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Analytical and Bioanalytical Chemistry (v.366, #6-7)
Proteomics. Concepts and perspectives by R. Kellner (pp. 517-524).
Within the last five years the field of proteomics has changed the understanding of molecular biology. Proteins manifest physiological as well as pathophysiological processes in a cell or an organism, and proteomics describes the complete protein inventory in dependence on in vivo parameters. Disease mechanism or drug effects both affect a protein profile and, vice versa, characterising protein profiles reveals information for the understanding of disease and therapy. Analytical methods for proteomics are based on conventional tools for protein characterisation. The technical challenge is the complete coverage of physico-chemical properties for thousands of proteins. Nucleic acids display a relative chemical homogeneity and therefore genomics was considered more promising in the past than proteomics. Further improvements in proteomics technologies will likely change this course with proteomics complementing genomics as a tool to study life sciences.
Miniaturized total analysis systems for biological analysis by S. C. Jakeway; A. J. de Mello; E. L. Russell (pp. 525-539).
This review article discusses and documents the basic philosophies, concepts and current advances in the field of μ-TAS development, with special emphasis on applications in the arena of biosciences. After a brief overview of miniaturization theory and fabrication techniques, areas of microfluidic component development, detection protocols, biochemical assays, and integrated biological analyses are addressed.
Biosensors and biochips: advances in biological and medical diagnostics by T. Vo-Dinh; B. Cullum (pp. 540-551).
In the past two decades, the biological and medical fields have seen great advances in the development of biosensors and biochips capable of characterizing and quantifying biomolecules. This review is meant to provide an overview of the various types of biosensors and biochips that have been developed for biological and medical applications, along with significant advances over the last several years in these technologies. It also attempts to describe various classification schemes that can be used for categorizing the different biosensors and provide relevant examples of these classification schemes from recent literature.
Cell-based biosensors by C. Ziegler (pp. 552-559).
Different classes of cell-based biosensors are introduced. These include devices to measure cell-cell contact and set-ups to determine metabolic products. Main emphasis is put on sensors based on nerve-cell networks which are able to detect neuro-active compounds. The different experimental set-ups are explained and examples for typical applications are given. A main point concerns new achievements and prospects for future developments.
Electron-transfer mechanisms in amperometric biosensors by K. Habermüller; M. Mosbach; W. Schuhmann (pp. 560-568).
The function of amperometric biosensors is related to electron-transfer processes between the active site of an (immobilized) enzyme and an electrode surface which is poised to an appropriate working potential. Problems and specific features of architectures for amperometric biosensors using different electron-transfer pathways such as mediated electron transfer, electron-hopping in redox polymers, electron transfer using mediator-modified enzymes and carbon-paste electrodes, direct electron transfer by means of self-assembled monolayers or via conducting-polymer chains are discussed.
Nanoscale fluorescent sensors for intracellular analysis by J. Lu; Z. Rosenzweig (pp. 569-575).
There is a growing interest in the development of submicron optochemical sensing devices. Miniaturization of sensors to nano-dimensions decreases their typical response time down to the millisecond time scale. Their penetration volume is reduced to a few cubic micrometers and they exhibit a spatial resolution at the nanometer scale. In this review the fabrication of submicron optical fiber fluorescent sensors and particle-based fluorescent nanosensors is described. The functional characteristics of these exciting miniaturized fluorescent sensors and their applications for quantitative measurement of intracellular analytes are demonstrated.
Label-free detection of biomolecular interaction by optical sensors by H.-M. Haake; A. Schütz; G. Gauglitz (pp. 576-585).
Since the first label-free optical biosensor was commercialized in 1990 a rising number of publications have demonstrated the benefits of direct biomolecular interaction analysis (BIA) for biology and biochemistry. This article first gives an overview of the historical development of different transducer principles used for the detection of BIA. Subsequently, the four major parts of a biosensor system: transducer, sample handling, surface/¶immobilization chemistry and test formats/data evaluation will be discussed, with a main focus on the test formats and data evaluation. The intention of this review is to present an introduction to the field and to point out the difficulties most frequently encountered.
Amperometric biosensors based on electrosynthesised polymeric films by F. Palmisano; P. G. Zambonin; D. Centonze (pp. 586-601).
The most significant goals achieved in the course of the last decade in the design of amperometric biosensors based on redox enzymes entrapped in electrosynthesised polymeric films are reviewed. Particular emphasis is devoted to non-conducting polymers with built-in permselectivity that revealed very promising materials for designing fast-response and interference-free, H2O2 detecting, amperometric biosensors. The role of surface analytical techniques to provide structural information allowing a better understanding of polymers properties and their relationship with the ultimate performance of the final device is also outlined. The most relevant applications of amperometric biosensors based on electropolymerised films to real samples analysis are also reviewed and some possible future trends highlighted.
Thickness shear mode resonators (“mass-sensitive devices”) in bioanalysis by M. Kaspar; H. Stadler; T. Weiß; Ch. Ziegler (pp. 602-610).
A short overview of function and experimental set-ups of acoustic wave devices is given which, in contrast to other bioanalysis techniques, are based on a mechanical transduction mechanism. The most frequently used device is the thickness shear mode resonator (TSMR), which in the last few years was intensively employed in biosensor applications. TSMR biosensor studies in the field of nucleic acid interaction, adsorption of proteins to surfaces and immunosensing are reviewed. A main point concerns the interpretation of the sensor response not only in terms of mass loading, which underestimates the capabilities of these devices.
Characterization of implantable biosensor membrane biofouling by Natalie Wisniewski; F. Moussy; W. M. Reichert (pp. 611-621).
The material-tissue interaction that results from sensor implantation is one of the major obstacles in developing viable, long-term implantable biosensors. Strategies useful for the characterization and modification of sensor biocompatibility are widely scattered in the literature, and there are many peripheral studies from which useful information can be gleaned. The current paper reviews strategies suitable for addressing biofouling, one aspect of biosensor biocompatibility. Specifically, this paper addresses the effect of membrane biofouling on sensor sensitivity from the standpoint of glucose transport limitations. Part I discusses the in vivo and in vitro methods used to characterize biofouling and the effects of biofouling on sensor performance, while Part II presents techniques intended to improve biosensor biocompatibility.
Electrochemical immunoassays by A. Warsinke; A. Benkert; F. W. Scheller (pp. 622-634).
Immunoassays (IA) use the specific antigen antibody complexation for analytical purposes. Radioimmunoassays (RIA), fluorescence immunoassays (FIA) and enzyme immunoassays (EIA) are well established in clinical diagnostics. For the development of hand-held devices which can be used for point of care measurements, electrochemical immunoassays are promising alternatives to existing immunochemical tests. Moreover, for opaque or optically dense matrices electrochemical methods are superior. Potentiometric, capacitive and amperometric transducers have been applied for direct and indirect electrochemical immunoassays. However, due to their fast detection, broad linear range and low detection limit, amperometric transducers are preferred. Competitive and non-competitive amperometric immunoassays have been developed with redox compounds or enzymes as labels.This review will give an overview of the most frequently applied principles in electrochemical immunoassays. The potential of an indirect competitive amperometric immunoassay for the determination of creatinine within nanomolar range and the circumvention of the most serious problem in electrochemical immunoassays, namely regeneration, will be discussed.
Immunochromatographic techniques – a critical review by M. G. Weller (pp. 635-645).
Hyphenated techniques have become very popular during the last decade. Nevertheless, the use of biochemical methods, such as immunoassays, in conjunction with instrumental methods, such as chromatography, have not gained widespread acceptance. This review critically discusses many of the implemented and potential options for such coupled systems or components, which might be useful for such systems, including immunoaffinity extraction, immunoaffinity chromatography, immunochemical detectors, immunoblotting, receptor assays, enzyme inhibition assays, displacement assays, flow-injection immunoassays, miniaturized techniques and stationary phases such as restricted access materials or molecularly imprinted polymers. The performance of immunochromatographic systems is discussed regarding their ability to solve highly complex and demanding analytical problems.
Immunoanalytical techniques for pesticide monitoring based on fluorescence detection by U. Schobel; C. Barzen; G. Gauglitz (pp. 646-658).
In the field of environmental analysis there is still great potential for development and application of immunoanalytical techniques (IT). Heterogeneous and homogeneous immunoassays (IA), flow-injection immunoanalysis (FIIA) and immunosensors (IS) with different detection principles have been developed. In this review we focus on fluorescence methods for pesticide monitoring published since 1992. These techniques offer a high degree of selectivity and, in principle, sensitivity. Restrictions on the limits of detection (LOD) due to background signals are minimized by development of solid-phase separation systems, new fluorescent probes, and new instrumentation.
Immunosensors in clinical analysis by R. -I. Stefan; J. F. van Staden; H. Y. Aboul-Enein (pp. 659-668).
Clinical analysis requires methods of high reliability. The importance of immunosensors in clinical analysis is discussed. Due to the fact that the construction of immunosensors plays a very important role in their response characteristics, different types of immunosensor designs are highlighted. The performances of immunosensors are discussed taking into account the type of transducer utilized for construction.
Nano-electrospray ionization mass spectrometry: addressing analytical problems beyond routine by M. Karas; U. Bahr; T. Dülcks (pp. 669-676).
The advent of nano-electrospray ionization (nano-ESI) has considerably extended the usability of ESI in the analytical mass spectrometric laboratory. One of the remarkable features of nano-ESI is its extremely low sample consumption. Only a few microliters of analyte solution (10–5–10–8 M) are sufficient for molecular weight determination and structural investigations by MS/MS. But nano-ESI is more than just a minimized-flow ESI; the low solvent flow rate also affects the mechanism of ion formation. As a consequence, the area of ESI-MS applications is significantly enhanced. Oligosaccharides, glycosides as well as glycoproteins can be analyzed more easily than with normal ion spray. The same holds for the analysis of non-covalent complexes sprayed directly from aqueous solutions.
Mass spectrometric identification of proteins and characterization of their post-translational modifications in proteome analysis by M. R. Larsen; P. Roepstorff (pp. 677-690).
High-throughput DNA sequencing has resulted in increasing input in protein sequence databases. Today more than 20 genomes have been sequenced and many more will be completed in the near future, including the largest of them all, the human genome. Presently, sequence databases contain entries for more than 425.000 protein sequences. However, the cellular functions are determined by the set of proteins expressed in the cell – the proteome. Two-dimensional gel electrophoresis, mass spectrometry and bioinformatics have become important tools in correlating the proteome with the genome. The current dominant strategies for identification of proteins from gels based on peptide mass spectrometric fingerprinting and partial sequencing by mass spectrometry are described. After identification of the proteins the next challenge in proteome analysis is characterization of their post-translational modifications. The general problems associated with characterization of these directly from gel separated proteins are described and the current state of art for the determination of phosphorylation, glycosylation and proteolytic processing is illustrated.
Interfacing matrix-assisted laser desorption/ionization mass spectrometry with column and planar separations by A. I. Gusev (pp. 691-700).
This paper presents a critical review of off-line and on-line coupling of matrix-assisted laser desorption/ ionization (MALDI) mass spectrometry to liquid column separations (e.g. HPLC, GPC and CE) and planar separations (e.g. PAGE and TLC). Off-line MALDI analysis of fractions collected from HPLC, GPC and CE or spots scraped and extracted from TLC and PAGE has already become a routine practice for many laboratories. MALDI has also been used to obtain mass spectra directly from TLC plates and PAGE. The direct analysis methods range from dot-blotted samples to two-dimensional scanning of the entire gels/plates. Various combinations of on-line coupling of MALDI with column separations are also reviewed. The review discusses the strengths and limitations associated with different off-line and on-line coupling approaches.
Mass spectrometry for direct determination of proteins in cells: applications in biotechnology and microbiology by J. J. Dalluge (pp. 701-711).
A number of different procedures have been developed in recent years that utilize mass spectrometry for the direct determination of proteins in complex mixtures of biological origin. Specific examples of these include the use of matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) or directly combined liquid chromatography-electrospray ionization mass spectrometry (LC/ESI-MS) for rapid profiling of protein expression in bacterial and eucaryotic cells and cell-free extracts. Approaches to sample cleanup, contaminant removal, and initial separation of analytes on-line for the direct determination of proteins in cells using MALDI- and ESI-MS are discussed. Advantages of these techniques over traditional biochemical methods are highlighted, and a critical review of their utility and potential as standard tools in the biomolecular and microbiological research laboratory is presented.
Infrared and Raman imaging of biological and biomimetic samples by R. Salzer; G. Steiner; H. H. Mantsch; J. Mansfield; E. N. Lewis (pp. 712-726).
Established methods for imaging of biological or biomimetic samples, such as fluorescence and optical microscopy, magnetic resonance imaging (MRI), X-ray tomography or positron emission tomography (PET) are currently complemented by infrared (both near-IR and mid-IR) as well as Raman spectroscopic imaging, whether it be on a microscopic or macroscopic scale. These vibrational spectroscopic techniques provide a wealth of information without a priori knowledge of either the spectral data or the composition of the sample. Infrared radiation does not harm the organism, no electric potential needs to be applied, and the measurements are not influenced by electromagnetic fields. In addition, no extrinsic labeling or staining, which may perturb the system under investigation, has to be added. The immense volume of information contained in spectroscopic images requires multivariate analysis methodologies in order to effectively mine the chemical and spatial information contained within the data as well as to analyze a time-series of images in order to reveal the origin of a chemical or biochemical process. The promise and limitations of this new analytical tool are surveyed in this review.
Vibrational circular dichroism: a new spectroscopic tool for biomolecular structural determination by P. L. Polavarapu; Ch. Zhao (pp. 727-734).
Vibrational circular dichroism (VCD) in the past two decades has developed into a powerful new structural tool. A concise review of the applications of VCD to determine the structures of various biological molecules, namely peptides and proteins, nucleic acids and carbohydrates, is provided.
Scanning electrochemical microscopy: a new way of making electrochemical experiments by G. Nagy; L. Nagy (pp. 735-744).
A short review is given on scanning electrochemical microscopy (SECM). The historic background of the technique is briefly summarized and the basic principles outlined. The three different directions of its use: chemical microscopic imaging, the measuring of physicochemical constants and coefficients, and use as a micromachining tool are briefly discussed. The general built-up of the SECM apparatus is described. Preparation and use of several different measuring tips are introduced. A few examples are given of the application of SECM measurement in different studies.
Single-molecule detection in solution: a new tool for analytical chemistry by C. Zander (pp. 745-751).
Single-molecule detection (SMD) is becoming more and more popular in the scientific community and is on the threshold to become a technique for laboratory use. Therefore, conceivable applications as well as optimized conditions for SMD will be discussed. To point out the possibilities of SMD, the signal-to-background ratio and the detection efficiency, in combination with the probability of misclassification, will be contemplated.
Bio- and chemiluminescence in bioanalysis by A. Roda; P. Pasini; M. Guardigli; M. Baraldini; M. Musiani; M. Mirasoli (pp. 752-759).
Analytical chemiluminescence and bioluminescence represent a versatile, ultrasensitive tool with a wide range of applications in diverse fields such as biotechnology, pharmacology, molecular biology, clinical and environmental chemistry. Enzyme activities and enzyme substrates and inhibitors can be efficiently determined when directly involved in luminescent reactions, and also when they take part in a reaction suitable for coupling to a final light-emitting reaction. Chemiluminescence detection has been exploited in the fields of flow-injection analysis and column-liquid chromatographic and capillary-electrophoretic separative systems, due to its high sensitivity when compared with colorimetric detection. It has widely been used as an indicator of reactive oxygen species formation in cells and whole organs, thus allowing the study of a number of pathophysiological conditions related to oxidative stress. Chemiluminescence represents a sensitive and rapid alternative to radioactivity as a detection principle in immunoassays for the determination of a wide range of molecules (hormones, food additives, environmental pollutants) and in filter membrane biospecific reactions (Southern, Northern, Western, dot blot) for the determination of nucleic acids and proteins. Chemiluminescence has also been used for the sensitive and specific localization and quantitation of target analytes in tissue sections and single cells by immunohistochemistry and in situ hybridization techniques. A relatively recent application regards the use of luminescent reporter genes for the development of bioassays based on genetically engineered microorganisms or mammalian cells able to emit visible light in response to specific inorganic and organic compounds. Finally, the high detectability and rapidity of bio- and chemiluminescent detection make it suitable for the development of microarray-based high throughput screening assays, in which simultaneous, multianalyte detection is performed on multiple samples.
Photoproteins as luminescent labels in binding assays by J. C. Lewis; S. Daunert (pp. 760-768).
Certain marine organisms produce calcium-activated photoproteins that allow them to emit light for a variety of purposes, such as defense, feeding, breeding, etc. Even though there are many bioluminescent organisms in nature, only a few photoproteins have been isolated and characterized. The mechanism of emission of light in the blue region is the result of an internal chemical reaction. Because there is no need for excitation through external irradiation for the emission of bioluminescence, the signal produced has virtually no background. This allows for the detection of the proteins at extremely low levels, making these photoproteins attractive labels for analytical applications. In that regard, the use of certain photoproteins, namely, aequorin, obelin, and the green fluorescent protein as labels in the design and development of binding assays for biomolecules has been reviewed. In addition, a related fluorescent photoprotein, the green fluorescent protein (GFP), has been recently employed in bioanalysis. The use of GFP in binding assays is also discussed in this review.
Reporter gene bioassays in environmental analysis by S. Köhler; S. Belkin; R. D. Schmid (pp. 769-779).
In parallel to the continuous development of increasingly more sophisticated physical and chemical analytical technologies for the detection of environmental pollutants, there is a progressively more urgent need also for bioassays which report not only on the presence of a chemical but also on its bioavailability and its biological effects. As a partial fulfillment of that need, there has been a rapid development of biosensors based on genetically engineered bacteria. Such microorganisms typically combine a promoter-operator, which acts as the sensing element, with reporter gene(s) coding for easily detectable proteins. These sensors have the ability to detect global parameters such as stress conditions, toxicity or DNA-damaging agents as well as specific organic and inorganic compounds. The systems described in this review, designed to detect different groups of target chemicals, vary greatly in their detection limits, specificity, response times and more. These variations reflect on their potential applicability which, for most of the constructs described, is presently rather limited. Nevertheless, present trends promise that additional improvements will make microbial biosensors an important tool for future environmental analysis.