摘要:

Paul BohnPaul Bohnreceived his B.S. from Notre Dame in 1977 and the Ph.D. in Chemistry from Wisconsin-Madison in 1981. After a two-year stint at Bell Laboratories, he joined the faculty at the University of Illinois. In August 2006, he joined the faculty at the University of Notre Dame as the Arthur J. Schmitt Professor of Chemical and Biomolecular Engineering and Professor of Chemistry and Biochemistry. Professor Bohn's research interests include: molecular transport on the nanometer length scale, developing new optical spectroscopic measurement strategies for surface and interfacial structure–function studies, optoelectronic materials and devices and chemical sensors, and molecular approaches to nanotechnology.Steven A. SoperSteven A. Sopergraduated with a Ph.D. from the University of Kansas in 1989 and then served as a Post-doctoral Fellow at Los Alamos National Laboratory. He joined the faculty at Louisiana State University (LSU) in 1991 and was named the William L. & Patricia Senn Professor in 2002. He is also a Professor of Mechanical Engineering and an adjunct Professor of Biological Sciences. Prof. Soper's research focuses on BioMEMS/BioNEMS, single molecule detection, and new bioassay developments. He has received various awards, such as the R&D 100 Award (1993), the Charles E. Coates Award for Contributions to Chemical/Engineering Research in Louisiana (2001), the A.A. Benedetti-Pinchler Microchemical Award (2006) and an LSU Distinguished Research Award (2008). He has accumulated over 225 peer-reviewed research publications and has mentored 30 Ph.D. students.Xinrong ZhangXinrong Zhangwas born in Xian, China, received his Bachelor's and Master's degrees in Chemistry from Shaanxi Normal University, China, and his Ph.D degree in analytical chemistry from the University of Ghent, Belgium. He received a Professor position in the Department of Chemistry, Tsinghua University, China in June 1998. His current research interests are focused on developing optical and mass spectrometric techniques for biomedical and environmental analysis, including nanomaterial-based chemiluminescence sensor arrays, ICPMS-based immunoassays and ambient ion source for mass spectrometry. He has published over 150 papers in international journals and several book chapters on these topics. He chaired the 11th International Symposium on Luminescence Spectrometry and was a member of the Organizing Committee of BCEIA 2009.Boris MizaikoffBoris Mizaikoffreceived his Ph.D. in Analytical Chemistry at the Vienna University of Technology in 1996. Heading the Chemical Sensor Laboratory (CSL) he has been responsible for numerous research projects in the field of chemical IR sensors, including 4 multinational projects funded by the European Union. In 1997, he joined the University of Texas, Austin, USA as a post-doctoral fellow. In October 2000, he finalized his Habilitation at the Vienna University of Technology. In 2000, he became a faculty member at the Georgia Institute of Technology, School of Chemistry and Biochemistry, heading the Applied Sensors Laboratory (ASL). In 2004, he became the Director of the Focused Ion Beam Center (FIB2Center) at Georgia Tech, and has been a member of the Center for Cell and Molecular Signaling at Emory University, School of Physiology. In the autumn of 2007, he joined the faculty at the University of Ulm, Germany, as a Chaired Professor heading the Institute of Analytical and Bioanalytical Chemistry. His research interests focus on optical sensors, biosensors and biomimetic sensors operating in the mid-infrared spectral range, applications of novel IR light sources (e.g.quantum cascade lasers, system miniaturization and integration based on micro- and nano-fabrication, multifunctional scanning nanoprobes, scanning probe tip integrated nano(bio)sensors, focused ion beam (FIB) microscopy, development of chemical recognition interfaces for separation and sensing applications, chemometric data evaluation, advanced vibrational spectroscopic techniques, environmental analytical chemistry, process analytical chemistry and biomedical diagnostics. Dr Mizaikoff is an author/co-author of over 130 peer-reviewed publications, 14 patents and numerous invited contributions at scientific conferences.Duncan GrahamDuncan Grahamis Professor of Chemistry at the University of Strathclyde, Glasgow. He has a research group of around 30, and over 100 publications to date. He is also a co-founder of the Centre for Molecular Nanometrology and is a co-founder and director of D3 Technologies Ltd (www.d3technologies.co.uk).Graham CooksGraham Cookswas born in South Africa and received a Ph.D. at the University of Natal, Pietermaritzburg and also from Cambridge University, UK. He is a Distinguished Professor of Chemistry at Purdue University where he has spent the bulk of his career. His interests involve the construction of mass spectrometers as well as studies of their fundamentals and applications. Early in his career, he contributed to the concept and implementation of MS/MS as a method of mixture analysis and to desorption ionization, especially matrix-based SIMS methods. These interests led more recently to the construction of miniature ion trap mass spectrometers and their application to problems of trace chemical detection. His work on ionization methods has contributed to the ambient method of desorption electrospray ionization (DESI). Applications of this method in tissue monitoring, forensics and in pharmaceutical applications are a major current activity. He is also interested in molecular chirality (‘handedness’) and the possible role of the amino acid serine in the biochemical origins of life. Graham Cooks is a past President of the American Society for Mass Spectrometry. He has been honored by awards from the American Chemical Society and other organizations and his work is highly cited. He has trained 107 Ph.D. students in analytical chemistry.Justin GoodingJustin Goodingis the leader of the Biosensor and Biodevices Research Group at the University of New South Wales. He obtained a DPhil from Oxford University under the guidance of Prof. Richard Compton before becoming a post-doctoral research associate at the Institute of Biotechnology at Cambridge University. In 1997 he returned to his native Australia as a Vice-Chancellor Post-Doctoral Research Fellow at the University of New South Wales before taking up an academic position in 1998. He was promoted to full Professor in 2005. His research interests lie in biosensors, biointerfaces and surface chemistry.Pavel MatousekPavel Matousekobtained his M.Sc. and Ph.D. degrees in physics from the Czech Technical University, Prague, the Czech Republic, the latter in partnership with the Rutherford Appleton Laboratory, Oxfordshire, UK. Since 1991, he has worked at the Central Laser Facility, Rutherford Appleton Laboratory in the areas of time-resolved and steady-state Raman spectroscopy, non-linear optics and high-power lasers. He pioneered the Kerr gated method for the rejection of fluorescence from Raman spectra and the concept of Spatially Offset Raman Spectroscopy (SORS), developing it for a wide range of applications including the non-invasive probing of biological tissues, security screening and pharmaceutical quality control. He has published over 150 peer-reviewed articles and filed 10 patents. Pavel's honours include the 2009 Charles Mann Award for Applied Raman Spectroscopy from the Federation of Analytical Chemistry and Spectroscopy Societies (FACSS), shared 2002 and 2006 Meggers Awards from the Society for Applied Spectroscopy (SAS) and the 2008 Measurement in Action Award from the Institution of Engineering and Technology (IET). Recently, he acted as the Chair of the Meggers Award Selection Committee of the SAS, the International Delegate of the Governing Board of the SAS and will serve as the Program Chair of FACSS 2011 (Reno, NV). He is also a member of the Editorial Board ofApplied Spectroscopy. Pavel is presently a Fellow of the Science and Technology Facilities Council (STFC), a Visiting Professor of University College London and a director of Cobalt Light Systems Ltd, a spinout company commercialising SORS technology.

ISSN:0003-2654    

DOI:10.1039/b924763g

出版商:RSC    

年代:2009

数据来源: RSC

摘要:

IntroductionIn the past decade, there have been significant advances in the fabrication and utilization of microfabricated analytical devices and their integration into micro total analytical systems (µTAS).1Advances in the development of microfluidic chips have been driven by successes in the fabrication of structures in a variety of different substrates.2These chips have the advantages of portability due to miniaturization, reduced sample and reagent consumption, process automation and the accelerated speed of reactions and analysis for high-throughput processing.3Microfluidic systems have been proposed as a means to reduce time-consuming sample treatment and analysis steps to increase the throughput in proteomics.4,5Unfortunately, this has not yet been fully realized due to the lack of fully automated systems.Proteomics has become a main research topic in the areas of chemistry, biology, and even engineering since sequencing of the human genome was completed.6–9For example, cell functions can be elucidated at the molecular level by analyzing proteins with the help of a number of landmark developments in biological and computer sciences.10Most proteomic analyses rely on the combination of two-dimensional gel electrophoresis with mass spectrometry fingerprinting for the identification of complex protein mixtures.11An alternative, shotgun sequencing, uses multi-dimensional separation of proteolytic fragments generated from intact proteins followed by mass spectrometric peptide mapping and database searching.12Effective separation tools with efficient digestion protocols are required for both multi-dimensional and shotgun approaches to identify individual proteins.13Furthermore, the sample preparation steps such as digestion, separation, and cleanup can be time consuming and labor-intensive.14Maintaining high sensitivity and high protein sequence coverage with low sample consumption and high throughput are the analytical challenges for the development of a fully automated proteomic analysis system.15Efficient digestion of intact proteins is an indispensable component of systems for fast and accurate protein identification.16,17To achieve optimal peptide mass fingerprinting, the efficiency of digestion must be maximized. Three different approaches are used for proteolytic protein digestion: in-gel,18in-solution,19and solid-phase microreactor.20In-gel digestion is achieved by cutting out two-dimensional gel electrophoretic bands that contain the proteins of interest followed byin situdigestion.21The main drawback of this method is the limited accessibility to proteins inside the gel matrix, which results in a lower digestion efficiency.22Also, destaining procedures can cause poor digestion yields due to residual destaining solvents.23A second approach for digesting proteins is in-solution digestion, which is applied to protein mixtures directly suspended in a buffer. This approach requires long incubation times with relatively high digestion temperatures to achieve high efficiency at a reasonable reaction rate.24For example, a 6–24 h incubation time at 37–57 °C leads to by-products resulting from trypsin autolysis, non-specific cleavage, and deamidation.24–26The third digestion approach uses a microreactor with a proteolytic enzyme immobilized chemically or adsorbed physically onto a support.27,28This approach has many advantages in terms of fast response, low sample/reagent consumption, and high throughput.29Also, a solid-phase bioreactor minimizes sample loss during treatment and reduces autolysis products of trypsin due to the stability of the immobilized enzyme.30In addition, the high enzyme-to-substrate ratio afforded by solid-phase reactors gives a higher digestion efficiency compared to in-solution digestion.31The digestion efficiency of solid-phase microreactors depends on the geometry of the reactor, the digestion temperature, the compositions of digestion solvents, and the transport velocity of the target protein through the reactor.31–34Also, the digestion efficiency can be enhanced by physical means such as microwave energy35and an ultrasound-assisted method.36,37One of the limitations associated with solid-phase reactors for digestion is their poor kinetics due to the slow mass transport of proteins to the reactor surface.38In contrast to in-solution digestion, proteins in a solid-phase microreactor must diffuse to the immobilized enzyme to undergo digestion. Therefore, optimized support geometries for the microreactors are required to reduce mass transfer limitations.39–41The basic step that can be implemented toward increasing the efficiency of digestion by reducing the reaction rate is to move from a simple open-channel bioreactor to a three-dimensional (3D) format. This bioreactor type can improve the digestion efficiency due to the high surface area-to-volume ratio compared to an open channel resulting in reduced diffusion paths and an increase in the number of encounters between the substrate and immobilized enzyme.41,42Various bioreactor types have been developed to improve the digestion efficiency using 3D formats, for example, reactors packed with trypsin-loaded beads,43sol–gels,44and monolithic porous networks.45Fast and efficient digestion of proteins can be achieved with these 3D approaches due to their higher surface area-to-volume ratio proteolysis reactions, which take between 5 s and 1 h with these geometries. Even though monolithic bioreactors provide fast reaction kinetics, relatively long times are required for preparation due to the multiple steps required.44–47When monomers with different polarities are used for monolithic columns, the preparation of homogeneous supports is also hindered.48In a previous study, we developed a simple and fast digestion and deposition microfluidic device with an open-channel bioreactor that was operated by pressure-driven flow.49As indicated above, the limitation in this open-channel bioreactor format was the relatively long diffusion distances, which resulted in a diffusion-limited digestion rate due to the relatively small diffusion constants of proteins. A 3D structured bioreactor can be achieved by introducing microposts inside the open-channel bioreactor. A micropost-structured bioreactor can be manufactured in a simple fashion using micro-replication of a polymeric material from a mold master in a single step because it does not require bead packing or the formation of a polymer monolith within the channel. Also, inter-micropost distances are fixed, which provides reproducible devices because of the precise microfabrication processes.50,51Furthermore, the support structures are fixed in a desired location within the device and can provide unrestricted substrate access to the immobilized enzyme.Electrokinetically-driven flow inside a microchannel has many advantages over pressure-driven flow for bioreactor digestion. An electrokinetic flow eliminates the need for a mechanical pumping system, allows easy control of forward and reverse flow, and provides a flat flow profile in the microchannel.52In addition, the applied electric field can induce protein conformational changes, which can provide efficient enzymatic cleavage to aid in protein digestion.53In this study, we report on the fabrication, assembly, and testing of a novel trypsin immobilized poly(methyl methacrylate) (PMMA) microfluidic chip with micropost-structured channels. The microfluidic chip was fabricated using hot embossing and trypsin was covalently immobilized on the surface of the PMMA microposts using a UV-mediated surface modification protocol. This system employed an electric field to transport proteins through the bioreactor and move the peptides from the enzymatic reactor directly onto a MALDI target. The electrokinetically-driven flow was used to deposit the chip eluent on a MALDI target plate using a robotic fraction collector system. Cytochromecwas used as a model protein for optimizing the performance of the system and for evaluating digestion efficiency in terms of sequence coverage. The performance of this system using molecular standard proteins such as bovine serum albumin (BSA), phosphorylaseb, and β-casein was also demonstrated. Finally, intactEscherichia coli(E. coli) was used to demonstrate bacterial fingerprint analysis using this system.

ISSN:0003-2654    

DOI:10.1039/b916556h

出版商:RSC    

年代:2009

数据来源: RSC

摘要:

IntroductionWhile most high-throughput biosensors rely on optical methods such as fluorescence or surface-plasmon resonance to detect biological binding events,1–7there is great interest in biosensors that involve direct electrical signal transduction. The use of surfaces modified with specific biomolecules as the basis for biological sensing is particularly attractive because sensors of this type could be more easily integrated into very high-density arrays, interfaced to microprocessors, and directly linked to electrical signal-processing methods for detecting biological molecules in real-time.8–11Understanding the electrical response of surfaces with attached biomolecules is complicated because the overall electrical response contains contributions from the aqueous solutions, the biological layers, and the silicon or other materials that serves as a mechanical and electrical support.Previous studies of electrical detection of biomolecules have focused primarily on changes in DC conductivity that accompany biological binding processes, especially DNA hybridization. These studies have shown that the charge on the DNA molecule, for example, can inhibit diffusion of redox agents to the electrode surface, thereby modifying the resistance across the interface.10,12–16While DC measurements provide a measurement of overall conductivity, measurements of AC electrical properties can provide a wealth of information about biologically-modified interfaces because the physical and chemical structure at the interface are reflected in the amplitude and phase of the electric current. Perhaps most importantly, a great deal of insight into the mechanism of the analytical signal transduction can be obtained from measurements of electrical properties as a function of frequency. The frequency-dependent properties of surfaces modified with biological molecules can be characterized using techniques such as cyclic voltammetry and electrochemical impedance spectroscopy (EIS).17–20The previous studies have pointed out two important limitations to the present use of electrical detection for biological systems. First, most electrical detection systems have used redox agents to facilitate electron transfer and have used applied potentials of up to several volts in order force a net current through the biomolecules. However because potentials of even <0.5 V and currents of less than ∼100 µA cm−2are known to alter the hybridization of DNA21,22and are likely to modify protein binding, electrical measurements that involve net current flow may be unintentionally modifying the system they are intended to measure. Measurements of delicate biological systems benefit from measurements at lower potentials and low currents. Second, because biomolecules have many different sites that can interact with a surface, understanding the electrical response requires having well-defined, highly reproducible surface chemistry to achieve interfaces with known physical and chemical structure. Most previous EIS studies of biological binding have used multilayer films or other complex structures,17,23that have made it difficult to achieve a fundamental understanding of the electrical signal transduction process, particularly in the case of proteins.Here, we use the biotin–avidin system as a model to investigate the intrinsic electrochemical response induced by protein binding. By using very well-defined, covalent chemistry to link the biomolecules to the surfaces, we are able to prepare very reproducible, biotin-modified surfaces of gold, silicon, and glassy carbon. Impedance spectroscopy measurements show that the binding of avidin to a single monolayer of surface-tethered biotin molecules can easily be detected in the nanomolar concentration range even in the absence of any auxiliary redox agents, provided that the measurements are performed in specific frequency ranges. By characterizing the frequency response and how it changes in response to biotin–avidin binding and then coupling this with electrical circuit modeling, our results are able to provide important new insights into the mechanism of signal transduction and the physical factors that control the analytical sensitivity.

ISSN:0003-2654    

DOI:10.1039/b307591e

出版商:RSC    

年代:2003

数据来源: RSC

摘要:

IntroductionThe immunosensor based on surface plasmon resonance (SPR) has been receivingincreasing attention in recent years, due to its potential as a label-free,real time, rapid, high selectivity immunoassay technique.1,2However, its major disadvantage for bioanalytical applications is that itis difficult to use for detection of low concentration or low molecular massanalytes. The detection limit isca.1–10 nM for a 20-kDa moleculeand is even higher for smaller molecules.3Many researchers used commercial sensor chips with an extended coupling dextranmatrix to increase reasonably the surface loading of biomolecules, comparedto a monolayer of proteins immobilized directly on a gold surface.4,5However, despite the signal enhancement affordedby the dextran matrix, the sensitivity of SPR was still finite and low molecularmass analytes could not be detected even using this kind of sensor chips.Other strategies have been proposed to enhance the response signal by usinga latex particle,6colloidal Au7and liposome.8Here, we present a novel strategyfor improving the sensitivity of SPR immunosensing using a streptavidin–biotinylatedprotein complex.

ISSN:0003-2654    

出版商:RSC    

年代:2000

数据来源: RSC

摘要:

Aim of investigationBreath analysis has a significantly long history. An early authoritative discussion of the methodology of breath analysis and its possible value in clinical diagnosis and therapeutic monitoring was given 25 years ago by Manolis.1At that time the major diagnostic method was gas chromatography with mass spectrometry, GC/MS, by which several trace compounds were detected in the breath of healthy individuals and this remains an important analytical method in this research area.2,3In the interim there have been important developments in analytical methods that have increased the armoury available to the research scientists and clinicians. In particular, the development of proton transfer reaction mass spectrometry, PTR-MS,4and selected ion flow tube mass spectrometry, SIFT-MS,5,6have added a new dimension to breath research in that on-line, real time analyses of exhaled breath can now be carried out. The introduction of spectroscopic and electrochemical analytical techniques, best exemplified by their use in detecting and quantifying nitric oxide in exhaled breath,7,8are also being shown to be useful for the detection of small molecules. The more recent developments are reported in detail in a recent book on breath research.3Accurate analyses of several trace compounds (metabolites) can be obtained in single breath exhalations in real time using SIFT-MS.5This allows non-invasive, painless breath analysis that can be used by frail patients and even children, the results being immediately available to the health professional. This is a real step forward in the anticipated introduction of breath analysis into the clinical setting. Using SIFT-MS, several compounds have been accurately quantified in the exhaled breath of many healthy adult volunteers and concentration/population distributions have been constructed that provide the reference ranges for these compounds in the exhaled breath of healthy people.9,10These data provide the baseline levels for analogous studies of patients in diseased states and are an important step towards the “holy grail” of detecting minimal, (early stage) diseaseviabreath analysis.11Although progress in the recognition of new volatile biomarkers of disease and infection by breath analysis is slow, there have been some developments, notable examples being the GC/MS work by Phillipset al.in comparing the levels of branched chain hydrocarbons in the breath of cancer patients and healthy volunteers12and the detection ofPseudomonasinfection in the airways of patients with cystic fibrosis by the presence of enhanced levels of hydrogen cyanide in their exhaled breath.13For obvious reasons, there is a great desire to find biomarkers in breath for the presence of malignant tumours in the body. This might aid early detection, which is known to greatly improve the prognosis, especially so for lung cancer.14,15Current progress in the development of a diagnostic test for lung cancer through the analysis of breath volatiles, including acetaldehyde, has been recently reviewed by Mazzone.16,17In support of this, attention has been directed towards the study of the volatile compounds emitted by cancer cell linesin vitroin the hope that this would provide a focus for the breath analysis investigations. Several years ago, we used SIFT-MS to investigate the volatile compounds released by CALU-1 and SK-MES lung cancer cell lines cultured in complete media.18The notable result of this study was that acetaldehyde was generated by both cell lines in close proportion to the number of cells in the culture medium, which were typically (50–80) × 106, the generation rate of acetaldehyde molecules being about 106per cell per minute. Since that time this work has been taken up by others, notably by Amann and colleagues in Innsbruck, who have reported conflicting results.19A recent study in the United States20has reported that acetaldehyde is released by HL60 leukaemia cells at approximately the same rate as that seen for the CALU-1 and SK-MES cells in the SIFT-MS study. But a recent report, as yet unpublished, indicates that a smaller number (5 × 106) of SK-MES cells actually consume acetaldehyde when this is deliberately added to the support medium.21It is also seen that both acetaldehyde and ethanol are present in the headspace of the media used in the absence of the cells and so it has been suggested that the increase in acetaldehyde seen on introducing the cells is due to the partial conversion of the ethanol to acetaldehyde by the cells. This certainly needs to be investigated; it is commented on later in this paper.On this basis of the total evidence we decided to revisit this work first to more thoroughly investigate the source of ethanol and acetaldehyde emission from the medium used for these studies, then to check our earlier work on CALU-1 lung cancer cell lines and to extend this study by also investigating volatile emissions from two other cell lines, namely the normal lung epithelial cells NL20, and the non-malignant telomerase positive lung fibroblast cells 35FL121 Tel+ that can both be cultured to large numbers. We again focused on measurement of acetaldehyde, but by exploiting a very recent development of SIFT-MS22we are able to measure simultaneously the production of carbon dioxide by the cells, which turns out to be a very significant addition.

ISSN:0003-2654    

DOI:10.1039/b916158a

出版商:RSC    

年代:2009

数据来源: RSC

摘要:

For some time there has been increasing research interest in the pulmonary circulation of vessels in the animal fetus or neonatal state. In particular, extensive work has been performed with respect to the chemical factors (vasoactive agents) that are responsible for the constriction or dilatation of specific blood vessels. As a direct consequence of all this work, the conclusion has been reached that quantitative measurement of molecules such as NO, O2and CO inside small vessels, in a specific location of dimensions of the order of a micrometer, is highly desirable. Although recognised as extremely challenging in terms of acquisition, such data would prove to be invaluable in the conduction of medical research in physiology. An additional, but exciting problem, is whether it is feasible to mount such a putative detection system in tandem with a device that is capable of physical measurement such as that of vessel internal pressure (relevant to the resistance to blood flow). In order to provide a backcloth as to the precise nature of the analytical challenge, some research examples over recent years with respect to aspects of physiology are traced in the following brief remarks.In the middle 1990s an instrument was devised for the measurement of the isometric tension from isolated small arteries and veins obtained from the lungs of term fetal lambs.1The particular interest in studying these vessels, which have an internal diameter around 200 μm, was to examine the influence of known agents such as endothelin-I on the prostaglandin synthetic system, with respect to perinatal pulmonary hemodynamics. This agent had been thought to mediate a dilatation or constriction of vessels. In overall terms there was an interest as to the role played by oxygen tension and the molecule, indomethacin. In summary, among a number of observations, it was found that small arteries are endowed with a prostaglandin relaxing mechanism that becomes functional on raising the PO2from fetal to neonatal levels. In a further study, an investigation of the mechanism of hypoxic vasoconstriction (pulmonary vasculature constriction) in the same animal was performed.2At the time of this work there was debate as to whether the mechanism was connected to enhanced production of a constrictor or the reduced formation of a dilator in the vessel wall itself. In this connection it had previously been demonstrated that prostaglandin and NO-based relaxation processes are partially governed by oxygen tension. In summary, hypoxia contracted both vesselsin vitro, with the contraction being greater in arteries. From these results and a number of studies performed with various agents it was concluded that hypoxia tone could be ascribed primarily to the intramural production of endothelin-I.In contemporary times, questions have been posed regarding NO-activation.3To look at this issue further preterm lamb was studied. This was instigated by the idea that arteries operate both as an analytical sensor and effector when it comes to responses to oxygen tension. (This notion will be of considerable interest to the bioanalytical scientist). Experimentally, the role of inhibitors to NO synthesis and the effects of various agents, which influence pulmonary relaxation, were examined. The overall conclusion was reached that preterm pulmonary arteries possess viable effector mechanisms for contraction and relaxation, although the capability for these processes to be activated by PO2changes is much less than previously encountered.Very recently, attention has been switched to addressing pulmonary issues regarding mouse physiology, as a model for the human configuration. As an example, one of the interests with respect to human physiology is the structure, ductus arteriosus, which is a muscular shunt in the fetus, which connects the pulmonary artery with the aorta.4This allows blood to bypass the unexpanded lungs. At birth this structure closes as the infant begins normal lung function. The effectors, which cause the ductus to retain patency and closure, are the subjects of some debate. Again, as for the cases described above the mechanisms are thought to involve prostaglandins and NO. Using mice strains with targeted deletion of genes allows the study of particular aspects of physiology, in this case the system for ductus closure.In vitroandin vivomethods for the investigation of genetically modified mice were employed with respect to the activity of the entity (receptor) responsible for the closure of the ductus. It was concluded that the receptor involved does mediate the response to oxygen, but that the ductus still closes postnatally, likely a process connected the withdrawal of relaxing influences. There is a view that this type of research is highly relevant with respect to the medical welfare of infants.Turning to the nature of the problem to be posed to the analytical scientist, it is manifestly obvious that a comprehensive understanding of the interaction of complex biological systems with active molecules such as NO, and much more recently CO, in blood requires not only quantification of levels of these species in the structure but also measurement of concentration withtimein aspecific location. Historically, a wide variety of methods for the detection of NO, in particular, have appeared in the literature. These include intermittent and continuous measurement based on chemiluminescence, electron spin resonance, spectrophotometry, chromatography, electrochemical, optrode and semiconductor technologies. With regard to the requirement for continuous detection in biological applications, Kikuchiet al.5used a fiber-optic configuration for the chemiluminescence measurement of NO release from a kidney on-line. An electrochemical method composed of a selective Nafion membrane (Ni-porphyrin complex) and differential pulse voltammetry was used to examine NO in blood and plasma.6However, realisticin vivomeasurements have not figured prominently in the literature. In 1996, Tschudiet al.7used a bundle of carbon fibers for the detection of NO in aorta and mesenteric arteries of rats. With regard to measurement in humans an amperometric sensor was used to measure NO concentration in a vein in the hand.8Very recently the Schuhmann group has been employing porphyrin-based electrochemical devices to monitor NO from biological samples such as the retina of rats.9Clearly, in order to progress to the measurement of NO (and CO) in resistance vessels of genetically-modified mice, quantum advances with respect to detection strategy are needed. This application requires quantification of active molecules present in the fluid cross-section-wise across the vessel. The arteries and veins of mice have very small internal diameters and, accordingly, to generate site-specific chemical information the detecting device must be of a true ‘nanotechnology’ dimension. As indicated above, it is recognised that the analytical literature contains possible ingredients for such a sensor. However, the fabrication of a sensor capable of assisting the physiologist here must measure concentration faithfully even in the face of likely protein surface adsorption. Furthermore, there is also the daunting task of including a system that can be interrogated so that chemical data can be collected for future evaluation. Finally, it is worth noting that there is interest in the process of performing research on ultra small devices fabricated for the purpose of the measurement of physical parameters such as pressure. It would be highly desirable to generate detectors that operate in a tandem fashion, that is, combine physical and chemical measurement (for both NO and CO) in the same structure. There is clearly a dearth of such structures in the microelectronic fabrication literature.

ISSN:0003-2654    

DOI:10.1039/b211414n

出版商:RSC    

年代:2002

数据来源: RSC

摘要:

1. IntroductionThe presence of trace quantities of water within oil can present a significant corrosion hazard and is of particular concern in the chemical and petroleum industries where the elevated temperatures encountered during the processing of non-aqueous feedstocks can substantially exacerbate the process. A bewildering number of strategies have been developed to minimise the degradation that can occur as a result of external environmental factors but moisture contamination within the internal surfaces of pipework, reactor bodies or metallic storage vessels can be a particularly pernicious problem.1Dissolved iron resulting from the corrosion of steel casings could potentially be used as a versatile indicator of material fatigue and through being able to monitor changes in the concentration of the metal ion, structural failure of the various containment systems could be predicted. The aim of the present Communication has been to develop a procedurally simple protocolthat can enable the detection of labile iron within oil products whilst meeting the detection demands levied by the selective quantification of the ion at the trace level.The direct determination of iron within oil samples tends to be hampered by the low concentration of the target and the difficulties encountered in handling the non-aqueous fluid.2Extraction of the iron into an aqueous layer is undoubtedly the preferred route though achieving this is a non-trivial task that often requires recourse to elaborate separation and sample digestion procedures. The methodology proposed herein relies upon the ultrasonically induced emulsification of the oil with a small quantity of aqueous acid.3The latter serves to collect and effectively pre-concentrate the target iron. It was envisaged that the removal of the ultrasound field would result in the separation of the respective layers and thus present a facile method through which the iron could be rendered accessible to analysis.Through extracting the iron into the aqueous phase it should be possible to utilise simple colorimetric techniques to provide a semi quantitative on-site or field assessment of the iron content. Transferability of the approach would clearly be dependent upon the acquisition of selectivity and to this end we have sought to investigate the applicability of one such protocol. Our approach seeks to exploit the highly specific colorimetric response that can arise through the complexation of iron(iii) with aminothiol ligands such as cysteine. It must be acknowledged that the coordination of iron with such ligand systems can be somewhat complicated and involve a number of competing reactions,4,5as indicated byScheme 1. Adaptation of the system for analytical purposes however may be relatively straightforward and holds considerable merit given the selectivity of the response (particularly when compared with otherligand systems such as bipyridyl6–8or phenanthroline.9,10Reaction pathway and analytical signalThe analytical characteristics of the assay procedure and the efficacy of coupling it to the ultrasonic extraction protocol have been assessed. The applicability of the technique was evaluated through examining the recovery of iron within a commercial kerosene sample.

ISSN:0003-2654    

DOI:10.1039/b109852g

出版商:RSC    

年代:2001

数据来源: RSC

摘要:

IntroductionThe detection of different forms of arsenic in industrial, biological and environmental samples has been the target of increasing attention in recent years. Many arsenic compounds are known to be toxic and the exposure of humans and animals especially, and ecosystems in general, to arsenic remain of international concern. The toxicity of arsenic depends strongly on its chemical form. The inorganic compounds are far more toxic than their organic metabolites. Four of the more toxic arsenic compounds are dimethylarsinate (DMA), arsenate (As(v)), monomethylarsonate (MMA)) and arsenite (As(iii)) of which the later is most toxic.1It is important to monitor even low concentrations of arsenite in aquatic systems.2On sabbatical leave from: Department of Chemistry, Kurdistan University, P.O. Box, 416, Sanandaj, Iran.For the determination of arsenic species in aquatic samples where the concentration of arsenic are usually below 1 µM L−1, highly sensitive techniques are required owing to the low concentration of the species. When the analytical techniques employed do not offer sufficient detection capability for such determination, preconcentration and separation steps are always necessary.There are several options available to the analytical community for the detection of arsenic compounds including hydride generation atomic fluorescence spectrometry2–4and inductively coupled plasma mass spectrometry.5,6Unfortunately these embrace the most expensive instrumental methodologies. Recently electrochemical methods especially stripping voltammetry have been used for the detection of arsenic.7–11Mercury electrodes have been used for these stripping methods but usually another metal such as copper is required to form an intermetallic compound with arsenic at the mercury electrode surface.9Gold electrodes and also glassy carbon or pyrolytic graphite electrodes modified with gold films have been used successfully for the detection of arsenic with anodic stripping potentiometry and anodic stripping voltammetry.12–14However, there are often problems associated with arsenic voltammetry at solid electrodes such as limited sensitivity, poor precision, low electron transfer reaction, high overvoltages at which the electron transfer process occurs, low stability over a wide range of solution composition and for optimum reproducibility the electrode surfaces were re-plated between each measurements, which makes this approach inconvenient for routine analysis. A rather disappointingly low sensitive method for the titration of As(iii) with electrogenerated iodine in microelectrode arrays has been reported.15The chemical modification of inert substrate electrodes with redox active thin films offers significant advantages in the design and development of electrochemical sensors. In operation, the redox active sites shuttle electrons between the substrate electrode and analytes with a significant reduction in activation overpotential and ideally, less surface fouling and oxide formation compared to inert substrate electrodes. A wide variety of compounds have been used as electron transfer mediatorviamodification of different electrode surfaces.The use of boron doped diamond as a robust electrode substrate is well established due to its wide potential window in aqueous solutions,16low background currents,17,18long term stability19and low sensitivity to dissolved oxygen.20BDD has recently been utilized electroanalytically as a suitable electrode substrate for determination of several metals such as Ag,21Pb,22Cu23and Mn.24However As(iii) is not oxidized inside the potential window of aqueous solutions at the surface of BDD electrodes. Accordingly for the detection of arsenic at the surface of BDD the surface should be modified with a thin film of electron transfer mediator. BDD25and GC26electrodes modified with iridium oxide have been used for the electrocatalytic oxidation of hydrogen peroxide and insulin. Also electrodeposited iridium oxides have been used as pH electrodes.27,28Recently we reported the application of BDD electrodes modified with oxide layers of metals such as Ag,29,30Sn31and Pb.32In the present study the BDD electrodes modified with electrodeposited iridium oxide are investigated by voltammetry and atomic force microscopy (AFM). The modified electrodes are used for the electrocatalytic oxidation of As(iii), and finally the analytical performance of an iridium oxide modified BDD is described as an amperometric sensor for arsenic determination.

ISSN:0003-2654    

DOI:10.1039/b312285a

出版商:RSC    

年代:2003

数据来源: RSC

摘要:

Welcome to issue 1 ofThe Analyst, 2007. We take this opportunity to highlight the latest developments in both the journal and RSC Publishing.

ISSN:0003-2654    

DOI:10.1039/b616853c

出版商:RSC    

年代:2006

数据来源: RSC

摘要:

Ana Maria Oliveira Brett obtained her BSc degree in Chemistry from the University of Coimbra (Portugal) in 1973 and her PhD with John Albery in Electrochemistry from Imperial College of Science and Technology, London University, UK, in 1980. She continued as a NRDC Postdoctoral Fellow for a year working on aspects of photoelectrochemistry. In 1981 she was appointed to a Lectureship in Chemistry at Coimbra University. She was awarded the DSc degree from the University of Coimbra in 2002. Ana Maria’s research is centered on fundamental aspects in the areas of bioelectrochemistry, the study of electron transfer reactions of compounds of biological interest, and bioelectroanalysis, the development of enzymes and DNA biosensors. Current efforts include studies of the morphology of DNA adsorbed at solid charged interfaces, electrochemical detection of the mechanisms of DNA–drug interactions and evaluation of oxidative damage caused to DNA by health hazardous compounds. Related research is concerned with the study of electron transfer reactions of antioxidants and understanding the free-radical-induced damaging aspects of the chemistry of disease processes. She is a member of several Scientific Societies and has been an active member collaborating during different periods as Division Officer of Analytical Electrochemistry and Bioelectrochemistry, for the International Society of Electrochemistry (ISE), and since 1994 is a Member of the Council of the International Bioelectrochemical Society (BES). Research activity is documented by more than 90 papers published, co-author of 2 undergraduate/graduate textbooksElectrochemistry. Principles, Methods and Applications, 1993 andElectroanalysis, 1998, both Oxford University Press, 6 chapters in multi-author books, attending and presenting research work at research conferences, and has been invited to present more than 40 lectures since the 1980s. She has served on the Editorial Advisory Board ofBioelectrochemistry and Bioenergetics, and is presently one of the Associate Editors ofBioelectrochemistry.

ISSN:0003-2654    

DOI:10.1039/b211390m

出版商:RSC    

年代:2002

数据来源: RSC