54 research outputs found

    Bulk and Surface Acoustic Wave Sensor Arrays for Multi-Analyte Detection: A Review

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    Bulk acoustic wave (BAW) and surface acoustic wave (SAW) sensor devices have successfully been used in a wide variety of gas sensing, liquid sensing, and biosensing applications. Devices include BAW sensors using thickness shear modes and SAW sensors using Rayleigh waves or horizontally polarized shear waves (HPSWs). Analyte specificity and selectivity of the sensors are determined by the sensor coatings. If a group of analytes is to be detected or if only selective coatings (i.e., coatings responding to more than one analyte) are available, the use of multi-sensor arrays is advantageous, as the evaluation of the resulting signal patterns allows qualitative and quantitative characterization of the sample. Virtual sensor arrays utilize only one sensor but combine itwith enhanced signal evaluation methods or preceding sample separation, which results in similar results as obtained with multi-sensor arrays. Both array types have shown to be promising with regard to system integration and low costs. This review discusses principles and design considerations for acoustic multi-sensor and virtual sensor arrays and outlines the use of these arrays in multi-analyte detection applications, focusing mainly on developments of the past decade

    Development of biosensors for mycotoxins detection in food and beverages

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    Mycotoxins are secondary metabolites of mould, which are ubiquitous in a large variety of food and feed commodities. Thousands of mycotoxins exist, but only a few present significant damages and poisonous properties. Among them, the aflatoxins and ochratoxins are considered to be the most toxic and widely spread in the world and therefore, represent a real threat for human/animal life. Depending on a number of factors like the intake levels, duration of exposure, mechanisms of action, metabolism and defense mechanisms, mycotoxins elicit a wide spectrum of toxicological effects leading to both acute and chronic disease, liver and kidney damage, skin irritation, cancer, immune suppression, birth defects or even death. To address the adverse effects of mycotoxin contaminants in food and feed, health authorities in many countries all over the world have become active in establishing regulations to protect their citizens and livestock from the potential damages caused by those compounds. The European Commission, the US Food and Drug Administration (FDA), the World Health Organization and the Food and Agriculture Organization of the United Nations have set up regulations and maximum levels for major mycotoxins in foods and feeds. To fulfill expectations of these regulatory limits, there is an increasing need for the development and validation of new, simple, fast and precise methods for toxins detection. Therefore, this thesis reveals different strategies for rapid, cost-effective and ultrasensitive bioanalysis of two major mycotoxins: aflatoxin M1 and ochratoxin A. Inhibition competitive assays with surface plasmon resonance spectroscopy (SPR, optical technique), quartz crystal microbalance (QCM, acoustic device) and electrochemical based readout were developed and compared. Presented biosensors were challenged in a red wine and milk samples with no need for pre-treatment or pre-concentration of the sample extract. In order to prevent fouling on the sensor surface by the constituents present in milk samples, the gold surface of the sensor chip was modified and different surface architecture and compared (antifouling polymer brushes and self-assembled monolayer - SAM). Complete resistance to the non-specific interactions was observed for coating with p(HEMA) brushes resulting in two times lower LOD compared to that on thiol SAM. The SPR biosensor for AFM1 allowed for highly sensitive detection in milk with an excellent precision (the average calculated CV was below 4%), limit of detection of 18 pg mL−1 for p(HEMA) brushes and 38 pg mL-1 for thiol SAM and with the analysis time of 55 min. It is worth highlighting that it is the first time that an SPR chip modified with such polymer brushes was used for real time detection of a small target antigen opening a new avenue for highly precise analysis. In the case of wine samples tested for OTA detection, a simple but very effective pre-treatment procedure was successfully applied. It was proved that the addition of the 3% of the binding agent poly(vinylpyrrolidone) (PVP) to red wine completely reduces non-specific interactions by binding polyphenolic compounds (which may be responsible for inactivation of antibody and blocking the sensor surface) through hydrogen bonding, making their elimination easier. Moreover, in this study, the authors evaluated the influence of gold nanoparticles (AuNPs) on signal enhancement and thereby biosensor sensitivity. For this purpose two assays were performed: with and without implementation of NPs. Obtained results allowed for OTA detection at concentrations as low as 0.75 ng mL−1 however, its limit of detection was improved by more than one order of magnitude to 0.068 ng mL−1 by applying AuNPs as a signal enhancer. The combination of indirect competitive assay and AuNPs with QCM-D gave a straightforward tool, which can simultaneously measure frequency and dissipation changes resulting in information about the sensitivity but also about the mass attached to the sensor surface as well as viscoelastic properties and the hydration state of the film. A linear detection range of 0.2–40 ng mL-1 has been achieved with LOD of 0.16 ng mL-1. The same assay format was also tested in voltammetric detection of mycotoxins using modified gold screen printed electrodes (AuSPE). An excellent LOD of 15 ng mL-1 for OTA and 37 pg mL-1 for AFM1 were obtained. Additionally, AuSPE modified with SAMs based on different types of alkanethiols (long and short chains) were tested and compared in terms of electron transfer resistance. Proposed biosensors offer vast range of advantages such as high sensitivity (at pg or ng levels), short analysis time (55 min) in comparison to for example, ELISA which require multiple steps that translates to prolonged analysis time, possibility for online monitoring, characterization of binding kinetics, low consumption of primary antibody (cost reduction), excellent antifouling surface and simple pre-treatment procedure. Combining all most desirable aspects of a good biosensor such as high sensitivity, low costs, short analysis time and simple but effective cleaning-up technique make proposed approaches an important and very promising tools for widespread biosensing applications

    INTERACTIONS OF LIGNIN DIMERS WITH ENGINEERED SURFACES AND MODEL CELL MEMBRANES FOR DESIGN OF LIGNIN-BASED MATERIALS

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    Capitalizing on byproducts of industrial and agricultural economies is among the utmost goals of sustainability. Of particular interest for commercial upgrading is lignin, a phenolic biopolymer found in the cell walls of plants which is the second most abundant biopolymer on Earth after cellulose. Due to its heterogeneous structure, deconstructing lignin to selected small molecules for use as chemicals or advanced materials has been elusive. This work capitalizes on a “bottom up” approach to the synthesis of lignin oligomers of known bond chemistry to better understand their interfacial interactions. The potential pharmacological mechanism of lignin deconstruction components and their toxicological effect on biological systems is currently relatively unexplored. Herein, the interaction of three lignin-derived small molecules (lignin dimers with varying chemical functionality) with lipid bilayers (model cell membranes) was investigated via quartz crystal microbalance with dissipation monitoring (QCM-D) studies of binding and differential scanning calorimetry (DSC) measurements of the change in lipid bilayer phase behavior as a function of dimer concentration. Our results demonstrate that minor differences in structure of lignin molecules have a significant impact on their ability to penetrate into model cell membranes. To show that the lignin oligomers under investigation have the potential to impart surfaces with lignin-like properties (e.g. pharmacological and toxicological properties), a hydrophobic lignin dimer which was previously shown to interacts strongly with model cell membrane was chemically modified to covalently attach to mesoporous silica nanoparticles (MSNPs). The ability of lignin dimer-functionalized particles to interact with and disrupt lipid bilayers was compared to MSNPs functionalized with eugenol, a natural aromatic pharmaceutical found in cloves. While eugenol-grafted particles showed evidence of weak interactions with the bilayer, dimer-grafted particles with the same concentration caused considerable lipid mass loss associated with disruption of up to ~93% of the membrane, suggesting higher biocidal activity. The structure of lignin suggests that it is not only a potential therapeutic and pharmacological substance, but also a promising source of aromatic chemicals. Developing methods to selectively separate and purify lignin oligomers from the complex lignin depolymerization mixture remains an ongoing challenge. Binding of β-cyclodextrin (CD) (a truncated cone-shaped molecule with a hydrophilic exterior and a hydrophobic cavity) to three lignin dimers with different chemical structures was studied using Isothermal Titration Calorimetry (ITC). The thermodynamic parameters (K, ΔH, ΔS, and ΔG) of formation of dimer:β-CD complexes were measured and compared. The results demonstrated that differences in the thermodynamics of CD-lignin interactions can be used to develop selective separation strategies for lignin-derived small molecules. For example, binding with β-CD of a dimer containing a bb bond is entropically driven (due to hydrophobic effects) while favorable enthalpy of interactions drives binding of a dimer with a different bond (bO4). A surface modification technique was also proposed to attach β-CD directly to mesoporous silica nanoparticles, with a goal of using the silica particles for selective capture of lignin-derived small molecules. In sum, this work established structure−function relationships for well-defined lignin derivatives at biologically relevant surfaces. A strategy to create lignin-conjugated silica surfaces was developed and it was shown that bio-inspired materials comprising lignin small molecules have the potential to serve as a platform for novel antimicrobial coatings and therapeutic carriers. Moreover, the potential of β-cyclodextrin to selectively separate lignin oligomers from lignin deconstruction mixture was studied, and a strategy to create immobilized cyclodextrin-functionalized surfaces was proposed

    Development of gas sensors for binary mixtures and solvent-free sample preparation techniques based on polymeric membranes

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    Tese de doutoramento. Engenharia Química. 2005. Faculdade de Engenharia. Universidade do Port

    Molecular imprinting science and technology: a survey of the literature for the years 2004-2011

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    Hybridisation of plasmonic and acoustic biosensing devices

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    Monolithically integrating multiple sensing technologies shows a great potential to perform quantitative measurements for multiple biomarkers of diseases and also provide more insight towards one single biochemical event. The localised surface plasmon resonance spectroscopy measures the change in the refractive index arising from the molecular adsorption on the metallic nanostructures. Acoustic sensors, such as surface acoustic wave sensor and quartz crystal microbalance, measure the variation of its mechanical oscillation caused by the sum of the deposited molecules and the solvent coupled to the adsorbed molecules. Both techniques are known independently as having applications in in-situ, label-free sensing and analysis of biological binding reactions. Due to their complementary properties, the integration of both can prove to be a valuable tool for studying biomolecules on sensing surface. This thesis reports on the development of a hybrid biosensing device that integrates localised surface plasmonic sensing and acoustic sensing technologies. Gold nanodisk arrays as localised surface plasmon resonance sensing device was studied in visible region using three substrates: borosilicate glass, lithium niobate and quartz. The design, simulation, fabrication and characterisation of the gold nanodisk arrays, and the sensing performance optimisation were investigated using glass substrate. Lithium niobate, as a piezoelectric material has surface acoustic wave compatibility and this study can pave the way towards the development of hybrid sensing devices. The study on lithium niobate demonstrated the feasibility of a localised surface plasmon resonance device utilising a high refractive index, birefringent and piezoelectric substrate. Using quartz as the substrate, the design and fabrication of a hybrid sensor were performed, which integrated localised surface plasmonic resonance into a quartz crystal microbalance for studying biochemical surface binding reactions. The coupling of localised plasmon resonance nanostructures and a quartz crystal microbalance allows optical spectra and quartz crystal microbalance resonant frequency shifts to be recorded simultaneously, and analysed in real time for a given surface adsorption process. This integration has the potential to be miniaturised for application in point-of-care diagnostics

    Artificial Olfaction in the 21st Century

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    The human olfactory system remains one of the most challenging biological systems to replicate. Humans use it without thinking, where it can measure offer protection from harm and bring enjoyment in equal measure. It is the system's real-time ability to detect and analyze complex odors that makes it difficult to replicate. The field of artificial olfaction has recruited and stimulated interdisciplinary research and commercial development for several applications that include malodor measurement, medical diagnostics, food and beverage quality, environment and security. Over the last century, innovative engineers and scientists have been focused on solving a range of problems associated with measurement and control of odor. The IEEE Sensors Journal has published Special Issues on olfaction in 2002 and 2012. Here we continue that coverage. In this article, we summarize early work in the 20th Century that served as the foundation upon which we have been building our odor-monitoring instrumental and measurement systems. We then examine the current state of the art that has been achieved over the last two decades as we have transitioned into the 21st Century. Much has been accomplished, but great progress is needed in sensor technology, system design, product manufacture and performance standards. In the final section, we predict levels of performance and ubiquitous applications that will be realized during in the mid to late 21st Century

    Abstracts of Papers Presented at the 2008 Pittsburgh Conference

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    Síntesis y caracterización de polímeros de impresión molecular para aplicaciones analíticas

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    [Resumen] Los polímeros de impresión molecular (MIPs) se caracterizan por ser materiales sintéticos con propiedades de reconocimiento molecular altamente específicas y selectivas, característica que los ha convertido en herramientas analíticas indispensables en numerosas aplicaciones. Esta tesis doctoral comprende el desarrollo de distintas estrategias de diseño de polímeros impresos para simplificar y optimizar su obtención, además de las metodologías involucradas en la evaluación de sus propiedades de enlace, el estudio de la naturaleza de la interacción analito-MIP y el mecanismo mediante el cual se produce dicha unión, la caracterización morfológica del polímero impreso y su aplicación como material adsorbente en la extracción de diversos analitos (drogas de abuso y sus metabolitos, aditivos migrantes de envases plásticos alimentarios, sustancias indicadoras de la calidad en alimentos) en muestras reales (fluidos biológicos humanos, aceite de oliva, carne de pescado). Al mismo tiempo, describe la preparación de una nueva configuración de MIPs en forma de pastilla, que en su empleo como material adsorbente en extracción en fase sólida, genera una novedosa metodología MISPE que permite trabajar en matrices complejas con volúmenes muy bajos de muestra.[Resumo] Os polímeros de impresión molecular (MIPs) caracterízanse por ser materiais sintéticos con propiedades de recoñecemento molecular altamente específicas e selectivas, característica que os converteu en ferramentas analíticas indispensables en numerosas aplicacións. Esta tese doctoral comprende o desenvolvemento de distintas estratexias de deseño de polímeros impresos para simplificar e optimizar a súa obtención, ademáis das metodoloxías involucradas na avaliación das súas propiedades de enlace, o estudo da natureza da interacción analito-MIP e o mecanismo mediante o cal prodúcese dita unión, a caracterización morfolóxica do polímero impreso e a súa aplicación como material adsorbente na extracción de diversos analitos (drogas de abuso e os seus metabolitos, aditivos migrantes de envases plásticos alimentarios, sustancias indicadoras da calidade en alimentos) en mostras reais (fluídos biolóxicos humanos, aceite de oliva, carne de peixe). Ao mesmo tempo, describe a preparación dunha nova configuración de MIPs en forma de pastilla, que no seu emprego como material adsorbente en extracción en fase sólida, xera unha novedosa metodoloxía MISPE que permite traballar en matrices complexas con volumes moi baixos de mostra.[Abstract] Molecularly imprinted polymers (MIPs) are synthetic materials with highly specific and selective molecular recognition properties, making them indispensable analytical tools for a large number of applications. This dissertation includes the development of several design strategies to simplify and optimize the synthesis of molecularly imprinted polymers, in addition to the methodologies involved in the evaluation of their binding properties, the study of analyte-MIP interaction and the adsorption mechanism, the morphological characterization of the imprinted polymers and the application of MIPs as adsorbent materials for the extraction of diferent analytes (drugs of abuse and their metabolites, additives of food packaging, food quality indicators) from real samples (human biological fluids, olive oil, fish meat). At the same time, this work describes the preparation of a new configuration of imprinted polymers (pills) which, used as adsorbent materials in solid phase extraction, generate a new MISPE methodology to work in complex matrices with very low sample volumes

    Novel ceramic membranes for water purification and food industry

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