Master of Science
Umesh R. Desai
Glycosaminoglycans (GAGs) are linear, polydisperse polysaccharides consisting of alternating amino sugars and either a uronic acid or galactose residue. They are ubiquitous components of the extracellular matrix and are present on cell surfaces and in basement membranes. GAGs are highly negatively charged as a result of many sulfate and carboxylic acid groups, and are extremely heterogeneous in both their structure and in their physicochemical properties. This complexity in structure is attributed to the alterations in residue types, glycosidic bond linkage, sulfation levels, sulfation positions, and chain lengths during biosynthesis. GAGs interact with a wide number of proteins and modulate various biological functions. Many of these functions are implicated in disease states, spanning from cancer to viral infection. Given this, decoding the fine structure of GAGs is a key step in the analysis required for understanding the biochemical basis of GAG-protein interaction and their subsequent biological and therapeutic roles. As a consequence, efforts towards the development of analytical procedures to characterize these molecules have been performed, however, many challenges exist.
Heparin and its related GAG heparan sulfate (HS) are microheterogeneous, linear polysaccharides composed of repeating disaccharide units of uronic acid (1à4) linked to glucosamine. The heterogeneous nature of heparin and HS chains, both in length and charge, coupled with the low levels usually present in most biological samples, has made the detailed analysis of their structure very challenging. To address this challenge, literature methods use enzymatic or chemical digestion to depolymerize heparin and HS into smaller oligosaccharides before analysis. For exhaustive enzymatic digestion, a cocktail of the enzymes heparinase I, II, and III have been used to cleave glycosidic bonds and form unsaturated oligosaccharides. Various techniques are then used to separate and analyze heparin and HS oligosaccharides. The studies discussed here present our efforts in the development of simple and sensitive analytical procedures for the analysis of GAGs in human plasma.
In addition to quantitative analysis of GAGs in biological fluids, analytical technologies have also to be developed for GAG mimetics. The Desai lab has developed a series of fully synthetic GAG mimetics called non-saccharide glycosaminoglycan mimetics (NSGMs), consisting of an aromatic backbone with key sulfate groups. One promising NSGM designed and synthesized in the lab is G2.2, a potent and selective inhibitor of colorectal cancer stem cells (CSCs). However, its poor oral bioavailability prompted the design of several lipid-modified analogs to improve its pharmacokinetics. Of the more promising lipid analogs evaluated, G8C contains the G2.2 backbone attached to a cholesterol moiety via an octyl linker. To evaluate its drug-like properties, a robust and sensitive method for quantification of G8C in human plasma was needed. The studies discussed here present our efforts in the development of simple and sensitive analytical procedures for the analysis of GAGs and NSGMs in human plasma.
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Available for download on Wednesday, May 06, 2026