Bio(macro)molecules at solid surfaces
Living organisms are able to “sense” solid surfaces. This function seems to be the result of multiple and complex processes involving biomechanical behavior, morphological organization at different scales, biochemical signaling, secretion of biomacromolecules, etc. Through many examples in Nature, it has been shown that biomacromolecules play a pivotal role to mediate the interaction between organisms and solid surfaces. The fundamental knowledge of the mechanisms taking place at the molecular level requires coping with the complexity of the interfaces. In the context of biomaterials research, the adsorption of proteins is a ubiquitous phenomenon which dictates the biological function of the material, i.e. molecular recognition, cell adhesion, biochemical signaling, etc.
The role of proteins to control cell-material interaction has been observed in numerous situations and has guided the elaboration of surfaces with highly controlled biofunctionality. Moreover, it has led to the emergence of the concept of “biological identity of materials” which arises on the fact that cells do not interact with a bare surface but rather with a surface coated with biomolecules, essentially proteins. As a matter of fact, the presence of specific biomacromolecules on the surface of material may convert it into “biologically recognizable material”. This may be achieved in a controlled way by tuning surface properties.
Our contribution includes investigations on:
(i) biomolecule adsorption under UHV conditions (e.g. ion beam deposition),
(ii) real state of inorganic solid surfaces,
(iii) surface functionalization for the control biomacromolecule adsorption, organization and bioactivity,
(iv) layer-by-layer assembly for the incorporation of bioactive macromolecules.
We probe a variety of interfaces of biological interest at the nanoscale by means of surface science techniques, particularly X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and quartz crystal microbalance with dissipation monitoring (QCM-D). These include :
Protein adsorption
Self-assembly of fatty acids
Protein-mineral interaction
Collagen self-assembly
Collagen is the major protein of extracellular matrices (ECMs) in animal kingdom. In vivo, collagen self-assembles and interacts with both soft and hard compounds to form hierarchical three-dimensional networks surrounding cells, such as in hard biomineralized tissues, cartilage, tendon, and skin.
The basic building blocks of many collagen-based tissues are collagen fibrils. Fibrillogenesis is a cell-regulated process which involves (i) intermolecular interactions, determined by the intrinsic properties of tropocollagen molecules, and (ii) covalent bonds of chemical nature and/or mediated by enzymes. In vitro, the self-assembly of collagen into reconstituted fibrillar networks may be achieved in aqueous solutions by modulating physicochemical conditions, typically temperature, pH, ionic strength and the type of ions.
The self-assembly of collagen at solid/liquid interface is of major interest for the design of biomimetic systems in the context of biomaterials science and tissue engineering, owing to its major role to mediate cell-material interaction.
We probe collagen self-assembly both in biomimetic systems and in biological tissues :
Collagen network (in vitro)
® Degabriel
Collagen fibrils (in vivo)
® Cornette
® Jaabar
Glenohumeral capsule
Meniscus
Biomineralization
The biogenic calcium phosphate (CaP) crystallization is an outstanding process that requires the combination of specific physicochemical conditions and (bio)chemical reactions, resulting in the formation of a mineral phase in the extracellular matrix (ECM). The precise mechanisms of nucleation and growth of the mineral phase remain largely unexplained, particularly at early stages. We have conducted investigations based on the concept of enzyme-assisted mineralization. This approach explores the intriguing mechanism by which organisms direct CaP crystallization through a combination of (i) chemical environment, (iii) controlled-generation of CaP precursors and (iii) nanoscale confinement.
Our investigations contribute to the reconciliation of the disparate “chemical” and “physiological” views regarding the mineralization processes, and offer news ways to design biomimetic nanostructured materials for broad biomedical applications.
