The frequency of reports concemmg the interface of biological reco- tion elements to signal transduction technologies has risen dramatically over the last decade. Because any one of a wide variety of biological recognition elements (e. g. , antibodies, receptors, DNA, microorganisms, or enzymes) can theoretically be interfaced with any one of a wide variety of signal transducers (e. g. , optical, electrochemical, thermal, or acoustic), the potential range of devices and techniques can be bewildering. The purpose of this volume and the previous volume in this series is to provide a basic reference and startmg point for investigators in academics, mdustry, and government to begin or expand their biosensors research. This volume, Methods in Biotechnology vol. 7: Affinity Biosensors: Techniques and Protocols, describes a variety of classical and emerging transduction technologies that have been interfaced to bioaffinity elements (e. g. , antibodies and receptors). Some of the reasons for the expansion in the use of affinity-based biosensors include both advances in signal transduction technologies (e. g. , fiber optics, microelectromcs, and microfabrication) and the availability of bioafflmty elements. More specifically, with respect to biological recognttion elements, commercially and noncommercially produced antibodies directed toward a variety of analytes have become widely available. In addition, te- niques for the purification and stabilization of receptors have also significantly improved. As a result of these recent advances in the field, biosensors research and development projects are being pursued by mvestigators from a wide range of disciplines.

In 1962 Clark and Lyons pioneered the concept of a biosensor. They p- posed immobilizing enzymes at electrochemical detectors to form "enzyme el- trodes" in order to expand the analyte range of ther base sensor. Smce then, the field of blosensors has greatly expanded. Some of the reasons for the expansion include both advances in signal transduction technologies and the incorporation of different biological sensing elements (Table 1). As a consequence, there are now a bewildering array of permutations of the biological sensing element and signal transducers that can be used to c- struct a biosensor. The purpose of the two volumes of Protocols and Te- niques in Biosensors is to provide a basic reference tool and starting point for use by graduate students, postdoctoral and senior researchers, and technicians m academics, industry, and government research establishments, to enable rapid entry into the field of biosensors. There are a variety of approaches that researchers employ to select a combination of bioaffinity elements and signal transducers. One commonly used approach is to identtfy the compound or compounds of interest; identify the biological molecule that yields an appropriate recognitionlselectivtty and dynamic concentration range for the assay; and choose an assay format and signal transduction technology that will meet the analytical requirements for the proposed application, This volume, Enzyme and Microbial Biosensors: Techniques and Protocols, describes a variety of transduction technologies that have been interfaced to enzymes and microorganisms.

The frequency of reports concemmg the interface of biological reco- tion elements to signal transduction technologies has risen dramatically over the last decade. Because any one of a wide variety of biological recognition elements (e. g. , antibodies, receptors, DNA, microorganisms, or enzymes) can theoretically be interfaced with any one of a wide variety of signal transducers (e. g. , optical, electrochemical, thermal, or acoustic), the potential range of devices and techniques can be bewildering. The purpose of this volume and the previous volume in this series is to provide a basic reference and startmg point for investigators in academics, mdustry, and government to begin or expand their biosensors research. This volume, Methods in Biotechnology vol. 7: Affinity Biosensors: Techniques and Protocols, describes a variety of classical and emerging transduction technologies that have been interfaced to bioaffinity elements (e. g. , antibodies and receptors). Some of the reasons for the expansion in the use of affinity-based biosensors include both advances in signal transduction technologies (e. g. , fiber optics, microelectromcs, and microfabrication) and the availability of bioafflmty elements. More specifically, with respect to biological recognttion elements, commercially and noncommercially produced antibodies directed toward a variety of analytes have become widely available. In addition, te- niques for the purification and stabilization of receptors have also significantly improved. As a result of these recent advances in the field, biosensors research and development projects are being pursued by mvestigators from a wide range of disciplines.

In 1962 Clark and Lyons pioneered the concept of a biosensor. They p- posed immobilizing enzymes at electrochemical detectors to form "enzyme el- trodes" in order to expand the analyte range of ther base sensor. Smce then, the field of blosensors has greatly expanded. Some of the reasons for the expansion include both advances in signal transduction technologies and the incorporation of different biological sensing elements (Table 1). As a consequence, there are now a bewildering array of permutations of the biological sensing element and signal transducers that can be used to c- struct a biosensor. The purpose of the two volumes of Protocols and Te- niques in Biosensors is to provide a basic reference tool and starting point for use by graduate students, postdoctoral and senior researchers, and technicians m academics, industry, and government research establishments, to enable rapid entry into the field of biosensors. There are a variety of approaches that researchers employ to select a combination of bioaffinity elements and signal transducers. One commonly used approach is to identtfy the compound or compounds of interest; identify the biological molecule that yields an appropriate recognitionlselectivtty and dynamic concentration range for the assay; and choose an assay format and signal transduction technology that will meet the analytical requirements for the proposed application, This volume, Enzyme and Microbial Biosensors: Techniques and Protocols, describes a variety of transduction technologies that have been interfaced to enzymes and microorganisms.

Nucleic acids are the fundamental building blocks of life and are found in all living things. In recent years, their functions have been shown to extend beyond the Watson-Crick base pair recognition of complementary strands. Molecules (known as aptamers) consisting of 40-50 nucleotides have been isolated that are able to bind a broad range of molecules with high affinity and specificity. The molecules recognized by aptamers range from small organic molecules to proteins, cells and even intact viral particles. Catalytic DNA molecules called NAzymes (RNAzyme or DNAzyme) have also been shown to exist and, when combined with aptamers, are known as aptazymes. These biomolecules can be used to develop smart and innovative biosensors for environmental analysis. Monitoring of contaminants in the air, water and soil is a key component in understanding and managing risks to human health and ecosystems. This, in conjunction with the time and cost involved in traditional chemical analysis, means there is a growing need for simple, rapid, cost-effective and portable screening methods. Biosensors are compact devices which complement current field screening and monitoring methods. This book demonstrates the incredible opportunities that nucleic acids can offer to environmental analytical chemistry. The chapters: show how nucleic acids have a pivotal role in the development of smart biosensors for environmental monitoring; describe the development of biosensors based on aptamers and NAzymes for the detection of organic and inorganic pollutants; deal with the use of nucleic acid based biosensors for environmental toxicity screening, and detail the use of nanomaterials, as well as miniaturization and lab-on-a-chip technologies, for nucleic acid based biosensing systems.