In recent years there has been growing environmental concern regarding ‘microplastics’: microscopic plastic granules, fibres and fragments, categorised as <1 or <5 mm diameter. Microplastics are manufactured to be of a microscopic size, or derive from the photo- and mechanical degradation and subsequent fragmentation of larger plastic litter. Microplastics debris has been identified in the water column and sediments of marine and freshwater ecosystems across the globe, although difficulties in sampling and isolating smaller particulates has resulted in the abundance of <333 µm microplastics being under-reported. Microplastics are bioavailable to a range of aquatic organisms, including fish, seabirds and benthic invertebrates, and can be trophically transferred. The consumption of plastic debris can result in gut blockages, heightened immune response and a loss of lipid reserves. The potential risk to food security, and thereby human health, has led regulators to call for better understanding of the fate and effects of microplastic debris on marine life. Here I tested the hypothesis that microplastics can be ingested by and may negatively impact upon zooplankton. Zooplankton encompass a range of aquatic animals that form a key trophic link between primary producers and the rest of the marine food web. I used a suite of feeding experiments, bio-imaging techniques and ecotoxicological studies to explore the interactions and impacts of polystyrene microplastics on marine zooplankton. My results demonstrate that a range of filter-feeding zooplankton taxa, including copepods and bivalve and decapod larvae, have the capacity to ingest microplastics. Microplastics significantly reduced algal feeding in the copepods Centropages typicus and Calanus helgolandicus. With prolonged microplastic exposure C. helgolandicus produced smaller eggs with reduced hatching success, and had reduced survival owing to declining energetic reserves. Microplastics egested by copepods significantly altered the properties and sinking rates of faecal pellets, with potential repercussions for marine nutrient flux. This investigative work highlights that microplastics pose a significant risk to the health of animals at the base of the marine food web.

Mechanochemically synthesized cobalt oxide-based particles are employed for the catalytic reduction of 4-nitrophenol (4NP), a toxic water contaminant. This reduction produces 4‑aminophenol (4AP), a less toxic, pharmaceutical precursor for drugs such as paracetamol. The indicated reduction has been completed previously using noble metals and/or catalysts requiring extensive solvent use, and time as part of their preparation. The cost and synthesis of these noble metal catalysts hinders the sustainable broad scale application as an environmental remediation solution. The catalyst synthesis explored in this study utilizes the green chemistry technique of vibratory ball-milling and annealing cobalt oxide-based particles at different temperatures, producing unique agglomerates with differing surface structure and catalytic properties. Additional investigation into the mechanism through temperature, pH, and change in pressure over the reaction is completed. Further analysis shows that these catalysts are efficient for the reduction of 4-amino-3-nitrophenol and 2-amino-5-nitrophenol with unique catalytic rates. Finally, it is found that the application of this reduction in a flow process has potential for use on a broader scale.

Colistin is a polypeptide antibiotic used as a "last resort" effective against Gram-negative bacteria. However, increase in its consumption in veterinary medicine in the last 30 years has led to the development of bacterial resistance even to colistin. The application of slurry to soil containing unmetabolized colistin and resistant bacteria poses a risk, because the resistance of bacteria to colistin can be further developed and spread to other components of the environment. Therefore, this work was focused on the creation and optimization of extraction and analytical methods for soil samples containing colistin. Colistin was detected by liquid chromatography in connection with mass spectrometry (HPLC/MS and UPLC/MS/MS). Many extraction solutions have been tested in connection with ultrasonic extraction and purification on various SPE columns, yet colistin has not been successfully extracted from the soil. Colistin was successfully detected only in the slurry extract. The reason why colistin was not detected in soil extracts could be the sorption of colistin on soil organic matter or the formation of complexes of colistin with humic substances.

Evidence suggests that pesticide exposure is a risk factor for atherosclerosis, a pathology involving oxidative stress and dysregulated cholesterol metabolism in monocytes and macrophages as vital causative factors. This research focused on understanding two different mechanisms by which organochlorine and organophosphate pesticides may contribute to atherogenesis. First, the ability of organochlorine insecticides to contribute to elevated oxidative stress was investigated. Urinary concentrations of F2-isoprostanes (a systemic oxidative stress biomarker) and serum levels of the persistent organochlorine compounds p,p’-DDE, trans-nonachlor and oxychlordane were quantified in human samples and the association of these factors with diagnosis of atherosclerosis was described in a cross-sectional study. Subsequently, the ability of three bioaccumulative organochlorine insecticides, trans-nonachlor, dieldrin and p,p’-DDE, to induce the production of superoxide radical anion via NADPH oxidase activation in cultured human THP-1 monocytes through a phospholipase A2 (PLA2)-derived arachidonic acid (AA) signaling cascade was investigated. Trans-nonachlor induced NOX-dependent generation of superoxide/ROS (as measured using three distinct assay types) and stimulated the phosphorylation and membrane translocation of the p47phox regulatory subunit (two biomarkers of Nox activation). Measurement of arachidonic acid and eicosanoid release from OC-exposed monocytes by LC-MS/MS analysis subsequently confirmed the role of PLA2 as a central signaling node in the induction of reactive oxygen production in this process. To investigate a separate mechanism by which organophosphate toxicity may contribute to atherosclerosis, the ability of the esterase/lipase carboxylesterase 1 (CES1), a major enzyme target of OP toxicants, to regulate endocannabinoid and cholesterol homeostasis in human macrophages was assessed. Experimental ablation of CES1 activity altered cholesterol uptake, but not efflux in macrophage foam cells in vitro. Numerous genes involved in the cholesterol homeostatic process, including scavenger receptors (SR-A, CD36), cholesterol transporters (ABCA1, ABCG1), nuclear receptors (LXR, PPAR) and oxysterol forming enzymes (CYP27A1), were profoundly downregulated in CES1 knockdown cells. CES1 appears to play a broad central role in both normal macrophage physiology and the homeostatic response to modified LDL, potentially by liberating esterified molecules from lipoprotein particles that serve as ligands for transcription factors such as PPAR and LXR that control the expression of genes critical to the cholesterol metabolic process.

No description available.

A fusion protein composed of antibody fragments and β-lactamase was earlier created by Kojima et al. (2011), with antigen specificities against a bone disease marker and a pesticide. The enzyme was circularly permutated and fused to the variable heavy and light chain antibody fragments, thereby ensuring inactivity until binding of the target antigen triggered enzyme activation. Upon activation, the β-lactamase produced a colorimetric signal, which indicated antigen presence. In this work, a similar strategy was used to create two novel fusion proteins composed of circularly permuted β-lactamase and superfolder green fluorescent protein with anti-benzo[a]pyrene variable antibody fragments. The fusion proteins were designed and expressed in E. coli for the development of a single-step visual immunoassay. It was hypothesized that the cp reporter proteins would be activated once the binding of B[a]P to the variable antibody fragments occurred, and this interaction was expected to produce a detectable colorimetric or fluorescent signal. Although positive results were obtained in one instance, substantial supportive evidence in favour of the hypothesis could not be obtained. / SENTINEL Bioactive Paper Network, Natural Sciences and Engineering Research Council of Canada (NSERC), Canada Research Chairs Program.