Building structured, functional materials inspired by nature: Using peptides, peptoids, and polymerizations
The assembly of peptide and peptide?inspired building blocks into functional, well?defined, multi?length scale materials represents an exciting, rapidly expanding research field that bridges the principles of polymer science and engineering with a tremendous breadth of biomolecular interactions. The advantageous features of peptides, including their biocompatibility, functional diversity, and high purity, are complemented by the breadth of potential applications that may arise from their resultant structures and assemblies. Applications in biology (tissue scaffolding and drug conjugation), electronics (electron and/or ion?conduction), and membranes (ion capture and ultrafiltration) represent a few of many examples where such biologically rich materials hold potential for enabling new routes to enhanced materials performance. Achieving successful solution and interfacial assembly techniques for peptides and other peptidomimetic materials requires obtaining a deep understanding of their design principles and limitations, as well as their amenability to structure formation when subjected to a variety of environmental conditions, such as pH, solvent, and temperature, to which such assembly methods may be exquisitely sensitive. This review especially focuses on mechanisms and the product of oligo? and polypeptide assembly, often resulting in the formation of extended, wire?like structures obtained by solution methods, with inclusion of peptoid?based structures and the complementary roles of polymerizations and step?by?step synthetic methods. Moreover, we describe relationships between naturally occurring peptide?based structures, such as Geobacter pili, that in turn inspire self?assembly of peptide?based structures, composites with polymer materials, and assemblies therefrom.