UC Davis

Proteoglycans are a class of biomolecules that play an important and ubiquitous role in the body, with their roles ranging from maintaining tissue mechanical properties to regulating cell signaling. Many of these functions are carried out by the glycosaminoglycan (GAG) chains that decorate the proteoglycan core protein, with glycans chondroitin sulfate (CS), dermatan sulfate, and heparan sulfate regulating growth factors and water content through their negatively charged polysaccharide chains. Additionally, the free-floating GAGs heparin and hyaluronic acid (HA) play important roles in tissue function, such as modulation of enzymes and supporting cell mobility. Because of their important biological roles, as well as their relatively simple structure, multiple easily accessible reactive moieties, and commercial availability, many groups have sought to GAGs for biomedical applications. In this dissertation, we explore the engineering of GAGs to suppress inflammation, starting with a study regarding the balance of the chemical modification of GAGs and the perseveration of their bioactivity. Here, we discuss the fabrication of hydrogels from thiolated CS (CS-SH) and thiolated HA (HA-SH), demonstrating how increased thiolation of these GAGs impairs their recognition by hyaluronidase and GAG-targeting peptides, suggesting reduced biorecognition. Subsequent studies build off these findings, with these DPN hydrogels employed in the context of osteoarthritic joint inflammation. Articular chondrocytes encapsulated in GAG DPN hydrogels demonstrated a suppressed inflammatory response, as shown through reduced secretion of pro-inflammatory cytokines and reduced proliferation. Finally, the GAGs CS and heparin were conjugated with collagen targeting peptides to prevent platelet activation following endothelial denudation. The spacer sequence and C-terminal modification of the peptides were optimized to improve conjugation efficiency and collagen binding ability, improving the effectiveness of the peptide-glycan molecule. Overall, these studies serve as groundwork studies for the engineering of GAGs in the contexts of the prevention of inflammation through balancing the modification of GAGs for increased functionality with the preservation of the potent bioactive signals from the GAG themselves.