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BIOMIM Report Summary

Project ID: 259370
Funded under: FP7-IDEAS-ERC
Country: France

Mid-Term Report Summary - BIOMIM (Biomimetic films and membranes as advanced materials for studies on cellular processes)

Bioinspired and biomimetic materials take inspiration from the most complex naturally organized chemical and biological structures, including proteins, lipids, extracellular matrix components and cell constituents. The main objective nowadays in the field of biomaterials is to design highly performing bioinspired materials learning from natural processes. Importantly, biochemical (presence of chemical ligands and growth factors), physical (matrix stiffness) and topographical (morphogen gradients) are all key parameters that can affect cellular processes including adhesion, migration and differentiation. The control of processes occurring at biomaterials surface is also of prime importance to guide the cell response. The main aim of the current project is to employ planar biopolymeric films and lipid membranes as novel functional bio-nanomaterials. Our strategy is based on two related projects focusing on different aspects of cellular processes.
The first project deals with the rational design of smart films for tissue regeneration with foreseen applications in musculoskeletal tissue engineering. In WP2, we have designed biopolymeric self-assembled coatings that possess 1) controlled bioactivity by incorporation of growth factors, especially bone morphogenetic proteins (BMP) and 2) controlled film stiffness obtained by creating covalent bonds between the polycation and polyanion forming the biopolymeric films.
Using these films and mesenchymal precursors as cellular models, we have revealed so far hidden phenomena on the cellular processes, ie adhesion, migration and differentiation, when the growth factors are delivered from the biomaterial in a matrix-bound manner. We have decorticated the molecular mechanisms leading to the cell response, which involves BMP receptors that trigger osteogenic differentiation but also cell adhesion receptors . These results are of utmost importance for cell biologists but also for applications of these films as bioactive coatings in the field of orthopedic implants.
In WP1, we have shown using infrared spectroscopy that the BMP secondary structure is preserved when the protein is trapped in the film. We also evidenced that the film can be dried and that its vertical section can be imaged by scanning electron microscopy using well-defined protocols. Furthermore, we have now experimental evidences that the protein is internalized by the cells. We are currently studying the internalization route using confocal microscopy and high resolution scanning electron microscopy.
In WP3, we have developed films presenting a spatial control of their stiffness and of the growth factor to more more closely mimicking the cell microenvironment in vivo. More precisely, we have created either sharp or continuous gradients of film properties using microtechniques and microfluidics. Importantly, we have shown that the cells respond to these spatial patterns by positioning themselves collectively and by differentiating in a spatially controlled manner.
Finally, in WP4, we are also working at the molecular level to investigate the role of important proteins that are involved in cell adhesion and motility, the ERM proteins (erzin, radixin, moesin). By producing recombinant proteins and by preparing model lipid membranes containing an important phosphoinoitide, we are reconstituting in vitro the linkage between the plasma membrane and the cell cytoskeleton (mostly F-actin filaments). Here again, we use these well-defined microenvironments in vitro to simplify the complexity of the interactions that occur in cellulo. We have shown that moesin and ezrin behave very similarly when they are in contact with PIP2-containing membranes but that moesin is much more resistant to degradation by enzymes.
At this date, the project has involved three post-doctoral researchers and five PhD students, who worked in collaboration with several researchers in Grenoble, in France, in Belgium, Germany and in the US. It has led to 14 publications in peer reviewed scientific journals and a large number of presentations at international conferences.

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