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PubMedDate not supplied

Biosensors and biochips: advances in biological and medical diagnostics.

In the past two decades, the biological and medical fields have seen great advances in the development of biosensors and biochips capable of characterizing and quantifying biomolecules. This review is meant to provide an overview of the various types of biosensors and biochips that have been developed for biological and medical applications, along with significant advances over the last several years in these technologies. It also attempts to describe various classification schemes that can be used for categorizing the different biosensors and provide relevant examples of these classification schemes from recent literature.

Biosensing Techniques↗

PubMedDate not supplied

Amperometric biosensors based on electrosynthesised polymeric films.

The most significant goals achieved in the course of the last decade in the design of amperometric biosensors based on redox enzymes entrapped in electrosynthesised polymeric films are reviewed. Particular emphasis is devoted to non-conducting polymers with built-in permselectivity that revealed very promising materials for designing fast-response and interference-free, H2O2 detecting, amperometric biosensors. The role of surface analytical techniques to provide structural information allowing a better understanding of polymers properties and their relationship with the ultimate performance of the final device is also outlined. The most relevant applications of amperometric biosensors based on electropolymerised films to real samples analysis are also reviewed and some possible future trends highlighted.

Animals↗

PubMedDate not supplied

Characterization of implantable biosensor membrane biofouling.

The material-tissue interaction that results from sensor implantation is one of the major obstacles in developing viable, long-term implantable biosensors. Strategies useful for the characterization and modification of sensor biocompatibility are widely scattered in the literature, and there are many peripheral studies from which useful information can be gleaned. The current paper reviews strategies suitable for addressing biofouling, one aspect of biosensor biocompatibility. Specifically, this paper addresses the effect of membrane biofouling on sensor sensitivity from the standpoint of glucose transport limitations. Part I discusses the in vivo and in vitro methods used to characterize biofouling and the effects of biofouling on sensor performance, while Part II presents techniques intended to improve biosensor biocompatibility.

Biocompatible Materials↗

PubMed2003

Presence of N-acyl homoserine lactones in soil detected by a whole-cell biosensor and flow cytometry.

Quorum sensing enables bacteria to regulate expression of certain genes according to population density. N-acyl homoserine lactone (AHL)-based quorum sensing is known to be widespread among gram-negative bacteria. Several bacterial whole-cell biosensors for AHL detection have been developed and some were used in in situ studies of AHL production. From these studies our knowledge of the significance of quorum sensing in various environments has been improved. However, very little is known about production of AHLs in soil environments. In the present study, an approach for detecting AHL production in bulk soil was developed. A whole-cell biosensor based on the regulatory region of the lux-operon from Vibrio fischeri fused to gfp was constructed, resulting in a luxR-PluxI-gfpmut3*-fusion in the high copy plasmid, pAHL-GFP. Escherichia coli MC4100 harboring pAHL-GFP responded to the AHL-compound N-octanoyl homoserine lactone (OHL) by expressing green fluorescence. In situ application of E. coli MC4100/pAHL-GFP was tested by adding OHL in different concentrations to sterile soil microcosms. E. coli MC4100/pAHL-GFP were incubated in the soil microcosms and extracted by an improved Nycodenz-extraction method optimized for flow cytometry. The presence of induced cells was then verified by single-cell analysis by flow cytometry. OHL concentrations between 0.5 and 50 nmol per g soil were detected. When introducing the AHL-producing Serratia liquefaciens to soil microcosms, expression of green fluorescent protein was induced in E. coli MC4100/pAHL-GFP. Thereby, the ability of this strain to detect excretion of AHLs by S. liquefaciens in sterile soil was shown. The use of an improved extraction method and a whole-cell biosensor combined with flow cytometry analysis proved to be promising tools in future studies of AHL production by microbial populations in soil environments.

4-Butyrolactone↗

PubMed2005

Application of cyanide hydrolase from Klebsiella sp. in a biosensor system for the detection of low-level cyanide.

A partially purified preparation of cyanide hydrolase (cyanidase) from a bacterium, Klebsiella sp., was applied as a biocatalyst in a biosensor system for low-level cyanide detection. In the biosensor system cyanide hydrolase converts cyanide into formate and ammonia. The formate produced in the cyanide degradation was detected with a formate biosensor, in which formate dehydrogenase (FDH; E.C. 1.2.1.2) was co-immobilized with salicylate hydroxylase (SHL; E.C. 1.14.13.1) on a Clark electrode. The principle of the formate sensor is that FDH converts formate into carbon dioxide using beta-nicotinamide adenine dinucleotide hydrate (NAD(+)). The corresponding NADH produced is then oxidized to NAD(+) by SHL using salicylate and oxygen. The oxygen consumption is monitored with the Clark electrode. The optimum buffer pH and temperature for the enzymatic hydrolysis of potassium cyanide were studied. The preliminary experiments including the pretreatment of cyanide with cyanide hydrolase and then detection by the formate sensor gave a detection limit at 7.3 micromol l(-1) cyanide. The linear range of the calibration curve was between 30 micromol l(-1) and 300 micromol l(-1) cyanide.

Ammonia↗

PubMed2005

Development of a biosensor for measuring plasma fibrinogen based on an enzyme kinetic model.

A biosensor has been designed for measuring plasma fibrinogen concentrations based on an enzyme kinetic model. The values obtained correspond linearly to those of a clinical method but have a higher sensitivity within the normal range of fibrinogen. By using the disposable biosensor technology, this method is easy to follow, quick (within 2 min) and precise (with coefficients of variation to be as low as below 5%) and requires only a small amount of plasma sample (<50 microl). This biosensor technology also holds potential for use in point-of-care diagnostics.

Animals↗

PubMed2006

Electrochemically platinized carbon paste enzyme electrodes: a new design of amperometric glucose biosensors.

A platinized carbon paste prepared via electrodeposition had a preferential electrocatalytic action toward H(2)O(2). Therefore, we have developed a new amperometric glucose biosensor based on the immobilization of glucose oxidase on to the electrochemically platinized carbon paste. The proposed biosensor is free of potential interferences due to its cathodic detection of glucose at the potential of 0.0 V (vs. Ag/AgCl). It also shows acceptable analytical performance in terms of linearity (6 x 10(-5)to 1.2 x 10(-2)M, r = 0.998), detection limit (2 x 10(-5)M), response time (20-30 s), reproducibility (RSD = 4.4%), and storage life (t(0.80) = 45 days). All these advantages of the biosensor raise potential possibilities for its medical or other biotechnical applications.

Biosensing Techniques↗

PubMed1994

Real-time-analysis of the calcium-dependent interaction between calmodulin and a synthetic oligopeptide of calcineurin by a surface plasmon resonance biosensor.

The calcium-dependent interaction between calmodulin (CaM) and the synthetic oligopeptide of a predicted CaM-binding region of human calcineurin A-2 was analysed with an automated surface plasmon resonance biosensor, BIAcore. The oligopeptide was immobilized to a biosensor chip via the amino-terminal cysteine residue by a thiol-disulphide exchange method. The biosensor chip was regenerated by an EGTA-containing buffer after each analysis. Kinetics experiments showed that CaM bound with a high affinity to the oligopeptide in a Ca(2+)-dependent manner. The estimated rate constants of association (kass) and dissociation (kdiss) were 2.3 x 10(5) M-1.s-1 and 3.9 x 10(-3)s-1, respectively. The ratio of kdiss/kass, 1.7 x 10(-8) M, was in good agreement with the dissociation constant (Kd) of 2.4 x 10(-8) M determined from the equilibrium phase.

Amino Acid Sequence↗

PubMed1994

Affinity ranking of influenza neuraminidase mutants with monoclonal antibodies using an optical biosensor. Comparison with ELISA and slot blot assays.

A recently developed alternative to the more traditional techniques for studying antigen-antibody interactions has been examined. This method involves the use of an optical biosensor employing surface plasmon resonance detection. In this system one of the reactants is immobilized on the sensor surface and other reactants are passed over the sensor surface sequentially at a constant flow rate. Binding phenomena are detected in real time from changes in the angle at which surface plasmon resonance occurs. This is dependent, among other things, on changes in the refractive index (which is directly proportional to the mass) at or near to the sensor surface. Applications of this biosensor technique for comparing the binding of related neuraminidases, purified from escape mutants of influenza virus NWS/G70C/75 (N9), to two antibody Fab fragments, are described. These results were compared with those obtained from ELISA and slot blot assays on the same neuraminidases interacting with the same two monoclonal antibodies. The biosensor method was shown to be highly specific, permitting rapid screening of binding in such antigen-antibody systems.

Antibodies, Monoclonal↗

PubMedDate not supplied

Medical and surgical applications of space biosensor technology.

Researchers in space life sciences are rapidly approaching a technology impasse. Many of the critical questions on the impact of spaceflight on living systems simply cannot be answered with the limited available technologies. Research subjects, particularly small animal models like the rat, must be allowed to function relatively untended and unrestrained for long periods to fully reflect the impact of microgravity and spaceflight on their behavior and physiology. These requirements preclude the use of present hard-wired instrumentation techniques and limited data acquisition systems. Implantable sensors and miniaturized biotelemetry are the only means of capturing the fundamental and critical data. This same biosensor and biotelemetry technology has direct application to Earth-based medicine and surgery. Continuous, on-line data acquisition and improved measurement capabilities combined with the ease and flexibility offered by automated, wireless, and portable instruments and data systems, should provide a boon to the health care industry. Playing a key role in this technology revolution is the Sensors 2000! (S2K!) Program at NASA Ames Research Center. S2K!, in collaboration with space life sciences researchers and managers, provides an integrated capability for sensor technology development and applications, including advanced biosensor technology development, spaceflight hardware development, and technology transfer and commercialization. S2K! is presently collaborating on several spaceflight projects with dual-use medical applications. One prime example is a collaboration with the Fetal Treatment Center (FTC) at the University of California at San Francisco. The goal is to develop and apply implantable chemical sensor and biotelemetry technology to continuously monitor fetal patients during extra-uterine surgery, replacement into the womb, through birth and beyond. Once validated for ground use, the method will be transitioned to spaceflight applications to remotely monitor key biochemical parameters in flight animals. Successful application of NASA implantable biosensor and biotelemetry technologies should accelerate the advancement of this and other modern medical procedures while furthering the exploration of life in space.

Aerospace Medicine↗

PubMed1994

Highly stable first-generation biosensor for glucose utilizing latex particles as the enzyme-immobilizing matrix.

The ability of polystyrene latex beads to immobilize glucose oxidase was applied to construct a stable biosensor for glucose. This biosensor measures glucose by detecting the hydrogen peroxide produced by the enzyme. The biosensor performance was studied by amperometry. Glucose concentrations ranging from 1 to 50mM can be measured with this sensor. The sensor is active over a broad range of pH and is very stable, which makes it suitable for a number of possible applications.

Biosensing Techniques↗

PubMed1988

The nature of biosensor technology.

The biosensor exploits the unique specificity of biological recognition events by coupling an enzyme, antibody or other biorecognition species to a transducing device. Interaction of the biocomponent with substrate or antigen is thus converted into a suitable quantitative output. The development of these biosensors is a multidisciplinary effort, exploiting many of the emerging semiconductor and optics technologies and integrating many traditional assay techniques. The impact of these biosensors is likely to be wide-ranging, with applications in medical and industrial environments as well as a variety of other fields.

Biological Assay↗

PubMed1990

In vivo voltammetry with micro-biosensors for analysis of neurotransmitter release and metabolism.

In vivo voltammetry involves the electrochemical detection of central oxidisable substances in situ. In association with this technique micro carbon fibre electrodes (CFE) are able to separate ascorbic acid (Peak 1) from 3,4-dihydroxyphenylacetic acid (DOPAC) plus dopamine (DA) (Peak 2) and 5-hydroxyindoleacetic acid (5-HIAAA) plus serotonin (5-HT) (Peak 3) in vitro. In vivo these biosensors detect the amine metabolites, due to their high extracellular concentration (microM) compared to the amines (nM). In addition homovanillic acid (HVA) (or 3-methoxytyramine (3-MT) in pargyline-pretreated mice) (Peak 4) and somatostatin (Peak 5) were also measured in vivo. However, potassium-stimulated release of DA has been directly monitored in pargyline pretreated mice. In addition, low concentrations (nM) of DA and 5-HT can now be selectively monitored in vitro with new biosensors coated with Nafion which repels negatively charged species including acid metabolites. In vivo, the combination of the Nafion-CFE and normal CFE allowed simultaneous measurements of release and metabolism of 5-HT, respectively. This permitted the observation that changes in 5-HT release are not necessarily reflected by changes in 5-HIAA levels. At present we are developing a Nafion biosensor to monitor basal extracellular DA. Electron microscope studies have shown radical modifications in the surface and structure of carbon fibres following chemical and electrical pretreatments, which may be involved in the development of sensitivity and selectivity displayed by the pretreated CFE towards electroactive compounds. A new approach for selective detection of neuroamines is the analysis of their stimulated fluorescence using LASER. In vitro, the fluorescence of 5-HT is in fact clearly distinguishable from that of 5-HIAA. The feasibility of this methodology in vivo using fiber optic probes will be explored.

Animals↗

PubMed1990

Flow injection analysis and biosensors: applications for biotechnology and environmental control.

Our experience in industrial bioprocess monitoring and environmental control let us develop a concept for biosensor research which distinguishes itself from other, more popular, approaches. Biosensors must improve and/or simplify existing state-of-the-art analysis systems. Only the parallel development of biosensors and their complementary metrology leads to industrially sound solutions. The combination of flow injection analysis with immobilized enzymes in the form of enzyme columns is already used today for the solution of on-line analytical problems in bioprocesses and environmental control.

Biosensing Techniques↗

PubMed1996

Analysis of kinetic data of antibody-antigen interaction from an optical biosensor by exponential curve fitting.

An optical biosensor system employing a resonant mirror (RM), with a stirred cuvette has been used to follow the interaction of a recombinant antibody fragment with its antigen, hen egg lysozyme. The data generated by the biosensor were analysed in order to determine the kinetic constants for the interaction using a linear transform (derivative analysis). For comparison the data were also analysed using an exponential curve fitting routine. It was demonstrated that the exponential curve fitting method produced results which were in agreement with the existing linear transform method. It was also shown that early fitting of the association phase response, using the exponential curve fitting routine between 0 and 70 s after sample addition, yielded sufficient information to provide a prediction of Kon. The potential use of the optical biosensor for the rapid monitoring of protein production and purification is discussed.

Animals↗

PubMed1996

An analysis of antigen-antibody binding kinetics for biosensor applications utilized as a model system: influence of non-specific binding.

The influence of non-specific binding on the specific binding of antigen in solution to antibody immobilized on a biosensor surface is presented for first-, one and a half-, second-, and other order reactions occurring under external diffusion-limited conditions. Both single-step and dual-step binding of antigen to antibody is considered. For a half-order reaction the value of the ratio of non-specific binding to specific binding (alpha) does not affect the rate of specific binding since a single curve represents the binding curve for alpha = 0 to 0.5. An increase in the alpha value leads to a decrease in the rate of binding and in the amount of antigen bound specifically to the antibody on the surface for first-, one and a half-, and second-order reactions. Also, an increase in the reaction order increases the sensitivity of the specific binding to the alpha value. An increase in the antigen concentration in solution increases the amount and the rate of specific binding for first-, one and a half-, and second-order reactions. The introduction of non-specific binding leads to complexities in the specific binding of the antigen for the one and half- and second-order reactions as the antibody concentration on the surface is varied. When non-specific binding is present there is an optimum value of the antibody concentration on the surface that yields the maximum rate and amount of antigen specifically bound for one and a half- and second-order reactions. Though this optimum amount of antibody immobilized on the surface is the same for the one and a half- and second-order reactions, it is different for different alpha values. No such complexities are observed for first-order reactions. The inclusion of non-specific binding in the analysis provides a more realistic picture of the binding of the antigen in solution to the antibody immobilized on the surface. The figures that show the numerically calculated binding rates for different orders when non-specific binding is present, represent the most useful part of the analysis for readers who are interested in constructing biosensors, and should assist in the control and manipulation of these interactions at the surface. These curves can be used to interpret a far from ideal binding of antigen to an immobilized antibody surface or vice versa. More-or-less all of the analysis should also be applicable to analytical systems that would not be classified as biosensors (that is, immuno and receptor assays).

Antibodies↗

PubMed1996

Toxicity order of cholanic acids using an immobilised cell biosensor.

There is considerable published evidence of the use of cells of various species to evaluate the toxicity of numerous compounds, many of pharmaceutical interest. The coupling of cell colonies with a suitable transduction device has led to the development in recent years of toxicity biosensors based on the alteration of a process or a cell metabolic function by the toxic substance under examination. A biosensor based on immobilised yeast cells (Saccharomyces cerevisiae) has been developed recently in this department for the purpose of performing a rapid toxicity test in aqueous environmental matrices. This biosensor has now been used in the toxicity screening of a number of sodium salts of conjugated and free cholanic acids. The "toxicity degree" scale, which was found by placing in decreasing order the values of the slopes of the straight lines obtained by quantifying changes in the behaviour of the respirometric curve, plotted before and after incubation, using known concentrations of cholanic acid sodium salts, was: deoxycholic acid > chenodeoxycholic acid > ursodeoxycholic acid > cholic acid, for free cholanic acids; and glycodeoxycholic acid > glycochenodeoxycholic acid > glycocholic acid, for glycocholanic acids. These values are in good agreement with published toxicity data obtained in vitro. This sensor can thus be considered to provide a valid instrument for the preliminary evaluation of the toxicity of organic compounds or drugs.

Biosensing Techniques↗

PubMed1991

A microbial biosensor for trimethylamine using Pseudomonas aminovorans cells.

A biosensor system based on the difference in the oxygen uptake response of two microbial electrodes was developed to monitor trimethylamine (TMA). The first electrode, constructed using Pseudomonas aminovorans grown on TMA, was sensitive to TMA, trimethylamine N-oxide (TMAO), dimethylamine (DMA) and monomethylamine (MMA). The second electrode responding to TMAO, DMA and MMA was prepared using Ps. aminovorans grown on TMAO. The difference in oxygen uptake was linearly related to the TMA concentration in the range of 5-26 microM. The minimum detectable level was 2.6 microM and the relative standard deviation was determined to be 14% for 16 repeated analyses. When operated and stored at 30 degrees C, the response of the system was stable for only 2 days. However, when the biosensor system was operated at 30 degrees C but stored overnight at 4 degrees C, the system was stable up to 20 days. The biosensor system was applicable for the determination of TMA in fish tissue extracts and the results compared well with those determined by HPLC.

Animals↗