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PubMedDate not supplied

Biosensor immunoassay of ivermectin in bovine milk.

A rapid and sensitive biosensor immunoassay was developed for determination of ivermectin residues in bovine milk. A detection limit of 16.2 ng/mL was achieved. A Biacore optical biosensor based on surface plasmon resonance was used, and a range of extraction techniques was investigated. In the final assay procedure, ivermectin was extracted with acetonitrile followed by C8 solid-phase extraction cleanup. It was proven experimentally that 2 methods of milk storage, freezing or addition of mercury-containing compounds as preservatives, could be used without considerable change in detected concentrations (samples were fortified with ivermectin after storage). The average values for milk samples spiked at 100 and 50 ng/mL concentrations were 102.6 and 51.5 ng/mL, respectively. Extraction and analysis of 20 milk samples were performed within a single working day.

Animals↗
PubMedDate not supplied

Interference-free biosensor based on screen-printing technology and sol-gel immobilization for determination of acetaldehyde in wine.

A monoenzymatic amperometric biosensor was developed for the detection of acetaldehyde. The sensor is based on the association of screen-printed carbon electrodes and aldehyde dehydrogenase immobilized by a sol-gel entrapment method. Modification of screen-printed carbon electrodes with Reinecke salt of Meldola's Blue (MBRS) resulted in highly sensitive and interference-free nicotinamide-adenine dinucleotide (NADH) detectors. Based on MBRS-mediated oxidation of NADH at -150 mV versus pseudo Ag/AgCl, acetaldehyde was determined in the range 10-260 microM, compatible with wine quality monitoring. The method of immobilization based on sol-gel entrapment was optimized to obtain the best compromise between sensitivity and operational stability. The sensor response was stable for 40 consecutive assays with methyltrimethoxysilane used as alkoxide precursor, thus allowing a possible calibration of the sensor before each measurement. The biosensors were used to analyze French wines. The method was validated with a commercially available enzymatic kit based on a standard spectrophotometric method.

Acetaldehyde↗
PubMed2002

The use of biosensors to study GPCR function: applications for high-content screening.

Plasma membrane-associated G protein-coupled receptors (GPCRs) initiate the transmission of multiple intracellular signals leading to a myriad of physiological and pathophysiological effects. The downstream signaling events associated with occupation of the GPCR and activation of the G-protein include the generation of numerous second messenger molecules to provide the necessary signal amplification within the appropriate intracellular compartment to transmit a specific signal from the cell surface to the cell interior. The complex process of signal transmission also requires a series of highly orchestrated events which includes the translocation of cellular proteins to discreet intracellular destinations. A better understanding of these events has made it possible to design assays to examine multiple endpoints within whole cells. In this review we describe recent advances in assay biology and instrumentation useful for broadening our understanding of the molecular events associated with GPCR activation. This review will focus on novel cell-based approaches using fluorescent biosensors, such as fluorescent dyes and fluorescent protein tags, to generate information-rich data from multiple cellular targets--a process that has been referred to as high-content screening. High-content screening applications will be discussed as they pertain to specific signal transduction cascades initiated upon GPCR activation and examples of specific biosensors will be provided.

Animals↗
PubMed2003

The mitochondria from beef heart as biosensors for the selective monitoring of phenols.

We propose a simple and rapid procedure which allows for the selective monitoring in solution of toxic compounds which behave as uncouplers of the oxidative phosphorylation. Since all phenols, are uncouplers of the oxidative phosphorylation, the procedure allows for the selective monitoring in solution of phenols even in presence of other toxic compounds. The biological sensor are the mitochondria from beef heart. This biosensor is easily available without a stabular and therefore the biosensor and the whole procedure is very simple and not expensive. By linear regression analysis, it results that the procedure well predicts the response of the standard fish method to phenols. Therefore the procedure can be utilized as prescreening analysis for the monitoring the phenols in aqueous samples.

Animals↗
PubMedDate not supplied

[Analysis of specific nucleotide sequences. DNA biosensors].

Information about common molecular-biological approaches for the determination of the specific nucleotide sequences in genetic materials was given in the review. Main attention was paid to consideration of the ways for DNA biosensor creation. The information about the types of such biosensors was presented in detail and characteristics of the developed devices were cited. Separately the question about the use of the instrumental analytical approaches for the identification of genetic materials of individual pathogenic microorganisms was viewed.

Animals↗
PubMed1992

[Development and application of biosensors for medical field].

Methods for the selective determination of organic compounds in biological fluids, such as blood, are very important in clinical analyses. Most analyses of organic compounds can be performed by spectrophotometric methods, based on specific enzyme-catalyzed reactions. However, because of the complicated procedure, these methods cannot be applied directly to bed-side monitoring. Alternatively, biosensors based on enzymes and electrochemical transducers possess excellent sensitivity for biological substrates and can determine a single compound in a biological fluid directly without need for a prior separation step. Therefore, in the past several years, many kinds of biosensors have been developed, and implantable microbiosensors for a body organ have also been reported.

Biomedical Engineering↗
PubMedDate not supplied

A cerebrospinal fluid glucose biosensor for diabetes mellitus.

A cerebrospinal fluid (CSF) glucose biosensor is introduced. The biosensor is a polarimeter that measures the rotation of plane polarized light proportional to glucose concentration. Preliminary in vitro studies revealed a linear response with good sensitivity over a range of glucose solutions (0-400 mg/dl). Anesthetized, adult dogs underwent intravenous glucose loading, and these preliminary in vivo studies resulted in good correlation (r = 0.98) between CSF polarimeter readings and CSF glucose by laboratory assay. This in vivo correlation suggests that both mutarotation of glucose anomer and changes from other optically active substances present in CSF are either negligible or constant over the range of glucose concentrations studied. The CSF polarimeter showed a significant rise soon after the intravenous loading of glucose (1-30 min) but a longer lag time (45-60 min) between the peak blood glucose and peak CSF polarimeter reading. This preliminary work extends, to the CSF, the concept of measuring optical rotation.

Animals↗
PubMed1992

[Biosensors and clinical analysis].

Method for the selective determination of organic compounds in biological fluids, such as blood, are very important in clinical analyses. Most analyses of organic compounds can be performed by spectrophotometric methods based on specific enzyme-catalyzed reactions. However, on account of the complicated procedure, these methods cannot be applied directly to bed-side monitoring. Alternatively, biosensors based on enzymes and electrochemical transducers possess excellent sensitivity for biological substrates and can determine directly a single compound in a biological fluid without need for a prior separation step. Therefore, in several years, many kinds of biosensors have been developed, and implantable microbiosensors for a body organ have also been reported. In the near future, an artificial pancreas fabricated by micromachine technology will be developed.

Biosensing Techniques↗
PubMedDate not supplied

[Study of immobilization and properties of urease for creation of a biosensor based on semiconductor structures].

Many-sided investigations of urease immobilization methods were carried out to create the biosensor devices on the base of semiconductor structures. Special attention was concentrated on the biomembrane formation by means of urease and bovine serum albumin (BSA) cross-linking by gaseous glutaraldehyde. Optimal conditions for the formation process were selected which preserve about 20% of total urease activity after the cross-linking. The properties of enzyme immobilized by the above-mentioned method have been comprehensively studied. They included the urease activity dependence on pH, ionic strength, incubation buffer capacity as well as the enzyme stability during its functioning, storing and thermoinactivation. As was shown, for immobilized ureas Km value for urea at pH 7.0 and 20 degrees C is 1.65 time less than for free enzyme. In the presence of EDTA (1 mM) the enzyme activity in the biomembrane is practically unchanged under a month storing. Biomembrane possesses good adhesion to silicon surface and its swelling level under different conditions does not exceed 35%. The conclusion is made about the prospects of the used method of biomembrane formation for biosensor technology based on semiconductor structures.

Enzyme Stability↗
PubMed2004

ADMET biosensors: up-to-date issues and strategies.

This insight review introduces the new concepts, theories, technology, instruments, frontier issues, and key strategies of ADMET (absorption, distribution, metabolism, elimination, and toxicity) biosensors, from the fermi to the quantum levels. Information about ADMET, originating from one author's invention, a patented pharmacotherapy for rescuing cardio-cerebral vascular stunning and regulating vascular endothelial growth-factor signaling at the post-genomic level, can be detected by a new generation of ADMET biosensor. This is a single-cell/single-molecule field-effect transistor (FET) hybrid system, where single molecules or single cells are assembled at the FET surface in a high density array manner via complementary metal-oxide-semiconductor (CMOS)-compatible technologies. Within a given nanometer distance, ADMET-mediated oxidation-reduction (redox) potentials, electrochemistry responses, and electron transfer processes can be simultaneously and directly probed by the gates of field-effect transistor arrays. The nanometer details of the functional coupling principles and characterization technologies of DNA single-molecule/single-cell FETs, as well as the design of lab-on-a-chip instruments, are indicated. Four frontier issues and key strategies are elucidated in detail. This can lead to innovative technology for high-throughout screening of labs-on-chips to resolve the pharmaceutical industry's current bottleneck via novel, FET-based drug discovery and single-molecule/single-cell screening methods, which can bring about a pharmaceutical industry revolution in the 21st century.

Animals↗
PubMed1992

Development of a non-invasive transcutaneous blood glucose monitoring method using an ISFET biosensor.

A transcutaneous blood glucose monitoring method has been developed by combining an SOS/ISFET (silicone-on-sapphire/ion sensitive field effect transistor) biosensor with an SEF (suction effusion fluid) collecting technique. The SEF collecting cell has a stainless steel mesh at its bottom which is kept in a weak vacuum condition so as to suck up transcutaneous SEF and deposit it in a reservoir above. An ISFET biosensor, consisting of immobilized enzyme membranes, enables the detection of glucose concentrations in very small samples. The method has been successfully applied to non-invasive monitoring of human blood glucose levels during tests involving 75 g OGTT (oral glucose tolerance test). Glucose concentrations measured with SEF showed good correlation with those obtained directly from serum. Results suggest the feasibility of a portable blood monitoring system.

Biosensing Techniques↗
PubMed2005

Development of an amperometric hypoxanthine biosensor for determination of hypoxanthine in fish and meat tissue.

A hypoxanthine (Hx) biosensor based on immobilized xanthine oxidase (XO) as the bio-component was developed and studied for the rapid analysis of fish (sweet water and marine) and goat meat samples. The biosensor was standardized for the determination of Hx in the range of 0.05 to 2 mM. Crosslinking with glutaraldehyde in presence of BSA as a spacer molecule was used for the method of immobilization. One layer of gelatin (10%) was applied over the immobilized enzyme layer to reduce the leaching out of enzyme from the membrane (cellulose acetate) matrix. The optimum pH of the immobilized system was determined to be 8.5 at 25 degrees C instead 7.0-7.2 for free enzyme system. Km and Vmax values were determined for the immobilized system. The developed sensor was applied to determine the amount of Hx present in fish and meat over a period of time. The stability of the enzyme immobilized membrane was also tested over a period of 30 days.

Animals↗
PubMed2002

[Fiber-optic biosensor].

Fiber-optic biosensor is now becoming a new research direction in biosensors. In recent 10 years it has got a compelling development and has been applied to medical pathogens, food toxicity, water pollution, biochemical weapons, fast detection for environmental samples, etc. In this paper its development is given out in detail.

Biosensing Techniques↗
PubMed2004

[Oriented immobilization of human IgG by protein A on imaging ellipsometry biosensor].

The biosensor based on optical imaging ellipsometry, can be used to detect directly, without labeling, the surface concentration of biomolecules on solid surface. The feasibility of using protein A to immobilize antibody on the silicon surface of the imaging ellipsometry biosensor was investigated in this study. The results showed that the anti-IgG immobilized by the protein A on silicon surface could bind effectively human IgG, and the human IgG immobilized on silicon surface by protein A bound more polyclonal antibody molecules than that immobilized on silicon surface directly, suggesting that protein A might block the surface to prevent the absorption of human IgG on surface directly, which might compromise its native configuration. The silicon surface modified with protein A is expected to be used to immobilize a variety of antibodies, as protein A can bind selectively the Fc regions of many mammalian IgG. The combination of imaging ellipsometry and the protein A surface modification has the potential to be developed into immunoassays of high sensitivity.

Biosensing Techniques↗
PubMedDate not supplied

Determination of pantothenic acid in foods by optical biosensor immunoassay.

An optical biosensor inhibition immunoassay was developed using a specific pantothenic acid-binding protein for the quantitation of free pantothenic acid (vitamin B5) in foodstuffs. Samples were prepared by a simple extraction procedure in buffer, and vitamin content was estimated against authentic calibrants in the same buffer. Performance parameters included a working range of 10-5000 ng/mL, a limit of detection of 4.4 ng/mL, precision relative standard deviation of 5.4-7.1% over a range of concentrations, and recoveries > 95% in the matrixes tested. A wide range of foodstuffs, including National Institute of Standards and Technology reference samples, were tested in 3 independent laboratories and the results were compared with microbiological assay and liquid chromatography/mass spectrometry (LC/MS) methods. The results indicate that the biosensor technique is appropriate for the estimation of pantothenic acid in a wide range of foodstuffs.

Biosensing Techniques↗
PubMedDate not supplied

[Optical biosensor study and molecular modeling of interactions between cytochrome P450cam and cytochrome b5].

The formation of complexes of cytochrome P450cam (P450cam) with full-length cytochrome b5 (d-b5) and its tryptic water-soluble fragment (t-b5) was analyzed using a two-channel IAsys+ optical biosensor. It was found that t-b5 can form complexes with P450cam, while d-b5 does not interact with P450cam. The involvement of amine groups of P450cam in the complex formation was demonstrated. The temperature dependence of t-b5(im)/P450cam complex formation was measured. The association rate constant (k(on)) increased with temperature, while the dissociation rate constant (k(off)) practically remained unchanged. It was concluded that hydrophobic interactions play a key role in the complex formation, while electrostatic interactions are significant for complex stabilization. Based on temperature dependence the activation energy, enthalpy and entropy of complex formation were calculated. It was shown that the entropy component plays a key role in t-b5(im)/P450cam interaction. Computer modeling of P450cam/t-b5 and P450cam/d-b5 interactions was carried out. Using the method of molecular docking some hypotheses of protein-protein complexes were advanced and the best ones were selected based on geometric complementarity, calculated binding energy and probability of electron tunneling between proteins. The computer modeling has shown that only P450cam and t-b5 can form the stable complex. These results are in good agreement with the experimental data obtained with the optical biosensor.

Amino Acid Sequence↗