Cyclodextrin Based Multivalent Glycoprobes for Targeting, Imaging and Drug Delivery

Abstract

Designing multivalent template structures have immense importance not only to amplify the carbohydrate-protein interactions but also from the perspective of translational chemistry. Significant progress has been achieved in this regard using glyco-nanoparticles, glycodendrimers and glycopolymers. However, other important issues regarding the preparation of multivalent carbohydrates are related to the orientation, spacing and local concentration of the carbohydrates with respect to external stimuli. Therefore, it is important to form a general scaffold which are facile, robust, presents tunable symmetry and exhibit optical and electrochemical properties to develop a direct probing system. Inspired by the large number of supramolecular assembly of adamantyl/β-cyclodextrin associated complexes, I explored poly-glycosyl β-cyclodextrin probes in the synthesis next generation diagnostic, biosensing and imaging tools. In the following chapters, I have investigated the role of different carbohydrate constructs-from cyclodextrin scaffods-and their application in targeting, imaging, and drug delivery. Chapter 1 summarizes different strategies for preparing cyclodextrin based multivalent probes probes and their major applications in biosensing, imaging, and other biological or medical applications. To address fundamental aspects of cyclodextrin-based interactions that were developed in the Kikkeri group, different types of cyclodextrin based systems ranging from photoswitchable glycodendrimers to glycopeptides structures in order to fine tune the spatial and the topology structures of the carbohydrate ligands required in such systems. Chapter 2 demonstrates the inherent chirality of glycodendrimers as one of the promising factors to generate different spatial carbohydrate micro-environments to modulate the specific carbohydrate-protein interactions. By exploiting the host-guest strategy and chiral Ru(II) complexes (Δ and Λ) and mannose capped β-cyclodextrin (β-CD), we generated a library of homologous metallo-glycodendrimers (MGDs) of size 50-70 nm. These nanoclusters can enantioselectively bind to specific C-type lectins and displayed selectivity in cellular uptake. We also discovered their potential clathrin-mediated endocytotic pathway in DC-SIGN and SIGNR3-transfected cell lines. Finally, in vivo biodistribution and sequestration of MGDs was determined to decipher the role of chirality mediated spatial arrangement in carbohydrate-mediated interactions. Chapter 3 deals with the synthesized Ru(II)-bis sugar capped β-cyclodextrin derivatives to demonstrate selective controlled delivery of metal complex into cancer cells. Cell viability assay and imaging studies revealed that hepta glycosylated-CD capped Ru(II) complexes xii exhibited cytotoxic activities in cancer cells with IC50 values close to other Ru(II) complexes. The death inducer was found to accumulate favourable to the endoplasmic reticulum (ER) and induced ER stress in cells. The upregulation of CHOP and, caspase-3 and 12 disturbed the ER morphology initiating apoptosis pathway. Chapter 4 reports the synthesis of glyco-quantum dots using sonochemical procedure. The high sugar density on QDs resulted in selective colloidal aggregation with ConcanavalinA (ConA), Galanthus nivalis lectin (GNA) and Peanut agglutinin (PNA) lectins. Subsequently, in-vitro studies indicated that β-CD modification of QDs had good cell viability of human hepatocellular carcinoma cell line (HepG2) cells. Finally, flow cytometry and confocal imaging studies revealed that β-CDgal capped QDs undergo preferential binding with HepG2 cells compared to βCD capped QDs. These results clearly demonstrate that β-CD capped QDs could be a promising candidate for further carbohydrate based biomedical applications.