Biomimetic Systems

E. Sinner

Biological systems exhibit remarkable physical and chemical properties and have been always a source of inspiration for man-made matters. Biomimesis is a concept of designing materials, resembling biological systems in structure and/or function. Content of the ongoing work in our lab is the combination of biomimetic strategies and material science, leading toward so-called bio-inspired materials. Probing biomimetic composites, particular emphasis is placed on molecular building blocks located in interfacial positions, such as bio-membranes and their functional units, e.g. membrane proteins (see fig.1). In that, bio-membranes represent complex structural - functional units, optimized in their outstanding physical properties by matters of evolution. We mimic the structure of biomembranes using self-assembled planar lipid membranes. These artificial membranes are a suitable matrix for membrane proteins. Despite the central importance of membrane proteins, they remain under-explored territory. Thus, we generate biomimetic platforms for investigation of membrane protein with relevant biological function, such as cell adhesion receptors, G-protein coupled receptors and ion channels (see fig.2). The methods of molecular biology provide subtle tools to synthesize and equip molecules of interest with fluorescence or affinity tags in unrivalled molecular precision and rate of yield. These affinity tags have become indispensable as ‘molecular lanterns’ for reliable assignment, and/or purification and sterical control. Optical methods such as surface plasmons and microscopy are optimal tools for in vitro characterization of the surface related processes. Thus, binding of cell adhesion peptides, known for weak binding affinities are measured by plasmon enhanced fluorescence spectroscopy. Cellular behaviour, migration, differentiation, growth and adhesion on biomimetic composites are detected by means of microscopy, particularly probing biocompatibility, functionality and response of the bio-inspired materials.

left : Figure 1: Microscopy of a neuronal – differentiated murine stem cell (Hwei Ling Khor) with schematic magni-fication of the cellular membrane. right : Figure 2: Schematic picture of a surface-tethered artificial membrane with incorporated membrane protein (Eva Lemker and Rudi Robelek). In red: immuno-tag for specific antibody binding.

A.G. Milbradt, M. Loweneck, S. Krupka, M. Reif, E.K. Sinner, L. Moroder, C. Renner, “Photomodulation of conformational states. IV. Integrin-binding RGD-peptides with (4-aminomethyl)phenylazobenzoic acid as backbone constituent” Biopolymers. 77, 304-313, (2005)
M. A. Deverall, E. Gindl E, E.K. Sinner, H. Besir, J. Ruehe, M.J. Saxton, C.A. Naumann, “Membrane lateral mobility obstructed by polymer-tethered lipids studied at the single molecule level” Biophysical Journal. 88, 1875-1886, (2005)
E.K. Sinner, U. Reuning, F.N. Kok, B. Sacca,L. Moroder, W. Knoll, D. Oesterhelt, “Incorporation of integrins into artificial planar lipid membranes: characterization by plasmon-enhanced fluorescence spectroscopy”, Analytical Biochemistry. 333(2):216-224 (2004).