Self-assembling Peptides

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Objectives of the proposed research program: The overall objective of this research program is to develop multifunctional, injectable, hydrogels that are dynamically responsive to the presence of enzymes for the express purpose of controlling the release of therapeutic molecules. Of particular interest is the controlled release of peptides, proteins, and DNA. ******The fundamental mechanisms leading to nanofiber formation have not been clearly elucidated for this (RADA)4. Previous work (PNAS, 2005, 102(24):8414 – 8419) has shown that peptide self-assembly into micron long nanofibers, from globules, occurs within 60 seconds; a time frame that seems to defy a physical explanation. With respects to the addition of N-terminal amino acids, we have observed (in preparation) that amino acid chemistry, and their subsequent hydration state, can greatly affect this assembly process. Now that these two components have been identified as being crucial to nanofiber formation, further work will focus on elucidating the effect of altering the actual amino acid chemical makeup to understand the role individual components have on self-assembly process. Furthermore, in order for these systems to be applied for controlled drug delivery, our previous work has shown that N-terminal amino acids can be used to specifically modify the population size of different water types within these highly hydrated hydrogels: non-freezing bound, freezing bound, unbounded free. Despite efforts understanding the enzymatic activity toward idealized peptide domains in solution (Biomaterials, 2011, 32(5): 1301-1310) little to no work has been conducted on investigating enzymatic activity within the complex hydrogel structure, where the presence of the nanofiber, as well as types of waters, and regional viscosity may affect the apparent activity of enzymes. These topics will be further outlined within this grant.******Novelty and expected significance of the work to a field or fields: It is expected that this work will provide a framework for understanding the physicochemical aspects involved in the self-assembly of RADA4 nanofibers, hopefully presenting a mechanism that explains the rapid assembly of these molecules. Correlating water structures and regional viscosity in these hydrogels should allow for a better understanding of the effect nanofiber chemistry has on the mobility and activity of enzymes. Although some work has investigated enzyme action as a function of waters, understanding this in the realm of a hydrogel will be crucial to furthering a biophysical understanding of enzyme action in complex media.