Browsing by Author "Gailer, Jurgen"
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- ItemOpen AccessApplication of Metallomics Tools to Probe the Toxicological Chemistry of Cadmium and Mercury with Blood Plasma Constituents(2023-04-24) Gautam, Astha; Gailer, Jurgen; Musgrove, Amanda S.; Thurbide, Kevin M.The chronic low-level exposure of humans to toxic metal pollutants is associated with severe adverse health effects, but the involved biomolecular mechanisms in the bloodstream - which ultimately define the exposure-response relationships - are incompletely understood. The inorganic pollutants that I focused on include the nephrotoxin Hg2+ and the carcinogen Cd2+. Human serum albumin (HSA) - the most abundant plasma protein - has distinct binding sites for Hg2+ and Cd2+ and it is implicated in their delivery to target organs, but the role that L-cysteine (Cys) and D,L-homocysteine (hCys) play in this process is less well understood. To gain insight into the roles that these biomolecules play in this translocation from bloodstream to target organs I applied analytical tools. In the first step, we identified the toxicologically relevant Cd-Cys complexes that can be formed under physiological conditions of blood plasma. To this end, we employed an anion exchange HPLC column coupled to a flame atomic absorption spectrometer (FAAS) and we used a mobile phase that resembled protein free blood plasma. The observation of the retention behaviour of Cd2+ on this HPLC-FAAS system as a function of increasing Cys concentrations allowed us to observe the on-column formation of mixed CdCysxCly complexes, some of which were characterised by X-ray absorption spectroscopy. In the second step, we wanted to gain insight into the role that HSA plays in the translocation of Hg2+ and Cd2+ to organs. To this end, a size-exclusion chromatography (SEC) coupled on-line to an inductively coupled plasma atomic emission spectrometer (ICP-AES) was employed. The injection of an HSA-Hg/Cd complex with increasing mobile phase concentrations of Cys and hCys allowed us to observe the integrity of the HSA-Hg/Cd complex, which provided new insight into the translocation of Cd2+ and Hg2+ to toxicological target organs.
- ItemOpen AccessThe cisplatin/serum albumin system: A reappraisal(Elsevier, 2019-09-01) Massai, Lara; Pratesi, Alessandro; Gailer, Jurgen; Marzo, Tiziano; Messori, LuigiSince the first approval of cisplatin for cancer treatment in 1978, a lot of attempts have been carried out to characterize in detail its interactions with serum albumin, by far the most important and most abundant plasma protein. The state of the art of those studies was recapitulated by Keppler and coworkers in a comprehensive review article which appeared in Chem. Rev. in 2006. Yet, the general picture was still rather incomplete at that time due to the lack of conclusive structural data. We report here on the main achievements obtained on this system in the period 2006–2018 and try to describe what is now clearly ascertained and what are the still open issues. Remarkably, a detailed structural characterization of this metallodrug/protein system was recently gained thanks to the resolution of the crystal structure of a cisplatin/serum albumin adduct; crystallographic results are nicely complemented by independent MS data. Accordingly, detailed information is obtained on the number and the location of the platinum binding sites. In turn, metallomics investigations permitted to monitor platination of this serum protein in real blood samples. Thus, a rather complete molecular description of the system could be achieved. Conversely, the biological and pharmacological profiles of platinum drugs/serum albumin adducts were drafted in a couple of specific studies; however the results on theses issue are in our opinion still preliminary and controversial and more studies are needed, aimed in particular at establishing clear correlations between the nature of the various platinum/serum albumin derivatives and their biological actions. In any case, the relevance and the impact of cisplatin/serum albumin adducts are herein highlighted and future perspectives briefly depicted.
- ItemEmbargoDisinfection By-Product Precursor Identification and Formation Potential in a Full-Scale Wastewater Reuse Facility: A Year-Long Study(2023-12-13) Perez Perez, Jorge Alberto; Kimura-Hara, Susana; Gailer, Jurgen; Thurbide, Kevin BWater scarcity is a critical global challenge, prompting the exploration of innovative solutions to ensure sustainable safe drinking water. Wastewater reuse has emerged as a promising approach to address this issue, offering a means to augment water supplies while reducing environmental impacts. This research project investigates the effectiveness of advanced wastewater treatment processes to remove contaminants that form toxic disinfection by-products ( DBPs). Wastewater samples were collected monthly over the course of a year (April 2022-April 2023) after various treatment stages including treated wastewater secondary effluent, ultrafiltration, ultrafiltration followed by ozone, and ultrafiltration followed by reverse osmosis. This investigation also included the characterization of the organic matter through spectroscopy techniques, and the formation potential of six regulated and unregulated DBP families after chlorination and chloramination, which are the two most commonly used disinfectants. To unravel the complex organic matter and obtain detailed monitoring of seasonal changes in wastewater before disinfection fluorescence analysis along with Parallel Factor Analysis was carried out in each type of water. Organic matter characterization further revealed that the main constituents in wastewater are related to three main groups: humic acid like, soluble microbial products like, and aromatic protein like. The concentrations of these groups change over the seasons but are also transformed over the treatment process, especially after ozone. Disinfection was performed on each water sample under uniform formation conditions. To quantify the DBPs present after disinfection gas chromatography and tandem mass spectrometry techniques were employed. The study identified 30 DBPs from six families of DBPs: trihalomethanes, haloacetonitriles, halonitromethanes, haloketones, iodinated trihalomethanes, and haloacetaldehydes. By comparing the results from fluorescence and disinfection analysis, the research established connections between the precursor concentrations and DBPs formed during disinfection, alongside other parameters used to monitor water quality after treatment. Correlations between total precipitation (i.e. snow, rain), nitrate, bromide, and DBP formation potential were found. This project also involved the evaluation of the cytotoxicity and genotoxicity of the treated waters to better understand the potential health risks associated with the presence of DBPs and demonstrate the relevance of nitrogen compounds and the utilization of chloramine in the presence of nitrogen-based DBPs, and in consequence the toxicity related to their occurrence in waters. The results obtained from this approach offer valuable insights into identifying DBP precursors and the overall safety of the disinfected wastewater, providing critical information for decision-makers and water treatment practitioners.
- ItemEmbargoIndividual and mixture toxic effects of monohaloacetonitriles to a human cell model(2023-12-20) Jayawardana, Amarasinghe Senadeerage Dona Prabhani Thilina Kumari; Kimura-Hara, Susana; Gailer, Jurgen; Goodarzi, Aaron; Derksen, Darren; Charrois, JeffHaloacetonitriles (HANs) are an emerging class of nitrogen-containing disinfection by-products (DBPs) and have been reported up to a maximum of 41 µg/L in treated drinking water. There is a growing interest in HANs because they are more cyto- and genotoxic than the regulated carbon-based DBPs and have been recently reported as key drivers in overall drinking water toxicity. However, most data presented thus far has focused on monitoring cell toxicity in animal and human cancer-derived cell models with an uncertain relevance to human health. Additionally, those studies have not addressed the possibility of HAN degradation in cell culture conditions. Therefore, the observed effects may come from HANs or HAN-degradation products. In this study I aimed to assess the stability of HANs in cell culture media and the toxic effects of DBPs to a normal tissue-derived human cell model. First, the stability of 8 HANs was evaluated under cell culture conditions used in in vitro toxicological studies (37°C, pH=7.4, for 3 days). Mono-HANs were stable during the incubation period; however, the stability of di- and tri-HANs declined significantly. Di- and tri-HANs transformed into their corresponding haloacetamides and haloacetic acids (HAAs), which are less cytotoxic than HANs. To obtain a more accurate measurement of HAN toxicity, it is recommended to consider changing cell culture media for di- and tri-HANs daily. Then, individual mono-HANs and their mixtures were evaluated for chronic cytotoxicity to a normal tissue-derived human cell model. Cytotoxicity was measured using cell viability and cell growth. HAN toxicity increased in the order of ClCH2CN << BrCH2CN < ICH2CN. At lower concentrations, the mixture of BrCH2CN+ICH2CN had the highest combined cytotoxicity. ClCH2CN demonstrated additive/synergistic effects in the presence of BrCH2CN and ICH2CN. Those results confirmed the previous conclusions from Chinese hamster ovary cell-based assays: cytotoxicity of HANs increased in the order of ClCH2CN << BrCH2CN < ICH2CN. In addition, the cytotoxicity of mono-HAAs and their binary and tertiary mixtures were also evaluated. From the tested HAAs, ClCH₂COOH was the least cytotoxic compound. BrCH₂COOH and ICH₂COOH had similar cytotoxicity. ClCH₂COOH + BrCH₂COOH had the least combined cytotoxicity, and ClCH₂COOH + IAA had the highest combined cytotoxicity. Afterward, the experimental results were compared with toxicity models to evaluate the type of toxic interactions (i.e., additivity, synergism, and antagonism). This study provided a primary understanding of the DBPs as mixtures. Lastly, cell metabolites were extracted and identified after cell exposure to CH3CN. The lowest concentration that negatively affects cells was determined using the non-monotonic dose-response curves for the reduction of cell viability and growth of RPE-1hTERT cells. From these experiments, 1 mM CH3CN was chosen as the non-cytotoxic concentration to treat cells for the metabolomic study. Then, two solvent mixes were evaluated to identify the solvent mix that extracted the most metabolic features. A solvent mix of 80% methanol and 20% H2O was selected. Cells treated with CH3CN for 72 h did not induce a significant change in the metabolic profile of RPE-1hTERT cells. To my knowledge, this is the first attempt to characterize the toxicity of HANs and HAAs to a normal tissue-derived human cell model. Mono-HANs' and mono-HAAs' toxicity to RPE-1hTERT cells increased with the change of halogen substitute from chlorine to bromine/iodine. Although the combined effects of mono-HANs were antagonistic, the combined effects of mono-HAAs were synergistic, implying that HANs and HAAs may affect different cellular mechanisms. Moreover, to the best of my understanding, this study is the first to measure the cytotoxicity of CH3CN to a normal tissue-derived human cell model. The observation of this study concludes that exposure to a lower dose (< 1mM) of CH3CN does not cause cytotoxic effects to RPE-1hTERT cells nor significantly alter the metabolic profile of RPE-1hTERT cells.
- ItemEmbargoInvestigation of electrolytes and separators for redox flow batteries(2024-01-03) Nguyen, Hoang Oanh; Thangadurai, Venkataraman; Gailer, Jurgen; Marriott, Robert; Shi, YujunBatteries as energy storage and conversion technologies, especially redox flow batteries (RFBs), have gained momentum in electric grids. The state-of-the-art RFB uses vanadium-based raw materials for their electrolytes; hence, they are called vanadium redox flow batteries, VRFB. While VRFB performance is well studied, their sluggish kinetics and precipitation issues still need to be addressed. In chapter 4 of this thesis, a raw material for VRFB, vanadium pentoxide V2O5, is studied. The studies involve long-term solubility monitoring, electrochemical screening, and spectral studies. V2O5 long-term solubility increased by adding a 5% volume of hydrochloric acid or methanesulfonic acid. Its electrochemistry performance also improved. A three-fold increase was observed in the diffusion coefficient of the ion VO2+ (formed from dissolving V2O5 in acid) and of the kinetic rate constant of the electron transfer process. Electrochemistry and spectral data proved the mechanism of the improvement. The additives provide extra protons for the dissolution of V2O5. The -OH groups or -CH3SO3- anions in methanesulfonic acid increase the solution’s wettability on the carbon electrode surface. The Cl- anions in hydrochloric acid form coordinated complexes with the dissolved vanadium ions, reducing the chance for clustering and precipitating. In chapter 5 of this thesis, RFB performance is studied. The V2O5-based solution with HCl additive is chosen as the positive electrolyte. An organic quinone solution, made from anthraquinone-2,6-disulfonate sodium (AQDS 2,6) dissolved in sulfuric acid, is chosen as the negative electrolyte. To facilitate the use of a hybrid inorganic – organic ‘vanadium || organic quinone’ cell, a silica gel separator is employed. The silica gel separator is made by dispersing silica into an acidic solution, which is identical to the solutions used to dissolve V2O5 or AQDS-2,6. The full cell has a capacity of 4 AhL-1, energy efficiency of 81.4%, and capacity retention of 97% after 500 cycles. Its voltage losses were predicted from the previous electrochemistry screening studies and analyzed from the full cell data. The reactions were confirmed using spectral data. The results demonstrate the potential for this system to be used in next-generation RFBs for energy storage applications.
- ItemOpen AccessMetal Species in Biology: Bottom-Up and Top-Down LC Approaches in Applied Toxicological Research(Hindawi Publishing Corporation, 2013-02-19) Gailer, JurgenSince the inception of liquid chromatography (LC) more than 100 years ago this separation technique has been developed into a powerful analytical tool that is frequently applied in life science research. To this end, unique insights into the interaction of metal species (throughout this manuscript “metal species” refers to “toxic metals, metalloid compounds, and metal-based drugs” and “toxic metals” to “toxic metals and metalloid compounds”) with endogenous ligands can be obtained by using LC approaches that involve their hyphenation with inductively coupled plasma-based element specific detectors. This review aims to provide a synopsis of the different LC approaches which may be employed to advance our understanding of these interactions either in a “bottom-up” or a “top-down” manner. In the “bottom-up” LC-configuration, endogenous ligands are introduced into a physiologically relevant mobile phase buffer, and the metal species of interest is injected. Subsequent “interrogation” of the on-column formed complex(es) by employing a suitable separation mechanism (e.g., size exclusion chromatography or reversed-phase LC) while changing the ligand concentration(s), the column temperature or the pH can provide valuable insight into the formation of complexes under near physiological conditions. This approach allows to establish the relative stability and hydrophobicity of metal-ligand complexes as well as the dynamic coordination of a metal species (injected) to two ligands (dissolved in the mobile phase). Conversely, the “top-down” analysis of a biological fluid (e.g., blood plasma) by LC (e.g., using size exclusion chromatography) can be used to determine the size distribution of endogenous metalloproteins which are collectively referred to as the “metalloproteome”. This approach can provide unique insight into the metabolism and the plasma protein binding of metal species, and can simultaneously visualize the dose-dependent perturbation of the metalloproteome by a particular metal species. The concerted application of these LC approaches is destined to provide new insight into biochemical processes which represent an important starting point to advance human health in the 21st century.
- ItemOpen AccessSelective Separation of Polar Unsaturated Organics Using a Water Stationary Phase in Gas Chromatography(2022-04) Marno Jones, Amberley; Thurbide, Kevin; Gailer, Jurgen; Achari, Gopal; Thangadurai, VenkataramanIn this thesis, a water stationary phase is explored as a novel means of selectively separating unsaturated analytes in gas chromatography. Several unsaturated/saturated analyte pairs consisting mainly of alcohols and carboxylic acids were examined using both a 30 m conventional non-polar HP-5 column and an 11 m water phase column. For most investigated on the HP-5 column, analytes often eluted very close to each other (~6-12 seconds apart) with poor resolution. By comparison, the shorter water phase column well separated each of the analogue pairs by about 3-8 minutes or more. As well on the water phase, analytes with a triple bond were much more retained than those with two double bonds, which in turn were much more retained than those with one double bond. Conversely, on the HP-5 column these were poorly separated if at all. Next, the addition of various metal ion salts to the water phase was explored. While Ca2+ ion produced modest increases in selectivity, the addition of Ag+ ion was most influential and further increased the original water phase selectivity by a factor of 2.3. This also illustrated the flexibility of the system to be adjusted for such separations as a variety of metal ion salts could be easily dissolved into the water stationary phase for this investigation. Lastly, an exploration of unsaturated analyte separations found that cis/trans isomers were baseline resolved on the water phase but co-eluted on a 30 m conventional polar Carbowax column. Similarly, positional isomers varying the location of the double bond were found to separate with a selectivity value near 1.1 on the Carbowax column, whereas on the water phase column they yielded a value of 1.3 and eluted in the reverse order. The mechanistic implications of OH---pi bonding in the water phase was discussed as a potential origin for the selectivity observed. The method was applied to gasoline, model contaminated water, essential oil, and food stuff analysis. Results indicate that this method could be a very useful means of selectively separating such unsaturated analytes.
- ItemOpen AccessSynthesis and Use of Selenonic Acids as Epoxidation Catalysts and Mechanistic Investigation of the Antioxidant Drug Ebselen(2023-08) Sands, Kai Neil; Back, Thomas George; Derksen, Darren; Ling, Chang-Chun; Gailer, Jurgen; Gravel, MichelSelenium and selenium dioxide have long been known to effect the oxidation of organic substrates, first appearing in the early 20th century as a method of dehydrogenating hydrocarbons. Little progress was made in the use of organoselenium reagents in organic synthesis until the early 1970’s when the selenoxide syn-elimination was shown to be a general method for the installation of double bonds. This reinvigorated the field of organoselenium chemistry, and over the ensuing decade several new selenium-mediated oxidations were developed, including the epoxidation and dihydroxylation of alkenes, Baeyer-Villiger oxidations and the oxidation of phenols to quinones. Many studies of these reactions have invoked a peroxyseleninic acid as the active oxidant, though little evidence was provided at the time to support these claims. Contrary to these early reports, we found that the peroxyseleninic acid is a relatively poor epoxidizing agent due to its facile decomposition to a mixed selenonium-selenonate salt. This salt is stable in the solid state, but generates the corresponding selenonic acid in the presence of hydrogen peroxide. The selenonic acid itself is inactive towards epoxidations; however, in the presence of excess peroxide, rapid epoxidation occurs. This shows that the selenonic acid must be further activated, presumably to the benzeneperoxyselenonic acid. Although selenonic acids were first reported more than a century ago, they have been studied far less frequently and have found little application as synthetic reagents when compared to their seleninic acid analogues. This is in large part due to difficulties in their preparation and characterization, which led to errors in their structure identification in earlier work. Given the newfound importance of selenonic acids in oxidation reactions, a new protocol for the efficient and expedient synthesis of selenonic acids was needed. This was achieved in a one-pot reaction starting from readily available aryl bromides to furnish a range of aryl selenonic acids bearing electron-donating and -withdrawing groups in good to high yields. Finally, organoselenium compounds can mimic the selenoenzyme glutathione peroxidase, which protects cells against oxidative stress by reducing peroxides in the presence of the tripeptide thiol glutathione. Ebselen is arguably the most studied such mimetic; however, there is still considerable uncertainty in its mechanism of action. The final portion of this thesis is a systematic reinvestigation of several key reactions of the proposed catalytic cycles in order to gain further insight into its mechanism which may allow for the design of better glutathione peroxidase mimetics.