New precious metal compounds in cancer therapy

Includes abstract.Includes bibliographical references (leaves 139-160).Cisplatin is one of the most effective cancer medications currently available. However, it is seriously limited by patient toxicity and drug resistance. As such, there is a real need for altemative treatments. Some compounds of gold(l) have been found to be biologically active in various contexts, including in killing cancer cells. The metal centres gold(lIl) and rhodium(lI) are isoelectronic to the platinum(ll) centre in cisplatin, and some of their compounds have been shown to have biological activity. The aims of this work were to prepare pyridinecontaining complexes of the three metal centres gold(I), gold(llI) and rhodium(I), and assess these complexes for in vitro anti-cancer activity. Phenyl pyridine and ferrocenylpyridine complexation was achieved with all three metal centres described above. With gold(I), either a chloride or pentafluorophenyl counter-anion was used. The rhodium(l) complexes contained 1,5-cyclooctadiene moieties linked to the metal centre via diene complexation, and a chloride counter-anion. Phenylpyridine complexes of gold(lIl) were achieved via standard reaction with tetrachloroaurate anion. However, the analogous ferrocenylpyridine complexes display unusually low stability and other unexpected physical properties, and are believed to be highly novel chlorobridged gold dimers. The 4-phenylpyridine complex of rhodium(l) was initially found to be active against cancer cells in vitro. It was, however, demonstrated that this activity was actually due to the breakdown product of this compound in DMSO. It was found that this breakdown product interacts with DNA, implying a similar mechanism of action to cisplatin. This is supported by the fact that a cisplatin-resistant cell line displays hjgh cross-resistance against this product. (4-Phenylpyridine)gold(l) (pentafluorophenyl) was also found to be extremely active against cell lines in vitr

Removal of cytostatic platinum compounds and recovery of precious metal from aqueous wastestream

Over the last decades, a strong antropogenic increase in platinum concentrations in the environment is observed. While catalytic converters used in cars and industry contribute to elevated levels in vegetation and soils, hospitals intensely discard platinum from their effluents to surface waters. Since the discovery of its cytostatic properties by Rosenberg, cisplatin and other platinum coordinating compounds such as carboplatin and more recently oxaliplatin are extensively used in chemotherapy for cancer treatment. After ingestion and interaction with DNA, the drugs are biodegraded and excreted by patients through urine – either in hospital or at home - to remain mostly untreated. Biomaterials are ubiquitous distributed over the world and ready available with equal performance. They show a promising potential as sorbent for pollutants from wastewaters. The precious metal containing material can be separated from solution as a solid and be processed and valorised afterwards. In a screening step, several natural wood-based materials and dried microalgal biological flocs have been tested for their sorption efficiency towards cytostatic platinum compounds

Properties and applications of metastable precious metal intermetallic compounds

University of Technology, Sydney. Faculty of Science.Precious metal alloys and compounds have myriad applications in the fast-expanding horizons of the commercial and industrial worlds. They are also fascinating topics for scientific research. These materials have a long history, with gold and silver amongst the very earliest metals used by humans. Over the past millennia, the primary applications of the precious metals and their alloys have been in the ever-lucrative jewellery manufacturing industry. The traditional alloys have been perfected in over three thousand years of experience. However, in the recent past, precious metal alloys and compounds have also found themselves a crucial place of pride in the burgeoning ‘advanced materials’ sector. Gold-based and platinum-based alloys and compounds are amongst the candidates being investigated for serving in those applications. In the present project I sought to explore how gold aluminide and platinum aluminide could be developed for further innovative applications. In particular, I initially became interested in the optical properties of these materials, with a view to developing their application in the jewellery industry. The PtᵪAl alloys are, however, also useful as precursors for producing nanoporous metal sponges. The availability of such samples from the first part of the project encouraged me to consider technological applications of the aluminides in the chemical catalysis industry in the second part of the project. The two parts are linked by virtue of starting with the same materials, which are fabricated and mostly characterized the same way. In both cases the samples are fabricated as thin films by direct-current magnetron sputtering and then various techniques are used to characterize their chemical composition, structures, morphologies and specific properties. The main difference comes only at the very end of each part, with the first group of materials being evaluated on their optical properties and the second on their sponge-forming properties. My work is developed around two hypotheses. First, I hypothesized that the compounds PtAl₂ (brassy yellow) and AuAl₂ (metallic purple) can be alloyed to yield a range of intermediate colours. It is generally stated that these compounds would be immiscible but I proposed that a series of metastable solid solutions could be formed by means of magnetron sputtering. Secondly, I hypothesised that the preparation of nanoporous platinum sponges from metastable (PtᵪAl) precursors would produce a different result than producing them from well-crystallized precursors, and that this could be exploited to provide a new way to control the morphology of such sponges. The work has showed that the attractive colours of the intermetallic compounds AuAl₂ (‘purple gold’) and PtAl₂ (‘golden platinum’) can be combined or mixed to produce an interesting colour spectrum. This may be of interest to the jewellery industry. A series of metastable solid solutions could be formed by using the magnetron sputtering technique, which enables users to produce any desired stoichiometry. In addition, procedures to reliably produce pure AuAl₂ and PtAl₂ thin films have been established. These have lattice parameters of 0.599 nm and 0.594 nm respectively, which are similar to those of bulk samples produced by vacuum arc melting. Addition control may be obtained by designing multilayer stacks of these intermetallic compound films, with both bi-layer and multi-layer films being produced in the present project. It was also shown that a metastable solid solution of Au and Pt could be formed by sputtering, with a co-deposited film of 54 at.%Au- 46 at.%Pt film forming a solid solution with a lattice parameter of 0.401 nm, which lies between that of pure Au films (0.408 nm) and pure Pt films (0.394 nm). This metastable solid solution could be reacted with a pure Al film to form a metastable solid solution of (Au,Pt)Al₂ after annealing. However, thin film stacks of AuAl₂ and PtAl₂ may be a better choice to tune colours of these two compounds as they are easier to control. Next I showed that Pt-Al alloys and intermetallic compounds can be de-alloyed in alkaline solutions to produce nanoporous platinum sponges. These nanoscale sponges can be used as chemical catalysts although I did not pursue this aspect myself. Rather, in this part of the project I considered how the microstructure of the precursor alloys could control the morphology of subsequent sponges. Once again, metastable precursors could be prepared by using magnetron sputtering, and produced a different morphology of sponges compared to those produced from well-crystallized precursors. Other processing parameters have also been studied. It was found that mole fraction (χAl) of Al in the precursor and the deposition temperature are the two most important factors. Precursors with χAl 0.90 were de-alloyed. These had originally consisted of a mixture of PtAl₆ and pure Al. It was also found that precursors that had been deposited at room temperature produced very different sponge morphologies to those that had been deposited at elevated temperature: in this case the amorphous precursors with 0.67 < χAl <0.96 produced sponge morphologies ranging from pinhole to unusual isotropic foamy. This work has shown that different morphologies of nanoporous platinum sponges can be produced by controlling the processing parameters. These sponges might be considered for use in specific catalytic or sensor applications because they can be fabricated using simple and cost-effective production techniques

The PGE-Au Mineralisation of the Skaergaard intrusion: precious metal minerals, petrography and ore genesis

The Skaergaard PGE-Au Mineralisation, alias the Platinova Reef, is hosted in a series of mineralisation levels within a suite of bowl-shaped macrorhythmic layers in the upper Middle Zone of the Skaergaard intrusion. The intrusion is exposed 68°N in East Greenland. The occurrence defines its own type due to its exceptional structure and mineralogy. A wealth of mineralogical data is available in laboratory reports for individual samples and in peer-reviewed publications, but none of these account for the lateral and stratigraphic distribution of PGE and Au parageneses in the gabbros of the intrusion. In this study, we collate and describe the mineralogical data for the first-formed PGE-rich and last-formed gold-rich mineralisation levels and integrate these with petrogenetic models. Recovery of &gt;4000 grains of precious metal phases allow a detailed study of their distribution and compositions throughout the mineralisation, re-equilibration during cooling, inter-grain relationships and relationships to Cu-Fe sulphides and the gabbroic host rocks. The sulphides are dominated by bornite, chalcocite and minor chalcopyrite. All other sulphides, such as pentlandite, are very rare. Fifty-four different precious metal phases are identified in this study, and include the new IMA approved minerals skaergaardite (PdCu), nielsenite (Pd3Pb) and naldrettite (Pd2Sb). Precious metal phases include (1) intermetallic compounds and alloys of Cu and Pd; (2) intermetallic compounds and alloys of Au and Cu (Ag); (3) sulphides of Pd, Cu (Ag, Cd, Hg, Tl); (4) arsenides of Pd (Pt, Ni) and (5) intermetallic compounds of Pd, Cu with Sn, Pb, Te (Sb, Bi). Skaergaardite (PdCu) is the dominant PGE mineral in the lower and main PGE mineralisation level (Pd5). It is accompanied at the western margin of the intrusions by the sulphides vasilite (Pd16S7) and vysotskite (PdS) but is rare at the eastern margin, which is dominated by plumbide zvyagintsevite (Pd3Pb). Gold phases include a suite of intermetallic compounds and alloys from AuCu3 to native gold and are dominated by tetra-auricupride (AuCu). Gold is concentrated in the tops of individual mineralisation levels and in the uppermost precious metal–bearing mineralisation level, followed by stratiform Cu-rich mineralisation levels. Precious metal parageneses demonstrate formation and re-equilibration from liquidus to subsolidus temperatures and control by local geochemical environments. The mineralisation is syn-magmatic and the result of fractionation and evolution in the remaining bulk-silicate liquid and crystal mushes. Fractionation led to sulphide saturation and formation of immiscible sulphide melt droplets. This was followed by reaction with mush melts and re-equilibration to lower temperatures, first under the roof and subsequently after slumping to the floor in mushes of macrorhythmic layers. Droplets of sulphide melt formed between 1030–1050°C and trapped precious metals. The subsequent reaction between sulphide melt and interstitial Fe-rich immiscible melt at c. 1015°C, and redistribution to coexisting melt and fluid, led to the separation of PGE, Au and Cu and their up- and inward transport. Magmatic fluids as well as volatile-rich residual silicate melts were retained in gabbros at the margins and resulted in precious metal parageneses in equilibrium with hydrous low-temperature silicate parageneses

Mn nanoparticles encapsulated within mesoporous helical n-doped carbon nanotubes as highly active air cathode for zinc–air batterie

The practical application of clean energy conversion and storage technologies, such as fuel cells and metal–air batteries, have been significantly impeded by the high cost and scarcity of precious metal catalysts used for the oxygen reduction reaction (ORR). Transitional metal/carbon compounds are a promising alternative to precious metal catalysts for the OR

Use of Desulfovibrio and Escherichia coli Pd-nanocatalysts in reduction of Cr(VI) and hydrogenolytic dehalogenation of polychlorinated biphenyls and used transformer oil

BACKGROUND Desulfovibrio spp. biofabricate metallic nanoparticles (e.g. ‘Bio-Pd’) which catalyse the reduction of Cr(VI) to Cr(III) and dehalogenate polychlorinated biphenyls (PCBs). Desulfovibrio spp. are anaerobic and produce H2S, a potent catalyst poison, whereas Escherichia coli can be pre-grown aerobically to high density, has well defined molecular tools, and also makes catalytically-active ‘Bio-Pd’. The first aim was to compare ‘Bio-Pd’ catalysts made by Desulfovibrio spp. and E. coli using suspended and immobilised catalysts. The second aim was to evaluate the potential for Bio-Pd-mediated dehalogenation of PCBs in used transformer oils, which preclude recovery and re-use.\ud RESULTS Catalysis via Bio-PdD. desulfuricans and Bio-PdE. coli was compared at a mass loading of Pd:biomass of 1:3 via reduction of Cr(VI) in aqueous solution (immobilised catalyst) and hydrogenolytic release of Cl- from PCBs and used transformer oil (catalyst suspensions). In both cases Bio-PdD. desulfuricans outperformed Bio-Pd E. coli by ~3.5-fold, attributable to a ~3.5-fold difference in their Pd-nanoparticle surface areas determined by magnetic measurements (Bio-PdD. desulfuricans) and by chemisorption analysis (Bio-PdE. coli). Small Pd particles were confirmed on D. desulfuricans and fewer, larger ones on E. coli via electron microscopy. Bio-PdD. desulfuricans-mediated chloride release from used transformer oil (5.6 $\pm$ 0.8 $\mu$g mL-1 ) was comparable to that observed using several PCB reference materials. \ud CONCLUSIONS At a loading of 1:3 Pd: biomass Bio-PdD. desulfuricans is 3.5-fold more active than Bio-PdE. coli, attributable to the relative catalyst surface areas reflected in the smaller nanoparticle sizes of the former. This study also shows the potential of Bio-PdD. desulfuricans to remediate used transformer oil

Long-Lived, Strongly Emissive, and Highly Reducing Excited States in Mo(0) Complexes with Chelating Isocyanides

Newly discovered tris(diisocyanide)molybdenum(0) complexes are Earth-abundant isoelectronic analogues of the well-known class of [Ru(α-diimine)3]2+ compounds with long-lived 3MLCT (metal-to-ligand charge transfer) excited states that lead to rich photophysics and photochemistry. Depending on ligand design, luminescence quantum yields up to 0.20 and microsecond excited state lifetimes are achieved in solution at room temperature, both significantly better than those for [Ru(2,2′-bipyridine)3]2+. The excited Mo(0) complexes can induce chemical reactions that are thermodynamically too demanding for common precious metal-based photosensitizers, including the widely employed fac-[Ir(2-phenylpyridine)3] complex, as demonstrated on a series of light-driven aryl–aryl coupling reactions. The most robust Mo(0) complex exhibits stable photoluminescence and remains photoactive after continuous irradiation exceeding 2 months. Our comprehensive optical spectroscopic and photochemical study shows that Mo(0) complexes with diisocyanide chelate ligands constitute a new family of luminophores and photosensitizers, which is complementary to precious metal-based 4d6 and 5d6 complexes and represents an alternative to nonemissive Fe(II) compounds. This is relevant in the greater context of sustainable photophysics and photochemistry, as well as for possible applications in lighting, sensing, and catalysis

Biomass-supported catalysts on Desulfovibrio desulfuricans and Rhodobacter sphaeroides

A Rhodobacter sphaeroides-supported dried, ground palladium catalyst (‘‘Rs-Pd(0)’’) was compared with a Desulfovibrio desulfuricans-supported catalyst (‘‘Dd-Pd(0)’’)and with unsupported palladium metal particles made by reduction under H2 (‘‘Chem-Pd(0)’’). Cell surface-located clusters of Pd(0) nanoparticles were detected on both D. desulfuricans and R. sphaeroides but the size and location of deposits differed among comparably loaded preparations.\ud \ud These differences may underlie the observation of different activities of Dd-Pd(0) and Rs-Pd(0) when compared with respect to their ability to promote hydrogen release from hypophosphite and to catalyze chloride release from chlorinated aromatic compounds. Dd-Pd(0) was more effective in the reductive dehalogenation of polychlorinated biphenyls (PCBs), whereas Rs-Pd(0) was more effective in the initial dehalogenation of pentachlorophenol (PCP) although the rate of chloride release from PCP was comparable with both preparations after 2 h

The phytoextraction of gold and palladium from mine tailings : this thesis is presented in fulfilment of the requirements for the degree of Master of Philosophy

The extraction of gold and palladium from a South African mine tailing (Klipfontein) and artificial substrate was examined. A variety of solutions were tested and extractants observed to dissolve large quantities of metal were subsequently used in trials investigating plant uptake of gold and palladium. Extraction by thiocyanate amended with an oxidising agent dissolved large amounts of gold and palladium from the test substrates. Various combinations of thiocyanate/Fe(III) and thiocyanate/H 2 O 2 were examined. Metal extraction in the thiocyanate/Fe(III) showed dependence on redox potential and acidity of the solution; this dependence was not observed in the thiocyanate/H 2 O 2 system where production of cyanide may be an important factor. The addition of iodide to thiocyanate/Fe(III) did not affect dissolution of metals. Thiourea was also tested. This chemical was shown to be a relatively poor extractant of gold and palladium, with and without an oxidant. Two plant species, Berkheya coddii and Brassica juncea, were investigated in plant trials. Initial experiments showed uptake of metals to be independent of plant species. Greatest metal uptake was achieved using cyanide as a chemical amendment, with nearly 500 ppm gold accumulation in B. juncea planted in artificial substrate and treated with 1 gL -1 KCN every day over 6 days. Nearly 13 ppm palladium had accumulated in these plants - the highest average concentration observed with any treatment. KCN also induced the largest metal uptake from Klipfontein substrate – nearly 1600 ppb gold and 7700 ppb palladium accumulation in B. coddii. As an exercise it was shown that the value of gold and palladium that would be recovered from a phytomining operation on Klipfontein substrate would be greater than the cost of cyanide added in such an operation. Plant uptake of gold and palladium from the mine tailing after treatment with thiocyanate plus an oxidant was poor. Gold and palladium uptake by B. coddii from artificial substrate after treatment with thiocyanate + H 2 O 2 was improved, with levels of accumulation similar to that of cyanide. Metal uptake by thiocyanate + Fe(III), however, remained poor. The conclusion of this thesis is that phytomining of gold and palladium offers large potential in both practical and research terms. The relative importance of the species thiocyanate, H 2 O 2 , and cyanide remain unknown in the thiocyanate/H 2 O 2 system and further research is needed to elucidate this behaviour