@article {17664, title = {Nanostructured multilayers for biomedical applications {\textendash} a combinatorial analysis using biomimetic elastin-like recombinamers and polysaccharides}, journal = {EUROMAT 2011}, year = {2011}, month = {2011-09-12 00:00:00}, address = {Montpellier, France}, abstract = {

Surface engineering is of the utmost significance to lead to the conception of devices with an improved performance in biotechnology and tissue engineering. In the past two decades, many techniques were employed in order to achieve significant advances in these areas. Among them, the layer-by-layer (LbL) adsorption has gathered attention for its simplicity, versatility and possibility of assembling nanostructured thin films. Although the buildup mechanisms are well known for model polyelectrolyte combinations, extrapolating to other materials is not a straightforward task, since there are numerous parameters to consider. Here, we present the main factors that influence the construction of multilayer films based on natural charged polysaccharides and elastin-like recombinamers (ELRs). ELRs are smart genetically engineered peptides which allow conceiving ultrathin films with biologically relevant sequences.

We demonstrated that the molecular weight (MW) of ELRs is one of the major factors influencing film construction, hindering it as MW increased. Against recent theories, this is explained by the increase of hydrophobicity of ELRs with increasing MW, consequently decreasing the balance of driving forces and increasing stripping of molecules at the surface. By using ELRs with charged residues, pH affected the buildup. Our results show that the presence of aminoacids with opposite charge to that of the used polysaccharide allows better buildup of films at pHs around the pKa of the latter. The presence of both positive and negative residues in the ELR structure did not affect negatively the construction of films. This indicates that the hydrophobic nature of ELRs favors hydrophobic interactions between nonpolar residues and a fraction of uncharged functional groups near the polysaccharide pKa, besides electrostatic interactions. Increasing the ionic strength improved the film buildup but not significantly. Such behavior was attributed to a combined effect of the reduction of electrostatic repulsion of the polysaccharides and the simultaneous increase of ELRs hydrophobicity, favoring hydrophobic interactions to a small extent. All favorable arrays of buildup conditions allowed the construction of coatings exhibiting pseudo-exponential thickness growth with a limit of 5 to 7 pairs of layers.

This work displays the potential to use natural and recombinant polymers to easily modify surfaces with increased biofunctionality for tissue engineering applications.

}, keywords = {Biomaterials, Biomimetic polymers, Elastin-like macromolecules, Multilayered films, self-assembly}, author = {Costa, R. R. and Arias, F. J. and Rodr{\'\i}guez-Cabello, J. C. and Mano, J. F.} }