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Biosensors: Theory and applications
mathematical equations, the explanation of their relevance and use, together with reference to other texts providing in-depth discussions of the theoretical background, is meticulous. Indeed, there is a scrupulous approach throughout the book to refer the reader to complementary texts. In general, the text is informative and readable, and understanding is enhanced by the use of tables, figures, photographs and appendices to provide extensive summaries of relevant data, definitions, mathematical formulae and suitable applications of technologies. All this is supported by an extensive index and dictionary of abbreviations. The editorial po!icy of the book is clear; the definition of instruments and sensor technolo~,ies includes those strictly based on the principles of physics and chemistry. Techniques arising out of other fields such as biochemistry and microbiology have been excluded; for example, DNA
Biosensors is a challen:ging subject to consider because of the complexity of the science and the large aud'bonce with disparate interests: students, mgineers, clinical surgeons, food scienfists, amongst others, in addition to expert instrument fabricators. This book tackles the subject in ten chapters, covering the principles of electrocbemistry, electrochemical transducers, enzyme-based electrochemical biosensors, fabrication and miniaturization techniques, optical technology, miscellaneous transducers, immunosensors, 'living' biosensors and future directions in sensor development. The introduction (Chapter I) summarizes definitions, outlines objectives, reviews the historical background and discusses the ideal characteristics of a sensor. The author proposes a broad definition of a biosensor: a measuring device that contains a biological element. In my opinion this is too broad; a carefully focussed definition is more useful. The author's objective is to review the theoretical basis for specific types of biosensor, particularly those based on electrochemical transducers. The historical background, albeit brief, is interesting, concise and well supported with references. Biosensor characteristics are clearly summarized with pithy, relevant text to provide helpful guidelines for validating sen-
and ATP-based methods of microbial detection, immunoassays, dipsticks, enzyme kits and flow cytometry. The text is largely descriptive with limited evaluation of the relevant merits of the different technologies for different food analytical requirements to guide the reader, As with all multi-author texts the quality of approach varies throughout; some authors treat the subject rigorously, particularly KressRogers, while others have a more casual approach. Disappointments include the chapter on NIRS, which only considers instruments produced by Infrared Engineerieg Ltd (Malden, UK) without mention of those from competitor companies, such as Perstorp Analytical (Maidenhead, UK). Also, the chapter on instrumental methods in the chemical quality control laboratory is only a cursory review. Highlights of the book for me include the discussion of impedance techniques for microbial assay - D.M. Gibson's voice and expertise jump
out of his text; and the chapter on water activity measurement, clearly a succinct transcription of expertise W. ROdel is to be congratulated. I hope that companion texts will soon be provided: a rigorous description of the theory and applications of instruments and methods arising from other fields such as biochemistry and microbiology; a rigorous scientific evaluation of the relative merits of different technologies and methods of food analysis; an informative unbiased synthesis of analytical need with the strengths of different sensor technologies. Kress-Rogers embarked on an ambitious task and has succeeded in providing the food industry and students with a useful textbook, and there is no doubt it will be kept close at hand for frequent reference.
Andrew 0 . Scott L~'ons Tetle~, Ltd, 325-347 Oldfield Lane North. C:.,eentbrd,UK U86 O,4Z.
Biosensors." Theory and Applications by DonaldG. Buerk,Techn0mic, 1993.5w. Fr. 187.00(x + 221 pages)ISBN0 87762 975 7
sor performance; the check list includes: sensitivity, calibration, linearity, detection limit, hysteresis, drift, response, membranes, signal/ noise ratio and measuring systems. A description of electrochemistry (Chapter 2) provides the theoretical basis and mathematical models to explain how biological reactions detecting analyles are translated by a transducer into an electronic signal that can be manipulated by modern microprocessors into understandable concentrations read by the user. The reasons for the use of measuring electrodes and reference electrodes, electrochemical transducers (potentiometric, amperometrlc, coulombic), different types of signals (e.g. normal pulse, cyclic, square wave, voltammerry) and the relationship between oxidation-,'eduction reactions and electrode response are discussed at length. Chapter 3 surveys electrochemical transducers, such as pH, metal oxide, oxygen, carbon dioxide, hydrogen peroxide, carbon surface and ionsensitive electrodes, and describes suitable applications. The explanation
Trendsin FoodScience& TechnologyJune1994 [Vol. 5]
of the performance of different electrodes is very useful for the nonspecialist because it reviews issues that are generally assumed as understood in other texts on biosensors. The discussion on the Clark electrode, extensively used for biosensors, and the carbon electrode is of particular interest. An account of enzyme and electrode electrochemical theory (Chapter 4), immobilization techniques and their limitations in sensor applications explains how biosensors work. Many of the issues of concern relating to the use of biosensors and typical applications are described in detail; applications considered include: glucose measurements for diabetics, urea for renal patients, alcohol, lactate blood levels for heart disease patients, ATP breakdown for fish freshness and cholesterol (organic phase enzyme biosensor). A standard descriptive format is used: the theory of sensor perfr,rmance, description of the application and a discussion of the issues A significant omission in this chapter is a reference to the 'ExactecT~t' blood glucose meter (Medisense, UK); 207
Book Reviews this was thought 1o be a major commercial break-through in the mid 198Os.
Chapter 5 provides a detailed explanation of the construction of miniature electrodes with a brief description of the field-effect transistor. Chapter 6, 'Optical technology', provides a relevant review of absorption and reflectance spectroscopy, chemi. luminescence, fluorescence, phosphorescence, haemoglobin and oximetry, optodes, optical waveguides and optical potentiometry. The final chapters summarize the mechanism of calorimetric, piezoelectric and surface acoustic wave devices (Chapter 7); antibody-based devices (Chapter 8); microbial and tissue-based devices (Chapter 9); and finally the future directions for biosensor development (Chapter t 0). The author sets a broad scope for the book but devotes much of the text to the theoretical considerations of different types of biosensor. This may be welcomed by the nonspecialist who needs to gain an introductory overview of the subject. The style is readable and easy to follow, a refreshing approach. The author's expertise in the electrochemistry of enzymes, electrodes and electrode miniaturization shines through lucid text. Moreover, the mathematical explanation of sensor performance
and the relationship between theory and practice is presented succinctly, giving a good summary of the considerations used in the science of biosensors. Overall, I would have preferred a more rigorous approach to the subject. The explanations of equations are clear and introduced in a relevant manner, but occasionally the text sadly lapses into jargon. Answers to the following questions would have been helpful: What does the equation describe? What are the basic assumplions? What are their limitations? What practical tips for usage overcome obvious difficulties? In addition, texts are cited without summarizing the relevant information; for example, 30 anions and cations detected by ion-selective electrodes were referred to without tabulating the important ions (Chapter 3). Limits of detection are stated without a relevant context; for example, the glucose detection limit is 25 nM (Chapter 3) what is the significance of this level? There is a lack of discussion concerning the relative rnerits of alternative electrodes for important applications; for example, is the xanthine oxidase electrode, the example cited, the most important application of the carbon electrode? Finally, the emphasis on theory rather than applications lessens the useiulness ,)f this book.
Designer Oil Crops: Breeding, Processing and Biotechnology editedby DenisI. Murphy,VCH, 1994. £75.00 (xvi + 317 pages)ISBN 3 527 30040 6
This is an extremely thorough vol- crops, current breeding procedures ume. It gives a fascinating panorama and developments in selection or of the state of current knowledge and biotechnology. Chapter 2 describes in exciting developments in an area of more detail the oils, fatty acids and plant selection and biotechnology derivatives clearly and concisely. that will have a major impact on food The bulk of vegetable oil produced is processing in the future. With the used in the food industry, predomiproducts of transgenic soybean, maize, nantly as margarine, frying oil, salad oils cotton and oilseed rape (canola) and texturizersof processedfoods. There likely to reach the market from 1995 is therefore great interest in whether onwards, it is very timely. easily grown oilseedscan be selectedor The editorial approach and layout genetically engineered to contain higher of the volume are good. An intro- amounts of oils or more-desirable oils. duction sets the scene and moves Another possibility is the industrial through a consideralion of the econ- use of oils from conventional oilseed omic context of oilseed production crops, including the manipulation of and oil usage to an extensive first their oil quality, c,.mtent and nature to chapter characterizing the major satisfy the needs o( these sectors. 208
In summary, the book provides an excellent discussion of the theoretical aspects of electrochemically based biosensors with little insight into the applications, especially for those interested in food analysis. In addition, reference to publications by key workers in the field of biosensors for food analysis are omitted; for example, A.P.F. Turner t (Cranfield Institute of Technology, UK); I. Karube-' (ResearchCenter for Advanced Science and Technology, Japan); and R.D. Schmid ~ (until recently Gesellschaft for Biotechnoligische Forschung mbH, Germany). In the author's terms I think one could argue the subject is addressed satisfactorily; however, I expected a more rigorous approach. I suggest food scientists who are looking for some accessible background reading on biosensors would find this a useful text.
Andrew O. Scott Lyons TetleyLid, 325-347 Oldfield LaneNorth, Greenford, UK UB6 0AZ.
References 1 Turner,A.P.F.,Karube,I. andWilson,G.S. (1987) Biosensors:Fundamentalsand Applications, OxfordUniversityPress 2 Karube,I., Sode,K.andTamiya,E.119901 I. Biotechnol. I S,267-282 3 Schmid,R.D.andWagner,G. (1990)Food Biotechnol. 411), 215-240
'Alternative' oil crops are also of great interest, for several reasons. They contain novel fatty acids, such as petroselinic acid from coriander, high-concentration lauric acids from Cuphea species and high-oleic acids from Euphorbia spp. These crops are unimproved (i.e. undomesticated) and, if characteristics such as pod shatter can be overcome, may provide high-value low-input alternatives to oilseed rape, sunflower and soybean. On the other hand, if the genes encoding the unusual oils can be isolated and transferred to conventional oilseed crops, very much higher yields might be obtained. Particularly important industrial uses of existing and novel oils, which may have some impact in the food industry, include lubricants, antifoaming agents, printing inks, plasticizers and glycerol derivatives. These are mentioned in Chapter 3 and covered in more detail in Chapter 7. The breeding of oil crops, including
Trendsin FoodScience& TechnologyJune1994 IVol. Sl
Biosensors is a challen:ging subject to consider because of the complexity of the science and the large aud'bonce with disparate interests: students, mgineers, clinical surgeons, food scienfists, amongst others, in addition to expert instrument fabricators. This book tackles the subject in ten chapters, covering the principles of electrocbemistry, electrochemical transducers, enzyme-based electrochemical biosensors, fabrication and miniaturization techniques, optical technology, miscellaneous transducers, immunosensors, 'living' biosensors and future directions in sensor development. The introduction (Chapter I) summarizes definitions, outlines objectives, reviews the historical background and discusses the ideal characteristics of a sensor. The author proposes a broad definition of a biosensor: a measuring device that contains a biological element. In my opinion this is too broad; a carefully focussed definition is more useful. The author's objective is to review the theoretical basis for specific types of biosensor, particularly those based on electrochemical transducers. The historical background, albeit brief, is interesting, concise and well supported with references. Biosensor characteristics are clearly summarized with pithy, relevant text to provide helpful guidelines for validating sen-
and ATP-based methods of microbial detection, immunoassays, dipsticks, enzyme kits and flow cytometry. The text is largely descriptive with limited evaluation of the relevant merits of the different technologies for different food analytical requirements to guide the reader, As with all multi-author texts the quality of approach varies throughout; some authors treat the subject rigorously, particularly KressRogers, while others have a more casual approach. Disappointments include the chapter on NIRS, which only considers instruments produced by Infrared Engineerieg Ltd (Malden, UK) without mention of those from competitor companies, such as Perstorp Analytical (Maidenhead, UK). Also, the chapter on instrumental methods in the chemical quality control laboratory is only a cursory review. Highlights of the book for me include the discussion of impedance techniques for microbial assay - D.M. Gibson's voice and expertise jump
out of his text; and the chapter on water activity measurement, clearly a succinct transcription of expertise W. ROdel is to be congratulated. I hope that companion texts will soon be provided: a rigorous description of the theory and applications of instruments and methods arising from other fields such as biochemistry and microbiology; a rigorous scientific evaluation of the relative merits of different technologies and methods of food analysis; an informative unbiased synthesis of analytical need with the strengths of different sensor technologies. Kress-Rogers embarked on an ambitious task and has succeeded in providing the food industry and students with a useful textbook, and there is no doubt it will be kept close at hand for frequent reference.
Andrew 0 . Scott L~'ons Tetle~, Ltd, 325-347 Oldfield Lane North. C:.,eentbrd,UK U86 O,4Z.
Biosensors." Theory and Applications by DonaldG. Buerk,Techn0mic, 1993.5w. Fr. 187.00(x + 221 pages)ISBN0 87762 975 7
sor performance; the check list includes: sensitivity, calibration, linearity, detection limit, hysteresis, drift, response, membranes, signal/ noise ratio and measuring systems. A description of electrochemistry (Chapter 2) provides the theoretical basis and mathematical models to explain how biological reactions detecting analyles are translated by a transducer into an electronic signal that can be manipulated by modern microprocessors into understandable concentrations read by the user. The reasons for the use of measuring electrodes and reference electrodes, electrochemical transducers (potentiometric, amperometrlc, coulombic), different types of signals (e.g. normal pulse, cyclic, square wave, voltammerry) and the relationship between oxidation-,'eduction reactions and electrode response are discussed at length. Chapter 3 surveys electrochemical transducers, such as pH, metal oxide, oxygen, carbon dioxide, hydrogen peroxide, carbon surface and ionsensitive electrodes, and describes suitable applications. The explanation
Trendsin FoodScience& TechnologyJune1994 [Vol. 5]
of the performance of different electrodes is very useful for the nonspecialist because it reviews issues that are generally assumed as understood in other texts on biosensors. The discussion on the Clark electrode, extensively used for biosensors, and the carbon electrode is of particular interest. An account of enzyme and electrode electrochemical theory (Chapter 4), immobilization techniques and their limitations in sensor applications explains how biosensors work. Many of the issues of concern relating to the use of biosensors and typical applications are described in detail; applications considered include: glucose measurements for diabetics, urea for renal patients, alcohol, lactate blood levels for heart disease patients, ATP breakdown for fish freshness and cholesterol (organic phase enzyme biosensor). A standard descriptive format is used: the theory of sensor perfr,rmance, description of the application and a discussion of the issues A significant omission in this chapter is a reference to the 'ExactecT~t' blood glucose meter (Medisense, UK); 207
Book Reviews this was thought 1o be a major commercial break-through in the mid 198Os.
Chapter 5 provides a detailed explanation of the construction of miniature electrodes with a brief description of the field-effect transistor. Chapter 6, 'Optical technology', provides a relevant review of absorption and reflectance spectroscopy, chemi. luminescence, fluorescence, phosphorescence, haemoglobin and oximetry, optodes, optical waveguides and optical potentiometry. The final chapters summarize the mechanism of calorimetric, piezoelectric and surface acoustic wave devices (Chapter 7); antibody-based devices (Chapter 8); microbial and tissue-based devices (Chapter 9); and finally the future directions for biosensor development (Chapter t 0). The author sets a broad scope for the book but devotes much of the text to the theoretical considerations of different types of biosensor. This may be welcomed by the nonspecialist who needs to gain an introductory overview of the subject. The style is readable and easy to follow, a refreshing approach. The author's expertise in the electrochemistry of enzymes, electrodes and electrode miniaturization shines through lucid text. Moreover, the mathematical explanation of sensor performance
and the relationship between theory and practice is presented succinctly, giving a good summary of the considerations used in the science of biosensors. Overall, I would have preferred a more rigorous approach to the subject. The explanations of equations are clear and introduced in a relevant manner, but occasionally the text sadly lapses into jargon. Answers to the following questions would have been helpful: What does the equation describe? What are the basic assumplions? What are their limitations? What practical tips for usage overcome obvious difficulties? In addition, texts are cited without summarizing the relevant information; for example, 30 anions and cations detected by ion-selective electrodes were referred to without tabulating the important ions (Chapter 3). Limits of detection are stated without a relevant context; for example, the glucose detection limit is 25 nM (Chapter 3) what is the significance of this level? There is a lack of discussion concerning the relative rnerits of alternative electrodes for important applications; for example, is the xanthine oxidase electrode, the example cited, the most important application of the carbon electrode? Finally, the emphasis on theory rather than applications lessens the useiulness ,)f this book.
Designer Oil Crops: Breeding, Processing and Biotechnology editedby DenisI. Murphy,VCH, 1994. £75.00 (xvi + 317 pages)ISBN 3 527 30040 6
This is an extremely thorough vol- crops, current breeding procedures ume. It gives a fascinating panorama and developments in selection or of the state of current knowledge and biotechnology. Chapter 2 describes in exciting developments in an area of more detail the oils, fatty acids and plant selection and biotechnology derivatives clearly and concisely. that will have a major impact on food The bulk of vegetable oil produced is processing in the future. With the used in the food industry, predomiproducts of transgenic soybean, maize, nantly as margarine, frying oil, salad oils cotton and oilseed rape (canola) and texturizersof processedfoods. There likely to reach the market from 1995 is therefore great interest in whether onwards, it is very timely. easily grown oilseedscan be selectedor The editorial approach and layout genetically engineered to contain higher of the volume are good. An intro- amounts of oils or more-desirable oils. duction sets the scene and moves Another possibility is the industrial through a consideralion of the econ- use of oils from conventional oilseed omic context of oilseed production crops, including the manipulation of and oil usage to an extensive first their oil quality, c,.mtent and nature to chapter characterizing the major satisfy the needs o( these sectors. 208
In summary, the book provides an excellent discussion of the theoretical aspects of electrochemically based biosensors with little insight into the applications, especially for those interested in food analysis. In addition, reference to publications by key workers in the field of biosensors for food analysis are omitted; for example, A.P.F. Turner t (Cranfield Institute of Technology, UK); I. Karube-' (ResearchCenter for Advanced Science and Technology, Japan); and R.D. Schmid ~ (until recently Gesellschaft for Biotechnoligische Forschung mbH, Germany). In the author's terms I think one could argue the subject is addressed satisfactorily; however, I expected a more rigorous approach. I suggest food scientists who are looking for some accessible background reading on biosensors would find this a useful text.
Andrew O. Scott Lyons TetleyLid, 325-347 Oldfield LaneNorth, Greenford, UK UB6 0AZ.
References 1 Turner,A.P.F.,Karube,I. andWilson,G.S. (1987) Biosensors:Fundamentalsand Applications, OxfordUniversityPress 2 Karube,I., Sode,K.andTamiya,E.119901 I. Biotechnol. I S,267-282 3 Schmid,R.D.andWagner,G. (1990)Food Biotechnol. 411), 215-240
'Alternative' oil crops are also of great interest, for several reasons. They contain novel fatty acids, such as petroselinic acid from coriander, high-concentration lauric acids from Cuphea species and high-oleic acids from Euphorbia spp. These crops are unimproved (i.e. undomesticated) and, if characteristics such as pod shatter can be overcome, may provide high-value low-input alternatives to oilseed rape, sunflower and soybean. On the other hand, if the genes encoding the unusual oils can be isolated and transferred to conventional oilseed crops, very much higher yields might be obtained. Particularly important industrial uses of existing and novel oils, which may have some impact in the food industry, include lubricants, antifoaming agents, printing inks, plasticizers and glycerol derivatives. These are mentioned in Chapter 3 and covered in more detail in Chapter 7. The breeding of oil crops, including
Trendsin FoodScience& TechnologyJune1994 IVol. Sl