Cellular response to nanoscale elastin-like polypeptide polyelectrolyte multilayers

Ionic elastin-like polypeptide (ELP) conjugates are a new class of biocompatible, self-assembling biomaterials. ELPs composed of the repeat unit (GVGVP)n are derived from the primary sequence of mammalian elastin and produced in Escherichia coli. These biopolymers exhibit an inverse transition temperature that renders them extremely useful for applications in cell-sheet engineering. Cationic and anionic conjugates were synthesized by the chemical coupling of ELP to polyethyleneimine (PEI) and polyacrylic acid (PAA). The self-assembly of ELP–PEI and ELP–PAA using the layer-by-layer deposition of alternately charged polyelectrolytes is a simple, versatile technique to generate bioactive and biomimetic surfaces with the ability to modulate cell–substratum interactions. Our studies are focused on cellular response to self-assembled multilayers of ionic (GVGVP)40 incorporated within the polymeric sequence H2N–MVSACRGPG–(GVGVP)40–WP–COOH. Angle-dependent XPS studies indicated a difference in the chemical composition at the surface (∼10 Å below the surface) and subsurface regions. These studies provided additional insight into the growth of the nanoscale multilayer assembly as well as the chemical environment that the cells can sense. Overall, cellular response was enhanced on glass substrata coated with ELP conjugates compared with uncoated surfaces. We report significant differences in cell proliferation, focal adhesions and cytoskeletal organization as a function of the number of bilayers in each assembly. These multilayer assemblies have the potential to be successfully utilized in the rational design of coatings on biomaterials to elicit a desired cellular response.