Design and Synthesis of Peptoids for the Development of Biomimetic Hydrogels

In recent decades, the development of biomimetic hydrogels has gained significant attention in the field of regenerative medicine and tissue engineering. Hydrogels are three-dimensional polymeric networks that possess the ability to retain substantial quantities of water. Their structural composition closely resembles the one of the extracellular matrix, which plays a crucial role in supporting cellular functions such as communication, growth, and motility. This project focuses on the design and synthesis of peptoids, N-substituted glycine oligomers, as building blocks towards the fabrication of novel biomimetic hydrogels. Peptoids offer several advantages over peptides, their natural counterparts, including enhanced proteolytic stability, ease of synthesis, and tunable properties. We developed a library of peptoids, each consisting of 16 monomers, featuring a modular backbone that includes both hydrophilic and hydrophobic monomers in specific sequences to encourage amphiphilicity and self-assembly. These peptoid sequences contain functional side chains like amines, carboxyls, alkynes, and azides, allowing for chemical conjugation and crosslinking through click chemistry. We synthesized the peptoids following the submonomer solid-phase synthesis protocol, then purified them using flash chromatography. Their purity and molecular weights were then confirmed by analytical HPLC (high-performance liquid chromatography) and MALDI-TOF (Matrix-assisted Laser Desorption/Ionisation Time-of-flight). We investigated the ability of our peptoids to self-assemble into nanostructures, i.e. nanoparticles, to promote gelation and modulate hydrogel mechanical properties. We studied the self-assembly properties of the nanoparticles by performing DLS (dynamic light scattering) and SEM (scanning electron microscopy). The purified peptoids were designed to form hydrogels through either covalent or non-covalent crosslinking mechanisms. Our HPLC and MALDI-TOF results confirmed that we were able to successfully synthesize and purify our designed peptoid building blocks. The DLS and SEM also confirmed the successful formation of the peptoid nanoparticles. Finally, we started investigating how structural variations in peptoid design influence the mechanical and physicochemical properties of the resulting hydrogels formed using click chemistry. We further investigated the swelling behavior of these hydrogels as well. These findings offer valuable insights into how the deliberate selection of specific sequences can significantly impact the formation of hydrogels. By comparing peptoid-based hydrogels with traditional polymer-based systems, we showed the unique advantages of peptoids as building block in the synthesis of biomimetic scaffolds.