Ionotropic and metabotropic signalling in neuronal development and differentiation

This thesis investigates ionotropic and metabotropic signalling mechanisms in developing neurons from human embryonic stem cell and primary sources. Focus is placed on the measurement of functional activity using primarily whole-cell patchclamp and Ca2+ imaging techniques These signalling mechanisms were investigated in undifferentiated human embryonic stem cells, hESC-derived neurons, fetal primary human neurons and neonatal primary mouse neurons. The results of this research are separated into three chapters. Preliminary work carried out on iPSC-derived neurons is also included as an indication of future direction Chapter 3: P2 Receptors in hESCs Purinergic signalling was shown to be active in undifferentiated hESC populations. Specifically, the activity of P2Y1 receptors was confirmed pharmacologically. This is a novel observation and indicates a mechanism for physiologically relevant signalling molecules to modify [Ca2+]i Chapter 4: Functional Characterisation of hESC-Derived and Primary Neurons Functional characteristics associated with neuronal development were measured in human embryonic stem cells during terminal neuronal differentiation in a chemically-defined medium. The presence and activity of voltage-gated Na+, K+ and Ca2+ channels were recorded, alongside data on neuronal excitability (Vm, iAP induction and threshold and spontaneous electrical activity). These data were also recorded in fetal hWGE- and neonatal mWGE-derived neurons for comparison. hESC-derived neurons were shown to be functionally more similar to fetal hWGEneurons suggesting an immature neuronal phenotype Chapter 5: GABAergic Signalling in hESC-Derived and Primary Neurons GABAergic signalling in hESC-, mWGE- and hWGE-derived neuronal populations was investigated. Focus was placed on hWGE-derived neurons and the developmental state of GABAergic responses. In fetal hWGE-derived neurons, a percentage of cells displayed an ‘inhibitory’ response to GABAAR activation. This is a novel observation with implications in human neuronal development. In vitro modulation of GABAergic signalling was also shown, providing potential tools for future research into this phenomenon Chapter 6: Future Developments and General Discussion iPSC-derived neuronal populations were shown to display basic neuronal functional properties. This work will form the basis of future studies on these cellsEThOS - Electronic Theses Online ServiceGBUnited Kingdo

Mesoporous silica nanoparticles with tunable pore size for tailored gold nanoparticles

The aim of this paper was to verify a possible correlation between the pore-size of meso- porous silica nanoparticles (MSNs) and the sizes of gold nanoparticles (AuNPs) obtained by an impreg- nation of gold(III) chloride hydrate solution in the MSNs, followed by a specific thermal treatment. Mesoporous silica nanoparticles with tunable pore diameter were synthesized via a surfactant-assisted method. Tetraethoxysilane as silica precursor, cetyl- trimethylammonium bromide (CTAB) as surfactant and toluene as swelling agent were used. By varying the CTAB–toluene molar ratio, the average dimension of the pores could be tuned from 2.8 to 5.5 nm. Successively, thiol groups were grafted on the surface of the MSNs. Finally, the thermal evolution of the gold salt, followed by ‘‘in situ’’ X-ray powder diffraction (XRPD) and thermogravimetric analysis (TGA), revealed an evident correlation among the degradation of the thiol groups, the pore dimension of the MSNs and the size of the AuNPs. The samples were characterized by means of nitrogen adsorption– desorption, transmission electron microscopy, small- angle X-ray scattering, XRPD ‘‘in situ’’ by synchro- tron radiation, and ‘‘ex situ’’ by conventional tech- niques, diffuse reflectance infrared Fourier transform spectroscopy, and TGA

Two different approaches for the synthesis of mesoporous silica nanoparticles with tunable diameter and pores size

Two combined approaches of Stöber method and supramolecular assembly of surfactant molecules, under assistance of different organic solvents, have been exploited for the synthesis of ordered MSNs with spherical morphology between 60- 200nm and pore size from 2.7 to 8nm

Structural study of a porous CuO-CeO2/ZrO2 system for the low-temperature total oxidation of carbon monoxide

A promising sol-gel surfactant-assisted method for the synthesis of micro- and mesoporous zirconia with nanometric dimension and high surface area was studied. The supports were impregnated with Ce and Cu nitrates solutions (20 wt% and 6 wt%, respectively) and tested in the CO total oxidation. Correlations between catalytic activity and properties were made using XRPD, N2 physisorption, TEM, DRIFT-IR, H2-TPR, Raman spectroscopy and XPS

Orthorhombic phase stabilization and transformation phase process in zirconia tantalum-doped powders and spark plasma sintering systems

The role of different amount (from 1 to 20 mol%) of tantalum Ta(V) into the zirconia lattice has been investigated in different powders systems prepared via co-precipitation and after calcination. The X-ray diffraction and Raman analyses, have confirmed the presence of an orthorhombic phase in all the samples. The stability of this phase has been investigated by “in situ” X-ray diffraction analysis from 100 °C to 1000 °C and after the subsequent cooling. A phase transformation mechanism, with the formation of a poor (monoclinic) and a rich phase (orthorhombic) in Ta has been consider in order to explain the XRD patterns obtained at different temperatures. The characterization of the orthorhombic phase on bulk ceramic specimens prepared via Spark Plasma Sintering (SPS) has been also investigated. SEM analysis has confirmed the presence of a two-phase system

Oxygen Hole States in Zirconia Lattices: Quantitative Aspects of Their Cathodoluminescence Emission

Systematic assessments of cathodoluminescence (CL) spectroscopy, Raman spectroscopy (RS), and Xray diffraction (XRD) are presented for pure zirconia and for a series of Y-doped zirconia powders (henceforth, simply referred to as undoped ZrO2 and YSZ powders, respectively) synthesized according to a coprecipitation method of Zr and Y chlorides. Emphasis is placed here on spectral emissions related to oxygen-vacancy sites (i.e., oxygen hole states) equally detected from undoped and Y-doped ZrO2 samples, either as intrinsic defects or, extrinsically induced, by means of cathodoluminescence. Most counterintuitively, the undoped ZrO2 sample (i.e., the one with presumably the lowest amount of oxygen vacancies) experienced the strongest CL emission. A progressive “quenching” effect on CL emission with increasing the fraction of Y3+ dopant could also be observed because the intrinsic vacancies present in the undoped lattice are the most efficient since they can trap two electrons to gain electrical neutrality. However, as soon as Y3+ ions are introduced in the system, those intrinsic vacancies migrate to Y-sites in next-nearest-neighbor locations, namely in a less efficient lattice location. This phenomenon is tentatively referred to as “delocalization” of vacancy sites. Moreover, the fact that Y-doped zirconia series presents quite similar CL spectra compared to the undoped zirconia could be an evidence that the radiative centers of undoped and Y-doped ZrO2 are basically the same. A fitting procedure has been made aiming to give a rational description of the variation of the spectra morphology, and a parameter able to describe the monoclinic to tetragonal phase transformation has been found. This parameter and the overall set of CL data enabled us to quantitatively assess polymorphic phase fractions by CL spectroscopy in the scanning electron microscope

Mesoporous zirconia nanoparticles as drug delivery systems: Drug loading, stability and release

Drug delivery systems have been a milestone in medical research in the last twenty years, still representing a key aspect of innovation and evolution in pharmacokinetics and pharmacodynamics. Among several proposed solutions, inorganic mesoporous materials could be a promising vehicle. Their specific chemical-physical properties make them ideal candidates for the adsorption and loading of active pharmaceutical ingredients (API). Recently, mesoporous zirconia nanoparticles (MZNs) have been described as a novel drug delivery system due to their high surface area and biocompatibility. In this work, we investigated the loading and release efficiencies of a wide range of API on MZNs characterized by suitable pore volume and versatility, focusing on the integrity of the released drugs investigated through solution NMR and ESI-MS techniques. In order to explore the potentialities of MZNs for biomedical applications, we selected ibuprofen, N-acetyl-L-cysteine, vancomycin, gentamicin, nitrofurantoin, and indomethacin as benchmark API characterized by a wide range of polarity, molecular weight and presence of different functional groups. MZNs showed to efficiently load and release most of the API investigated. Long time loadings were also investigated observing that, after more than three months, no side reaction occurred on the released drugs except for intrinsically more labile API like NTF and NAC. MZNs ensured high inertness towards a wide range of functional groups such as aliphatic and aromatic amides, acetals of sugar residues as well as several chiral moieties bearing tertiary stereocenters

Lanthanide-doped bismuth-based fluoride nanocrystalline particles: Formation, spectroscopic investigation, and chemical stability

Bismuth-based fluoride nanocrystalline particles have recently attracted much attention as hosts for luminescent ions such as lanthanides (Ln) being proposed for lighting devices and biological applications. However, a comprehensive investigation on the chemical properties of this family of materials, the growth of the nanoparticles, and information about the chemical and thermal stabilities are critical to assess the real potential of nanosystems. In this view, a combined experimental and theoretical approach is employed to investigate the crystalline and electronic structure of BiF3 and NaBiF4. A detailed spectroscopic investigation allows us to measure the exciton peaks of these fluoride compounds for the first time and to design the vacuum referred binding energy level diagram of the lanthanide-doped fluorides with respect to the valence and conduction bands of the hosts in comparison with conventional fluorides. In addition, temperature and water effects on the chemical stability of NaBiF4 were addressed, evidencing detrimental limitations and envisaging possible solutions in view of biological applications

Photoluminescence properties of YAG:Ce3+,Pr3+ phosphors synthesized via the Pechini method for white LEDs

We describe a facile route for synthesize YAG nanophosphors via Pechini-type sol–gel process for white light-emitting diodes technology. The wettype synthesis was followed by a heat treatment at 1,000 C for 4 h. We carried out a study of the luminescent properties of the YAG:Ce,Pr system varying the concentration of praseodymium from 0.125 to 2 mol% maintaining the quantity of cerium constant at 2 mol%. The diffractometric analysis confirmed the purity of the YAG phase. The luminescent analysis showed the typical Ce3? emission arising from the 5d ! 4f transitions overlapped with the sharper Pr3? emissions in the red region of the spectrum. The presence of energy transfer phenomenon was confirmed by PLE spectra of the samples and the appearance of concentration quenching at 0.5 mol% Pr was observed thanks to the decrease both of the intensity of praseodymium emission and mean lifetime