Quantification of biological or biochemical processes are of utmost importance for medical, biological and biotechnological applications. However, converting the biological information to an easily processed electronic signal is challenging due to the complexity of connecting an electronic device directly to a biological environment. Electrochemical biosensors provide an attractive means to analyze the content of a biological sample due to the direct conversion of a biological event to an electronic signal. Over the past decades several sensing concepts and related devices have been developed. In this review, the most common traditional techniques, such as cyclic voltammetry, chronoamperometry, chronopotentiometry, impedance spectroscopy, and various field-effect transistor based methods are presented along with selected promising novel approaches, such as nanowire or magnetic nanoparticle-based biosensing. Additional measurement techniques, which have been shown useful in combination with electrochemical detection, are also summarized, such as the electrochemical versions of surface plasmon resonance, optical waveguide lightmode spectroscopy, ellipsometry, quartz crystal microbalance, and scanning probe microscopy. The signal transduction and the general performance of electrochemical sensors are often determined by the surface architectures that connect the sensing element to the biological sample at the nanometer scale. The most common surface modification techniques, the various electrochemical transduction mechanisms, and the choice of the recognition receptor molecules all influence the ultimate sensitivity of the sensor. New nanotechnology-based approaches, such as the use of engineered ion-channels in lipid bilayers, the encapsulation of enzymes into vesicles, polymersomes, or polyelectrolyte capsules provide additional possibilities for signal amplification. In particular, this review highlights the importance of the precise control over the delicate interplay between surface nano-architectures, surface functionalization and the chosen sensor transducer principle, as well as the usefulness of complementary characterization tools to interpret and to optimize the sensor response.

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Electrochemical Biosensors - Sensor Principles and Architectures

http://cau.ac.kr/~jjang14/BioMEMS/Lazcka_BSBE_Pathogen_Detection_Review_2006.pdf

Pathogen detection: a perspective of traditional methods and biosensors.

2.2. New Approaches 707 2.2.1. Optical Sensor Systems 707 2.2.2. Mass Spectrometry 708 2.2.3. Ion Mobility Spectrometry 708 2.2.4. Gas Chromatography 709 2.2.5. Infrared Spectroscopy 709 2.2.6. Use of Substance-Class-Specific Sensors 709 2.3. Combined Technologies 710 3. Companies 710 4. Application Areas 710 4.1. Food and Beverage 712 4.2. Environmental Monitoring 715 4.3. Disease Diagnosis 716 5. Research and Development Trends 718 5.1. Sample Handling 719 5.2. Filters and Analyte Gas Separation 719 5.3. Data Evaluation 720 6. Conclusion 721 7. References 722

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Electronic nose: current status and future trends.

Since the discovery of carbon nanotubes in 1991 (ref. 1), there have been significant research efforts to synthesize nanometre-scale tubular forms of various solids. The formation of tubular nanostructure generally requires a layered or anisotropic crystal structure. There are reports of nanotubes made from silica, alumina, silicon and metals that do not have a layered crystal structure; they are synthesized by using carbon nanotubes and porous membranes as templates, or by thin-film rolling. These nanotubes, however, are either amorphous, polycrystalline or exist only in ultrahigh vacuum. The growth of single-crystal semiconductor hollow nanotubes would be advantageous in potential nanoscale electronics, optoelectronics and biochemical-sensing applications. Here we report an 'epitaxial casting' approach for the synthesis of single-crystal GaN nanotubes with inner diameters of 30-200 nm and wall thicknesses of 5-50 nm. Hexagonal ZnO nanowires were used as templates for the epitaxial overgrowth of thin GaN layers in a chemical vapour deposition system. The ZnO nanowire templates were subsequently removed by thermal reduction and evaporation, resulting in ordered arrays of GaN nanotubes on the substrates. This templating process should be applicable to many other semiconductor systems.

Single-crystal gallium nitride nanotubes.

Impedance biosensors are a class of electrical biosensors that show promise for point-of-care and other applications due to low cost, ease of miniaturization, and label-free operation. Unlabeled DNA and protein targets can be detected by monitoring changes in surface impedance when a target molecule binds to an immobilized probe. The affinity capture step leads to challenges shared by all label-free affinity biosensors; these challenges are discussed along with others unique to impedance readout. Various possible mechanisms for impedance change upon target binding are discussed. We critically summarize accomplishments of past label-free impedance biosensors and identify areas for future research.

/pdf/label-free-impedance-biosensors-opportunities-and-challenges-3b721lxxqy.pdf

Label-Free Impedance Biosensors: Opportunities and Challenges.

Research in the field of biosensors has enormously increased over the recent years. Since the development of the first biosensor by Clark in 1962, where an amperometric oxygen electrode was immobilised with an enzyme (glucose oxidase),1 many efforts have been invested to create functional hybrid systems. These functional hybrid systems often benefit from the coupling of the unique recognition and signal-amplification abilities of biological systems, that have been developed and optimised during millions of years of evolution, with an artificial man-made signal detection and amplification system. Thus, the combination of knowledge in bioand electrochemistry, solid-state and surface physics, bioengineering, integrated circuit silicon technology and data processing offers the possibility of a new generation of highly specific, sensitive, selective and reliable micro (bio-)chemical sensors and sensor arrays. Moreover, the rapid development of silicon technology has stimulated the fabrication of miniaturised analytical systems such as mTAS (micro total analysis system), ‘lab on chip’ sensors, electronic tongue devices and electronic noses.2–17 Among the variety of proposed concepts and different types of biosensors, the integration of biologically active materials together with an ISFET (ion-selective field-effect transistor) is one of the most attractive approaches. The ISFET was invented by Bergveld18 in 1970 and has been introduced as the first miniaturised silicon-based chemical sensor. In spite of distinct difficulties with regard to practical applications, the great interest in ISFET-based biosensors, so-called biologically modified field-effect transistors (BioFETs), has generated a great number of publications, a flow that shows no sign of diminishing. The reason therefore is that silicon-based fieldeffect devices are currently being the basic structural element in a new generation of micro biosensors; they provide a lot of potential advantages such as small size and weight, fast response, high reliability, low output impedance, the possibility of automatic packaging at wafer level, on-chip integration of biosensor arrays and a signal processing scheme with the future prospect of low-cost mass production of portable microanalysis systems; moreover, their possible field of applications reaches from medicine, biotechnology and environmental monitoring through food and drug industries to defence and security. This paper gives a review of recent and significant advances in the research and development of BioFETs. In planing this review, we have chosen to focus mainly upon developments occurring during the last six years (from 1995 to the end of 2001). A computer search of the Science Citation Index has found that more than 400 publications concerning ISFETs and BioFETs have appeared from January 1995 to December 2001, indicating the intensity of research activities devoted to this important task. This review is in general limited to journal articles and usually does not include patents, conference proceedings, reports or PhD theses. Some references to important works reported prior to 1995 have also been added to provide additional source material. The review is organised as follows: The principles of the ISFET and BioFET are described in section 2. Recent advances in the development of various types of BioFETs are reviewed in section 3. Here, some examples of current applications of BioFETs are presented, too. Concluding points and future prospects of BioFETs are discussed in section 4. Michael J. Schöning was born in Bruchsal, Germany, in 1962. He received his diploma in 1989 and Ph.D. in 1993, both in electrical engineering, from the Technical University (TH) Karlsruhe. In 1989 he joined the Institute of Radiochemistry at the Research Centre Karlsruhe, Germany. Since 1993 he has been with the Institute of Thin Films and Interfaces at the Research Centre Jülich, and since 1999 he has been a Professor of applied physics at the University of the Applied Sciences Aachen, Germany. His research interests include silicon-based chemical and biological sensors, thin film techniques, solid-state physics, semiconductor devices and microsystem technology.

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Recent advances in biologically sensitive field-effect transistors (BioFETs)

A critical evaluation of the possibilities and limitations of the label-free detection of deoxyribonucleic acid (DNA) hybridization by means of field-effect-based devices is discussed. A new DNA-detection method is introduced, which utilizes an ion-sensitive field-effect device as transducer. The upon the DNA hybridization induced redistribution of the ion concentration within the intermolecular spaces and/or the alteration of the ion sensitivity of the device is proposed as detection mechanism. The theoretical calculations predict a substantial change in the average ion concentration within the intermolecular spaces induced upon hybridization that are enough to obtain a detectable sensor signal.

Possibilities and limitations of label-free detection of DNA hybridization with field-effect-based devices

This paper gives a brief survey on biologically sensitive FEDs (field-effect devices) and introduces some recent approaches in this field. Basic concepts, functional principles and current trends in research and development for namely, ISFETs (ion-sensitive field-effect transistors), capacitive EIS (electrolyte-insulator-semiconductor) sensors and LAPS (light-addressable potentiometric sensor) structures will be presented.

Bio FEDs (Field‐Effect Devices): State‐of‐the‐Art and New Directions

The gas-sensing characteristics of bismuth ferrites with the compositions BiFeO 3 , Bi 4 Fe 2 O 9 , Bi 2 Fe 4 O 9 as new materials for semiconductor gas sensors are presented. Ceramic samples of composition BiFeO 3 show a high sensitivity to ethanol and acetone vapour. The response and recovery times, long-term stability and reproducibility of gas-sensitive elements, as well as the effect of humidity are studied. A comparison with the characteristics of gas-sensitive elements based on other materials shows the possibility of using bismuth ferrites as sensitive materials for semiconductor gas sensors.

Bismuth Ferrites: New Materials for Semiconductor Gas Sensors

Among the variety of transducer concepts pro- posed for label-free detection of biomolecules, the semi- conductor field-effect device (FED) is one of the most at- tractive platforms. As medical techniques continue to progress towards diagnostic and therapies based on bio- markers, the ability of FEDs for a label-free, fast and real-time detection of multiple pathogenic and physiologi- cally relevant molecules with high specificity and sensitiv- ity offers very promising prospects for their application in point-of-care and personalized medicine for an early diag- nosis and treatment of diseases. The presented paper re- views recent advances and current trends in research and development of different FEDs for label-free, direct elec- trical detection of charged biomolecules by their intrinsic molecular charge. The authors are mainly focusing on the detection of the DNA hybridization event, antibody-anti- gen affinity reaction as well as clinically relevant biomole- cules such as cardiac and cancer biomarkers.

Arshak Poghossian

Papers

Recent advances in biologically sensitive field-effect transistors (BioFETs)

Possibilities and limitations of label-free detection of DNA hybridization with field-effect-based devices

Bio FEDs (Field‐Effect Devices): State‐of‐the‐Art and New Directions

Bismuth Ferrites: New Materials for Semiconductor Gas Sensors

Label‐Free Sensing of Biomolecules with Field‐Effect Devices for Clinical Applications