Carbohydrate Synthesis for Biomedical Applications

Abstract

Glycoconjugates are carbohydrates covalently attached to non-sugar components such as proteins and lipids. They mediate cell growth, cell-cell communication, cellular differentiation and immune defenses in a living organisms. Due to diverse patterns of glycan, glycoconjugates have various applications for biomedical purposes. In this thesis, ‘protein cage –based nanoparticles for the recognition and binding of cell-surface lectins’, ‘oligosaccharide synthesis for HIV-1 vaccine’, ‘graphene-based biosensor for specific lectin detection’, and ‘protein cage-based nanoparticle for delivery vehicles’ are presented. Carbohydrates selectively recognize and target endogenous cell-surface lectins. Human ferritin protein cage nanoparticles (HFPCNs) are used as targeted-delivery platform for carbohydrate derivatives. Maleimide-terminated mannosyl and galactosyl derivatives were synthesized for binding to the surface of HFPCNs via thiol-maleimide Michael-type addition. Through fluorescent cell imaging, we confirmed specific interaction between polyvalently displayed mannosyl and galactosyl derivatives to DCEK and HepG cells, respectively. DC-SIGN specifically interact to HIV-1 viruses. DC-SIGN recognizes gp120, a glycan shield on HIV-1 viruses. To mimic the function of gp120, oligomannosyl derivatives were synthesized. Di-mannosyl derivatives were synthesized by glycosylation between glycosyl donor and acceptor. The chemical structure of di-mannosyl derivatives were characterized by thin layer chromatography (TLC), nuclear magnetic resonance spectroscopy (NMR), and electrospray ionization mass spectrometry (ESI-MS) Due to their novel mechanical, electrical, and chemical properties, graphene-based nanomaterials have potential for application of biosensors. Graphene-based FET-style biosensor was prepared for the recognition of lectin. Pyrene-mannosyl derivatives were synthesized for binding to graphene device and recognition of Concanavalin A. Non-covalent - stacking interaction was used in binding between graphene device and pyrene-mannosyl derivatives. Through UV-vis, Raman, and atomic force microscopic analysis, non-covalent binding was investigated. Graphene-based sensor recognized current-voltage characteristic of graphene-based biosensor showed selective recognition of Con A. Human heavy-chain ferritin (HHFn) is protein cage-based nanoplatform for delivery of biomolecules. The outer surface of HHFn is modified with β-cyclodextrin (β-CD) through thiol-maleimide Michael addition followed by copper (I)-catalyzed azide-alkyne cycloaddition (CuAAC). The hydrophobic central cavity of β-CD non-covalently interacts to FTIC-AD to form β -CD-C90 HHFn / FITC-AD inclusion complexes. FITC-AD is reversibly released from protein cage-based inclusion complexes.