(604h) Peptide Frameworks for Screening the Effects of Amino Acids on Assembly

The success of tissue regeneration depends on the scaffold used, and its properties. Ideal scaffolds should support and promote cell viability, while at the same time providing a structural and biological environment that promotes desired cellular functionalities. Reliable scaffolds should provide reproducible properties each of use. Hydrogels, made of self-assembling peptides are attractive alternatives as they are modular and under the same conditions, show consistent properties. We recently engineered various peptides by using “co-assembly of oppositely charged peptides” (CoOP) strategy. The peptides we designed self-assemble into one-dimensional fibers and form hydrogels with different mechanical properties, act as scaffold for tissue engineering. The overall aim of this study is to show the use of these hydrogels as scaffolds for cancer tissue engineering.

Discovery of small peptide domains with unique intermolecular interactions is essential for engineering new materials. Such discovery via screening all possible permutations of amino acids is impractical, while editing known peptides to create simple variations for a particular end product limits the achievable properties. Rather than attempt a brute-force approach, we instead combine these approaches and highlight the utility of “co-assembly of oppositely charged peptide” (CoOP), a framework that ‘encourages’ peptide assembly into a one-dimensional structure. CoOP is formed of only six amino acids, two of which form a “substitution domain” to study and correlate the influence of different amino acids on free energy differences of peptide aggregates, assembly kinetics, mechanism, and mechanical properties of the end product. A remarkable range of properties were observed via substitution of dialanine, ditrytophan, and diisoleucine. Diisoleucine assembles into fibrils instantaneously in water, at less than 25 M (0.002 w%) and form a gel at 10 mM (<1 w%) 1 at 200 Pa storage modulus, while dialanine system does not form fibrils in the concentrations studied. Importantly, both molecular simulations and experimental results indicate that salt bridges between the opposite charges initiate the assembly, and the subsequent stability is enhanced by the presence of an undisturbed hydrophobic core. We use an integrated computational and experimental approach to analyze the properties of CoOP with substituted domains. We probed the free energy of association and probability of amino acid contacts during co-assembly with atomic-resolution simulations and correlate them to the physical properties of the end product. Such correlation is possible because CoOP represents a unique, simple and elegant assembly framework, providing discovery and high-resolution examination of the effects of minimal substitutions of molecular interactions on peptide assembly and end-product properties. CoOP framework can be used to identify the structure – property interactions of self-assembling peptide-based biomaterials.