The Effect of Epimers, Glycosidic Linkage and the Sulfation Pattern of Glycosaminoglycan Components in Glycomics Research

Abstract

Every mammalian cell surface is decorated with 30 nm thickness of carbohydrates, namely glycans from the plasma membrane. These glycans are expressed either in conjugated systems (glycoproteins, proteoglycans, and glycolipids) or without conjugation (glycosaminoglycans such as hyaluronan). These glycans play a fundamental role in cell biology, such as cell-cell interactions that govern many normal and pathological processes. Consequently, a better understanding of structure-activity relationships of glycan will provide new insights into the specific biological process. In my thesis, I have investigated how the conformation plasticity of uronic acid, glycosidic linkage with galactosamine, and sulfation pattern on chondroitin sulfate (CS) regulate specific biological functions.

Chapter 1 summarizes various factors influencing the structure-activity relation of carbohydrates and thereby significances in biological activities. More specifically, we address basic structures and functions of glycocalyx. Followed by multivalent probes to study carbohydrate-protein interactions. Finally, we talk about the sulfation patterns of GAGs, particularly HS influence the carbohydrate-protein interactions. Chapter 2 describes a systematic investigation of preferential binding and therapeutic potential of two crucial non-sulfated and sulfated hexuronic acid derivatives (GlcA and IdoA) abundantly found in the glycosaminoglycan (GAG) family. We discovered 2,4-disulfated glucuronic acid (Di-S-GlcA) residue as a potential ligand for T. gondii recognition. The multivalent display of Di-S-GlcA significantly inhibited the interaction of the parasite with the host cell leading to decreased invasion of host cells. This finding paves the way for future use of Di-S-GlcA in therapeutic studies of T. gondii infection in in vivo model. Chapter 3 reports inverted cell culture technique to study glyconanoparticles selectivity. Briefly, glyco-nanoparticles are indispensable tool to target specific cell lines using the receptor-mediated exchange. However, nanoparticles have tendency to undergo sedimentation with increasing time and resulting in false biological results, including cytotoxicity and cellular internalization process. Here, provides a rational platform to improve the specificity, selectivity, and avoid results from sedimentation of NPs. Validated by a series of cytotoxicity assay and in vitro uptake studies, we showed that the inverted cell culture method could rapidly improve our knowledge of cell specificity. This simplicity and effectiveness of the system underscore its potential to accelerate nanoparticles research in biology. Chapter 4 deals with the late and preoxidized disaccharides building block approach for synthesizing chondroitin sulfate oligosaccharides. Regioselective benzylidine group opening or deprotection and sulfation yielded oligo-CS-E/A/C analogs in moderate overall yields. Later, the disaccharide CS analogs were functionalized on gold nanoparticles via tripodal conjugation to targeting cancer and glioblastoma cells. We found that the specific sulfation code regulate CD44 mediated uptake in MDA-MB-231 and U87 glioblastoma cell lines, showing the nanomedical application of these glyco-nanostructures.