Biosensor principles and applications

8O F.N. Marzulli and H.L Maibach, Dermatotoxi~logy, Fourth Edition, Hemisphere Publishing Corp., New York, 1991, i063 pages. Perhaps, as in the rest of life, the reader of this book must learn to take the bad with the good. When coupled with the excessive length o f this book, however, the reader may have to do some sorting to find those chapters which are worthwhile. A number of new chapters have been included in the fourth edition. These cover subjects such as physicochemical factors in transdermal trmlsport, pharmacokinetic modeling, dermal metabolism and in vitro methodology. O f particular note are chapters written by Magee (chapter 1 ), and Kao and Carver (chapter 9). In the first chapter, Philip Magee lays out a comprehensive review of the physicochemical properties of the stratum corneum and permeant drugs which are important to transport. John Kao and Mike Carver have contributed an elegant chapter on skin metabolism. This chapter is by far the most thoughtful and comprehensive discourse on dermal metabolism that these reviews have seen to date. In addition, Jim McDoagal's description of physiologically based pharmacokinetic modeling is a good introduction to the subject, while Henry Mcguire provides an up to date analysis of photoallergy testing with insight to the relative merits of various tests. The Fourth edition of Dermatotoxicology reviewed here contains new material, including a chapter on transdermal delivery systems, along with updated versions of chapters in the previous edition. Unfortunately, all too often that updating is modest, or non-existent. For example, of the 89 references in updated chapter 21, less than 8% of the papers cited were written after 1987. This hardly fits the description of a contemporary or comprehensive review. A number of the chapters in this book are very superficial in their treatment of the subject matter. For example, chapter 5 ("Percutaneous Absorption and Skin Decontarrdnation of PCBS") is full of assertions without referenees. It. pa~ie~

ular, in the Discussion section of this chapter, which is all of 1.5 pages in length, the term "plx)bably'" occurs three times, while "'perhaps could be" and "may be" appear once each. It is difficult to find definitive statements of cause and effect. Furthermore, only one of 13 references were to papers which appeared after 1987. Chapters 10 and 14 are exhaustive descriptions of predictive test methods; however, the reader does not gain insight from the extensive skin toxicological experience of the authors. Thus, these chapters, while bibliographic, do not provide the reader with an authoritative perspective on dermatotoxicological methods. The results are cited, not reviewed. In conclusion, while extensive, much of the fourth edition is a restatement of previous editions. The book is not without redeeming qualities, however, which are of potentk.l ~lu~ to the transdermal researcher. Hopefully, the fifth edition will emphasize quality over qugntity. RUSSELLO. POTTS, Ph.D. (.'ygnusThera~e~u~cSystems THOMASS. SPENCER, Ph.D. 400 Penobscot Drive Redwood City. CA 94063, U.S.A.

L.J. Blum and P.R. Coulet, Biosensor Principles andApplications. Marcel Dekker, Inc., New York, 1991, 357 pp. A number of excellent biosensors digests have come out of the United Kingdom in recent years. Weighing in with a contribution from the other side of the English Channel are Loie Blum and Pierre Coulet, with the latest volume in the Marcel Dekker series on Bioproeess Technology. Joined by 20 leading authorities in the field, they have put together 14 chapters on biosensors '~echnology. Following a long standing tradition of biosensor authors and speakers alike, Coulet begins the book ( c h a p t e r , ) b~" offe~'ing u~ ii~ definition o~

a biosensor; a device that combines a biologically derived sensing element with a suitable transducer. The remainder of the book examines the numerous types of sensing elements and transdueers that make the field so interdisciplinary. Four chapters are devoted to biosensors based on electrochemical transducers. Bardeletti, Sdchaud and Coulet (chapter 2) present a chapter on enzyme electrodes, which contains a number of excellent tables summarizing the design and performance ofbiosensors for biological fluid and foodstuff analyses, and commercial glucose and lactate analyzers. Bannister, Higgins and Tarner (chapter 3) discuss the approaches used to construct amperometric immunosensors. Potentiometric biosensors utilizing either enzymes or antibodies as the recognition element are reviewed by Kauffmann and Guilbault (chapter 4). Kuriyama and Kimura contribute a chapter (chapter 7) on microfabricated biosensors based on ion-sen:,itive field-effect transistors (ISFETs). The approaches used for patterning enzyme layers on silicon wafers are reviewed, though since this is such a rapidly moving field, some interesting papers by groups at Neuchatel and Twente have come out since this went to press. Optical biosensors are covered in three chapters. Chemically mediated fiber~ptic biosensors, primarily those in which an enzymatic reaction is coupled to a fiber optic oH or pOz sensor, are reviewed by Schaffar and Woltbeis (chapter 8 ). Arnold (chapter 9) describes fiber optic biosensors in which a mediator is not necessary, such as those based on fiuorometrlc detection of NADH. Finany, Blum and Gautier ( chapter I 0 ) cover fiber optic biosensors based on biolumineseence and chemiluminescence, an area which has not received much attention in other reference books. Chapters on calorimetric and acoustic transduction are also included. Danialsson (chapter 5) provides both a tutorial introduction and a thorough review of enzyme thermistor devices. Luong and Guilbault (chapter 6) describe the state of the art in piezoelectric crystal biosensors, and conclude by presenting the obstacles to

be overcome for this promising technology. The remaining chapters in the book include a chapter on immunosensors by Aizawa (chapter 11 ), which is a brief summary of the approaches used for immunosensing (e.g. nonlabeled vs. labeled, types of labels used, transduction methods, etc. ). A chapter on microbial sensors by Karube and Chang (chapter 12) describes sensors for such diverse analytes as glucose, alcohol, ammonia gas, methane, glutamic acid, cephalosporin and sodium nitrite. Vadgama and Desai (chapter 13) address one of the most difficult challenges in biosensing, that of developing sensors for in vivo use. Taking a broader view of biosensors than does Coulet, they describe sensors for in vivo monitoring of O:, CO2, pH and other ions, and glucose. Readers of this journal will be interested to learn that a paragraph was devoted to a discussion of the glucose-responsive gels developed at the University of Washington for controlled release of insulin. Blum and Coulet conclude this book with a chapter in which they speculate about future trends and prospects in the field (chapter 14). They believe that new developments in molecular biology and chemistry, such as site-directed mutagenesis and catalytic antibodies, will be used to develop new sensing layers for biosensors, and that microfabricated transducers will become increasingly important. Blum and Coulet have done an excellent job in organizing this volume. The contributors are first rate, and represent just about every topic of current interest in biosensing (with the possible exception of receptor protein-based sensors). Far the most part, individual chapters begin with enough introductory material to bring the novice up to speed, yet provide a broad enough survey of the current literature tlmt the expert will also want to take a look. N.[L'SHEPPARD,JR.

Department of Biomedical Engineet~v~g The Johns Hopkins University Baltimore, AID. U.S.A.