Rare earth doped nanomaterials as potential contrast agents for optical/magnetic resonance imaging

The research work presented in this thesis focuses on the fabrication of rare earth (RE) doped nanomaterials as potential contrast agents for optical and magnetic resonance imaging. Owing to the sharp and intense emission obtained over the range of visible to the near-infrared regions in a wide variety of hosts, RE-doped nanomaterials have attracted strong interests as contrast agents in bioimaging applications. The current study has successfully demonstrated the fabrication of fluorescent, and bifunctional magnetic-fluorescent RE-doped nanomaterials as contrast agents for bioimaging. At first, doping of different RE ions in yttrium oxide (Y2O3) host was investigated to fabricate the down- and up-conversion fluorescent nanoparticles. Effect of different synthesis parameters and type of RE dopants was investigated, and optimum conditions in relation to synthesis temperature, time, and concentration of RE dopants were reported and discussed. Spherical nanocrystals and nanorods could selectively be produced by varying different synthesis conditions. An evolution mechanism has been proposed to elucidate the morphology transformation to nanorods from nanocrystals.DOCTOR OF PHILOSOPHY (SCBE

Single-phase NaDyF4:Tb3+ nanocrystals as multifunctional contrast agents in high-field magnetic resonance and optical imaging

The current work reports single-phase, terbium-doped sodium dysprosium fluoride (NaDyF4:Tb3+) nanocrystals with green luminescence and good T2 contrast in 7.0-T MRI phantom and animal imaging. The current nanocrystals demonstrate good potential as a dual modal contrast agent for high-field magnetic resonance (MR) and fluorescence imaging

Ultra-long Magnetic Nanochains for Highly Efficient Arsenic Removal from Water.

The contamination of drinking water with naturally occurring arsenic is a global health threat. Filters that are packed with adsorbent media with a high affinity for arsenic have been used to de-contaminate water - generally iron or aluminium oxides are favored materials. Recently, nanoparticles have been introduced as adsorbent media due to their superior efficiency compared to their bulk counter-parts. An efficient nanoadsorbent should ideally possess high surface area, be easy to synthesize, and most importantly offer a high arsenic removal capacity. Achieving all the key features in a single step synthesis is an engineering challenge. We have successfully engineered such a material in the form of nanochains synthesized via a one step flame synthesis. The ultra-long γ-Fe2O3 nanochains possess high surface area (151.12 m2 g-1), large saturation magnetization (77.1 emu g-1) that aids in their gas phase self-assembly into long chains in an external magnetic field, along with an extraordinary arsenic removal capacity (162 mg.g-1). A filter made with this material exhibited a relatively low-pressure drop and very little break-through of the iron oxide across the filter

Sublethal Effects of CuO Nanoparticles on Mozambique Tilapia (<i>Oreochromis mossambicus</i>) Are Modulated by Environmental Salinity

<div><p>The increasing use of manufactured nanoparticles (NP) in different applications has triggered the need to understand their putative ecotoxicological effects in the environment. Copper oxide nanoparticles (CuO NP) are toxic, and induce oxidative stress and other pathophysiological conditions. The unique properties of NP can change depending on the characteristics of the media they are suspended in, altering the impact on their toxicity to aquatic organisms in different environments. Here, Mozambique tilapia (<i>O. mossambicus</i>) were exposed to flame synthesized CuO NP (0.5 and 5 mg·L⁻¹) in two environmental contexts: (a) constant freshwater (FW) and (b) stepwise increase in environmental salinity (SW). Sublethal effects of CuO NP were monitored and used to dermine exposure endpoints. Fish exposed to 5 mg·L⁻¹ CuO in SW showed an opercular ventilation rate increase, whereas fish exposed to 5 mg·L⁻¹ in FW showed a milder response. Different effects of CuO NP on antioxidant enzyme activities, accumulation of transcripts for metal-responsive genes, GSH∶GSSG ratio, and Cu content in fish gill and liver also demonstrate that additive osmotic stress modulates CuO NP toxicity. We conclude that the toxicity of CuO NP depends on the particular environmental context and that salinity is an important factor for modulating NP toxicity in fish.</p></div

BET and Zeta Potential of CuO NP.

<p>(<b>A</b>) BET isotherm of the CuO NP (powder). (<b>B</b>) Zeta Potential (ZP) of the NP sample taken from FW5 tanks over the time. Day 0 represents the ZP of the NP right after mixing to the fresh water of the fish tank. The ZP of the NP remained fairly constant though out the experiments. The dotted line showed as a guide.</p

Expression of metal-responsive genes.

<p>Transcripts levels analysis by qPCR in liver (black bars) and gills (white bars). Transcript accumulation of (<b>A</b>) <i>Cytochrome P450 1A</i> (<i>CYP1A</i>), and (<b>B</b>) <i>Metallothionein</i> (<i>MT</i>). The genes were analyzed by qPCR in gills and liver, and normalized as function of the levels of endogenous control <i>β-Actin</i> gene. FW0, fresh water; FW0.5, FW plus 0.5 mg·L⁻¹ CuO; FW5, FW plus 5 mg·L⁻¹ CuO; SW0, increasing salinity; SW0.5, SW plus 0.5 mg·L⁻¹ CuO; SW5, SW plus 5 mg·L⁻¹ CuO. Results expressed as percentage of relative quantification. Significant different means by Anova on ranks analysis are shown with ‡ (<i>P</i> value), and significant differences between FW-SW at the same CuO NP concentration (Dunn's post test, <i>P</i><0.05) are shown with §. Asterisks represent significant difference compared to the respective FW0 control by Wilcoxon Signed Rank test (*, <i>P</i><0.05; ** <i>P</i><0.025). <i>n</i>×treatment = 5.</p

Characterization of CuO NP used in the present study.

<p>(A) Representative transmission electron microscopy (TEM) images of the CuO NP at two magnifications. The polydisperse size distribution of CuO NP (n = 245) determined from TEM images is shown in the insert. The average size of the NP is shown (mean ± <i>SD</i>). (B) X-Ray diffraction (XRD) pattern of the NP. The X, and Y axes of the XRD represents the angles (2θ) of incident X-ray beam and the corresponding diffraction peak intensity.</p

Glutathione levels in livers and gills of CuO NP exposed fish in different salinities.

<p>Total glutathione (GSH+GSSG, top panel); Oxidized glutathione (GSSG) and reduced glutathione (GSH) levels (center panel). The ratio GSH/GSSH is shown in bottom panel. FW0, fresh water; FW0.5, FW plus 0.5 mg·L⁻¹ CuO; FW5, FW plus 5 mg·L⁻¹ CuO; SW0, increasing salinity; SW0.5, SW plus 0.5 mg·L⁻¹ CuO; SW5, SW plus 5 mg·L⁻¹ CuO. Expressed as mean nmol.mg tissue⁻¹ ± <i>SD</i>. Groups with significant different means by Anova analysis are shown with ‡ (<i>P</i> value). Letters denote groups showing non significant differences by Tukey's post-test (<i>P</i><0.05). <i>n</i>×treatment = 5.</p