Date of Award

2018

Degree Type

Dissertation

Degree Name

Doctor of Philosophy in Clinical-Bioanalytical Chemistry

Department

Chemistry

First Advisor

Sun, Xue-Long

Subject Headings

Biology, Cellular Biology, Chemistry

Abstract

Carbohydrate recognition has come to the forefront of biological aiming to uncover the mechanisms of physiological and pathological processes. Cell surface glycans are involved in processes including cellular adhesion, cell signaling, and immune response. A new approach for profiling cell surface glycans has great potential for a wide range of biomedical applications. Lectins have been conventionally used to determine the structure and function of glycoproteins, however, their numbers are still restricted compared to the number of glycan structures. Boronic acid has proven a remarkable small molecule capable of binding diols in aqueous solution. This interaction indicates boronic acid derived molecules may serve as lectin mimetics for profiling and targeting cell surface glycans. In the first part of this dissertation study the specific binding site of boronic acid to individual pyranosides was confirmed followed by the synthesis and evaluation of protein-boronic acid conjugates as lectin mimetics. 3-aminophenylboronic acid was conjugated to gluco-, manno- and galactopyranosides, followed by methylation, both under basic conditions. Based on a specific permethylation product for the carbohydrate, boronic acid specificity towards 1,2 and 1,3 diol configurations was confirmed by 1H, 13C NMR, and mass spectrometry. As a result, unique binding profiles were observed for each pyranoside. Next, bovine serum albumin (BSA)-PBA conjugates were synthesized in a density controlled affording multivalent lectin mimetics. The resultant BSA-PBA conjugates were characterized by SDS-PAGE and MALDI-TOF MS. Cell surface glycan binding capacity was confirmed by a competitive lectin assay examined by flow cytometry. Macrophages express lectins as receptors for specific immune responses. Synthetic glycans are candidates for targeting cell surface lectins and for immunomodulation applications. In the second part of this dissertation, novel N-glycan polymers were synthesized and their immunomodulation effects were examined. N-linked glycopolymers were synthesized via cyanoxyl-mediated free radical polymerization (CMFRP). Then, their cytotoxicity and cell activation abilities against RAW 264.7 cells were examined. As a result, N-glycan polymers showed no cytotoxicity at a concentration of 1,250 mg/mL except the N-alpha-2,6-sialolactosyl polymer, which proved cytotoxic at 1250 µg/mL. N-alpha-2,3-sialolactosyl polymer showed the strongest activity for inducing cell surface marker expression compared to controls, indicating high macrophage modulation activity.

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