The Experts below are selected from a list of 1740 Experts worldwide ranked by ideXlab platform
Juan G Santiago - One of the best experts on this subject based on the ideXlab platform.
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web based open source tool for Isotachophoresis
Analytical Chemistry, 2021Co-Authors: Alexandre S Avaro, Supreet Singh Bahga, Yixiao Sun, Kaiying Jiang, Juan G SantiagoAbstract:We present the development of a client-side web-based simulator for complex electrophoresis phenomena, including Isotachophoresis. The simulation tool is called Client-based Application for Fast Electrophoresis Simulation (CAFES). CAFES uses the broad cross-browser compatibility of JavaScript to provide a rapid and easy-to-use tool for coupled unsteady electromigration, diffusion, and equilibrium electrolyte reactions among multiple weak electrolytes. The code uses a stationary grid (for simplicity) and an adaptive time step to provide reliable estimates of ion concentration dynamics (including pH profile evolution), requiring no prior installation nor compilation. CAFES also offers a large database of commonly used species and their relevant physicochemical properties. We present a validation of predictions from CAFES by comparing them to experimental data of peak- and plateau-mode Isotachophoresis experiments. The code yields accurate estimates of interface velocity, plateau length and relative intensity, and pH variations while significantly reducing the computation time compared to existing codes. The tool is open-source and available for free at https://microfluidics.stanford.edu/cafes.
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microfluidic Isotachophoresis theory and applications
arXiv: Chemical Physics, 2021Co-Authors: Ashwin Ramachandran, Juan G SantiagoAbstract:Isotachophoresis (ITP) is a versatile electrophoretic technique which can be used for sample preconcentration, separation, purification, and control and acceleration of chemical reactions. Although the basic technique is nearly a century old and widely used, there has been a persistent need for an easily approachable, succinct, and rigorous review of ITP theory and analysis. This is important as interest and adoption of the technique has grown over the last two decades, especially because of its implementation into microfluidics and integration with on-chip chemical and biochemical assays. We here provide a review of ITP theory with a strong emphasis on steady and unsteady transport starting from physicochemical first principles including conservation of species, conservation of current, the approximation of charge neutrality, and pH equilibrium of weak electrolytes. We combine these generally applicable (to all types of ITP) theoretical discussions with applications of ITP in the field of microfluidic systems, particularly on-chip biochemical analyses. Our discussion includes principles governing ITP focusing of weak and strong electrolytes, ITP dynamics in peak and plateau modes, experimental tools and detection methods, applications of ITP for on-chip separations and trace analyte manipulation, review of simulation tools, and design considerations and challenges for microfluidic ITP systems. We conclude with remarks on possible future research directions. The intent of this review is to help make ITP analysis and design principles more common and widely available among scientific and engineering communities, and to provide a rigorous basis for increased adoption of ITP into microfluidics.
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simultaneous optical and infrared thermal imaging of Isotachophoresis
Analytica Chimica Acta, 2020Co-Authors: Alexandros Terzis, Ashwin Ramachandran, Jinliang Kang, Juan G SantiagoAbstract:Joule heating in Isotachophoresis (ITP) can limit minimum assay times and efforts to scale up processed sample volumes. Despite its significance, the dynamics of Joule heating on spatiotemporal temperature fields in ITP systems have not been investigated. We here present novel measurements of spatiotemporal temperature and electromigration fields in ITP. To achieve this, we obtain simultaneous and registered optical and infrared thermal images of the ITP process. We conduct a series of experiments at constant current operation and vary the leading electrolyte concentration to study and highlight the importance of buffer-dependent ionic conductivity on the resulted temperature rise. The measurements demonstrate a substantial increase of temperature in the adjusted trailing electrolyte region, and the propagation of a thermal wave in the ITP channel with a velocity equal to that of the electromigration front. We present scaling of the experimental data that indicates the dependence of front velocity and temperature rise on current density and ionic conductivity. The current study has direct application to the design and optimization of scaled-up ITP systems and the validation of numerical models of Joule heating.
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Isotachophoresis applied to biomolecular reactions
Lab on a Chip, 2018Co-Authors: Charbel Eid, Juan G SantiagoAbstract:This review discusses research developments and applications of Isotachophoresis (ITP) to the initiation, control, and acceleration of chemical reactions, emphasizing reactions involving biomolecular reactants such as nucleic acids, proteins, and live cells. ITP is a versatile technique which requires no specific geometric design or material, and is compatible with a wide range of microfluidic and automated platforms. Though ITP has traditionally been used as a purification and separation technique, recent years have seen its emergence as a method to automate and speed up chemical reactions. ITP has been used to demonstrate up to 14 000-fold acceleration of nucleic acid assays, and has been used to enhance lateral flow and other immunoassays, and even whole bacterial cell detection assays. We here classify these studies into two categories: homogeneous (all reactants in solution) and heterogeneous (at least one reactant immobilized on a solid surface) assay configurations. For each category, we review and describe physical modeling and scaling of ITP-aided reaction assays, and elucidate key principles in ITP assay design. We summarize experimental advances, and identify common threads and approaches which researchers have used to optimize assay performance. Lastly, we propose unaddressed challenges and opportunities that could further improve these applications of ITP.
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influx and production rates in peak mode Isotachophoresis
Analytical Chemistry, 2016Co-Authors: Charbel Eid, Juan G SantiagoAbstract:We present an analytical model useful in the design of peak-mode Isotachophoresis (ITP) experiments. The model quantifies sample influx and production rates, the latter in applications where ITP is used to accelerate chemical reactions. We include analysis of the effect of initial sample placement location. We derive and identify key nondimensional parameters for the general case of weak electrolyte buffer ions in terms of sample placement (injection mode), initial concentrations, fully ionized mobilities, and reaction kinetic constants. We then discuss how to use these parameters in the optimal design of peak-mode ITP assays and highlight regimes of particular interest. We clearly identify a quasi-equilibrium regime wherein production rates increase until they equal the influx rate of the low abundance sample species. The model and analysis are generally applicable to both cationic and anionic ITP assays and likely to a wide range of sample species.
Petr Boček - One of the best experts on this subject based on the ideXlab platform.
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electrolyte system strategies for anionic Isotachophoresis with electrospray ionization mass spectrometric detection 2 Isotachophoresis in moving boundary systems
Electrophoresis, 2013Co-Authors: Petr Gebauer, Zdena Mala, Petr BočekAbstract:This contribution is the second part of the project on strategies used in the selection of electrolyte systems for anionic ITP with ESI-mass spectrometric detection. It presents ITP as a powerful tool for selective stacking of anionic analytes, performed in a nonconventional way in moving-boundary systems where two co-anions are present in both the leading and terminating zones. The theoretical background is given to substantiate the conditions for the existence and migration of ITP boundaries in moving-boundary systems and stacking of analytes at these boundaries. The practical aspects of the theory are shown in form of stacking-window diagrams that bring immediate information about which analytes are stacked in a given system. The presented theory and strategy are illustrated and verified on the example of analysis of a model mixture of salicylic acid, ibuprofen and diclofenac, and comparison of regular and free-acid ITP with moving-boundary ITP systems formed by formic and propionic acids and ammonium as counterion.
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electrolyte system strategies for anionic Isotachophoresis with electrospray ionization mass spectrometric detection 1 regular Isotachophoresis and free acid Isotachophoresis
Electrophoresis, 2013Co-Authors: Zdena Mala, Petr Gebauer, Petr BočekAbstract:The subject of this work is the definition of a simple model based on general ITP theory that allows describing and predicting the behavior of ITP systems compatible with ESI-MS detection. The model is exemplified by anionic ITP of weak acids that represent an interesting potential application field of ITP-ESI-MS. Suitable ESI-compatible electrolyte systems of very simple composition are proposed including a special free-acid ITP arrangement. The properties of these systems are discussed using illustrative diagrams of their stacking windows. The use of anionic ITP-ESI-MS in negative-ion ESI mode is reported for the first time and its suitability for sensitive trace analysis is demonstrated. The presented ITP-ESI-MS application example comprises a free-acid ITP system formed of formic and propionic acids and direct injection analysis of ibuprofen and diclofenac in waters with quantitation limits of the order 10(-10) M.
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recent progress in capillary Isotachophoresis
Electrophoresis, 2000Co-Authors: Petr Gebauer, Petr BočekAbstract:This article is a continuation of previous reviews and summarizes the progress of analytical capillary Isotachophoresis since 2000. Papers reviewed include methodological and instrumental aspects as well as analytical applications. Included are also papers using Isotachophoresis and/or isotachophoretic principles as part of multidimensional separation schemes.
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sample stacking in capillary zone electrophoresis principles advantages and limitations
Electrophoresis, 2000Co-Authors: J Jozef L Beckers, Petr BočekAbstract:The principles of stacking procedures are described and their properties are discussed, including the fundamentals of the behavior of zone boundaries and the consequences of the self-correcting properties of boundaries in moving boundary electrophoresis, Isotachophoresis, and zone electrophoresis. Further, the diverse possibilities of stacking procedures and the unavoidable destacking are described, and several examples of practically applied stacking procedures are given, besides many references to applications. Some limitations in the use of stacking procedures are discussed. The paper is arranged in such a way that it can serve both as an introduction into the field and as a reference overview.
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Isotachophoresis in zone electrophoresis
Journal of Chromatography A, 1999Co-Authors: Ludmila Křivánková, Pavla Pantůckova, Petr BočekAbstract:Abstract Conditions for existence of transient Isotachophoresis (ITP) in zone electrophoresis are quite common. Transient ITP can either be induced by the composition of the sample or by the composition of the electrolyte system or result from the first step during capillary ITP–capillary zone electrophoresis (CZE) combination. This paper brings a comprehensive analysis of the problem and description of the effects of transient ITP on the migration time, separation efficiency and the detection sensitivity of the CZE analysis. Theoretical considerations are accompanied by model experimental examples. It is shown that in cases where transient ITP can be controlled, the effects of transient ITP can be employed for improvement of the performance of the analysis. Further, it is shown that the combination of capillary ITP–CZE is by far superior. It enables one to inject large sample volumes, to reach efficient sample clean-up, and to separate and to detect trace analytes under optimum conditions.
Lewis A Marshall - One of the best experts on this subject based on the ideXlab platform.
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purification of nucleic acids using Isotachophoresis
Journal of Chromatography A, 2014Co-Authors: Anita Rogacs, Lewis A Marshall, Juan G SantiagoAbstract:Reviewed are methods of nucleic acid (NA) extraction and sample preparation using an electrophoretic purification and focusing method called Isotachophoresis (ITP). ITP requires no special surface chemistries or geometric structures, and can be achieved in a compact system with no moving parts. ITP is also compatible with a wide range of samples and lysing methods. Described are general principles of ITP, considerations around the application of ITP to biological samples (e.g., blood, urine and saliva), ITP electrolyte design considerations for fast and selective NA purification, and examples of ITP compatible lysing methods. Several of the challenges associated with purification of NAs are presented as well as methods to address these. Lastly, specific examples of lysing methods and ITP chemistries are described for purification of NA including host and pathogenic DNA, pathogenic rRNA, and host micro-RNA from complex sample matrices.
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integrated printed circuit board device for cell lysis and nucleic acid extraction
Analytical Abstracts, 2012Co-Authors: Lewis A Marshall, Liang Li Wu, Sarkis Babikian, Mark Bachman, Juan G SantiagoAbstract:Preparation of raw, untreated biological samples remains a major challenge in microfluidics. We present a novel microfluidic device based on the integration of printed circuit boards and an Isotachophoresis assay for sample preparation of nucleic acids from biological samples. The device has integrated resistive heaters and temperature sensors as well as a 70 µm × 300 µm × 3.7 cm microfluidic channel connecting two 15 µL reservoirs. We demonstrated this device by extracting pathogenic nucleic acids from 1 µL dispensed volume of whole blood spiked with Plasmodium falciparum. We dispensed whole blood directly onto an on-chip reservoir, and the system's integrated heaters simultaneously lysed and mixed the sample. We used Isotachophoresis to extract the nucleic acids into a secondary buffer via Isotachophoresis. We analyzed the convective mixing action with micro particle image velocimetry (micro-PIV) and verified the purity and amount of extracted nucleic acids using off-chip quantitative polymerase chain reaction (PCR). We achieved a clinically relevant limit of detection of 500 parasites per microliter. The system has no moving parts, and the process is potentially compatible with a wide range of on-chip hybridization or amplification assays.
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integrated printed circuit board device for cell lysis and nucleic acid extraction
Analytical Chemistry, 2012Co-Authors: Lewis A Marshall, Liang Li Wu, Sarkis Babikian, Mark Bachman, Juan G SantiagoAbstract:Preparation of raw, untreated biological samples remains a major challenge in microfluidics. We present a novel microfluidic device based on the integration of printed circuit boards and an Isotachophoresis assay for sample preparation of nucleic acids from biological samples. The device has integrated resistive heaters and temperature sensors as well as a 70 μm × 300 μm × 3.7 cm microfluidic channel connecting two 15 μL reservoirs. We demonstrated this device by extracting pathogenic nucleic acids from 1 μL dispensed volume of whole blood spiked with Plasmodium falciparum. We dispensed whole blood directly onto an on-chip reservoir, and the system’s integrated heaters simultaneously lysed and mixed the sample. We used Isotachophoresis to extract the nucleic acids into a secondary buffer via Isotachophoresis. We analyzed the convective mixing action with micro particle image velocimetry (micro-PIV) and verified the purity and amount of extracted nucleic acids using off-chip quantitative polymerase chain r...
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extraction of dna from malaria infected erythrocytes using Isotachophoresis
Analytical Chemistry, 2011Co-Authors: Lewis A Marshall, Crystal M Han, Juan G SantiagoAbstract:We demonstrate a technique for purification of nucleic acids from malaria parasites infecting human erythrocytes using Isotachophoresis (ITP). We release nucleic acids from malaria-infected erythrocytes by lysing with heat and proteinase K for 10 min and immediately, thereafter, load sample onto a capillary device. We study the effect of temperature on lysis efficiency. We also implement pressure-driven counterflow during ITP extraction to extend focusing time and increase nucleic acid yield. We show that the purified genomic DNA samples are compatible with polymerase chain reaction (PCR) and demonstrate a clinically relevant limit of detection of 0.5 parasites per nanoliter using quantitative PCR.
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sample dispersion in Isotachophoresis
Journal of Fluid Mechanics, 2011Co-Authors: Giancarlo Garciaschwarz, Lewis A Marshall, Moran Bercovici, Juan G SantiagoAbstract:We present an analytical, numerical and experimental study of advective dispersion in Isotachophoresis (ITP). We analyse the dynamics of the concentration field of a focused analyte in peak mode ITP. The analyte distribution is subject to electromigration, di!usion and advective dispersion. Advective dispersion results from strong internal pressure gradients caused by non-uniform electro-osmotic flow (EOF). Analyte dispersion strongly a!ects the sensitivity and resolution of ITP-based assays. We perform axisymmetric time-dependent numerical simulations of fluid flow, di!usion and electromigration. We find that analyte properties contribute greatly to dispersion in ITP. Analytes with mobility values near those of the trailing (TE) or leading electrolyte (LE) show greater penetration into the TE or LE, respectively. Local pressure gradients in the TE and LE then locally disperse these zones of analyte penetration. Based on these observations, we develop a one-dimensional analytical model of the focused sample zone. We treat the LE, TE and LE‐TE interface regions separately and, in each, assume a local Taylor‐Aris-type e!ective dispersion coe"cient. We also performed well-controlled experiments in circular capillaries, which we use to validate our simulations and analytical model. Our model allows for fast and accurate prediction of the area-averaged sample distribution based on known parameters including species mobilities, EO mobility, applied current density and channel dimensions. This model elucidates the fundamental mechanisms underlying analyte advective dispersion in ITP and can be used to optimize detector placement in detection-based assays.
Petr Gebauer - One of the best experts on this subject based on the ideXlab platform.
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electrolyte system strategies for anionic Isotachophoresis with electrospray ionization mass spectrometric detection 2 Isotachophoresis in moving boundary systems
Electrophoresis, 2013Co-Authors: Petr Gebauer, Zdena Mala, Petr BočekAbstract:This contribution is the second part of the project on strategies used in the selection of electrolyte systems for anionic ITP with ESI-mass spectrometric detection. It presents ITP as a powerful tool for selective stacking of anionic analytes, performed in a nonconventional way in moving-boundary systems where two co-anions are present in both the leading and terminating zones. The theoretical background is given to substantiate the conditions for the existence and migration of ITP boundaries in moving-boundary systems and stacking of analytes at these boundaries. The practical aspects of the theory are shown in form of stacking-window diagrams that bring immediate information about which analytes are stacked in a given system. The presented theory and strategy are illustrated and verified on the example of analysis of a model mixture of salicylic acid, ibuprofen and diclofenac, and comparison of regular and free-acid ITP with moving-boundary ITP systems formed by formic and propionic acids and ammonium as counterion.
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electrolyte system strategies for anionic Isotachophoresis with electrospray ionization mass spectrometric detection 1 regular Isotachophoresis and free acid Isotachophoresis
Electrophoresis, 2013Co-Authors: Zdena Mala, Petr Gebauer, Petr BočekAbstract:The subject of this work is the definition of a simple model based on general ITP theory that allows describing and predicting the behavior of ITP systems compatible with ESI-MS detection. The model is exemplified by anionic ITP of weak acids that represent an interesting potential application field of ITP-ESI-MS. Suitable ESI-compatible electrolyte systems of very simple composition are proposed including a special free-acid ITP arrangement. The properties of these systems are discussed using illustrative diagrams of their stacking windows. The use of anionic ITP-ESI-MS in negative-ion ESI mode is reported for the first time and its suitability for sensitive trace analysis is demonstrated. The presented ITP-ESI-MS application example comprises a free-acid ITP system formed of formic and propionic acids and direct injection analysis of ibuprofen and diclofenac in waters with quantitation limits of the order 10(-10) M.
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recent progress in analytical capillary Isotachophoresis
Electrophoresis, 2011Co-Authors: Zdena Mala, Petr GebauerAbstract:This paper brings a survey of papers on analytical capillary ITP published since 2012 until the first quarter of 2014. These papers are ranged according to their nature, the techniques used, and the instrumentation employed. The sequence of the related chapter titles is as follows: Theory and simulations, techniques and instrumentation, single-column and column-switching applications of ITP, ITP in microfluidic systems, on-line ITP-CZE and transient ITP (tITP) techniques and applications. The review shows the position of analytical capillary ITP among contemporary separation techniques and implies the potential future trends.
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recent progress in capillary Isotachophoresis
Electrophoresis, 2000Co-Authors: Petr Gebauer, Petr BočekAbstract:This article is a continuation of previous reviews and summarizes the progress of analytical capillary Isotachophoresis since 2000. Papers reviewed include methodological and instrumental aspects as well as analytical applications. Included are also papers using Isotachophoresis and/or isotachophoretic principles as part of multidimensional separation schemes.
Zdena Mala - One of the best experts on this subject based on the ideXlab platform.
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electrolyte system strategies for anionic Isotachophoresis with electrospray ionization mass spectrometric detection 2 Isotachophoresis in moving boundary systems
Electrophoresis, 2013Co-Authors: Petr Gebauer, Zdena Mala, Petr BočekAbstract:This contribution is the second part of the project on strategies used in the selection of electrolyte systems for anionic ITP with ESI-mass spectrometric detection. It presents ITP as a powerful tool for selective stacking of anionic analytes, performed in a nonconventional way in moving-boundary systems where two co-anions are present in both the leading and terminating zones. The theoretical background is given to substantiate the conditions for the existence and migration of ITP boundaries in moving-boundary systems and stacking of analytes at these boundaries. The practical aspects of the theory are shown in form of stacking-window diagrams that bring immediate information about which analytes are stacked in a given system. The presented theory and strategy are illustrated and verified on the example of analysis of a model mixture of salicylic acid, ibuprofen and diclofenac, and comparison of regular and free-acid ITP with moving-boundary ITP systems formed by formic and propionic acids and ammonium as counterion.
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electrolyte system strategies for anionic Isotachophoresis with electrospray ionization mass spectrometric detection 1 regular Isotachophoresis and free acid Isotachophoresis
Electrophoresis, 2013Co-Authors: Zdena Mala, Petr Gebauer, Petr BočekAbstract:The subject of this work is the definition of a simple model based on general ITP theory that allows describing and predicting the behavior of ITP systems compatible with ESI-MS detection. The model is exemplified by anionic ITP of weak acids that represent an interesting potential application field of ITP-ESI-MS. Suitable ESI-compatible electrolyte systems of very simple composition are proposed including a special free-acid ITP arrangement. The properties of these systems are discussed using illustrative diagrams of their stacking windows. The use of anionic ITP-ESI-MS in negative-ion ESI mode is reported for the first time and its suitability for sensitive trace analysis is demonstrated. The presented ITP-ESI-MS application example comprises a free-acid ITP system formed of formic and propionic acids and direct injection analysis of ibuprofen and diclofenac in waters with quantitation limits of the order 10(-10) M.
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recent progress in analytical capillary Isotachophoresis
Electrophoresis, 2011Co-Authors: Zdena Mala, Petr GebauerAbstract:This paper brings a survey of papers on analytical capillary ITP published since 2012 until the first quarter of 2014. These papers are ranged according to their nature, the techniques used, and the instrumentation employed. The sequence of the related chapter titles is as follows: Theory and simulations, techniques and instrumentation, single-column and column-switching applications of ITP, ITP in microfluidic systems, on-line ITP-CZE and transient ITP (tITP) techniques and applications. The review shows the position of analytical capillary ITP among contemporary separation techniques and implies the potential future trends.