Prof. (apl.) Dr. Reiner Dahint – Biosensors and Biomaterials Research Group

Proteins and lipids at liquid/solid interfaces are of crucial importance in the design of biofunctional interfaces. For example, adsorbed protein layers determine the biocompatibility of implants and may control bacterial adhesion. Upon surface contact, proteins commonly undergo structural changes, which will alter their activity and biological function. Also, in combination with lipids, proteins are valuable model systems to mimic cell membrane function. Thus, in order to improve our understanding of biofunctional interfaces, a strong need exists to develop surface analytical tools, which facilitate in situ characterization on a molecular level.

Due to its in situ capability, non-destructive character and the short wavelength of neutron beams, neutron reflectometry offers a very attractive approach to the analysis of layer structures on the nanometer scale. It provides detailed information on the amount of adsorbed species as well as the thickness, density and hydration of the absorbate. In combination with surface sensitive infrared spectroscopy (ATR-FTIR), additional information is obtained on specific molecular groups of the adsorbate as well as on molecular conformation.

We have, thus, set-up a new time-of-flight neutron reflectometer at the Helmholtz Center Berlin (HZB), which is especially adapted to biological samples and, for the first time, facilitates simultaneous in situ ATR-FTIR characterization. Dedicated sample environments have been developed to study biological films as a function of applied pressure, shearing forces and temperature. As a model application we presently investigate the phase behavior and stability of immobilized oligolamellar lipid bilayer films under load and shear, which is important in bio-lubrication and the search for advanced implant materials, such as artificial joints.