Al(OH)(3) facilitated synthesis of water-soluble, magnetic, radiolabelled and fluorescent hydroxyapatite nanoparticles

Magnetic and fluorescent hydroxyapatite nanoparticles were synthesised using Al(OH)3-stabilised MnFe2O4 or Fe3O4 nanoparticles as precursors. They were readily and efficiently radiolabelled with 18F. Bisphosphonate polyethylene glycol polymers were utilised to endow the nanoparticles with excellent colloidal stability in water and to incorporate cyclam for high affinity labelling with 64Cu

Conjugates of lanthanide chelates and phenylboronates for molecular recognition of tumors

Molecular imaging has become a highly important tool in medicine. Recent technological developments allow visualization of molecular events in vivo on a level that has never been achievable before. The importance of chemistry in medical science is growing due to the demand of specific agents for biological targets. This thesis describes a multidisciplinary search for optimized contrast agents for MRI. The sensitivity of this major high-resolution technique can be enhanced by the application of an imaging reporter in combination with a targeting vector, which includes the optimization of the physicochemical properties of the lanthanide(III)-complexes and their recognition ability towards the overexpressed target on the tumor cells. Understanding of the water coordination behavior of lanthanide complexes is crucial as the efficiency of MRI contrast agents is determined by the number of coordinated water molecules and their exchange rate the bulk water. The first part of this thesis describes the physical methods for determination of these parameters, followed by an 17O NMR study on pyridine based Ln(III)-chelates with extremely fast water exchange. The increase of the specificity of the agents is another approach to optimize the contrast. Therefore, the second part of the thesis deals with the development of a phenylboronic targeting agent for the visualization of tumors based on the molecular recognition of sialic acid overexpressed on the surface of cancerous cells. The recognition mechanism is elucidated by a fundamental multinuclear NMR study, while the feasibility of the targeting is confirmed by the results of a series of incubation experiments with the human glioma cell line and a radioactive 160Tb-complex bearing two phenylboronic targeting groups. Finally, the in vivo delivery and release of the novel targeting agent to the tumor site was realized by use of thermo-sensitive liposomes with a carefully tuned transitional temperature for hyperthermia.Applied Science

Exploration and exploitation of the uncommon pH profile of the dynamic covalent interactions between boronic acids and N-acetylneuraminic acids

In this review, the chemical mechanisms behind the interactions between boronic acids and N-acetylneuraminic acids, which have been widely utilized in biomedicine in recent decades, will be examined. It will also be highlighted that the affinity of boronic acids for N-acetylneuraminic acids is dependent on pH and is complementary to their affinity for other common monosaccharides found in glycocalyces. Through various examples from the literature, the unique pH profile of the boronic – N-acetylneuraminic acids acid interaction and its uses in biomedicine will be illustrated.BT/Biocatalysi

Nanoparticles of lanthanide oxysulfate/oxysulfide for improved oxygen storage/release

Lanthanide oxysulfates have the ability to store and release large volumes of oxygen under oxidizing/reducing conditions, rendering them interesting as automotive catalysts. Herein we demonstrate a remarkable improvement of both processes by utilization of nanoparticles compared to the bulk materials. A further improvement of the catalytic activity was achieved by cost-effective doping with 1.9 wt% of Ni.BT/BiocatalysisBT/Biotechnolog

Potential of MRI in radiotherapy mediated by small conjugates and nanosystems

Radiation therapy has made tremendous progress in oncology over the last decades due to advances in engineering and physical sciences in combination with better biochemical, genetic and molecular understanding of this disease. Local delivery of optimal radiation dose to a tumor, while sparing healthy surrounding tissues, remains a great challenge, especially in the proximity of vital organs. Therefore, imaging plays a key role in tumor staging, accurate target volume delineation, assessment of individual radiation resistance and even personalized dose prescription. From this point of view, radiotherapy might be one of the few therapeutic modalities that relies entirely on high-resolution imaging. Magnetic resonance imaging (MRI) with its superior soft-tissue resolution is already used in radiotherapy treatment planning complementing conventional computed tomography (CT). Development of systems integrating MRI and linear accelerators opens possibilities for simultaneous imaging and therapy, which in turn, generates the need for imaging probeswith therapeutic components. In this review, we discuss the role of MRI in both external and internal radiotherapy focusing on the most important examples of contrast agents with combined therapeutic potential.BT/BiocatalysisRST/Applied Radiation & Isotope

The chemical consequences of the gradual decrease of the ionic radius along the Ln-series

In the periodical system, the lanthanides (the 15 elements in the periodic table between barium and hafnium) are unique in the sense that their trivalent cations have their valence electrons hidden behind the 5s and 5p electrons. They show a gradual decrease in ionic radius with increasing atomic number (also known as the lanthanide contraction). The resulting steric effects determine to a large extent the geometries of complexes of these ions. Here, we discuss these effects, particularly upon the properties of the complexes in aqueous solution, for selected families of Ln3+-complexes of oxycarboxylate and aminocarboxylate ligands. The physical properties of the cations are very different, which is very useful for the elucidation of the configuration, conformation and the dynamics of the complexes by X-ray techniques, NMR spectroscopy, and optical techniques. Often the structural analysis is assisted by computational methods.</p

The search for panchromatic light-harvesting systems: Ternary and binary antennae based on self-organised materials

This study presents a series of light-harvesting materials, where multiple chromophores are organised into host-guest silica-micelle structures at specific locations by means of self-assembly strategies. Binary and ternary mesoscopic antennae were realized, using organometallic complexes and organic dyes as energy transfer units and varying their content and localization to manipulate transfer rate and efficiency inside the materials. Steady-state and time-resolved UV–vis spectroscopy revealed that the three-dye systems show excitation energy cascade from intramicellar dyes to a silica-grafted acceptor, with transfer efficiencies of 20–24 % per step and overall light emission spanning the whole visible range. The two-dye system reaches analogous panchromatic response, featuring almost-white light emission and 47 % efficient transfer, by exploiting the blue-green dual emission of a metallosurfactant as energy donor inside the micellar template and the red emission of a rhodamine acceptor on the silica framework. Both systems show that control over the donor-acceptor distances can be achieved to a certain extent in complex mesoscopic materials and that a vast potential is available for transfer and colour tuning, and specific use of the materials as solid-state sensitisers

The chemical consequences of the gradual decrease of the ionic radius along the Ln-series

In the periodical system, the lanthanides (the 15 elements in the periodic table between barium and hafnium) are unique in the sense that their trivalent cations have their valence electrons hidden behind the 5s and 5p electrons. They show a gradual decrease in ionic radius with increasing atomic number (also known as the lanthanide contraction). The resulting steric effects determine to a large extent the geometries of complexes of these ions. Here, we discuss these effects, particularly upon the properties of the complexes in aqueous solution, for selected families of Ln3+-complexes of oxycarboxylate and aminocarboxylate ligands. The physical properties of the cations are very different, which is very useful for the elucidation of the configuration, conformation and the dynamics of the complexes by X-ray techniques, NMR spectroscopy, and optical techniques. Often the structural analysis is assisted by computational methods.BT/Biocatalysi

Pt/Al2O3 Catalyzed 1,3-Propanediol Formation from Glycerol using Tungsten Additives

Screening of four commercial catalysts (Pt/Al2O3, Pt/SiO2, Pd/Al2O3, and Pd/SiO2) and four acidic additives (hydrochloric, tungstic, phosphotungstic, and silicotungstic acids) shows that the combination of a platinum hydrogenation catalyst with tungsten containing acidic additives yields 1,3-propanediol from aqueous glycerol. The performance of the best catalytic system Pt/Al2O3 with silicotungstic acid as an additive was optimized by experimental design, capturing the influence of reaction time, glycerol concentration, acid concentration, pressure, and temperature on the formation of 1,3-propanediol from glycerol. High 1,3-propanediol yield in an aqueous batch system can be achieved (49?% conversion, 28?% selectivity) with excellent 1,3-propanediol to 1,2-propanediol ratios. A mechanistic interpretation is given for this bifunctional system, supported by the relative stability of 1,3-propanediol in comparison with 1,2-propanediol under the chosen reaction conditions.ChemE/Chemical EngineeringApplied Science