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Detecting and identifying pathogen bacteria is essential to ensure quality at all stages of the food chain and to diagnose and control microbial infections. Traditional detection methods, including those based on cell culturing, are tedious and time-consuming, and their further application in real samples generally implies more complex pretreatment steps. Even though state-of-the-art techniques for detecting microorganisms enable the quantification of very low concentrations of bacteria, to date it has been difficult to obtain successful results in real samples in a simple, reliable, and rapid manner. In this Article, we demonstrate that the label-free detection and identification of living bacteria in real samples can be carried out in a couple of minutes and in a direct, simple, and selective way at concentration levels as low as 6 colony forming units/mL (CFU) in complex matrices such as milk or 26 CFU/mL in apple juice where the pretreatment step of samples is extremely easy. We chose Escherichia coli ( E. coli ) CECT 675 cells as a model organism as a nonpathogenic surrogate for pathogenic E. coli O157:H7 to test the effectiveness of a potentiometric aptamer-based biosensor. This biosensor uses single-walled carbon nanotubes (SWCNT) as excellent ion-to-electron transducers and covalently immobilized aptamers as biorecognition elements. The selective aptamer-target interaction significantly changes the electrical potential, thus allowing for both interspecies and interstrain selectivity and enabling the direct detection of the target. This technique is therefore a powerful tool for the immediate identification and detection of microorganisms. We demonstrate the highly selective detection of living bacteria with an immediate linear response of up to 10(4) CFU/mL. The biosensor can be easily built and used, is regenerated without difficulty, and can be used at least five times with no loss in the minimum amount of detected bacteria.

We present an active null test system adapted to test lenses and wavefronts with complex shapes and strong local deformations. This system provides greater flexibility than conventional static null tests that match only a precisely positioned, individual wavefront. The system is based on a cylindrical Shack-Hartmann wavefront sensor, a commercial liquid crystal programmable phase modulator (PPM), which acts as the active null corrector, enabling the compensation of large strokes with high fidelity in a single iteration, and a spatial filter to remove unmodulated light when steep phase changes are compensated. We have evaluated the PPM's phase response at 635 nm and checked its performance by measuring its capability to generate different amounts of defocus aberration, finding root mean squared errors below λ/18 for spherical wavefronts with peak-to-valley heights of up to 78.7λ, which stands as the limit from which diffractive artifacts created by the PPM have been found to be critical under no spatial filtering. Results of a null test for a complex lens (an ophthalmic customized progressive addition lens) are presented and discussed.

A new reduced-size solid-state electrode using carbon nanotubes as the transducing layer has been developed for the direct determination of Ca(2+) in sap, overcoming problems encountered by commercial ISEs analysing real complex samples. We show that this solid-contact ISE, which can be easily miniaturized, can be used directly in diluted real samples without any other pretreatment. The performance parameters of the new ISE include a Nernstian slope and excellent stability, good coefficients of selectivity, range of linearity (10(-5) to 10(-2.5) M) and limit of detection (10(-6.2) M), thus making it an excellent tool for determining Ca(2+) in a wide range of plant species.

We describe in detail the different steps involved in the construction of a carbon nanotube field-effect transistor (CNTFET) based on a network of single-walled carbon nanotubes (SWCNTs), which can selectively detect human immunoglobulin G (HIgG). HIgG antibodies, which are strongly adsorbed onto the walls of the SWCNTs, are the basic elements of the recognition layer. The nonspecific binding of proteins or other interferences are avoided by covering the nonadsorbed areas of the SWCNTs with Tween 20. The CNTFET is a reagentless device that does not need labels to detect HIgG.

A solid contact ion-selective electrode using for the first time multi-walled carbon nanotubes (MWCNT) for the transducer material was developed for detecting perchlorate in water. To demonstrate the excellent ion-to electron transducer ability of the MWCNTs, a 15 microm thick layer of carboxylated MWCNT was deposited between an acrylic membrane selective to perchlorate ions and a glassy carbon rod used as the substrate and electrical conductor. The electrodes showed a Nernstian response of 57 mV decade(-1) (standard deviation of 3 mV decade(-1) over time and different electrodes) across a wide linear range of 10(-6) to 10(-2) M. The limit of detection was 10(-7.4) M of perchlorate. The response time was less than 10 s for activities higher than 10(-6) M and the intermediate-term potential stability shows a small drift of 0.22 mV h(-1) recorded over 5 hours. The electrode displays a selectivity comparable to liquid-contacted ISEs containing the same membrane.

Flow cytometry has become a valuable tool in food microbiology. By analysing large numbers of cells individually using light-scattering and fluorescence measurements, this technique reveals both cellular characteristics and the levels of cellular components. Flow cytometry has been developed to rapidly enumerate microorganisms; to distinguish between viable, metabolically active and dead cells, which is of great importance in food development and food spoilage; and to detect specific pathogenic microorganisms by conjugating antibodies with fluorochromes, which is of great use in the food industry. In addition, high-speed multiparametric data acquisition, analysis and cell sorting, which allow other characteristics of individual cells to be studied, have increased the interest of food microbiologists in this technique. This mini-review gives an overview of the principles of flow cytometry and examples of the application of this technique in the food industry.

In this paper we report a biosensor for the fast, ultrasensitive and selective determination of bisphenol A in water. It is based on a field effect transistor (FET) in which a network of single-walled carbon nanotubes (SWCNTs) acts as the conductor channel. SWCNTs are functionalized for the first time with a nuclear receptor, the estrogen receptor alpha (ER-alpha), which is adsorbed onto the SWCNTs and acts as the sensing part of the biosensor. SWCTNs are subsequently protected to prevent the non-specific binding of interferences. With this biosensor we can detect picomolar concentrations of BPA in only 2 min of analysis. Selectivity has been tested against possible interferences such as fluoranthene, pentacloronitrobenzene and malathion, and this is the first device that experimentally shows that small molecules can also be selectively detected at ultralow concentrations using a CNTFET biosensor.

We report a field effect transistor (FET) based on a network of single-walled carbon nanotubes (SWCNTs) which can selectively detect human immunoglobulin G (HIgG). HIgG antibodies, which are strongly adsorbed onto the walls of the SWCNTs, are the basic elements of the recognition layer. The non-specific binding of proteins and the effects of other interferences are avoided by covering the non-adsorbed areas of the SWCNTs with Tween 20. The selectivity of the sensor has been tested against bovine serum albumin (BSA), the most abundant protein in plasma. HIgG in aqueous solution with concentrations from 1.25 mg L(-1) (8 nM) can be readily detected with response times of about 10 min. The SWCNT networks that form the basis of the sensor are easily grown by chemical vapour deposition. Silver screen-printed electrodes make the sensor quick to build. The sensitivity obtained with this sensor is similar to other FET devices based on SWCNTs built using much more complicated lithography processes. Moreover, the sensor is a reagentless device that does not need labels to detect HIgG.

We report a new type of ion-sensitive field effect transistor (ISFET). This type of ISFET incorporates a new architecture, containing a network of single-walled carbon nanotubes (SWCNTs) as the transduction layer, making an external reference electrode unnecessary. To show an example of its application, the SWCNT-based ISFET is able to detect at least 10(-8) M of potassium in water using an ion-selective membrane containing valinomycin.

Gas detection is important for controlling industrial and vehicle emissions, household security and environmental monitoring. In recent decades many devices have been developed for detecting CO(2), CO, SO(2), O(2), O(3), H(2), Ar, N(2), NH(3), H(2)O and several organic vapours. However, the low selectivity or the high operation temperatures required when most gas sensors are used have prompted the study of new materials and the new properties that come about from using traditional materials in a nanostructured mode. In this paper, we have reviewed the main research studies that have been made of gas sensors that use nanomaterials. The main quality characteristics of these new sensing devices have enabled us to make a critical review of the possible advantages and drawbacks of these nanostructured material-based sensors.

We describe how to calculate uncertainty in the determination of aflatoxin B(1) in nuts and maize using an HPLC method with prederivatisation with trifluoroacetic acid and fluorescence detection. The uncertainty is easily calculated using the information obtained from the participation in several proficiency tests. All the sources of uncertainty are grouped in two terms: (1) matrix variability, intermediate precision and sample heterogeneity, and (2) method concordance. This methodology has the advantage that no extra work needs to be done because all the information to calculate uncertainty comes from proficiency tests. The uncertainty values were calculated using samples whose concentration ranged between 2 and 20 microg L(-1). The relative standard uncertainty computed for aflatoxin B(1) was 16.3%.

The trueness of an analytical method can be assessed by calculating the proportional bias of the method in terms of apparent recovery. If the apparent recovery does not differ significantly from one, the analytical method has not a significant bias. If this is the case, the bias is neglected and the uncertainty associated with this bias is included in the uncertainty budget of results. However, when assessing trueness there is always a probability of incorrectly concluding that the proportional bias is not significant. Therefore, the uncertainty of results may be underestimated. In this paper, we study how non-significant bias affects the uncertainty of analytical results. Moreover, we study how to avoid the underestimation of uncertainty by including the non-significant bias calculated in the uncertainty budget. To answer these questions, we have used the Monte-Carlo method to simulate the process of estimating the apparent recovery of a biased analytical method and, subsequently, the future results this method provides. The results of the simulation show that non-significant bias may underestimate the uncertainty of analytical results when bias contributes in more than 20% to the overall uncertainty. Uncertainty is specially underestimated when bias contributes in more than 50% to the overall uncertainty.

Abstract Methods that quickly assess microbial density and aggregation in soil and sediments are needed in environmental microbiology. We report a flow cytometry method that uses the green and orange emission of the fluorochrome SYTO-13 to discriminate between bacteria and clay-humic acid particles. This approach distinguishes single or clustered bacteria, and clusters of bacteria and abiotic particles during the growth of the biosurfactant-producing strain Pseudomonas aeruginosa 19SJ on solid phenanthrene in the presence of humic acid-clay complexes.

A flow cytometric protocol to detect and enumerate heterotrophic nanoflagellates (HNF) in enriched waters is reported. At present, the cytometric protocols that allow accurate quantification of bacterioplankton cannot be used to quantify protozoa for the following reasons: i) the background produced by the bacterial acquisitions does not allow the discrimination of protozoa at low abundance, ii) since the final protozoan fluorescence is much higher than the bacterioplankton fluorescence (more than 35 fold) the protozoa acquisitions lie outside the range. With an increase in the fluorescence threshold and a reduction of the fluorescence detector voltage, low fluorescence particles (bacteria) are beneath the detection limits and only higher fluorescence particles (most of them heterotrophic nanoflagellates) are detected. The main limitation for the application of the cytometric protocol developed is that a ratio of bacteria/HNF below 1000 is needed. At higher ratios, the background of larger cells of bacterioplankton makes it difficult to discriminate protozoa. The proposed protocol has been validated by epifluorescence microscopy analyzing both a mixed community and two single species of HFN: Rhynchomonas nasuta and Jakoba libera. Taking into account the required bacteria/HNF ratio cited above, the results provide evidence that the flow cytometric protocol reported here is valid for counting mixed communities of HNF in enriched seawater and in experimental micro or mesocosms. In the case of single species of HNF previous knowledge of the biological characteristics of the protist and how they can affect the effectiveness of the flow cytometric count is necessary.

We developed a robust regression technique that is a generalization of the least median of squares (LMS) technique to the field in which the errors in both the predictor and the response variables are taken into account. This simple generalization is limited in the sense that the resulting straight line is found by using only two points from the initial data set. In this way a simulation step is added by using the Monte Carlo method to generate the best robust regression line. We call this new technique 'bivariate least median of squares' (BLMS), following the notation of the LMS method. We checked the robustness of the new regression technique by calculating its breakdown point, which was 50%. This confirms the robustness of the BLMS regression line. In order to show its applicability to the chemical field we tested it on simulated data sets and real data sets with outliers. The BLMS robust regression line was not affected by many types of outlying points in the data sets.

A cost-effective strategy combining chemical analysis and bioassays for the identification of polar toxic compounds in sewage sludge is reported. ToxAlert 100 bioluminescence inhibition assay was used in combination with chemical analysis involving extraction, clean-up, chromatographic separation and mass spectrometry detection. This methodology was applied to real samples of sludge from three wastewater treatment plants (WWTP) located in Catalonia (Spain) during a 3 month period. In the first step, sewage sludge was lyophilized, treated by sonication with a mixture of methanol and chloroform and finally cleaned up using a sequential solid phase extraction (SSPE) with an octadecylsilica cartridge (C18) in series with a polymeric Lichrolut EN cartridge (Lic EN). In the second step, the toxicity of each fraction of the sludge sample was investigated using the ToxAlert 100. The unequivocal identification and quantification of polar organic cytotoxic substances present in the fractionated extracts were determined by liquid chromatography-mass spectrometry (LC-MS). Major toxic compounds identified were: non-ionic polyethoxylated surfactants (nonylphenol polyethoxylates, alcohol polyethoxylates), their intermediates (polyethylene glycol polyethoxylated, nonylphenol carboxylates and polyethoxylated alcohol carboxylates), linear alkylbenzenesulfonates and heavy metals. The toxic response (in terms of bioluminescence inhibition using ToxAlert 100), defined by the 50% effective concentration (EC50), and the toxicity units (TU) for every standard non-ionic surfactant were calculated. The results provided the identification of polar cytotoxic compounds as well as the evaluation of their contribution to the total toxicity observed in sewage sludge.

The present work describes the development and optimization of a capillary (zone) electrophoresis/mass spectrometric (CE/MS) analysis method for polar hydrophilic aromatic sulfonates (ASs). The compounds were detected by negative ion electrospray ionization (NIESI) and selected ion monitoring (SIM). In comparison with CE/UV, for CE/MS a lower-concentration volatile ammonium acetate buffer (5 mM) without organic modifier and a higher separation voltage were better suited for separation. Sensitivity of CE/MS was slightly better than for CF/UV, with the limit of detection (LOD) ranging between 0.1 and 0.4 mg l(-1). For verification of the CE/MS results, ASs were also analysed by ion-pair liquid chromatography/diode array UV detection coupled in series with electrospray mass spectrometry (IPC/DAD/ESI-MS). Real water samples of different waste water treatment plants (WWTPs) in Catalonia (NE Spain) were extracted by solid-phase extraction (SPE) with LiChrolut EN and analysed with CE/MS and LC/MS. ASs were found in influent and effluent water samples of the WWTPs in the microg l(-1) concentration range. LC/MS offered a higher separation efficiency and sensitivity than CE/MS. Therefore with LC/MS more compounds could be identified in the WWTPs. The persistency of the ASs was distinct: some compounds were well degraded during the water treatment process, while others were quite persistent.

Assessment of cell viability using methods which do not require cell culture is essential in the field of aquatic microbiology, since many bacteria known to be present in aquatic environments cannot be grown in culture. The study of bacterial biofilms, which previously needed an epifluorescent microscope, has recently been enhanced by the use of flow cytometry and confocal scanning laser microscopy (CSLM). A method based on the combination of several membrane potential related dyes, a membrane integrity dye and a redox probe was used to measure cell viability by flow cytometry and confocal laser microscopy. Rhodamine-propidium iodide (PI) double staining was used to discriminate viable from nonviable cells in CSLM observations. Membrane depolarization during E. coli and Salmonella starvation measured by DiBAC4(3) incorporation (flow cytometry and CSLM) was found to be in concordance with respiratory activity as detected by a tetrazolium salt (CTC) reduction.

Assessment of myocardial viability is a field of growing interest. This article summarizes the pathophysiology of myocardial stunning and hibernation; both phenomena are associated with the presence of dysfunctional, viable myocardium. The techniques that are currently available for the assessment of viability, and the clinical situations in which these assessments may be more useful are discussed.

In this paper, a new technique for assessing the accuracy of analytical methods using linear regression is reported. The results of newly developed analytical methods are regressed against the results obtained using reference methods. The new test is based on the joint confidence interval for the slope and the intercept of the regression line, which is calculated taking the uncertainties in both axes into account. The slope, intercept, and variances which are associated with the regression coefficients are calculated with bivariate least-squares regression (BLS). The new technique was validated using three simulated and five real data sets. The Monte Carlo method was applied to obtain 100 000 data sets for each of the initial simulated data sets to show the correctness of the new technique. The application of the new technique to five real data sets enables differences to be detected between the results of the joint confidence interval based on the BLS method and the results of the commonly used tests based on ordinary least-squares or weighted least-squares regression.

A 66-year-old woman with a previous history of chronic lung disease, without evidence of heart disease and without signs of left ventricular hypertrophy developed a dynamic intraventricular obstruction documented by a Doppler-derived gradient of 25 mmHg and by physical signs consisting of a brisk carotid pulse and a harsh systolic murmur while she was on treatment with theophylline and hexoprenaline. Both physical signs and Doppler-derived gradient disappeared after withdrawal of bronchodilator drugs.

Cholesterol embolism is a rare but serious complication of heart catheterization. We report a patient in whom cholesterol embolization syndrome developed after coronary angioplasty complicated by an acute myocardial infarction which was treated with streptokinase and heparin. The clinical outcome was satisfactory. Cholesterol embolism occurrence might have been precipitated in this patient by thrombolytic and anticoagulant therapy.

The propafenone kinetics after intravenous (i.v.) administration have been studied in the horse by a comparative analysis of compartmental and noncompartmental models. The pharmacokinetic parameters showed a large distribution (Vdss = 1021 +/- 211 L) and a high clearance (CI = 7019 +/- 1746 mL/min) of the drug. The plasma concentrations were very low, under 1 microgram/mL, in most cases; after 30 min these concentrations can be considered as nonefficient for the treatment of arrhythmia. There were no significant differences between pharmacokinetic parameters found with the use of compartmental and noncompartmental models.