Synthetic ganglioside analogues for sensitive biosensing : improved probes for antibodies and bacterial toxins

This thesis describes the synthesis of analogues of human gangliosides and applications thereof for the detection and inhibition of bacterial toxins and antibodies. An efficient glycosylation method was developed for the synthesis of ω-functionalized alkyl lactosides (Chapter 2). These lactosides were further used as starting compounds in chemo-enzymatic syntheses of analogues of human gangliosides GM3, GM2, GM1, GD1a and GalNAc-GD1a (Chapters 3 and 4). In addition, divalent, tetravalent and octavalent GM2 and GM1 gangliosides were obtained (Chapter 5). A complete NMR characterization of the synthesized compounds was performed (Chapter 3).
The potential of these ganglioside mimics to detect toxins and antibodies was shown in a variety of diagnostic tests:
- in inhibition studies of the synthesized oligosaccharide-linked dendrimers with the cholera toxin B-subunit (Chapter 5) unprecedentedly large multivalency effects were observed: the tetra- and octa- GM1-substituted dendrimers are, respectively, 80 000 and 380 000 times stronger than a monovalent GM1 derivative as binding ligands for the toxin;
- in various modified ELISAs the synthetic ganglioside analogues were used to modify the plates (Chapters 3, 4 and 6) and thus tested for their performance in the detection of the cholera toxin B-subunit and the B subunit of E. coli heat-labile enterotoxin;
- for the detection of IgG and IgM antibodies in serum samples from neuropathy patients by the covalently attached ganglioside analogues a proof of principle was demonstrated (Chapter 6).