BOOKS
Biosensors and Molten Salts Biosensors with Fiber Optics. Donald L. Wise and Lemuel B. Wingard, Jr., Eds. 416 pp. Humana Press, P.O. Box 2148, Clifton, NJ 07015. 1991. $80 Reviewed by Mark Arnold, Department of Chemistry, University of Iowa, Iowa City, IA 52242 This book is a compilation of 10 chapters written by experts in the field of fiber-optic chemical sensors. T h e e d i t o r s , D o n a l d Wise from Northeastern University and the late Lem Wingard from the University of Pittsburgh, have put these chapters t o g e t h e r in a logical format. Although there is a r a t h e r dramatic difference in the scope and tone of each chapter, this book offers something to novices and experienced researchers alike. For the novice, Chapters 1 and 2 present a ; rneral overview of the field. Cha). < is 3 - 8 discuss matters of importais e for biosensors based on fluorescence measurements through the evanescence field of a waveguide. Much of the material presented in this second group of chapters has not been published elsewhere Chapter 9 summarizes the developr ent of biosensors based on molecular luminescence. The final chapter p r e s e n t s new information on the in vivo performance of fiber-optic sensors for the blood gases. An introduction to biosensors is provided in Chapter 1 by Wingard and Ferrance (University of Pittsburgh School of Medicine). The term biosensor is defined, and the various types of biological components and transducers that can be used to build biosensors are presented. Finally, the analytical significance of biosensor technology is discussed in terms of potential applications. Chapter 2 is an outstanding review of the field of fiber-optic chemical sensors (FOCSs). Camara, Moreno, a n d Orellana (City U n i v e r s i t y of Madrid in Spain) discuss the relative
merits of fiber-optic devices and describe the classification schemes that can be used to categorize different types of FOCSs. The instrumental components required for this work are presented, along with different types of fiber-optic probe designs. Next, the major classes of FOCSs are described in considerable detail. This section, and indeed this entire chapter, is not restricted to biosensors, but to FOCSs of all types: those for pH, anions, cations, gases, biomolecules, and organic compounds. Last, an extensive list of reported FOCSs is provided. Overall, this chapter is succinctly written. The majority of this text centers around various chemical, physical, and instrumental aspects of evanescent wave biosensors (EWBs). This subject begins in Chapter 3 with a discussion by Haugland (Molecular Probes, Inc.) on the use of fluorescent dyes as labels. A general description of fluorescence is provided, with emp h a s i s on t h e i n s t r u m e n t a l a n d chemical properties required for detecting low fluorophore concentrations. The spectroscopic and physical p r o p e r t i e s of the most commonly used dyes are summarized. In addition, considerable attention is given to the conjugation c h e m i s t r y r e quired to attach these labels to biomolecules. This chapter ends with a discussion of recent attempts to develop the next generation of dyes for analytical applications. EWBs are discussed in more detail by Thompson and Ligler (Naval Research Laboratory) in Chapter 4. The optical properties of fiber optics are presented with a brief description of the evanescent field. Distal-tip and evanescent wave sensor designs are then compared in terms of component geometry and the function of the optical fiber. Key parameters for building an EWB are discussed, particularly the biological component, the fluorescence tag, and the methods used to synthesize protein-label conjugates and to immobilize biomolecules on the fiber surface. In addi-
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tion, several pages are devoted to an interesting discussion of ways to im prove the sensitivity of current EWB technology. Chapter 5, by Love and Button (Corning) and Slovacek (CibaCorning Diagnostics), provides a detailed theoretical description of fluorescence measurements through the evanescence field of an optical fiber. The mathematical functions that describe such measurements are derived from conventional ray theory. The resulting theory is analyzed to provide an indication of the analytical performance expected for EWBs and then experimentally evaluated by examining the sensitivity of evanescence wave measurements to various experimental parameters. Efforts by Bluestein, Craig, Slovacek, Stundtner, Urciuoli, Walczak, and Luderer (Ciba-Corning Diagnostics) to develop EWBs are summarized in Chapter 6. A general discuss i o n of b i o s e n s o r s b a s e d o n immunoglobulins, including a list of the requirements of the ideal immunosensor, is presented. This initial section is followed by a discussion of the basic concepts and relative merits of EWBs based on immunoglobulins. Details of the attempts by this research group to develop such a sensor for ferritin are presented. Critical issues include the basic design strategy, selection of optical fibers, antibody selection, and immobilization and antibody label conjugation reactions. The procedures used to measure and evaluate these sensors and the data processing scheme are likewise presented. Finally, sensor characteristics and response performance are evaluated. The optics and instrumentation required for EWB measurements are described by Lackie, Glass and Block (Ord, Inc.) in Chapter 7. The advantages of evanescence wave based fluorescence measurements with cylindrical waveguides (optical fibers), and the importance of the numerical aperture with respect to the intensity of the evanescence field and the
magnitude of t h e detected fluorescence signal, are discussed. Suitable optical arrangements are described, and the relative merits of various optical components are presented. The analytical performance of one such design is detailed. Finally, the concept of multiplex operation and the development of a prototype sensor for routine applications are presented. C h a p t e r 8, by Place (Dakopatts a/s), Sutherland (Abbott GmbH Dia g n o s t i c s ) , Riley ( U n i v e r s i t y of Utah), and Mangan (Commission of European Communities), pertains to the use of the evansecënce field associated with a continuous surface to investigate immunological reaction kinetics. This chapter starts with a review of antibodies as reagents and immunoassays. A detailed discussion of the kinetics of heterogeneous immunoassays serves as the basis for the authors' premise t h a t rate methods are preferred for real-time immunobiosensor measurements. Practical and theoretical considerations are presented in this rather thorough chapter. Finally, optical techniques designed to probe the solution interface of a continuous surface structure are discussed. The majority of this chapter is devoted to total internal reflection fluorescence, and surface plasma resonance techniques. Chapter 9, by Coulet and Blum (University of Lyon), deals with biosensors based on the detection of molecular luminescence. The variety of bioluminescence reactions available for biosensor development are described. A review is given for the immobilization methods, detection cell designs, and analytical performance for the firefly luciferase and bacterial bioluminescence reaction schemes. Hydrogen peroxide detection by various chemiluminescence reactions is also discussed. Finally, the concept of biosensors based on coupling these reactions with optical fibers is presented, and the response properties of such devices are summarized. Gottlieb (Random Technologies) and Divers and Hui (Puritan-Bennett Corp.), in the final chapter, discuss the development of fiber-optic sensors for blood gas measurements. This chapter has been included even though these sensors do not meet the definition of a biosensor proposed in the first chapter. Nevertheless, valuable information is shared; this chapter summarizes results from investigations designed to evaluate the in vivo performance of these sensors. Following a discussion of the clinical significance of blood gases, issues that are critical to in vivo sensing—
mainly biocompatibility and sterilization—are explored a n d various sensor design formats and response properties are presented. Three sections are devoted to oxygen, pH, and carbon dioxide sensors, with emphasis on the principle of operation and in vivo performance. Books such as this typically summarize and review published work. A unique aspect of this book is t h a t it presents a large volume of previously unpublished information; new information is provided in Chapters 4—7 and Chapter 10. For this reason, this book is highly recommended to those actively working in this field.
Molten Salt Techniques, Vol. 4. Robert J. Gale and David G. Lovering, E d s . 275 p p . P l e n u m P r e s s , 233 Spring St., New York, NY 10013. 1991. $75 Reviewed by Graham T. Cheek, Chemistry Department, U.S. Naval Academy, Annapolis, MD 21402 This volume continues the general emphasis of the series, concentrating on practical aspects of subjects of interest to molten salt practitioners. It also includes material from less familiar molten salt systems and techniques and provides experimental details as well as numerous references. Chapter 1 covers molten salt systems based on amides, concentrating on the physical and electrochemical properties of these interesting systems. Amide-based systems are not standard fare for most molten salt experimenters, and coverage of the techniques and applications provides a good introduction to their possible uses. Chapter 2 takes a somewhat different approach to molten salt technology; it presents methodology for evaluating physical properties of potentially useful molten salt components. A wide range of organic salts is studied by employing them as stat i o n a r y p h a s e s in g a s c h r o m a t o graphic columns and measuring retention times of various solutes on these phases. Practical information on column preparation and operation is provided in abundance, as are the appropriate equations for data treatment. The measurement of thermal properties of molten salts is important in many applications, and Chapters 3 and 5 provide excellent coverage of relevant experimental methods. Chapter 3 deals with the measure-
ment of t h e r m a l conductivity. The authors point out t h a t the high temperatures and electrical conductivity of most molten salts cause problems in the usual electrical methods of measurement; they present an optical method (laser flash technique) as a n effective m e a n s of overcoming these difficulties. Calorimetric methods for reactions carried out in molten salts are treated in Chapter 5. The presentation of high-temperature furnace design and sample handling is particularly thorough and gives a good overview of the types of reactions t h a t have been studied. The latter part of the chapter deals with nonreaction calorimetry (differential thermal analysis and differential scanning calorimetry) as applied to the study of phase transitions. Magnetic techniques (magnetic susceptibility, NMR, a n d electron spin resonance) are treated in Chapter 4, where coverage is intentionally restricted to high-temperature molten salt systems. Furnace designs are thoroughly covered, and probe systems compatible with the various techniques are presented in detail. Chapter 6 deals with high-pressure techniques and presents some interesting examples of substances t h a t become molten salts u n d e r highpressure conditions. The final chapter discusses molten salt battery systems and will perhaps be more familiar territory to molten salt workers t h a n are some of the other chapters. The L i - F e - S system is particularly well treated; great attention is given to pertinent phase diagrams, thermal behavior, and cell operating characteristics. Detailed descriptions of battery construction also are given. The technical level is appropriate for the intended readership, and the consistency in style is remarkably good considering the many international authors. The book has few, if any, typographical errors. The subject index is adequate, and most references are current (extending through 1989). By providing experimental details, this volume faithfully continues the tradition set by preceding volumes. Taken together with the companion volumes, it provides molten salt researchers with a very good treatment of modern techniques and is recommended for those working in the field in general. In addition, it provides an essential review of specific areas and includes practical details so that researchers can determine the feasibility of conducting proposed experiments in their own laboratories.
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