Metal ve metal oksit nanoparçacıkların geliştirilmesi ve potansiyel uygulama alanlarının incelenmesi

In the past few decades, nanoparticles have gained great importance in research and industry due to their adjustable chemical, physical, and biological properties. Gold nanoparticles (GNPs) and superparamagnetic iron oxide nanoparticles (SPIONs) are the two most studied and most attractive structures. These nanoparticles have been used in a variety of applications such as catalysis, sensors, energy, and medicine for therapeutic and imaging purposes. In this thesis, we aimed to develop extensive experience in gold nanoparticle synthesis and functionalization to control the particle size, stability, absorbance characteristics and surface chemistry to build a nanoparticle-based toolbox to be used in different applications from medicine to catalysis. For that purpose, a broad portfolio of functional gold nanoparticles by using different reducing and coating materials was produced. Cationic GNPs with polyethylenimine (PEI) is one of the target structures of this thesis due to its potential in gene delivery and polyelectrolytes nature. Anionic GNPs is another target structure for its potential in catalysis and medicine. In the field of SPIONs, sulfonic acid functionalized, small and stable SPIONs were produced as potential nanoparticles for a variety of purposes from targeted drug delivery and imaging to photo thermal therapy. In the second chapter, synthesis of small, cationic GNPs by the direct reduction of auric acid in a non-reducing solvent, water, with branched polyethylenimine (bPEI) in a broad pH range (3.0-9.0) was described. Basic pH, which was studied for the first time, emerged as a favorable condition to achieve good reducing power and surface passivation simultaneously, providing small particles (hydrodynamic size ca 6 nm) with enhanced long-term stability and sharper surface plasmon resonance peak (SPR). This synthetic method produces colloidal GNPs with bPEI in a broad molecular weight range (0.6, 1.8, 10, 25kDa). Molecular weight (MW) did not influence the crystal size much but the hydrodynamic size and the stability. This synthetic approach was adopted to GNPs produced by linear PEI (lPEI) in the third chapter. lPEI is accepted as more biocompatible than bPEI and in reduction of auric acid and stabilization of nanoparticles expected to behave differently since it lacks primary amines. Small, stable cationic GNPs were prepared for the first time with lPEI in water. Protonation and deprotonation of lPEI is a valuable variable for reduction, surface adsorption and stability. Impact of the PEI/Au ratio, polymer molecular weight (2.5 and 25 kDa), reaction pH (3.5 to 10), method of lPEI dissolution and post-synthetic pH on particle properties were studied. Finally, two different purification methods were evaluated to prevent the aggregation of GNPs. Protonation of PEI is needed for the synthesis and long-term stability of colloidal lPEI/GNPs regardless of the polymer MW. The best is to dissolve lPEI by protonation and to clean GNPs via controlled centrifugal precipitation. MW did not influence the hydrodynamic size, stability or particle shape, but low MW lPEI provided facetted particles. This simple one pot synthesis of small, stable cationic GNPs in water is a valuable, simple alternative for producing new cationic GNPs with even low molecular weight lPEI. In the fourth chapter, anionic gold nanoparticles were synthesized by a modified single-phase Brust-Schiffrin method by using 3-mercaptopropionic acid as the coating and NaBH4 as a reducing agent. Those nanoparticles were primarily prepared as a biocompatible nanocarrier for enhanced transport of polyclonal Immunoglobulin G (IgG) across blood-brain barrier (BBB) in sepsis treatment. These GNPs were decorated with glucose to pass BBB and IgG was conjugated to GNPs with acid cleavable hydrazone linkages. Synthetic parameters for glucose and polyclonal IgG conjugation to GNPs were thoroughly investigated. Since IgG was polyclonal, it had a wide range of isoelectric point (pH 6.3-8.9) making the optimization of reaction pH and order of functionalization quite challenging. Additionally, understanding the appropriate working environment with IgG was another challenge due to the bacterial attack. In the fifth chapter, synthesis of reproducible, functional, and stable gold nanoparticles with absorbance in the visible and near-infra red (NIR) region were described. Relatively new, gold-gold sulfide nanostructures with functional, stabilizing coatings were developed for the first time and their utility in drug delivery and photothermal therapy were investigated. In the last capter, a novel, green, one-pot aqueous synthesis method of sulfonic acid functionalized SPIONs were developed by utilizing the co-precipitation method and in-situ coating with (trihydroxysilyl)-1-propanesulfonic acid. The conventional synthesis method involves organic solvent. The new aqueous synthesis method described here is more suitable for biomedical applications. The proposed nanoparticle can be used in both catalysis and targeted combined therapies by loading cationic targeting molecules, drugs, and photosensitizers.