(691i) Complementary Peptide Coassemblies for Driving the Structural Order of Thermochromic and Optoelectronic Biomaterials

The hierarchical organization of natural peptides can be utilized as a synthetic tool for enabling properties in soft biomaterials that are highly reliant on molecular ordering and the formation of nanostructured networks. In this presentation, I will be discussing the utility of peptides as side chains with tunable noncovalent interactions that can modulate the properties of chromogenic and optoelectronic conjugated polymers, as well as the impact of the resulting bioscaffolds on morphology and behavior of excitable cells such as cardiomyocytes. First, I will present how electrostatically driven peptide coassemblies direct the conformation-dependent structural order and thermochromic behavior of peptide-functionalized chromogenic polymers (polydiacetylenes, PDAs) under neutral, aqueous environments. A suite of spectroscopic characterization tools, including solid-state nuclear magnetic resonance (ssNMR), ultraviolet-to-visible (UV-Vis) absorption, and Raman spectroscopy, were used to unravel the inherent structural order of model peptide-PDAs that control the chromatic phases that exist during thermochromic cycles. The positively charged peptide-PDA formed a β-sheet-like assembly with higher structural order than its disordered, negatively charged peptide-PDA. The equimolar coassembly resulted in a polymer with a more ordered structure than negatively charged peptide-PDA that still meets the geometric requirement for topochemical polymerization. Although all samples demonstrated thermochromicity, the coassembly experienced the least hysteresis in the aqueous state, and stabilization of the coexistence of blue and red phase chains was observed in the film state. In the latter half of this talk, I will present the utility of a sequence pair with charge complementarity for directing the order of energy donor and acceptor units to create photocurrent-generating bioscaffolds compatible with cardiac tissues. The structural, photophysical, and electrical properties of the coassembled materials provide important insights into the role of coassembly-driven photoinduced energy transport processes for this biomaterial. Importantly, our coassembled scaffolds can generate photocurrents both as dry films (~2 nA) and under aqueous environments (~12 nA) upon 415 nm illumination. Lastly, these complementary peptide coassemblies were interfaced with cardiomyocytes, and the cellular morphology of cardiomyocytes on our materials was visualized. In addition, their contractility indicates that the cardiac beating rate could follow the frequency of light pulses even without any optogenetic modification on the cells. Ultimately, with these stimulatory peptide-based nanomaterials, we hope to address long-standing challenges in the fidelity of human cardiac tissue models used for high-throughput drug screening or disease modeling.