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B. Schmid:
"Synthesis, surface chemistry modifications and characterisation of hybrid nanostructures";
Betreuer/in(nen): P. Ertl, S. Schrittwieser; Institut für Angewandte Synthesechemie, 2020; Abschlussprüfung: 29.06.2020.

Detection of biomarkers is of importance for a wide range of medical research applications, especially in the realm of Point-Of-Care diagnostics. In this thesis the synthesis of anisotropically shaped magnetic-core and gold-shell hybrid nanoparticles is stated. The nanoparticles are ellipsoid-shaped and possess ferromagnetic and plasmonic properties. Additionally, surface modification using different crosslinkers and antibodies was investigated. Further, a homogeneous rotating magnetic field assay for rapid protein analysis using optical transmission of nanoparticle dispersions was applied and customised. This technique is based on the optical detection of rotational dynamic changes of the mentioned hybrid nanoparticles upon specific interaction with antigens. The nanoparticles were synthesised using nanoimprint lithography and sputter deposition technologies and comprise layers of different material with specific functions. A hybrid layer system containing a nickel-iron-alloy as magnetic layer in the center and a gold surface was chosen. Via formation of thiol monolayers on gold surfaces, it was possible to bind polyethylene glycol based heterobifunctional crosslinkers containing thiol and carboxy or amino moieties irreversibly to the particle surface. Via EDC-NHS activation of the crosslinker carboxy groups, amide bonds between antibody amino groups and crosslinkers were established. Upon antigen binding, an antibody-antigen-antibody sandwich could be created resulting in an increase in particle volume due to the antigen-induced particle aggregation, which could be quantified via rotating magnetic field assay. Not only specific interactions but also unspecific formation of protein monolayers, also called coronas, could be detected. Two different target proteins, the soluble domain of the human epidermal growth factor receptor 2 - sHER2 and Fibroblast Growth Factor 23 protein or FGF23 protein, and their binding to antibodies immobilised onto the nanoparticle surface were investigated. Further, good stability of those nanoparticles under physiological conditions as well as low agglomeration tendencies could be proven. To prove the high uniformity of the particle geometry, SEM and AFM microscopy as well as dynamic light scattering measurements were conducted. Antibody presence and functionality could be proven via HRP colour assays and zeta potential measurements. Further, optical spectroscopy was performed to investigate agglomeration behaviour and stability of the nanoprobes.

Antikörper / Nanopartikel / Hybridnanostrukturen / Nanoimprintlithographie / Gold / Thiol / Bioassay/Nanoparticles / hybrid nanostructures / sputtering / nanoimprint lithography / gold / thiol / selfassembly / EDC-NHS / crosslinker / antibody