Hybrid Gold Nanoparticles for Nanomedical Applications

The present dissertation focuses on the synthesis of different sized gold nanoparticles (Au NPs), their phase transfer to aqueous solution, their characterization and functionalization for applications in modern nanomedicine. As this is a cumulative written dissertation the presented achievements were already published or are about to be published. However, the attempt is to describe the main goals and experimental emphases contributed during the time of this dissertation. The synthesis of Au NPs is described via two different reduction methods leading to different sized nanocrystals. For smaller NPs of about 4 nm core diameter, Au3+ ions are reduced by the addition of sodium borohydride. Bigger NPs with about 18.5 nm core diameter are produced by Au3+ reduction using citric acid. In both cases molecules need to be present that confer colloidal stability and lead to increased interparticle repulsion. Such stabilizing ligands may need to be replaced during a phase transfer to ensure water soluble NPs. They also serve in many cases as anchor point for functional modifications of the NP's surface and therefore have to be selected critically with regard to their intended application. After synthesis the Au NP's intrinsic stability needs to be verified against ionic strength, to ensure the NPs are suitable for additional functionalization reactions and also stable within physiological media. After thoroughly examination and analysis a promising hybrid NP system out of Au NPs and an amphiphilic polymer coating did not full fill the demanding criteria needed for functionalization and in vitro investigations. Amendments towards 17.8 nm Au NPs with polyethylene glycol (PEG) as polymer layer allowed water solubility of NPs, adequate colloidal stabilization and feasible targeted functionalization. The functionalization basically is to implement In3+ ions as label onto the polymer shell around the NP. Additionally a protein corona composed of bovine serum albumin (BSA) is adsorbed to the NPs surface that undergoes a prelabeling procedure using iodine. With the Au NP itself and the labeled polymer shell and protein corona, a triple labeled system is created that can be analyzed for its degradation within mammalian cell lines using inductively coupled plasma mass spectrometry (ICP-MS). Summarized a triple labeled system of Au NP, polymer shell and protein corona was synthesized for in vitro degradation testing that can be equipped with radio nuclide tracers that allow more complex degradation experiments on animals in future