The first study reports the development of a reusable, single-step system for the detection of specific substrates using oxidase-functionalized Fe3O4 nanoparticles (NPs) as a bienzyme system and using amplex ultrared (AU) as a fluorogenic substrate. In the presence of H2O2, the reaction pH between Fe3O4 NPs and AU was similar to the reaction of oxidase and the substrate. The catalytic activity of Fe3O4 NPs with AU was nearly unchanged following modification with poly(diallyldimethylammonium chloride) (PDDA). Based on these features, we prepared a composite of PDDA-modified Fe3O4 NPs and oxidase for the quantification of specific substrates through the H2O2-mediated oxidation of AU. By monitoring fluorescence intensity at 587 nm of oxidized AU, the minimum detectable concentrations of glucose, galactose, and choline were found to be 3, 2, and 20 £gM using glucose oxidase-Fe3O4, galactose oxidase-Fe3O4, and choline oxidase-Fe3O4 composites, respectively. The identification of glucose in blood was selected as the model to validate the applicability of this proposed method. The second study follows the first one. Using the catalytic activity of Fe3O4 NPs with AU to detect four kinds of neurotransmitter, such as dopamine, L-DOPA, adrenaline (epinephrine) and noradrenaline (norepinephrine). Because of there is specific interaction between Fe3O4 NPs and catecholamines (CAs), the Fe3O4 NPs will form CAs-Fe3O4 NPs composites in presence of CAs. The CAs on the Fe3O4 NPs surface must shelter the reaction between AU and H2O2, cause the fluorescence to be turned-off. The CAs just like a inhibitor, to inhibit the catalytic activity of Fe3O4 NPs. Therefore, we could use this inhibited system to detect the CAs compound concentration in the real sample.

Mesoporous materials attracted great interest due to their huge surface area and adjustable pore sizes. One of the important mesoporous materials is SBA-15 and has larger pore size, hydrothermal stability and thicker walls than other mesoporous materials. In this study, SBA-15 is synthesized by using sol-gel technique and cobalt oxide nanoparticles are incorporated in mesochannels by direct method. SBA-15 was produced from the self-assembly of non-ionic triblock co-polymer (Pluronic 123) and tetra ethyl ortho silicate (TEOS). Then cobalt chloride and cobalt nitrate were added at different loading ratios with two different addition sequences / after polymer and after TEOS. The loading ratios are in Si/Co mols and these ratios are / 15, 10, 5, 3, 1.5, 1 and 0.75 in increasing cobalt amount loaded. Characterization of the produced materials was performed by Powder X-Ray Diffraction (PXRD), Infrared (FTIR) analysis. Nitrogen Phisisorption measurements (BET and BJH Methods) were used to examine the textural properties of produced materials. By means of Transmission Electron Microscopy (TEM) the micro structures of materials were investigated. From the PXRD studies it is observed that the long range order of pores is preserved at even high loading amounts for cobalt chloride addition after TEOS. Co3O4 (JCPDS card no: 42-1467) crystallites are observed for Si/Co mol loading ratios 3, 1.5, 1 and 0.75. Above these loading ratios cobalt oxide is highly dispersed in SBA-15-type structure. FTIR studies revealed the formation of condensed silica network. From the Nitrogen Phisisorption measurements it is observed that addition of cobalt salt decreases the BET surface area of produced materials. All Nitrogen Adsorption-Desorption Isotherms are Type-IV, and has H-1 hysteresis which is a fulfillment of mesoporous structures according to IUPAC classification. BET surface area of samples loaded with cobalt chloride after TEOS possessed higher surface area than other samples. TEM images proved that at loading ratios above 3 there were not any cobalt oxide nanoparticles, cobalt oxide is highly dispersed on silica surface whereas at loading ratios 3 and below there were cobalt oxide nanoparticles embedded in the mesochannels for the samples prepared by addition of cobalt chloride after TEOS.

Current methods to diagnose and treat cancer often involve expensive, time-consuming equipment and materials that may lead to unwanted side effects and may not even increase a patient’s chance of survival. Thus, for a while now, a large part of the research community has focused on developing improved methods to detect, diagnose, and treat cancer on the molecular scale. One of the most recently discovered methods of cancer therapy is targeted therapy. These targeted therapies have potential to provide a patient with a form of personalized medicine because these therapies are biological molecules that specifically target other molecules involved with a cancer’s growth. Past trials using these therapeutic molecules, however, have led to controversial results, where certain patients responded better than others to the therapy for unknown reasons. Elucidating the reason behind these mixed results can be accomplished using metal nanoparticle technologies which could provide a bright signal to monitor the path that these therapeutic molecules take in vivo as well as enhance the molecule’s efficacy. Literature has shown that presenting targeting molecules in a dense manner to their target will increase these molecules’ binding affinity. This concept has been explored here to increase binding affinity of therapeutic molecules by attaching these molecules in a dense manner on the surface of gold nanoparticles, and correlating this increased affinity with therapeutic efficacy. Additionally, gold nanoparticles provide an easy surface for molecules to be functionalized on and have shown to be effective imaging, x-ray, and photothermal therapy agents. A major roadblock to using these gold nanoparticles clinically is their non-degradability and thus potential to cause long-term negative side effects in vivo. A platform for developing biodegradable gold nanoparticles is also explored here to take advantage of the gold nanoparticles’ excellent imaging and drug delivery capabilities while still allowing them to be used safely in the long term. / text

This research focuses on the microwave properties of nanoparticles for use as contrast and hyperthermia agents. Currently, visible light is used for irradiation of nanoparticles as hyperthermia agents. Additionally, visible/Near-infrared light is used for photoacoustic tomography (PAT) imaging. Compared to optical wavelengths, frequencies in microwave range transmit through tissue with high penetration depth . Thus, deep cancerous cells and malignant tissue may be treated and imaged. These nanoparticles could enable the use of a hybrid microwave/acoustic technique known as thermoacoustic tomography. Here, quantitative measurements of the heat generation in super paramagnetic iron oxide nanoparticle (SPIONs), gold nanoparticles (AuNPs), and gold nanoclusters (AuNCs) induced by microwave energy at 3 GHz, are presented and compared. Based on our experiments, SPIONs are the most efficient nanoparticles for microwave heating. Very high concentrations of SPIONs are able to convert microwave energy into heat about 22° C more than DI-water. AuNPs, which support plasmon resonances, do not provide heat under microwave irradiation as predicted by our computational analysis based on Mie Theory. AuNCs are a new form of ultra-small (<2.5 nm) AuNPs which do not support plasmonic resonances and have supra-molecular properties such as sub-conduction band transitions. Interestingly, AuNCs have the potential to absorb microwave energy and may provide an alternative to SPIONs. These nanoparticles had not yet been studied before in this frequency region. In addition, the absorption coefficient of nanoparticles were calculated using complex permittivity data from a dip probe kit and a Vector Network Analyzer (VNA) in a broad band range from 500 MHZ to 10 GHz. This method allows identification of best frequency region with highest penetration depth. In the last step, the nanoparticles with different concentrations were tested as exogenous contrast agents in a Thermoacoustic Tomography (TAT) system. TAT utilizes the penetration depth of microwave energy while producing high resolution images through acoustic waves. The addition of an exogenous contrast agent improves image quality by more effectively converting microwave energy to heat. The experiment reveals that the time resolved thermoacoustic signal (TA) from SPIONs is stronger than AuNPs and AuNCs and thus, the image contrast produced by SPIONs is stronger than the two other aforementioned nanoparticles.

Magister Scientiae - MSc (Chemistry) / Pulmonary Tuberculosis (TB) a disease second to HIV/AIDS is a global health problem that arises in two states; as an active state and as a latent state. Diagnosis of active TB is tedious and requires expensive procedures since there is no recognizable method for the sole detection of active TB. The current diagnosis consists of chest X-rays and multiple sputum cultures used for acid-fast bacilli detection. The TB diagnosis of children is particularly difficult which further complicates the diagnosis. Thus, rapid identification of this pathogen is important for the treatment and control of this infection to allow effective and timely therapy. In an effort to solve this issue, this study reports the development of immunosensors constructed with electroactive layers of amino groups functionalized graphene oxide (GO) doped respectively with green synthesized zinc oxide (ZnO NPs) nanoparticles and silver (Ag NPs) nanoparticles on glassy carbon electrodes. The surface morphology of GO, ZnO NPs, Ag NPs and their composites was revealed by employing High-Resolution Transmission Electron Microscopy (HR-TEM) and High-Resolution Scanning Electron Microscopy (HR-SEM) while the composition and structure of these materials were studied using Fourier Transform Infra-Red Spectroscopy (FTIR). The resultant graphene oxide-metallic composites were covalently attached with CFP-10 and/or ESAT-6 antibodies to achieve the electrochemical detection. The immunosensor was then used for the impedimetric and amperometric detection of anti-CFP-10 and/or anti-ESAT-6 antigens in standard solutions.

Iron oxides and arsenic are prevalent in the environment. With the increase interest in the use of iron oxide nanoparticles (IONPs) for contaminant remediation and the high toxicity of arsenic, it is crucial that we evaluate the interactions between IONPs and arsenic. The goal was to understand the environmental behavior of IONPs in regards to their particle size, aggregation and stability, and to determine how this behavior influences IONPs-arsenic interactions. A variety of dispersion techniques were investigated to disperse bare commercial IONPs. Vortex was able to disperse commercial hematite nanoparticles into unstable dispersions with particles in the micrometer size range while probe ultrasonication dispersed the particles into stable dispersions of nanometer size ranges for a prolonged period of time. Using probe ultrasonication and vortex to prepare IONPs suspensions of different particle sizes, the adsorption of arsenite and arsenate to bare hematite nanoparticles and hematite aggregates were investigated. To understand the difference in the adsorptive behavior, adsorption kinetics and isotherm parameters were determined. Both arsenite and arsenate were capable of adsorbing to hematite nanoparticles and hematite aggregates but the rate and capacity of adsorption is dependent upon the hematite particle size, the stability of the dispersion and the type of sorbed arsenic species. Once arsenic was adsorbed onto the hematite surface, both iron and arsenic can undergo redox transformation both microbially and photochemically and these processes can be intertwined. Arsenic speciation studies in the presence of hematite particles were performed and the effect of light on the redox process was preliminary quantified. The redox behavior of arsenite and arsenate were different depending on the hematite particle size, the stability of the suspension and the presence of environmental factors such as microbes and light. The results from this study are important and have significant environmental implications as arsenic mobility and bioavailability can be affected by its adsorption to hematite particles and by its surface mediated redox transformation. Moreover, this study furthers our understanding on how the particle size influences the interactions between IONPs and arsenic thereby clarifying the role of IONPs in the biogeochemical cycling of arsenic.

Understanding the size dependent dissolution of engineered nanoparticles is one important aspect in addressing the potential environmental and health impacts of these materials as well as their long-term stability. In this study, experimental measurements of size dependent dissolution of well-characterized zinc oxide (ZnO) nanoparticles with particle diameters in the range of 4 to 130 nm have been measured and compared at circumneutral pH (pH 7.5). Enhanced dissolution was found for the smaller particles with the largest enhancement observed in Zn2+(aq) concentrations for 4 nm diameter ZnO nanoparticles compared to larger-sized particles. Interestingly, size dependent dissolution was observed even though the nanoparticles aggregated with hydrodynamic diameters on the order of 1-3 m in diameter. Although these results are found to be in qualitative agreement with theoretical predictions used to predict the dissolution of solids, a linearized form of the Kelvin equation to calculate a bulk dissolution value for ZnO and a surface free energy yielded quantities inconsistent with known literature values. It is therefore concluded that deviations from solubility behavior from classical thermodynamics are due to a lack of the detailed knowledge of the surface free energy as well as its dependence on the details of the surface structure, surface properties, including the presence of different surface crystal facets and adsorbed ligands, as well of aggregation state. The presence of citric acid significantly enhances the extent of ZnO dissolution for all sizes such that no significant differences were observed for total Zn2+(aq) concentrations for nanoparticles between 4 to 130 nm. This can be attributed to ligand enhanced dissolution of ZnO nanoparticles where there is no dependence on size. Adsorption of citrates onto ZnO nanoparticles was observed using ATR-FTIR spectroscopy. A reversal of surface charge of ZnO nanoparticles was observed upon adsorption of citrates. Adsorption of negatively charged Cit3- onto ZnO nanoparticles make the surfaces negatively charged and this result in a repulsion between nanoparticles eventually leading to a lesser extent of aggregation. Formation of a stable suspension was also observed in the presence of citric acid. These trends observed in aggregation pattern are of great environmental and biological importance as citric acid is abandon in the environment as well as in human body.