Operation Camelthorn

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One-pot preparation of surface modified boehmite nanoparticles with rare-earth cyclen complexes

We report on the one-pot synthetic procedure of cyclen derivatives bearing three acetate groups attached on boehmite nanoparticles, the complexing capabilities of these inorganic–organic hybrid materials with rare earth cations, and the behaviour as contrast agents or fluorescence probes.Delgado Pinar, Estefania, [email protected] ; Frias Martinez, Juan Carlos, [email protected] ; Albelda Gimeno, Maria Teresa, [email protected] ; Alarcon Navarro, Javier, [email protected] ; Garcia-España Monsonis, Enrique, [email protected]

A Conductometric Indium Oxide Semiconducting Nanoparticle Enzymatic Biosensor Array

We report a conductometric nanoparticle biosensor array to address the significant variation of electrical property in nanomaterial biosensors due to the random network nature of nanoparticle thin-film. Indium oxide and silica nanoparticles (SNP) are assembled selectively on the multi-site channel area of the resistors using layer-by-layer self-assembly. To demonstrate enzymatic biosensing capability, glucose oxidase is immobilized on the SNP layer for glucose detection. The packaged sensor chip onto a ceramic pin grid array is tested using syringe pump driven feed and multi-channel I–V measurement system. It is successfully demonstrated that glucose is detected in many different sensing sites within a chip, leading to concentration dependent currents. The sensitivity has been found to be dependent on the channel length of the resistor, 4–12 nA/mM for channel lengths of 5–20 μm, while the apparent Michaelis-Menten constant is 20 mM. By using sensor array, analytical data could be obtained with a single step of sample solution feeding. This work sheds light on the applicability of the developed nanoparticle microsensor array to multi-analyte sensors, novel bioassay platforms, and sensing components in a lab-on-a-chip

Nanoencapsulation of luminescent 3-hydroxypicolinate lanthanide complexes

We have synthesized luminescent nanoparticles comprising a core of lanthanide complexes and shells of amorphous silica using reverse micelles as nanoreactors. 3-Hydroxypicolinate complexes of Eu(III), Tb(III), and the corresponding heteronuclear complexes have been investigated as the photoactive cores. The size of the silica particles is within the nanometer scale, which, together with the ability for surface biofunctionalization, opens up perspectives for their use in bioapplications. Optical studies of the as-prepared nanoparticles reveal that the luminescence properties of the 3-hydroxypicolinate complexes in the matrices are markedly different from their original features

Room-temperature preparation and characterization of poly (ethylene glycol)-coated silica nanoparticles for biomedical applications

Monodisperse, spherical, polyethylene glycol (PEG)–coated silica nanoparticles have been prepared at room temperature and characterized for the purpose of biomedical applications. The particles were synthesized by the hydrolysis of tetramethyl orthosilicate (TMOS) in alcohol media under catalysis by ammonia, and their size can range from about 50–350 nm in diameter. We studied the particle size and size distribution using a scanning electron microscope (SEM) and an asymmetric field-flow fractionation (AFFF) multiangle static light-scattering instrument. The chemical and/or physical binding of PEG to the silica nanoparticles was studied by infrared spectroscopy, and the weight percentage of PEG attached to the particles was quantified. The PEG-coated silica nanoparticles showed enhanced colloidal stability when redispersed into aqueous solutions from the dried state as a result of the steric stabilization function of the PEG polymer grafted on the surface of particles. A nonspecific protein-binding test was also carried out to show that the PEG coating can help reduce the protein adsorption onto the surface of the particles, relating to the biocompatibility of these PEG-coated particles. Also, the inclusion of magnetic nanoparticles into the silica particles was shown as an example of the possible applications of PEG-coated silica particles. These silica nanoparticles, as a matrix for encapsulation of certain reagents, have potential for applications to in vivo diagnosis, analysis, and measurements inside intact biologic systems. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 66A: 870–879, 2003Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/34427/1/10057_ftp.pd

Implementation of a proton therapy supervisory system for iThemba Labs

Thesis (MScEng)--Stellenbosch University, 2012.Please refer to full text for abstract

Characterization of graphene epoxy nanocomposite interface region by multiscale modelling

A dissertation submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science in Engineering, 2018The aim of this study was to characterize graphene epoxy nanocomposite interfacial region using multiscale modelling. Molecular dynamics was used to study the nanocomposite at nano scale and finite element analysis at macroscale to complete the multiscale modeling. Coupling of these two scales was done by the use of a property averaging method known as Irving Kirkwood method. One to three sheets (1.8 %, 3.7 % and 5.4 % graphene weight fraction) of graphene were respectively reinforced with epoxy polymer to form a graphene epoxy nanocomposite. The normal and shear forces at the interfacial region of graphene epoxy nanocomposite were investigated by displacing graphene from epoxy to analyze the mechanical properties including the Youngs Modulus, shear modulus and traction forces. Molecular dynamics simulations were further studied through radial distribution function and molecular energy. The effects of graphene on the density distribution of epoxy in the nanocomposites were also analyzed. The results showed that the density when graphene is added sheet by sheet relatively increases until saturation, and then progressively decreases to a bulk value in regions further away from the interface. Improvements in Youngs Modulus and shear modulus of graphene epoxy model compared to normal epoxy resin were noticed. The dispersed graphene sheet improved the Elastic Modulus more than the agglomerated graphene sheets. The normal and shear forces versus displacement were plotted in order to characterize the interfacial region properties. The elastic constants determined by molecular dynamics were higher than those predicted at macroscale analysis due to the difference in scales. The nanocomposite with 3.7 % weight fraction of graphene gave the best properties of the interfacial region. The results from this model also showed close agreement with the available numerical experiments results from the literature data.XL201

Design, synthesis and evaluation of quinazolinone analogues as monoamine oxidase inhibitors

MSc (Pharmaceutical Chemistry), North-West University, Potchefstroom Campus, 2018Parkinson’s disease (PD) is the second most common neurodegenerative disease after Alzheimer’s disease, and it is estimated to affect approximately 1% of the population over the age of 65. PD is characterised by non-motor and motor symptoms such as resting tremor, bradykinesia and muscle rigidity, which are a result of neuronal dopamine deficiency due to the progressive loss of the dopaminergic pathway that leads from the substantia nigra pars compacta (SNpc) to the striatum. Non-motor symptoms of PD include sleep disturbances, depression and anxiety. There is presently no cure for PD, and the present treatment can neither reverse nor stop the disease progression. However, PD can be treated symptomatically with a variety of therapies which include L-dopa, dopamine agonists, aromatic L-amino acid decarboxylase (AADC) inhibitors, catechol-O-methyltransferase (COMT) inhibitors and monoamine oxidase (MAO) B inhibitors. L-dopa has been the mainstay of PD treatment for over 30 years, and it remains the most effective treatment to date. However, L-dopa should be combined with a peripheral AADC inhibitor to ensure its neuronal bioavailability and to avoid its peripheral side-effects. MAO-B inhibitors have also been found effective in PD treatment because they enhance brain dopamine levels in PD, and thus alleviate the symptoms. The MAO-A and MAO-B enzymes are mitochondrial outer membrane-bound flavoproteins that catalyse the oxidative deamination of monoamine neurotransmitters dopamine, norepinephrine and epinephrine. The MAOs are differently distributed in the body, with MAO-A dominating in the intestines, heart and placenta, while MAO-B dominates in the brain, glial cells in the brain and liver. Oxidation of dopamine by MAO generates hydrogen peroxide and aldehyde derivatives, by-products which are potentially neurotoxic. MAO-B inhibitors increase brain dopamine levels and also reduce levels of hydrogen peroxide and aldehyde derivatives in the brain, and therefore are neuroprotective in this respect. MAO-A inhibitors are used clinically in treatment of depression, while MAO-B inhibitors are used as therapy for PD. Selective and reversible MAO inhibitors are more clinically acceptable because they do not cause the sideeffects that are associated with irreversible and non-selective MAO inhibition. The aim of the present study was to explore 4(3H)-quinazolinone as a scaffold for design of potent and selective MAO-B inhibitors. The MAO inhibitory potential of quinazolinones has been illustrated in several studies. A study conducted by Bahadur (1982) revealed that quinazolinones can inhibit MAO activity by as much as 80%. In their study, Bahadur (1982) discovered that the increase or decrease in MAO inhibitory activity of quinazolinones depends on the type of substituent, as well as the position at which it is attached. This is in agreement with similar studies carried out by Rastogi et al. (1972) and Lata et al. (1982). A number of studies have been conducted to evaluate quinazolinones as potential MAO inhibitors, but none have been done to study the structure-activity relationships (SARs) with respect to thiobenzyl and benzyloxy substitution. This study expanded on the SARs of MAO inhibition by quinazolinone derivatives to enable the design of novel potent MAO inhibitors of this chemical class. Particular attention was given to the benzyloxy and thiobenzyl derivatives of 4(3H)-quinazolinone. Chemistry: Two series of compounds were synthesised and evaluated as potential MAO inhibitors. The thioether (14 compounds), C6 mono- (12 compounds) and N3/C6 disubstituted (9 compounds) derivatives of 4(3H)-quinazolinone were synthesised using standard chemical procedures. The reactants were suspended in either ethanol or N,N-dimethylformamide (DMF) in the presence of a base. The products were precipitated with ice-cold water and were subsequently dried or recrystallised from appropriate solvents. The structures and purities were confirmed by NMR, MS and HPLC. MAO inhibition studies: To determine the 50% inhibitory concentration (IC50) values and selectivity index (SI), a fluorometric assay was carried out employing recombinant human MAOA and MAO-B as enzyme sources, and kynuramine as substrate. The first series consisted of 14 compounds, 12 of which exhibited good MAO-B inhibition properties, with IC50 values in the micromolar to sub-micromolar range. The most potent compound in this series (3k) exhibited an IC50 value of 0.142 μM. Interesting trends were observed through the SAR analyses of the compounds in this series. For example, meta-halogen substitution of the thioether derivatives dramatically increased the inhibitor potencies. A number of derivatives (5 of 21) in the second series showed selective inhibition of MAO-B. The disubstituted compounds 2b and 2h are notable as the most potent inhibitors in this series with IC50 values of 0.685 μM and 0.847 μM, respectively. However, meaningful SARs for MAO inhibition could not be derived because most compounds in this series did not inhibit the MAOs. The 4(3H)-quinazolinone derivatives were successfully synthesised in this study, and it may be concluded that they are potent and selective MAO-B inhibitors, thus promising leads for the future design of PD therapiesNational Research Foundation (NRF)Master