Purification of phosphoric acid by solvent extraction

This work follows a feasibility study (187) which suggested that a process for purifying wet-process phosphoric acid by solvent extraction should be economically viable. The work was divided into two main areas, (i) chemical and physical measurements on the three-phase system, with or without impurities; (ii) process simulation and optimization. The object was to test the process technically and economically and to optimise the type of solvent. The chemical equilibria and distribution curves for the system water - phosphoric acid - solvent for the solvents n-amyl alcohol, tri-n-butyl phosphate, di-isopropyl ether and methyl isobutyl ketone have been determined. Both pure phosphoric acid and acid containing known amounts of naturally occurring impurities (Fe P0 4 , A1P0 4 , Ca3(P04)Z and Mg 3(P0 4 )Z) were examined. The hydrodynamic characteristics of the systems were also studied. The experimental results obtained for drop size distribution were compared with those obtainable from Hinze's equation (32) and it was found that they deviated by an amount related to the turbulence. A comprehensive literature survey on the purification of wet-process phosphoric acid by organic solvents has been made. The literature regarding solvent extraction fundamentals and equipment and optimization methods for the envisaged process was also reviewed. A modified form of the Kremser-Brown and Souders equation to calculate the number of contact stages was derived. The modification takes into account the special nature of phosphoric acid distribution curves in the studied systems. The process flow-sheet was developed and simulated. Powell's direct search optimization method was selected in conjunction with the linear search algorithm of Davies, Swann and Campey. The objective function was defined as the total annual manufacturing cost and the program was employed to find the optimum operating conditions for anyone of the chosen solvents. The final results demonstrated the following order of feasibility to purify wet-process acid: di-isopropyl ether, methylisobutyl ketone, n-amyl alcohol and tri-n-butyl phosphate.

Skin delivery potency and antitumor activities of temozolomide ester prodrugs

Clinical trials have shown temozolomide to be an effective agent for treatment of malignant melanoma. In order to investigate its suitability for delivery via the skin, a series of temozolomide esters was synthesized as prodrugs. In vitro assays demonstrated temozolomide, temozolomide acid and the hexyl ester equi-effective against selected cancer cell lines. The susceptibility of the esters to enzyme hydrolysis and their effectiveness for application to the skin were investigated. The esters effectively diffuse through rat skin and the hexyl ester demonstrated profound potency for penetrating through skin. Topical application of 5% (w/v) hexyl ester in DMSO solution on a mouse model demonstrated a significant inhibition of tumor growth. These results suggest that temozolomide esters could be an effective alternative to temozolomide in the treatment of skin cancer. © 2005 Elsevier Ireland Ltd. All rights reserved.

Subthalamic nucleus neurones in slices from 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-lesioned mice show irregular, dopamine-reversible firing pattern changes, but without synchronous activity

The loss of dopamine in idiopathic or animal models of Parkinson's disease induces synchronized low-frequency oscillatory burst-firing in subthalamic nucleus neurones. We sought to establish whether these firing patterns observed in vivo were preserved in slices taken from dopamine-depleted animals, thus establishing a role for the isolated subthalamic-globus pallidus complex in generating the pathological activity. Mice treated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) showed significant reductions of over 90% in levels of dopamine as measured in striatum by high pressure liquid chromatography. Likewise, significant reductions in tyrosine hydroxylase immunostaining within the striatum (>90%) and tyrosine hydroxylase positive cell numbers (65%) in substantia nigra were observed. Compared with slices from intact mice, neurones in slices from MPTP-lesioned mice fired significantly more slowly (mean rate of 4.2 Hz, cf. 7.2 Hz in control) and more irregularly (mean coefficient of variation of inter-spike interval of 94.4%, cf. 37.9% in control). Application of ionotropic glutamate receptor antagonists 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) and 2-amino-5-phosphonopentanoic acid (AP5) and the GABAA receptor antagonist picrotoxin caused no change in firing pattern. Bath application of dopamine significantly increased cell firing rate and regularized the pattern of activity in cells from slices from both MPTP-treated and control animals. Although the absolute change was more modest in control slices, the maximum dopamine effect in the two groups was comparable. Indeed, when taking into account the basal firing rate, no differences in the sensitivity to dopamine were observed between these two cohorts. Furthermore, pairs of subthalamic nucleus cells showed no correlated activity in slices from either control (21 pairs) or MPTP-treated animals (20 pairs). These results indicate that the isolated but interconnected subthalamic-globus pallidus network is not itself sufficient to generate the aberrant firing patterns in dopamine-depleted animals. More likely, inputs from other regions, such as the cortex, are needed to generate pathological oscillatory activity. © 2006 IBRO.

Double-blind, placebo-controlled, randomized study of eicosapentaenoic acid diester in patients with cancer cachexia

Purpose: Eicosapentaenoic acid (EPA) has been proposed to have specific anticachectic effects. This trial compared EPA diethyl ester with placebo in cachectic cancer patients for effects on weight and lean body mass. Patients and Methods: Five hundred eighteen weight-losing patients with advanced gastrointestinal or lung cancer were studied in a multicenter, double-blind, placebo controlled trial. Patients were randomly assigned to receive a novel preparation of pure EPA at a dose of 2 g or 4 g daily or placebo (2g EPA, n = 175; 4 g EPA, n = 172; placebo, n = 171). Patients were assessed at 4 weeks and 8 weeks. Results: The groups were well balanced at baseline. Mean weight loss at baseline was 18% (n = 518). Over the 8-week treatment period, both intention-to-treat analysis and per protocol analysis revealed no statistically significant improvements in survival, weight, or other nutritional variables. There was, however, a trend in favor of EPA with analysis of the primary end point, weight, at 8 weeks showing a borderline, nonsignificant treatment effect (P = .066). Relative to placebo, mean weight increased by 1.2 kg with 2 g EPA (95% CI, 0 kg to 2.3 kg) and by 0.3 kg with 4g EPA (-0.9 kg to 1.5 kg). Conclusion: The results indicate no statistically significant benefit from single agent EPA in the treatment of cancer cachexia. Future studies should concentrate on other agents or combination regimens. © 2006 by American Society of Clinical Oncology.

The polymerization of lactic acid anhydrosulphite by anionic initiators

This thesis is primarily concerned with the synthesis and polymerization of 5-methyl-1;3, 2-dioxathiolan-4-one-2-oxide (lactic acid anhydrosulphite (LAAS)) using anionic initiators under various conditions. Poly(lactic acid) is a biodegradable polymer which finds many uses in biomedical applications such as drug-delivery and wound-support systems. For such applications it is desirable to produce polymers having predictable molecular weight distributions and crystallinity, The use of anionic initiators offers a potential route to the creation of living polymers. The synthesis of LAAS was achieved by means of an established route though the procedure was modified to some extent and a new method of purification of the monomer using copper oxides was introduced, Chromatographic purification methods were also examined but found to be ineffective. An unusual impurity was discovered in some syntheses and this was identified by means of 1H and 13C NMR, elemental analysis and GC-MS. Since poly-α-esters having hydroxyl-bearing substituents might be expected to have high equilibrium water contents and hence low surface tension characteristics which might aid bio-compatibility, synthesis of gluconic acid anhydrosulphite was also attempted and the product characterised by 1H and 13C NMR. The kinetics of the decomposition of lactic acid anhydrosulphite by lithium tert-butoxide in nitrobenzene has been examined by means of gas evolution measurements. The kinetics of the reaction with potassium tert-butoxide (and also sec-butyl lithium) in tetrahydrofuran has been studied using calorimetric techniques. LAAS was block co-polymerized with styrene and also with 1,3-butadiene in tetrahydrofuran (in the latter case a statistical co-polymer was also produced).

Tear and skin phospholipids:analysis and hydrogel analogues

This thesis is concerned with the analysis of phospholipids in the tear film and with the synthesis of phospholipids analogous to hydrogels. The work consists of two areas. The first area is the study of the phospholipids in the tear film, their nature and fate. The use of liquid chromatography mass spectrometry determined that the concentration of phospholipids in the tear film was less than previously thought. The analysis of the tear film phospholipids continued with thin layer chromatography. This showed the presence of diacylglycerides (DAGs) in the tear film at relatively high concentrations. The activity of an enzyme, phospholipase C, was found in the tear film. It was hypothesised that the low concentration of phospholipids and high concentrations of DAG in the tear film was due to the action of this enzyme. The second area of study was the synthesis of phospholipids analogous materials for use in ocular and dermal applications for use in ocular and dermal applications.For ocular applications the synthesis involved the use of the monomer N,N-dimethyl-N-(2-acryloylethyl)-N-(3-sulfopropyl) ammonium betaine (SPDA) in combination with 2-hdyroxyethyl methacrylate (HEMA). Charge-balanced membranes were also synthesised using potentially anionic monomers in conjunction with cationic monomers in stoichiometrically equivalent ratios also with HEMA as a commoner. Membranes of SPDA copolymers and charge-balanced copolymers proved to have some properties suitable for ocular applications. The dermal materials consisted of one family of partially hydrated hydrogels synthesised from SPDA in combination with ionic monomers: sodium 2-(acrylamido)-2-methyl propane sulfonate and acrylic acid-bis(3-sulfopropyl)-ester, potassium salt. A second family of partially hydrated hydrogels was synthesised from N-vinyl pyrrolidone in combination with the same ionic monomers. Both of the partially hydrated hydrogels synthesised proved to have some properties suitable for use as adhesives for the skin.

Novel high water content hydrogels

Hydrogels may be described as cross-linked hydrophilic polymers that swell but do not dissolve in water. The production of high water content hydrogels was the subject of investigation. Based upon copolymer compositions that had already achieved commercial success as biomaterials, new monomers were added or substituted in and the effects observed. The addition of N-isopropyl acrylamide to an acrylamide-based composition that had previously been designed to become a contact lens, produced materials that showed smart effects in that the water content showed dependence on the temperature of the hydrating solution. Such thermo-responsive materials have potential uses in drug delivery, ultrafiltration and cell culture surfaces. Proteoglycans in nature have an important role to play in structural support where a highly hydrophilic structure maintains lubricious surfaces. Certain functional groups that impart this hydrophilicity are present in certain sulphonate monomers, Bis(3-sulphopropyl ester) itaconate, dipotassium salt (SPI), 3-Sulphopropyl ester acrylate, potassium salt (SPA) and Sodium 2-(acrylamido)-2-methyl propane sulphonate (NaAMPS). These monomers were incorporated into a HEMA-based copolymer that had been designed initially as a contact lens and the resulting effects examined. Highly hydrophilic materials resulted that showed reduced protein deposition over the neutral core material. It is postulated that a sulphonate group would have a larger number of hydration shells around it than for example methacrylic acid, leading to more dynamic exchange and so reducing the adsorption of biological solutes. A cationic monomer was added to bring back the net anionic nature of the sulphonate hydrogels and the effects studied. Ionic interactions were found to cause a reduction in the water content of the resulting materials as the mobility of the network decreased, leading to stiffer but less extensible materials. The presence of a net dominant charge, whether negative or positive, appeared to act to reduce protein deposition, but increasing equivalence in the amount of both charges served to present a more 'neutral' surface and deposition subsequently increased. The grafting of hydrophilic hydrogel layers onto silicone elastomer was attempted and the results evaluated using dynamic contact angle measurements. Following plasma oxidation to reduce the surface energy barrier to aqueous grafting chemistry, it was found that the wettability of the modified elastomers could be significantly enhanced by such treatment. The SPA-grafted material in particular hinted at an osmotic drive for rehydration that may be exploited in biomaterials.

Investigating the modulation of oral drug absorption using in vitro models

Dipeptides can be absorbed into cells via the dipeptide transporter (which also transported tripeptides and dipeptide derivatives). The optimum conditions for measuring the inhibition of Gly-Pro uptake in Caco-2 cells were identified. A number of structure-activity relationships were identified. These included the effects of increasing the amino-acid chain-length, and the presence of a thiol or hydroxyl group in the side-chain increased IC50 while the presence of a hydroxyl group did not. The benzyl esters had lower or equal IC50 values compared to the parent dipeptides while the methyl esters had higher values. These results indicated that while molecular properties did affect IC50, the size, charge and composition of three particular groups caused the most significant effects, supporting the structure-activity relationship identified. An assay was developed using calcein-AM to show the inhibition of p-glycoprotein activity. There was no significant change due to the presence of mannitol but there was in the presence of clyclosporin A (p<0.01). Incubating the cells with the test solution for 30 minutes before the addition of the ester resulted in a significant (p<0.001) difference. The assay was specific for p-glycoprotein, as the presence MRP inhibitors had no effect (p>0.05). The modified protocol allowed the identification of p-glycoprotein inhibitors quickly and simply using a cell suspension of unmodified cells. The clinically relevant buffering of grapefruit juice to pH 7 led to a four-fold increase in intracellular calcein and hence significant inhibition of p-glycoprotein. Buffered orange and lemon juices had no effect on the assay. Flavone derivatives had previously been found to be inhibitors of CYP3A4 yet neither naringin nor naringenin had any significant effect at concentrations found in grapefruit juice. Of the other (non-grapefruit) flavone derivatives tested, hesperidin, found in orange juice, had no significant effect, kaempferol and rutin also had no effect while genistein significantly inhibited p-glycoprotein (results that support previous studies). Hydroxycinnamic acids had no effect on p-glycoprotein. Studies on other compounds found that the balance between inhibiting p-glycoprotein and disrupting cell membranes depends on the compound containing an oxygen atom and the size of the negative charge on it, as well as three-dimensional arrangement of the atoms.

Ionic and neutral hydrogels for dermal and ophthalmic applications

This thesis is concerned with the use of ionic and neutral hydrogels in dermal and ocular applications with particular reference to controlled release applications. The work consists of three interconnected themes.The first area of study is the use of skin adhesive bioelectrode hydrogels as ground plate electrodes for ophthalmic iontophoresis applications. The work provides a basis of understanding the relative contributions made by ionic monomers (such as sodium s-(acrylamide)-2-methyl propane sulphonate and acrylic acid-bis-(3-sulfopropyl-ester, potassium salt) and neutral monomers (such as acryloymorpholine, N,N-dimethylacrylamide and N-vinyl pyrrolidone) to adhesion, rheology and impedance of bioelectrode gels. The general advantage of neutral monomers, which have been used to successfully replace ionic monomers, is that they enable more effective control of independent anion and cation species (for example potassium chloride and sodium chloride) unlike ionic monomers where polymerisation produces an immobile polyanion thus limiting cation mobility. Secondly, release from a completely neutral hydrogel under the influence of mechanical shaking was studied for the case of crosslinked polyvinyl alcohol (PVA) containing low concentration of linear soluble PVA in a contact lens application. The soluble PVA was observed to be eluting by reptation from the lens matrix due to the mechanical action of the eyelid. This process was studied in an in vitro model, which in this research was used as a basis for developing a lens made with enhanced release polymer. The third area of work is related to the factors that control drug release (in particular non-steroidal anti-inflammatory drugs) from a hydrogel matrix. This links both electrotherapy applications, such as transcutaneous electrical nerve stimulation, in which the passive diffusion from the gel could be used in conjunction with enhanced transmission across the dermal surface with passive diffusion from a contact lens matrix and the development of therapeutic contact lenses.

Bifunctional organorhodium solid acid catalysts for methanol carbonylation

Robust, bifunctional catalysts comprising Rh(CO)(Xantphos) exchanged phosphotungstic acids of general formulas [Rh(CO)(Xantphos)]+n[H3–nPW12O40]n− have been synthesized over silica supports which exhibit tunable activity and selectivity toward direct vapor phase methanol carbonylation. The optimal Rh:acid ratio = 0.5, with higher rhodium concentrations increasing the selectivity to methyl acetate over dimethyl ether at the expense of lower acidity and poor activity. On-stream deactivation above 200 °C reflects Rh decomplexation and reduction to Rh metal, in conjunction with catalyst dehydration and loss of solid acidity because of undesired methyl acetate hydrolysis, but can be alleviated by water addition and lower temperature operation.

Total phospholipid fatty acid concentrations structrures of ODP Hole 191-1179 samples (Table 1)

Sediment samples ranging from 0.05 to 278 m below sea floor (mbsf) at a Northwest Pacific deep-water (5564 mbsl) site (ODP Leg 191, Site 1179) were analyzed for phospholipid fatty acids (PLFAs). Total PLFA concentrations decreased by a factor of three over the first meter of sediment and then decreased at a slower rate to approximately 30 mbsf. The sharp decrease over the first meter corresponds to the depth of nitrate and Mn(IV) reduction as indicated by pore water chemistry. PLFA-based cell numbers at site 1179 had a similar depth profile as that for Acridine orange direct cell counts previously made on ODP site 1149 sediments which have a similar water depth and lithology. The mole percentage of straight chain saturated PLFAs increases with depth, with a large shift between the 0.95 and 3.95 mbsf samples. PLFA stable carbon isotope ratios were determined for sediments from 0.05 to 4.53 mbsf and showed a general trend toward more depleted d13C values with depth. Both of these observations may indicate a shift in the bacterial community with depth across the different redox zones inferred from pore water chemistry data. The PLFA 10me16:0, which has been attributed to the bacterial genera Desulfobacter in many marine sediments, showed the greatest isotopic depletion, decreasing from -20 to -35 per mil over the first meter of sediment. Pore water chemistry suggested that sulfate reduction was absent or minimal over this same sediment interval. However, 10me16:0 has been shown to be produced by recently discovered anaerobic ammonium oxidizing (anammox) bacteria which are known chemoautotrophs. The increasing depletion in d13C of 10me16:0 with the unusually lower concentration of ammonium and linear decrease of nitrate concentration is consistent with a scenario of anammox bacteria mediating the oxidation of ammonium via nitrite, an intermediate of nitrate reduction.

(Table 2) Fatty acid composition of polychaetes sampled during POLARSTERN cruise ANT-XXIV/2

The fatty acid (FA) composition of representatives belonging to 18 polychaete families from the Southern Ocean shelf and deep sea (600 to 5337 m) was analysed in order to identify trophic biomarkers and elucidate possible feeding preferences. Total FA content was relatively low with few exceptions and ranged from 1.0 to 11.6% of total body dry weight. The most prominent FA found were 20:5(n-3), 16:0, 22:6(n-3), 18:1(n-7), 20:4(n-6), 18:0, 20:1(n-11) and 18:1(n-9). For some polychaete families and species FA profiles indicated selective feeding on certain dietary components, like freshly deposited diatom remains (e.g., Spionidae, Fauveliopsidae and Flabelligeridae) or foraminiferans (e.g., Euphrosinidae, Nephtyidae and Syllidae). Feeding patterns were relatively consistent within families at the deep stations, while the FA composition differed between the deep and the shelf stations within the same family. Fatty alcohols, indicative of wax ester storage, were found in almost all families (in proportions of 0.0 to 29.3% of total FA and fatty alcohols). The development of this long-term storage mechanism of energy reserves possibly displays an evolutionary strategy.

(Table 1) Organic acid analyses from ODP Leg 125 interstitial waters

For the first time, short-chain organic acids are described from serpentine-associated interstitial waters. In this geologic setting, formate typically dominates the organic acid assemblage. Within the forearc setting, the organic acids are associated only with unconsolidated serpentine. Their existence may be the result of alkaline hydrolysis of ester linkages in organic matter that has been entrained in the serpentine diapir.

Phospholipid fatty acid and quinone composition of sediments from ODP Leg 205 sites

Assessing the habitability of deep-sea sediments undergoing compaction, compression, and subduction at convergent margins adds to our understanding of the limits of the terrestrial biosphere. In this work, we report exploratory biomarker data on sediments obtained at Ocean Drilling Program (ODP) Sites 1253, 1254, and 1255 during drilling at the Costa Rica subduction trench and forearc sedimentary wedge. The samples selected for postcruise biomarker analyses were located within intervals of potentially enhanced fluid flow within the décollement and sedimentary wedge fault zones (Sites 1254 and 1255) and within basal carbonates at the reference site (Site 1253). The passage of fluids that are geochemically distinct from ambient interstitial water provides a disequilibrium setting that may enhance habitability. Biomarker data show low levels of microbial biomass in subseafloor sediments sampled at the Costa Rica convergent margin as deep as ~370 meters below seafloor.

Biomarkers in turbidites at ODP Sites 157-951 and 157-952

Free and ester-bound lipid biomarkers were analysed in oxidised and unoxidised parts of four distinct turbidites from the Madeira Abyssal Plain (MAP), which contained 1 to 2% organic carbon homogeneously distributed throughout the turbidites at the time they were deposited. These turbidites are well suited to study the effects of oxic degradation on lipid biomarkers without the complicating influence of varying organic matter sources, sedimentation rates, or bioturbation. One sample from the oxidised turbidite was compared with two samples from the unoxidised part of each turbidite. Postdepositional oxic degradation decreased concentrations of biomarkers by several orders of magnitude. The ester-bound lipids were degraded to a far lesser extent than their free counterparts were. The extent of degradation of different compounds differed substantially. Within a specific class of biomarkers, degradation also took place to a different extent, altering their distributions. This study shows that oxic degradation of the organic matter may have a profound effect on the biomarker fingerprint and may result in a severe bias in, for example, the interpretation of organic matter sources and the estimation of the palaeoproductivity of specific groups of phytoplankton.