Synthesis, Surface Modification and Purification of Silicon and Germanium Quantum Dots for Biological Applications

<p>Quantum dots have applications in biomedical fields such as bio-imaging and drug delivery systems. This thesis describes research on silicon and germanium nanoparticles (quantum dots) synthesis and surface modification for biological applications. Purification methods of these quantum dots were also explored. In chapter 6 the application of silica nanoparticles into dry eye diagnosis was studied. The purpose of this research is to contribute the application of nanotechnology into biological fields. The crystalinity of the quantum dots was characterised by Transmission Electron Microscopy (TEM) and Selected Area Electron Diffraction analysis (SAED). The molecules on the surface of the quantum dots were characterised by Fourier Transform Infrared spectroscopy (FTIR) and Nuclear Magnetic Resonance (NMR). Silicon quantum dots were synthesised with a microemulsion system and various types of molecules were attached on the surface of the silicon quantum dots. However, some of the capping molecules which have oxygen atoms tend to form bonds between oxygen and silicon. Therefore, in the later chapter (chapter 4) various chemical reactions were conducted on the molecules attached to the silicon quantum dots. The silicon quantum dots were capped with diene molecules and one of the double bonds was left on the terminal end. The terminal end double bonds were converted to the functional groups which contain oxygen atoms to form peptide bonds. In this way it was confirmed that it can reduce the risk of oxygen atoms to be attached on the surface of the silicon quantum dots. The molecules on the surface of the silicon quantum dots were characterised mainly by FTIR and ¹H NMR. Optical properties and cyto-toxicity of these silicon quantum dots were also measured and analysed depending on the surface molecules. Two synthetic approaches were taken to produce germanium quantum dots. The first approach was the microemulsion system at room temperature. Different combinations of the surfactant and capping molecules were tested. For the second approach, high temperature bench top system was applied. In this method the bio-friendly molecules which have high boiling points were chosen as capping agents. The surface molecules were characterised by FTIR spectroscopy. In chapter 6 the synthesis of dye molecules conjugated silica nanoparticles was described. The purpose of this research is to produce biologically safe nanoparticles which can be applied in dry eye diagnosis. Three different dyes were used to conjugate with the silica nanoparticles. Only fluorescein isothiocyanate (FITC) succeeded in conjugating with the nanoparticles. Optical properties of this sample were measured and compared with the free dye molecule. Also the sample was applied in human eyes to analyse the tear film layer. An overall conclusion and future plans for the research were given in the last chapter.In this chapter, ideas of overcoming the problems and improving the techniques conducted in the research were described.</p>

Synthesis, Surface Modification and Purification of Silicon and Germanium Quantum Dots for Biological Applications

<p>Quantum dots have applications in biomedical fields such as bio-imaging and drug delivery systems. This thesis describes research on silicon and germanium nanoparticles (quantum dots) synthesis and surface modification for biological applications. Purification methods of these quantum dots were also explored. In chapter 6 the application of silica nanoparticles into dry eye diagnosis was studied. The purpose of this research is to contribute the application of nanotechnology into biological fields. The crystalinity of the quantum dots was characterised by Transmission Electron Microscopy (TEM) and Selected Area Electron Diffraction analysis (SAED). The molecules on the surface of the quantum dots were characterised by Fourier Transform Infrared spectroscopy (FTIR) and Nuclear Magnetic Resonance (NMR). Silicon quantum dots were synthesised with a microemulsion system and various types of molecules were attached on the surface of the silicon quantum dots. However, some of the capping molecules which have oxygen atoms tend to form bonds between oxygen and silicon. Therefore, in the later chapter (chapter 4) various chemical reactions were conducted on the molecules attached to the silicon quantum dots. The silicon quantum dots were capped with diene molecules and one of the double bonds was left on the terminal end. The terminal end double bonds were converted to the functional groups which contain oxygen atoms to form peptide bonds. In this way it was confirmed that it can reduce the risk of oxygen atoms to be attached on the surface of the silicon quantum dots. The molecules on the surface of the silicon quantum dots were characterised mainly by FTIR and ¹H NMR. Optical properties and cyto-toxicity of these silicon quantum dots were also measured and analysed depending on the surface molecules. Two synthetic approaches were taken to produce germanium quantum dots. The first approach was the microemulsion system at room temperature. Different combinations of the surfactant and capping molecules were tested. For the second approach, high temperature bench top system was applied. In this method the bio-friendly molecules which have high boiling points were chosen as capping agents. The surface molecules were characterised by FTIR spectroscopy. In chapter 6 the synthesis of dye molecules conjugated silica nanoparticles was described. The purpose of this research is to produce biologically safe nanoparticles which can be applied in dry eye diagnosis. Three different dyes were used to conjugate with the silica nanoparticles. Only fluorescein isothiocyanate (FITC) succeeded in conjugating with the nanoparticles. Optical properties of this sample were measured and compared with the free dye molecule. Also the sample was applied in human eyes to analyse the tear film layer. An overall conclusion and future plans for the research were given in the last chapter.In this chapter, ideas of overcoming the problems and improving the techniques conducted in the research were described.</p>

FORMULASI, KARAKTERISASI DAN UJI STABILITAS MIKROEMULSI MINYAK NILAM (Pogostemon cablin Benth.)

Patchouli oil contains patchouli alcohol as the main component which is a tricyclic tertiary alcohol sesquiterpene compound that is insoluble in water. Microemulsion is a droplet dispersion technology that combines an insoluble liquid with another liquid. The role of surfactants in helping the dispersion process of microemulsion formulation is by reducing the interfacial tension. Microemulsion is a supersolvents carrier, so that both hydrophilic and lipophilic can be administered through a microemulsion system. The purpose of this study was to formulate patchouli oil into a stable microemulsion preparation. This research was conducted by making 4 preparations of patchouli oil microemulsion containing 5% (F1), 10% (F2), and 15% (F3) patchouli oil, and microemulsion without patchouli oil (F0). Evaluation of microemulsion preparations includes organoleptic test, pH measurement, density determination, viscosity test, freeze and thaw test, centrifugation test, and particle size analysis. The test results showed that the microemulsion containing 5% patchouli oil had the most stable characteristics compared to other formulas.

Preparation and Evaluation of Topical Microemulsion System Containing Metronidazole

Metronidazole is a synthetic nitroimidazole derived with antimicrobial and anti-inflammatory properties. The aqueous solubility of this drug is poor which results from low bioavailability. Limited effects on the removal of bacteria are shown in the local administration of plain metronidazole. The microemulsion system proves the efficacy of solubility and dissolution improvement of poorly watersoluble drugs such as metronidazole. The objective of this project work is to prepare and evaluate metronidazole containing topical water-in-oil microemulsion and to compare its effectiveness to other commercially available products. In this formulation, tween 80 is used as a surfactant and PEG 400 is used as a co-surfactant. In the oil phase, isopropyl myristate is used. Distilled water is used as the hydrophilic phase. The formulation of metronidazole containing microemulsion was evaluated for physicochemical parameters like pH, viscosity, conductivity, accelerated stability studies. In vitro release study was also performed to evaluate the release kinetics.

Rh-Catalyzed Reductive Amination of Undecanal in an Aqueous Microemulsion System Using a Non-Ionic Surfactant

The homogeneously catalyzed reductive amination of the long-chain aldehyde undecanal with diethylamine was performed in an aqueous microemulsion system using the non-ionic surfactant Marlophen NP8. The experiments showed that the used water-soluble rhodium/SulfoXantphos catalyst system is suitable for this reaction. The Rh-catalyzed formation of the alcohol by-product can be completely suppressed by the use of carbon monoxide with its stabilizing effect of the catalyst system. In addition to pressure and temperature, the most important parameters for the reaction performance of the reductive amination are the concentrations of reactants. Especially, the initial concentration of the aldehyde has a strong impact on the chemoselectivity, and the formation of aldol by-product due to the fact that both, the enamine condensation and the aldol condensation are equilibrium reactions.

Evaluation of Viscosity and Oxidative Stress Induction in Michigan Cancer Foundation-7 Cells Treated with Melatonin Associated with Microemulsion and Polyethylene Glycol 400

Breast cancer has a high incidence and causes death worldwide, especially in women. Melatonin is a hormone that affects the prevention and treatment of tumors, and its effects have improved when associated with a modified release system. Thus, this study aimed to investigate the effects of a microemulsined system containing melatonin and PEG 400 on cellular oxidative stress and viscosity in the co-culture of blood mononuclear cells (MN) and MCF-7 cells. The microemulsion system containing melatonin and PEG 400 was developed from a mixture of the oil and aqueous phases and stabilized with surfactants. Blood mononuclear cells (MN) obtained from voluntary donors and MCF-7 cells (ATCC) were maintained in culture in CO2 for 24 hours treated with melatonin or with the microemulsion system containing melatonin and PEG 400. The flow and viscosity curves were evaluated using a rheometer, and the oxidative stress was evaluated by superoxide release and superox-ide dismutase (SOD) determination by colorimetric methods. The microemulsion system containing melatonin and PEG 400 showed a stable, translucent, and homogeneous property. The viscosity was higher in MCF-7 cells and MN cells when in the presence of a microemulsion system containing melatonin and PEG 400. The rheological behavior of MN and MCF-7 cells did not change in the presence of melatonin. The microemulsion system with melatonin and PEG 400 increased SOD levels in cultures of MN cells co-cultured with MCF-7 cells. These results suggest that the microemulsified system interferes with the oxidative metabolism of MN cells in co-culture with MCF-7 cells, with a reduction in SOD enzyme levels without changing superoxide levels, which could probably be favorable to the antitumor action of blood MN cells.