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Abstract: Water security and quality are a global issue of concern, which have recently become alarming due to the growth of the human population, industrialisation and expanded agricultural activities. Biologically active compounds, such as pharmaceuticals and personal care products can have major adverse effects on aquatic organisms, and are therefore one of the biggest threats in water quality. Another major concern is the spread of waterborne pathogens, including multidrug resistant (MDR) bacteria, which can cause serious illnesses in humans. In order to maintain water abundance and quality, it is necessary that adequate wastewater treatment and analytical techniques allowing for sensitive and fast-response detection of water hazards are in place. Conventional (waste)water treatment technologies often fail to adequately remove all of the water hazards detailed above. Moreover, conventional analytical techniques currently used in water quality control are, although highly selective and sensitive, time-extensive, with throughput of merely 2 to 3 samples per hour, excluding the time for sample preparation. With respect to these drawbacks, research was proposed to explore new approaches for degradation of recalcitrant compounds, inactivation of microorganisms, and fast screening methods, which are listed in the second chapter of this dissertation as research objectives. In the third chapter, an extensive theoretical background on the hazards found in aquatic environment, namely pharmaceuticals and waterborne pathogens, is given. Pharmaceuticals enter the environment through several routes (disposal of unused medication via the toilet, pharmaceuticals passing through the human body unchanged/slightly transformed, animal excretions of pharmaceutically active compounds, insufficient wastewater treatment, etc.); therefore, traces of pharmaceuticals have repeatedly been reported in surface waters, groundwater, wastewater effluents, and even drinking water. Iodinated contrast agents (ICAs), as the compounds of interest in this project are further described. ICAs are eliminated from the human body practically unchanged; therefore a large proportion of them end up in municipal and hospital wastewater, where they can be present in concentrations of up to 2.4 g/L. Their ecotoxicity, degradation attempts, as well as detection monitoring in the environment are reviewed within the chapter. Additionally, waterborne pathogens, which account for 2.2 million deaths per year, are reviewed in this chapter, with emphasis on multidrug-resistant (MDR) bacteria. Although MDR infections are mostly prevalent in hospital environments, the presence of MDR bacteria in the environment is not a rarity. A high percentage of bacterial isolates in waters have been shown to be of an MDR phenotype. The theoretical background in analytical methods in water quality monitoring is also given in this chapter. Vanguard and rearguard techniques are explained, the first offering simple, cheap, and rapid sample screening, but sacrificing sensitivity and selectivity, whereas the second providing the highest quality information, excellent sensitivity and selectivity, but in expense of complicated and timely sample handling and high-cost instruments. By combining the two techniques the benefits of both can be exploited in a single system. The basic principles of thermal lens spectrometry (TLS) and its miniaturised version - the thermal lens microscopy (TLM) as fast screening methods providing high sensitivity are further explained, and their practical applications are reviewed. Furthermore, composite materials have recently been finding applications in water treatment technologies, as filter materials, adsorptives for pollutants, catalysts for degradation reactions, and disinfectants. The applications of three main types of composites: synthetic composites, biocomposites, and nanocomposites, are also reviewed within this chapter. The core of this dissertation is presented in the fourth and the fifth chapter, which examine two separate approaches for water treatment, as well as analytical methods for fast screening purposes. The fourth chapter is investigating options for degradation of iodinated X-ray agents (ICAs), namely diatrizoate, through biodegradation with extracellular enzymes of white rot fungus Dichomitus squalens, and chemical oxidation with manganese(III) acetate. Enzymatic degradation with laccase (Lac) and manganese peroxidase (MnP) at low enzymatic activities was unsuccessful, whereas at approximately 3-times higher activities the enzymes were capable of 60 % degradation in 12 days. Chemical oxidation of diatrizoate with manganese(III) acetate resulted in 85 % degradation in 12 days. Moreover, the suitability of microfluidic flow injection analysis coupled with thermal lens microscopy (μFIA-TLM) as a fast screening method for diatrizoate degradation was examined. The degradation was monitored through the release of iodide from the diatrizoate molecule. μFIA-TLM proved to be a preferable method over UV-Vis spectrophotometry, due to its higher sensitivity, sample throughput, and simple sample handling. Limit of detection (LOD) for μFIA-TLM method was estimated to be 0.14 µM in a 100 µm channel, which is 9 times lower than LOD obtained in UV-Vis measurements. In addition to μFIA-TLM and UV-VIS, high-pressure liquid chromatography (HPLC) was used to monitor the remaining parent compound in the reaction mix. In the fifth chapter, the second water treatment approach is described. This includes synthesis of biocomposite materials from cellulose (CEL) and keratin (KER), with metal (Ag0, AgCl, Au0) nanoparticles (NPs). Materials were characterised for presence, species, and size of NPs with X-ray diffraction (XRD) and with scanning electron microscopy (SEM). Nanoparticles were confirmed to be of expected species, with sizes as follows: 6.3 ± 0.5 nm for Au NPs, 12 ± 2 nm for Ag NPs, and 22 ± 1 nm for AgCl NPs. In order to evaluate antibacterial properties of the materials, contact tests with gram-negative (Escherichia coli and Pseudomonas aeruginosa) and gram-positive bacteria (Staphylococcus aureus, Methicillin-resistant S. aureus (MRSA), and Vancomycin-resistant Enterococcus faecalis (VRE)) were conducted. Direct-contact assay over 24 hours showed a dose and species-dependent antibacterial activity of [CEL:KER + Ag NPs] materials. The highest potency against the selected bacteria (up to 6-log of reduction) was observed for the material with 500 mg of Ag NPs. AgCl NPs appeared to be less potent than Ag NPs, whereas Au NPs exhibited antibacterial activity only against MRSA and VRE. In addition, antiviral properties of materials were investigated on selected bacteriophages (MS2, phiX174, and fr). However, biocomposite materials with 500 mg of Ag NPs and AgCl NPs, as well as, 240 mg of Au NPs did not exhibit any activity against selected bacteriophages. Biocompatibility with human fibroblasts was evaluated through a direct contact assay for 3 and 7 days of exposure. High concentrations of metal NPs turned out to be cytotoxic for human fibroblasts, whereas the amount of 69 mg of Ag NPs in [CEL:KER] was low enough not to affect the viability of the fibroblasts after 3 days of exposure. Composites with Ag NPs and AgCl NPs were also tested for leachability of NPs out of the materials. Both types of NPs were leaching out in two different forms, as silver ions, and as colloidal silver. Leaching of ionic silver from both materials stabilised after 3 days, whereas colloidal silver was still leaching out on the 7th day. The overall percentage of the total silver (ionic + colloidal) leached was only 0.04 % of silver incorporated in the material. In summary, this dissertation investigates alternative approaches for water treatment technologies, which could potentially serve as unit improvements of existing technologies, or as on-point pre-treatment technologies to facilitate further conventional water treatment techniques. It also demonstrates the suitability of μFIA-TLM for fast screening measurements in aquatic samples, offering high sample throughput, simple handling of the samples and superior sensitivity over the UV-Vis spectrophotometry.
Keywords: Antibacterial biocomposites, nanomaterials, water treatment technologies, multidrug-resistant bacteria, iodinated contrast agents, thermal lens microscopy, flow-injection analysis, microfluidics
Published in RUNG: 26.04.2017; Views: 8066; Downloads: 216
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Abstract: This lecture introduces the basic concepts and recent progres in theory, instrumentation and applications of thermal lens spectrometry, thermal lens microscopy and their utilization for highly sensitive, and high throughput detection in liquid chromatography, flow injectionanalysis in microfluidic systems.
Keywords: Thermal lens spectrometry, TLS microscopy, theory, applications
Published in RUNG: 01.03.2017; Views: 7151; Downloads: 1
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Abstract: Since the concentration of bioactive substances and infectious agents in organisms and in the environment are low highly sensitive techniques such as: chromatography technology coupled with mass spectrometry (GC/MS, LC/MS and LC–MS/MS) and transmission electron microscopy (TEM) are needed for their detection. These techniques are highly sensitive, but time consuming, requiring use of expensive apparatus and large quantities of reagents and organic solvents which are harmful for the environment. Because there is a growing need for analysis of a large number of environmental samples it is necessary to develop new, so called vanguard methods that enable rapid and reliable screening of large numbers of samples in the shortest possible time. Analysis with such “screening” methods are often less accurate or even semi-quantitative, but nevertheless allow reliable identification of nonproblematic samples and in practice they limit the use of demanding classical analytical methods to only a few percent of all the samples. Therefore, general objectives of the thesis were development of novel methods for sensitive, fast and cost effective detection of pharmaceuticals, viruses and viral particles in waters and biological fluids and for detection of their effects in organisms. Novel methods were based on the combination of TLS (Thermal Lens Spectrometry), microfluidics and immunological methods such as ELISA. TLS as highly sensitive technique (allowing detection of absorbances of less than 10-6) coupled with microfluidic technology allows detection of very low analyte concentration, shorter time for analysis, higher sample throughput and low consumption of reagents. In such combination microfluidic technology can simplify or speed up antigen-antibody or enzyme-substrate interactions in bioanalytical systems. Decisive advantage of microfluidic systems lies in the fact that small dimensions of such systems, composed of capillaries and micro-reactors with dimensions from about 10 to 100 µm, significantly reduce diffusion time, which is inversely proportional to second power of distance. However, highly sensitive detection techniques are needed in microfludic systems, because the amounts of analytes in detection volumes are generally small and optical interaction lengths are two to three orders of magnitude shorter than in conventional spectrometric techniques. By combining microscopic TLS (TLM) with microfluidic technique it is possible to reach very low limits of detection and at the same time shorten ELISA analysis time from 20 h to 20 minutes as was described before in the literature for detection of BNP (brain natriuretic peptide). TLM furthermore allows measurements of extremely small volumes (sub-microliter) as well as fast signal response (milliseconds). In this Dissertation specific goals were the development of new methods for detection of selected bioactive substances and infectious agents: -iodinated contrast agents -NGAL (neutrophil gelatinase associated lipocalin) as a new biomarker of contrast induced nephropathy (CIN) -antibodies against human papilloma viruses (HPV) viruses and HPV-16 pseudovirions. For the development of new method for detection of iodinated contrast agents chemical degradation of iodinated contrast agents was investigated as well, as a potential method for their removal from waste water. For the determination of NGAL, a commercially available ELISA kit was used as the basis for method development. In the initial experiments the final product of the reaction of substrate with enzyme HRP (horse radish peroxidase) was transferred from microtiter plate into a microfluidic system, which served just for the sample transport to TLM detector on microchip. With comparable speed analysis we achieved LOD of 1.4 pg/mL which is 7 times lower in comparison to commercial ELISA test (LOD=10 pg/mL). For further development of the method for detection of NGAL with µFIA-TLM magnetic nanobeads were used as a solid support for primary antibodies of ELISA assay. By applying appropriate magnetic field the antibodies were kept in microfluidic system, which also enabled binding of NGAL, secondary antibodies and reaction of substrate with HRP. Developed method for NGAL detection with LOD of 2.3 pg/mL compares favorably with LOD for commercial ELISA tests (10 pg/mL) in standard microtiter plates and significantly reduces the analysis time. TLM in combination with microchip for NGAL detection reduces the duration of individual incubation steps (from one hour to 5 minutes) and at the same time shortens total analysis time from four hours for commercial ELISA test to 35 minutes allowing higher sample throughput. Analysis of real blood samples was also performed and it has shown good agreement between NGAL concentrations measured by magnetic nanobeads based µFIA-TLM with the concentrations measured by a commercial ELISA test. Such short analysis time of analysis and possible further optimizations are opening new possibilities for application of µFIA-TLM in medical diagnostics and clinical research. By using appropriate antibodies the method for developed NGAL detection could be easily adopted for detection of different pharmaceuticals or pollutants in environmental samples. We have also developed a magnetic nanobeads based ELISA assay for detection of anti-HPV-16 L1 antibodies in the sera of HPV-16 infected women. To ensure the selectivity, HPV-16 pseudovirions were used as an antigen for anti-HPV-16 L1 antibodies, which were detected with secondary HRP labeled antibodies. Initially the ELISA assay for antibodies against HPV pseudovirions was performed on a microtiter plate and an LOD of 3.8 ng/mL was achieved by measurement on a microtiter plate reader. When performing a µFIA-TLM measurement of the final ELISA solution the LOD was reduced to 0.9 ng/mL. Similar to the method for NGAL detection based on magnetic nanobeads, these were used as solid support for HPV pseudovirions and after carrying out all the incubation steps of the ELISA test in microfluidic chip the final product of the reaction of substrate with HRP was detected on TLM. With magnetic nanobeads based ELISA assay with µFIA-TLM for measurement of antibodies against PsVs of HPV-16 virus an LOD of 0.6 ng/mL was achieved, which is six times lower in comparison to classic ELISA on microtiter plate. Furthermore, the analysis time was reduced from ten hours to 30 minutes. The novel method was successfully validated by analysis of real sera samples from women who were previously diagnosed for infection with HPV-16 virus. For determination of iodinated MRI contrast agents we developed a new method based on the measurement of concentration of released iodide which allows indirectly semi-quantitative detection of concentration of iodinated contrast agents. For iodide release from parent molecule of contrast agent we applied a chemical reaction with Cu2+ ions in the presence of H2O2. Released iodide was first oxidized into iodine and then extracted into chloroform. Contrast agents degradation reaction showed 70 % of efficiency for removal of iomeprol, taking into account the 60 % overall efficiency of iodide oxidation and extraction. The extract was injected into microfluidic chip and iodine concentration was determined with TLM. Chloroform as organic solvent with low thermal conductivity and high temperature coefficient of refractive index is a good choice for TLM measurement due to high TLS enhancement factor, which theoretically provides 40 times higher sensitivity of TLM measurements as compared to water and a four time improvement in sensitivity for each milliwatts of excitation power, when compared to spectrophotometry. The developed µFIA-TLM method for indirect determination of contrast agents based on detection of iodine provides around 60 times lower LOD, with low reagent and sample consumption in comparison to spectrophotometry. The LOD of 18 ng/mL for iomeprol achieved with TLM is 16 times lower in comparison to LOD of 294 ng/mL for iomeprol determination with HPLC. In comparison to LOD of 133 ng/mL for iomeprol achieved with detection of released iodide by ion chromatography, µFIA-TLM enables around 7 times lower LOD. HPLC and HPLC/MS analysis showed that the parent compounds is completely removed after 120 min. of chemical degradation and that different degradation products are formed by cleavage of one or two iodine atoms. By this we have shown that the applied chemical degradation is efficient for removal of iomeprol and could be applied for treatment of waste waters after further optimization and reduction of reaction time. New analytical methods developed within this work provide limits of detection for the selected compounds which are significantly lower (up to 60 times) in comparison to conventional analytical techniques based on transmission mode measurements. At the same time the new methods allows shorter time of analysis and higher sample throughput for the purpose of fast screening methods. Magnetic nanobeads based µFIA-TLM ELISA assays developed within this work offer several advantages in comparison to commercial ELISA tests on microtiter plates such as: higher surface for antibody binding, lower reagent consumption, and shorter analysis time. Although the TLS technique didn’t reach appropriate stage of development and applicability for routine chemical analysis, improved methods for detection of NGAL and antibodies against HPV viruses could be applied for clinical studies and development of commercial tests for detection of viruses or other bioactive substances, which are needed for diagnostic purposes in hospitals.
Keywords: ELISA, NGAL, PsVs, kontrastna sredstva, TLM
Published in RUNG: 02.02.2017; Views: 7748; Downloads: 281
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Abstract: The optimum reaction parameters for the interaction of hexavalent chromium [Cr(VI)] with diphenylcarbazide in microfluidic chips (μFIA) with thermal-lens microscopic detection were selected. The characteristic feature of the applied flow scheme is the injection of the reagent into the stream containing the test metal, which enables in-field and real-time monitoring of Cr(VI) simply by flowing the sample continuously through the microchip. The limit of detection of Cr(VI) under the selected conditions (signal generating wavelength, 514.5 nm; excitation power, 100 mW; detection position, 10 cm downstream from the mixing zone of the microchip; flow rate 10 μL min–1; injection volume, 1.4 μL) is 15 ng mL–1 (2.9 × 10–7 mol L–1). The linear range is 40 ng mL–1 – 10 μg mL–1 with a relative standard deviation no higher than 10% in the concentration range 0.1–1 μg mL–1. The online monitoring by this scheme provides the possibility of up to 360 analyses per hour.
Keywords: Photothermal lensing, thermal-lens microscopic detection, microfluidic applications, μFIA, hexavalent chromium, diphenylcarbazide
Published in RUNG: 12.12.2016; Views: 6160; Downloads: 0
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Keywords: thermal lens microscopy, food samples, bioactive compounds
Published in RUNG: 08.11.2016; Views: 6978; Downloads: 0
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