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Preface NEW CONCEPTS AND TECHNOLOGICAL ADVANCES that will influence the design, versatility, and reliability of the next generation of assays for small toxic molecules were the primary focuses of the symposium upon which this book is based. Some symposium participants and authors not previously involved in environmental immunoanalysis are now discovering new ways of accomplishing goals in this field. Gaining new perspectives on issues that affect the use and acceptance of immunoassays and related methods was also our objective. More new immunoassays are being reported worldwide every year. A few years ago, most studies using immunoassay were undertaken to vali date a particular test. Researchers now are using immunoassay as a pri mary data-gathering method, especially when immunoassays can costeffectively process numbers of samples that would be prohibitive with instrumental analysis. Immunoassays and related methods are also being put to new uses such as monitoring of manufacturing and remediation processes, and new pesticide discovery. Technologies for small-molecule recognition, incorporating knowledge from molecular biology, physics, and chemistry, are advancing rapidly. Dramatic advances defining antibody structure have been augmented by powerful molecular biological methods that allow antibody genes to be cloned and expressed in bacteria. Synthetic combinatorial antibody libraries with diversity vastly greater than the mammalian repertoire offer the possibility of obtaining antibodies that would be difficult or impossible to derive by conventional immunization. With molecular modeling and in vitro mutagenesis it is now possible to engineer new properties into anti bodies, enzymes, receptors, ion-channel subunits, and small recognition peptides. One of the potentially most significant advances is the demon stration that certain organic polymers can retain an "imprint" of a small molecule and specifically bind that compound in a detection method very similar to immunoassays. New synthesis schemes and computational tools are contributing to the design of better haptens and competitor molecules. Quantitative structure-activity parameters, including properties such as electrostatic potential of small analytes, are being correlated with recognition by bind ing molecules. Although these techniques were first used to develop improved antibodies and immunoassays, they apply to other molecular recognition systems as well. Combinatorial chemistry enables diverse ix
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repertoires of antibodies and other recognition proteins to be screened for binding to large arrays of ligands and ligand mimics (mimotopes). This strategy has implications for the discovery of new pesticides, inhibi tors, and drugs, as well as for antibody characterization and assay development. Some of the distinctions between antibody-based and instrumental analytical methods are disappearing. Concepts from physics are paving the way for development of miniaturized multianalyte assays, automated instrument-based immunomethods, and a variety of sensor formats. Flow injection, fluorescence polarization, and assay techniques using liposomes and magnetic particles have increased throughput and made immunoas says more versatile. Notable advances in sensor technology include the theory and implementation of miniaturized multiantibody, multianalyte arrays and development of reusable sensors for repeated measurements. Carefully designed immunoaffinity methods will reduce the cost, complex ity, and scale of residue recovery and sample cleanup and will increase reliability and sample throughput. One session of the meeting was devoted to identifying ways to speed and simplify the evaluation of immunoassay methods to foster acceptance by regulatory agencies. The chapters in the last section of this volume present new industry and regulatory agency perspectives on appropriate roles for immunoassay and criteria for acceptance. These chapters include proposed quality standards for kit manufacture and a set of guidelines for the validation and use of immunoassays as stand-alone procedures or in conjunction with instrumental methods. Throughout the symposium it was evident that considerable distance exists between the technologies that are being developed and those that are presently being validated and approved for regulatory purposes. The increase in practical use and validation of antibody-based and antibody like small-molecule detection methods is encouraging. As more experi ence is gained with the present generation of assays, newer methods are likely to be accepted faster. Advanced techniques and formats will raise new validation and quality-assurance issues. However, they may also be more versatile and reproducible, and will eliminate problems inherent in some of the present assays. Our hope is that this collection of papers provides an overview of relevant state-of-the-art research, a glimpse of future directions, and a stimulus for more efficient validation of the current methods. Acknowledgments We thank the chapter authors and especially the peer reviewers for their thoroughness and cooperation, the Agrochemicals Division for financial
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support, Anne Wilson of A C S Books for shepherding us through the edi torial process on schedule, and all of those who participated in making the symposium a source of new ideas and constructive solutions. JUDD O. NELSON University of Maryland College Park, MD 20742 A L E X A N D E R E. K A R U
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University of California Berkeley, C A 94720 ROSIE B. WONG American Cyanamid Agricultural Research Division Princeton, N J 08543 November 15, 1994
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