Glyko-DNA-funktionalisierte Goldnanopartikel : Synthese und Wechselwirkung mit Lektinen und Zellen

In the context of this work it was demonstrated that DNA-functionalized gold nanoparticles equipped with glycoconjugates were bound by carbohydrate binding proteins (lectins) in a specific manner. Biomolecular self recogonition led to the formation of particle lectin networks which were able to dissociate by two independent stimuli, namely temperature and addition of sugar. Further it was demonstrated that the uptake or binding of the nanoparticle conjugates by hepatocytes (HepG2) was mediated by charge driven interactions, as likely by scavenger receptors, while a specific recognition of the glyco termini by the asialoglycoprotein receptor (ASGP R) could not be proven. Amino-modified glyco conjugates (N-acetyl-D-glucosamin (GlcNAc) and (poly-)N-acetyllactosamin ((poly-)LacNAc)) were used for glyco functionalization of gold nanoparticles. By binding the amino group to N-hydroxysuccinimide esters the carbohydrates were coupled covalently with disulfide modified PEG ligands or oligonucleotides respectively which allow the binding to the surface of gold nanoparticles. The specific binding of different lectins (Griffonia (Bandeiraea) simplicifolia Lectin II (GS-II) or Galektin 1 and 8 respectively) to the carbohydrates in the periphery of the ligand shell led to cross-linking of the nanoparticles which was observable in a change of the plasmon band, an increase of the hydrodynamic diameter or in the formation of a structure factor in the scattering curve. By competition with free sugar particle networks were dissociated or the lectin-mediated assembly was inhibited. Networks built up by DNA-functionalized gold nanoparticles and lectins could further be dissociated by thermal DNA melting. In addition to specific interactions unspecific attractive interactions between DNA-functionalized gold nanoparticles and galectins were observed. Based on the specific addressability of lectins in solutions by glyco-DNA-gold nanoparticles ASGP-R, a cell membrane bound lectin with affinity for terminal D-galactose, should be addressed in order to achieve a specific uptake or binding of DNA-functionalized gold nanoparticles by certain cells. The interactions between di-LacNAc-DNA-functionalized gold nanoparticles and hepatocytes (HepG2 cells) were investigated. Besides ASGP-R these cells express scavenger receptors (SR-BI). By blocking both receptors with D-lactose and fucoidan respectively it was demonstrated by flow cytometry that di-LacNAc-DNA-functionalized gold nanoparticles were taken up likely by scavenger receptors while a specific interaction with the ASGP-R could not be demonstrated. Besides this other pathways for particle uptake are possible. Poly-LacNAc-DNA-functionalized gold nanoparticles could be potentially used to address galectin overexpressing cancer cells. This could lead to applications in the field of targeted drug release or gene regulation