ISFET based enzyme sensors

This paper reviews the results that have been reported on ISFET based enzyme sensors. The most important improvement that results from the application of ISFETs instead of glass membrane electrodes is in the method of fabrication. Problems with regard to the pH dependence of the response and the dynamic range as well as the influence of the sample buffer capacity have not been solved. As a possible solution we introduce a coulometric system that compensates for the analyte buffer capacity. If the pH in the immobilized enzyme layer is thus controlled, the resulting pH-static enzyme sensor has an output that is independent of the sample pH and buffer capacity and has an expanded linear range

Electrochemical biosensors: recommended definitions and classification

International audienceTwo Divisions of the International Union of Pure and Applied Chemistry (IUPAC), namely Physical Chemistry (Commission I.7 on Biophysical Chemistry, formerly Steering Committee on Biophysical Chemistry) and Analytical Chemistry (Commission V.5 on Electroanalytical Chemistry), have prepared recommendations on the definition, classification and nomenclature related to electrochemical biosensors; these recommendations could, in the future, be extended to other types of biosensors. An electrochemical biosensor is a self-contained integrated device, which is capable of providing specific quantitative or semi-quantitative analytical information using a biological recognition element (biochemical receptor) which is retained in direct spatial contact with an electrochemical transduction element. Because of their ability to be repeatedly calibrated, we recommend that a biosensor should be clearly distinguished from a bioanalytical system, which requires additional processing steps, such as reagent addition. A device which is both disposable after one measurement, i.e. single use, and unable to monitor the analyte concentration continuously or after rapid and reproducible regeneration should be designated a single-use biosensor. Biosensors may be classified according to the biological specificity-conferring mechanism or, alternatively, the mode of physicochemical signal transduction. The biological recognition element may be based on a chemical reaction catalysed by, or on an equilibrium reaction with, macromolecules that have been isolated, engineered or present in their original biological environment. In the latter case, equilibrium is generally reached and there is no further, if any, net consumption of analyte(s) by the immobilized biocomplexing agent incorporated into the sensor. Biosensors may be further classi®ed according to the analytes or reactions that they monitor: direct monitoring of analyte concentration or of reactions producing or consuming such analytes; alternatively, an indirect monitoring of inhibitor or activator of the biological recognition element (biochemical receptor) may be achieved. A rapid proliferation of biosensors and their diversity has led to a lack of rigour in defining their performance criteria. Although each biosensor can only truly be evaluated for a particular application, it is still useful to examine how standard protocols for performance criteria may be defined in accordance with standard IUPAC protocols or definitions. These criteria are recommended for authors, referees and educators and include calibration characteristics (sensitivity, operational and linear concentration range, detection and quantitative determination limits), selectivity, steady-state and transient response times, sample throughput, reproducibility, stability and lifetime

Dual monitoring of surface reactions in real time by combined surface-plasmon resonance and field-effect transistor interrogation

By combining surface plasmon resonance (SPR) and electrolyte gated field-effect transistor (EG-FET) methods in a single analytical device we introduce a novel tool for surface investigations, enabling simultaneous measurements of the surface mass and charge density changes in real time. This is realized using a gold sensor surface that simultaneously serves as a gate electrode of the EG-FET and as the SPR active interface. This novel platform has the potential to provide new insights into (bio)adsorption processes on planar solid surfaces by directly relating complementary measurement principles based on (i) detuning of SPR as a result of the modification of the interfacial refractive index profile by surface adsorption processes and (ii) change of output current as a result of the emanating effective gate voltage modulations. Furthermore, combination of the two complementary sensing concepts allows for the comparison and respective validation of both analytical techniques. A theoretical model is derived describing the mass uptake and evolution of surface charge density during polyelectrolyte multilayer formation. We demonstrate the potential of this combined platform through the observation of layer-bylayer assembly of PDADMAC and PSS. These simultaneous label-free and real-time measurements allow new insights into complex processes at the solid−liquid interface (like non-Fickian ion diffusion), which are beyond the scope of each individual tool.Fil: Aspermair, Patrik. Austrian Institute of Technology; Austria. CEST Competence Center for Electrochemical Surface Technologies; Austria. Centre National de la Recherche Scientifique; Francia. Universite Valencienne; Francia. Universite Lille; FranciaFil: Ramach, Ulrich. CEST Competence Center for Electrochemical Surface Technologies; AustriaFil: Reiner Rozman, Ciril. Austrian Institute of Technology; AustriaFil: Fossati, Stefan. Austrian Institute of Technology; AustriaFil: Lechner, Bernadette. Austrian Institute of Technology; AustriaFil: Moya, Sergio Enrique. Centro de Investigación Cooperativa en Biomateriales - CIC biomaGUNE; EspañaFil: Azzaroni, Omar. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; ArgentinaFil: Dostalek, Jakub. Austrian Institute of Technology; AustriaFil: Szunerits, Sabine. Centre National de la Recherche Scientifique; Francia. Universite Valencienne; Francia. Universite Lille; FranciaFil: Knoll, Wolfgang. Austrian Institute of Technology; Austria. CEST Competence Center for Electrochemical Surface Technologies; AustriaFil: Bintinger, Johannes. Austrian Institute Of Technology; Austri

Electrochemical Biosensors: Recommended Definitions and Classification

Two Divisions of the International Union of Pure and Applied Chemistry (IUPAC), namely Physical Chemistry (Commission I.7 on Biophysical Chemistry, formerly Steering Committee on Biophysical Chemistry) and Analytical Chemistry (Commission V.5 on Electroanalytical Chemistry), have prepared recommendations on the definition, classification and nomenclature related to electrochemical biosensors; these recommendations could, in the future, be extended to other types of biosensors. An electrochemical biosensor is a self-contained integrated device, which is capable of providing specific quantitative or semi-quantitative analytical information using a biological recognition element (biochemical receptor) which is retained in direct spatial contact with an electrochemical transduction element. Because of their ability to be repeatedly calibrated, we recommend that a biosensor should be clearly distinguished from a bioanalytical system, which requires additional processing steps, such as reagent addition. A device which is both disposable after one measurement, i.e. single use, and unable to monitor the analyte concentration continuously or after rapid and reproducible regeneration should be designated a single-use biosensor. Biosensors may be classified according to the biological specificity-conferring mechanism or, alternatively, the mode of physicochemical signal transduction. The biological recognition element may be based on a chemical reaction catalysed by, or on an equilibrium reaction with, macromolecules that have been isolated, engineered or present in their original biological environment. In the latter case, equilibrium is generally reached and there is no further, if any, net consumption of analyte(s) by the immobilized biocomplexing agent incorporated into the sensor. Biosensors may be further classified according to the analytes or reactions that they monitor: direct monitoring of analyte concentration or of reactions producing or consuming such analytes; alternatively, an indirect monitoring of inhibitor or activator of the biological recognition element (biochemical receptor) may be achieved. A rapid proliferation of biosensors and their diversity has led to a lack of rigour in defining their performance criteria. Although each biosensor can only truly be evaluated for a particular application, it is still useful to examine how standard protocols for performance criteria may be defined in accordance with standard IUPAC protocols or definitions. These criteria are recommended for authors, referees and educators and include calibration characteristics (sensitivity, operational and linear concentration range, detection and quantitative determination limits), selectivity, steady-state and transient response times, sample throughput, reproducibility, stability and lifetime

Particle-modified Surface Plasmon Resonance Biosensor

Surface plasmon resonance (SPR) biosensors have attracted great attention in scientific research in the past three decades. Extensive studies on the immobilisation of biorecognition elements have been conducted in pursuit of higher sensitivity, but trialled formats have focussed on a thin layer modification next to the plasmon film, which usually requires in situ derivatization. This thesis investigates an ‘off-chip’ immobilisation strategy for SPR biosensing using silica particles and considers the implications of a particle-modified evanescent field on the signal amplitude and kinetics, for an exemplar affinity binding between immobilised IgG and its anti-IgG complement. Submicron silica particles were synthesized as carriers for the bio-recognition elements. They were then immobilised to form a sub-monolayer on the gold film of an SPR biosensor using two methods: thiolsilane coupling and physical adsorption aided by mechanical pressure. The bio-sensitivity towards an antigen/antibody interaction was lower than an SPR biosensor with an alkanethiolate SAM due to the difference in ligand capacity and position in the evanescent field. The binding kinetics of antigen/antibody pair was found to follow the Langmuir model closely in a continuous flow configuration but was heavily limited by the mass transport from the bulk to the sensor surface in a stop-flow configuration. A packed channel configuration was designed with larger gel particles as ligand carriers, packed on top of a gold film to create a column-modified SPR biosensor. This sensor has comparable bio-sensitivity to the previous sub-monolayer particle-modified systems, but the binding and dissociation of the analyte was heavily dependent on mass transport and binding equilibria across the column. A bi-directional diffusion mechanism was proposed based on a two-compartment mass transport model and the expanded model fitted well with the experimental data. The column-modified sensor was also studied by SPR imaging and analyte band formation was observed and analysed. Using the lateral resolution, a multiplexing particle column configuration was explored, and its potential in distinguishing a multicomponent analyte.Agency for Science Technology and Research, Singapor