahint¹ — ¹Angewandte Physikalische Chemie, Universität Heidelberg — ²Paul-Scherrer-Institut, Villigen, Schweiz — ³Experimentalphysik IV - Festkörperphysik, Universität Bochum — ⁴Hahn-Meitner-Institut, Berlin

Despite their high medical relevance, the principles of lubrication in natural joints are still unclear. It is generally accepted, that the presence of hyaluronic acid (HA), the main component of the synovial liquid, plays an important role for the low friction observed. Furthermore, it is assumed that surface active lipids participate in the lubrication. Using a model system of lipid bilayers deposited on a polyelectrolyte (PE) cushion and in contact with HA solution, we started to investigate the effects of pressure and shear forces, as experienced by natural joints, on the internal structure of the SiO₂/PE/lipid/HA interface and the bulk HA solution by neutron reflectometry (NR), complemented by in situ ellipsometry and quartz crystal microbalance (QCM-D) measurements. Only on positively charged polyelectrolyte surfaces, the successful build-up of the model system could be demonstrated. By NR, the existence of an irreversibly absorbed, highly hydrated HA layer on top of the lipid membrane was proven. For shear rates above 2.5 min⁻¹ a swelling of the HA layer has been observed. Pressure dependent studies are presently underway.