Despite significant progress in anti-cancer therapy, current treatments are still controversial due to numerous side effects. Targeted immunotherapy recently emerged as an ideal alternative to improve treatment modalities for cancer patients. However, very limited approaches are available today and major issues remain to be addressed. In this context, we are interested in the design of biomolecular structures, innovative and bifunctional, able to hijack endogenous antibodies - which are naturally present in the human bloodstream - toward cancer cells without pre-immunisation. Since natural circulating antibodies are polyspecific and have the ability to interact with multiple carbohydrate antigens, we focused on the design of multivalent glycodendrimers, as ligands for endogenous antibodies. The first part of our study consisted in synthesizing several multivalent glycoconjugates, based on peptide scaffolds and obtained by chemoselective ligations. To evaluate their influence on antibodies, the nature of both the carbohydrate and the scaffold, and the valency were varied. Then, in a second part of the study, microarray assays were developed with a model lectin, the Helix Pomatia Agglutinin (HPA). Experimental procedures were designed to determine surface dissociation constant and IC₅₀ values, leading to the identification of high-affinity ligands for HPA in the nanomolar range. Microarray assays were confirmed by other analytical methods (BLI, ELLA). Finally, the assays on slides were adapted to human sera screening, in order to identify tridimensional architectures highly affine to sera antibodies. A large panel of glycoconjugates was screened by microarray with around twenty sera, leading to the determination of promising glycosylated structures, as antibody ligands. The latter could be subsequently used for our anti-cancer approach.