A novel family of glycopolythiophenes containing sialic acid or mannose ligands were prepared and evaluated for their ability to bind lectins, virus, and bacteria. For the set of glycopolythiophenes studied, the spacer-length between the polymer backbone and the ligand was varied to optimize binding interactions. The glycopolymers were blue-shifted (absorbance of ca. 400 nm) relative to the corresponding homo-polythiophenes (absorbance ca. 440 nm), suggesting a twisted conformation for the glycopolymers. The altered conformation is likely due to electrostatic or H-bonding interactions between the polymer chains, arising from the carbohydrate ligand. Further conformational changes in the polythiophene backbone were detected by the binding of specific receptors; lectins (wheat germ agglutinin, concanavalin A), Influenza virus, and Escherichia coli. The binding interactions result in an unusual red-shift in the visible absorption of the polymer backbone, suggesting a lengthening of the effective conjugated length upon interaction of the ligand with its congnate receptor. These conjugated glycopolymeric systems offer a potentially new platform for the detection of molecular binding interactions.

No abstract

The saccharide antigen, Gal beta1-3GalNAc or T antigen, is of biologic importance in many systems. It is a tumor-associated carbohydrate antigen, a temporally expressed antigen in germinal center B cells and cortical T cells, a parasite-associated antigen, a spermatozoa vitality marker and an antigen on aged red blood cells. It may play a role in normal cellular adhesion and in tumor cell metastasis. Well characterized monoclonal antibodies (MAb) to Gal beta1-3GalNAc will be useful for further studies in these areas. We developed an IgG3 MAb to Gal beta1-3GalNAc by immunizing the mice with a synthetic Gal beta1-3GalNAc-BSA conjugate. The MAb was analyzed using inhibition enzyme immunoassays with related synthetically prepared sugars to determine the restrictions involved in the antibody binding. Use of synthetic sugars as competitors enabled us to delineate the epitope restrictions on the binding activity of this monoclonal and will enable use of this MAb in studies concerning the biologic importance of this disaccharide.

Novel glycodendrimers based on N,N'-bis(acrylamido)acetic acid core with valencies between two and six were synthesized. The breast cancer-associated T-antigen carbohydrate marker, (beta-Gal-(1-3)-alpha-GalNAc-OR), was then conjugated by (i) 1,4-conjugate addition of thiolated T-antigen to the N-acrylamido dendritic cores and by (ii) amide bond formation between an acid derivative of the T-antigen and the polyamino dendrimers. The protein-binding ability of these new glycodendrimers was fully demonstrated by turbidimetric analysis and by enzyme-linked immunosorbent assay (ELISA) using peanut lectin from Arachis hypogaea and a mouse monoclonal antibody (MAb) FAA-J11 (IgG3). When tested as inhibitors of binding between MAb and a polymeric form of the T-antigen (T-antigen-co-polyacrylamide) used as a coating antigen, di- (17), tetra- (20), hexa- (21), and tetravalent (22) dendrimers showed IC(50) values of 174, 19, 48, and 18 nM, respectively. Two tetramers showed 120- to approximately 128-fold increased inhibitory properties over the monovalent antigen 6 used as a standard (IC(50) 2.3 mM). Heterobifunctional glycodendrimer bearing a biotin probe was also prepared for cancer cell labeling.