Protein-inspired multilayer nanofilms: science, technology and medicine

The field of polypeptide multilayer nanofilm research flourishes where study of protein structure and function shares a border with development of polyelectrolyte multilayers. The soil is fertile for creative input and promises a harvest of interesting results: the structure of a film can be predetermined on a layer-by-layer (LBL) basis, a huge variety of polypeptide sequences can be realized in large quantities by modern methods of synthesis, and the fabrication process is environmentally benign. In electrostatic LBL assembly, multilayer film assembly is driven primarily by coulombic interactions, but hydrophobic interactions and hydrogen bonds also contribute to film formation and stability, the amount depending on polypeptide design. Most peptides suitable for LBL assembly form films with a large percentage of beta-sheet at neutral pH; it would appear that beta-sheet is favored over alpha-helix in this context by the contribution to entropy of the number of ways of forming a beta-sheet from a single polypeptide chain. Film thickness and roughness depend rather substantially on amino acid composition. Promising applications of the polypeptide multilayer film platform technology include coatings for medical implant devices, scaffolds for tissue engineering, coatings for targeted drug delivery, artificial cells for oxygen therapeutics, and artificial viruses for immunization. In each case peptide structure is tailored to the application. Here we summarize recent results of experimental studies and computational work from our laboratory, showing how the study of protein structure has inspired the design of polypeptide films and pointing out new opportunities for technology development. This work also provides a brief introduction to polypeptide structure and multilayer films.