Sensitive Monitoring of Enterobacterial Contamination of Food Using Self-Propelled Janus Microsensors.

Food poisoning caused by bacteria is a major cause of disease and death worldwide. Herein we describe the use of Janus micromotors as mobile sensors for the detection of toxins released by enterobacteria as indicators of food contamination. The micromotors are prepared by a Pickering emulsion approach and rely on the simultaneous encapsulation of platinum nanoparticles for enhanced bubble-propulsion and receptor-functionalized quantum dots (QDs) for selective binding with the 3-deoxy-d-manno-oct-2-ulosonic acid target in the endotoxin molecule. Lipopolysaccharides (LPS) from Salmonella enterica were used as target endotoxins, which upon interaction with the QDs induce a rapid quenching of the native fluorescence of the micromotors in a concentration-dependent manner. The micromotor assay can readily detect concentrations as low as 0.07 ng mL-1 of endotoxin, which is far below the level considered toxic to humans (275 µg mL-1). Micromotors have been successfully applied for the detection of Salmonella toxin in food samples in 15 min compared with several hours required by the existing Gold Standard method. Such ultrafast and reliable approach holds considerable promise for food contamination screening while awaiting the results of bacterial cultures in a myriad of food safety and security defense applications.

Tailored magnetic carbon allotrope catalytic micromotors for 'on-chip' operations.

Carbon allotrope micromotors are proposed as active components in lab-on-a-chip systems. Highly rough carbon black tubular engines are used for fluorescence detection operations. The potential of ultrafast lectin carbon nanonotube micromotors with an inner anti-biofouling layer for selective transport of sugar modified particles (as cell mimics) in human plasma is illustrated.

Ultrafast Nanocrystals Decorated Micromotors for On-Site Dynamic Chemical Processes.

CdS-polyaniline-Pt and ZnS-polyaniline-Pt micromotors have been synthesized and characterized. The nanocrystals are generated "in situ" during the template electrosynthesis of the micromotors while being simultaneously trapped in the polymeric network, generating a hybrid structure. The presence of nanocrystal "edges" in the inner polyaniline layer result in a rough Pt catalytic surface and enhanced electron transfer for highly efficient bubble propulsion at remarkable speeds of over 2500 µm/s. The incorporation of CdS and ZnS nanocrystals impart several attractive functions, including cation-exchange based chemical transformation capabilities and enhanced photocatalytic performance. The remarkable ion-exchange properties of ZnS-polyaniline (PANI)-Pt micromotors are illustrated for the cation exchange of heavy metals cations. The superior photocatalytic performance of CdS-PANI-Pt micromotors is used for the enhanced photocatalytic oxidation of bisphenol A. Such self-propelled micromotors act as highly efficient dynamic platforms that offer significantly shorter and more efficient processes as compared with common static operations. The attractive properties of these micromotors will pave the way for diverse sensing, decontamination, energy generation, or electronic applications.

Labs-on-a-chip meet self-propelled micromotors.

This frontier review covers recent advances in the field of nanomaterial-based micromotors for the development of novel labs-on-a-chip (LOCs). In this review, we will discuss how carbon nanomaterials "on-board" of micromotors offer particular promise for diverse LOC applications. New trends in the field, directed towards the use of quantum dots and nanoparticles as functional materials for sophisticated micromotors, will be reviewed. Micromotor strategies using functionalized catalytic microengines to capture and transport (bio)molecules between the different reservoirs of LOC devices will also be covered. These recent advances are bringing closer our hopes for personalized medicine and food safety assurance, among others.

"Shoot and Sense" Janus Micromotors-Based Strategy for the Simultaneous Degradation and Detection of Persistent Organic Pollutants in Food and Biological Samples.

A novel Janus micromotor-based strategy for the direct determination of diphenyl phthalate (DPP) in food and biological samples is presented. Mg/Au Janus micromotors are employed as novel analytical platforms for the degradation of the non-electroactive DPP into phenol, which is directly measured by difference pulse voltammetry on disposable screen-printed electrodes. The self-movement of the micromotors along the samples result in the generation of hydrogen microbubbles and hydroxyl ions for DPP degradation. The increased fluid transport improves dramatically the analytical signal, increasing the sensitivity while lowering the detection potential. The method has been successfully applied to the direct analysis of DPP in selected food and biological samples, without any sample treatment and avoiding any potential contamination from laboratory equipment. The developed approach is fast (∼5 min) and accurate with recoveries of ∼100%. In addition, efficient propulsion of multiple Mg/Au micromotors in complex samples has also been demonstrated. The advantages of the micromotors-assisted technology, i.e., disposability, portability, and the possibility to carry out multiple analysis simultaneously, hold considerable promise for its application in food and biological control in analytical applications with high significance.

Lighting up micromotors with quantum dots for smart chemical sensing.

A new "on-the-fly" chemical optical detection strategy based on the incorporation of fluorescence CdTe quantum dots (QDs) on the surface of self-propelled tubular micromotors is presented. The motion-accelerated binding of trace Hg to the QDs selectively quenches the fluorescence emission and leads to an effective discrimination between different mercury species and other co-existing ions.

Multiplexed immunoassay based on micromotors and microscale tags.

This work reports on the coupling of antibody-functionalized micromotors and microwire-tagged proteins for rapid and multiplexed immunoassays. While micromotor-induced mixing accelerates the immunoreaction, tagging the proteins with microscopic particles of different sizes and shapes allows for their multiplexed discrimination, alerting of the presence of a biological threat.

Fast and reliable class-selective isoflavone index determination on carbon nanotube press-transferred electrodes using microfluidic chips.

Single-walled carbon nanotube press-transferred electrodes (SWPTEs) are new disposable electrodes where carbon nanotubes act as exclusive electrochemical transducers, being an excellent alternative to common approaches in the field. In the current work, these pioneering SWPTEs coupled to microfluidic chips (MCs) have been employed to develop their first real application. A class-selective electrochemical isoflavone index determination has been proposed for fast and reliable qualitative and quantitative assessment of class-isoflavones based on the co-migration of the total glycosides (TG) and total aglycones (TA) in less than 250 s with very good intra-SWPTE repeatability (RSDs ≤ 8%, n = 5) and inter-SWPTE reproducibility (RSDs ≤ 9%, n = 3). These novel SWPTEs are entering with important roles into the micro and nanotechnology scenes expanding new frontiers in the food analysis and health field.

Design of a composite amperometric enzyme electrode for the control of the benzoic acid content in food.

A graphite-Teflon-tyrosinase composite biosensor for the determination of benzoic acid in foodstuffs is reported. The biosensor functioning is based on the inhibition effect of benzoic acid on the biocatalytic activity of the enzyme in a reversed micelle working medium formed with ethyl acetate as the continuous phase, a 0.05 moll(-1) phosphate buffer solution of pH 7.4 (5%) as the aqueous dispersed phase, and 0.10 moll(-1) dioctyl sulfosuccinate (AOT) as the emulsifying agent. A potential value of -0.10 V, and a constant enzyme-substrate (phenol) concentration of 2.0x10(-4) moll(-1) were selected to carry out the amperometric inhibition measurements. The tyrosinase inhibition process by benzoic acid is reversible and of the competitive type, with an apparent inhibition constant of 0.016 mmoll(-1). The composite bioelectrodes allow the regeneration of the electrode surface by polishing and exhibit long-term operation and stability. A limit of detection of 9.0x10(-7) moll(-1) benzoic acid was obtained. An interference study from other substances which can be found in foodstuffs together with benzoic acid was performed. Taking advantage of the capabilities of reversed micelles as universal solubilization media, the composite tyrosinase electrode was used for the determination of benzoic acid in two different kind of samples: mayonnaise sauce, which is a highly hydrophobic matrix, and Cola soft drinks, a hydrophilic matrix for which practically no sample treatment is necessary.

Electrochemical enzyme immunoassays on microchip platforms.

A microfluidic device for conducting electrochemical enzyme immunoassays is described. The new "lab-on-a-chip" protocol integrates precolumn reactions of alkaline phosphatase-labeled antibody (anti-mouse IgG) with the antigen (mouse IgG), followed by electrophoretic separation of the free antibody and antibody-antigen complex. The separation is followed by a postcolumn reaction of the enzyme tracer with the 4-aminophenyl phosphate substrate and a downstream amperometric detection of the liberated 4-aminophenol product Factors influencing the reaction, separation, and detection processes were optimized, and the analytical performance was characterized. An applied field strength of 256 V/cm results in free antibody and antibody-antigen complex migration times of 125 and 340 s, respectively. A remarkably low detection limit of 2.5 x 10(-16) g/mL (1.7 x 10(-18) M) is obtained for the mouse IgG model analyte. Such combination of a complete integrated immunoassay, an attractive analytical performance, and the distinct miniaturization/portability advantages of electrochemical microsystems offers considerable promise for designing self-contained and disposable chips for decentralized clinical diagnostics or on-site environmental testing.

Optimization strategy and validation of one chromatographic method as approach to determine the phenolic compounds from different sources.

We have designed a novel working strategy to optimize a unique chromatographic method consisting of diode array detection for the analysis of the most representative phenolic compounds from different food sources. The simultaneous inclusion of standard phenolic compounds, phenolic compounds isolated from food sources and representative real extracts as an ultimate test in analysis has allowed to establish, for the first time, a unique liquid gradient to serve as an excellent medium for the investigation of phenolics in samples from different food sources. Under the optimized conditions, 21 commercially available phenolic compounds and 25 commercially unavailable phenolic structures were analyzed in less than 30 min. The chromatographic method was designed as an alternative for the provisional identification of these compounds before their full characterization. The optimized chromatographic method was carefully validated for precision and accuracy. A high reproducibility in the retention time (<2%), peak area and calibration slope (<5%) as well as recoveries higher than 95% were obtained in all cases. Consequently, the currently described method was successfully employed to study the phenolic compounds in the most representative food samples.

Fast separation of (poly)phenolic compounds from apples and pears by high-performance liquid chromatography with diode-array detection.

Polyphenolic compounds in apples and pears were analysed by HPLC on C18-modified silica. Gradient elution with phosphoric acid-methanol mixtures and phosphoric acid-acetonitrile mixtures gave complete separation of all polyphenolics of interest. The use of methanol as modifier was preferred because it provides a more rapid separation (20 min). Diode-array detection was used for the provisional identification of polyphenolic compounds not available as standards.

High-performance liquid chromatography with diode-array detection for the determination of phenolic compounds in peel and pulp from different apple varieties.

Quantitative analysis of phenolic compounds from four apple varieties (Golden and Red Delicious, Granny Smith and Green Reineta) using high-performance liquid chromatography with diode-array detection was carried out. For each variety, both peel and pulp were analysed. The identification of phenolic compounds was made by comparing their retention times and UV spectra with those of standards. The results revealed differences between pulp and peel in all cases studied. The highest levels of phenolic compounds were found in the peel. High levels of catechins and flavonol glycosides, especially rutin, were found in apple peels. Chlorogenic acid was the major peak in the pulp for all apple varieties studied except for Granny Smith. Significant quantitative differences between the apple varieties were also found, the Golden Delicious variety showing the lowest content of phenolic compounds and Green Reineta variety the highest. The recovery of phenolic compounds from both peel and pulp was measured in all apple varieties. The values ranged between 95 and 105%, indicating close to quantitative recovery for the method used.

[Oral premedication with clonidine in patients undergoing coronary revascularization surgery]. / Premedicación oral con clonidina en enfermos sometidos a cirugía de revascularización coronaria.

OBJECTIVES: To analyze the effect of premedication with clonidine on level of sedation, anesthetic requirements and hemodynamic repercussions in patients undergoing coronary revascularization. PATIENTS AND METHODS: Thirty patients were divided into two groups and randomly assigned for premedication with clonidine 0.005 mg/kg p.o. (C) or lorazepam 0.03 mg/kg p.o. (L), along with morphine 0.15 mg/kg i.m. and scopolamine 0.005 mg/kg i.m. in a prospective double-blind study. The level of sedation before surgery and anesthetic requirements in the two groups were compared, as were systolic and diastolic arterial pressure, heart rate and hemodynamics during and after surgery. Fentanyl was used for anesthetic induction in boluses of 0.15 mg every 10 seconds; maintenance boluses of 0.5 mg were used up to a maximum dose of 0.07 mg/kg. If hemodynamic variables analyzed (systolic and diastolic arterial pressure and heart rate) were not kept within 30% of baseline values with this regimen, isoflurane was added. RESULTS: No differences between the two groups were found for level of sedation. The total dose of fentanyl was lower in group C (0.052 +/- 0.002 mg/kg vs 0.058 +/- 0.002 mg/kg) (p < 0.05). The number of patients requiring isoflurane was similar (4/11 and 6/9) in both groups. The hemodynamic profile prior to extracorporeal circulation (ECC) revealed arterial pressures and heart rates to be lower in the group treated with clonidine (p < 0.05); after ECC systemic resistance in group C was lower (630 +/- 103 vs 795 +/- 106 din.s.cm-5) (p < 0.05) and this was not compensated for by a significant rise in cardiac index (2.62 +/- 0.09 vs 2.40 +/- 0.08 l/min/m2) at similar occlusion pressures. CONCLUSIONS: Use of clonidine in the type of patient studied does not improve the level of sedation over that achieved with lorazepam. Fentanyl requirements decreased with clonidine. With respect to hemodynamic profile, systemic vascular resistance fell in the clonidine group after removal of ECC, and thus this drug offers no advantages for routine premedication.

[Peroperative management of the orthotopic implant of a Jarvik-7 total cardiac prosthesis]. / Manejo peroperatorio del implante ortotópico de una prótesis cardíaca total modelo Jarvik-7.

A 31 years old woman with a terminal phase dilated cardiomyopathy and a ventricular ejection fraction of 0.12 was admitted to our hospital to be included in the cardiac transplantation program. When entering the hospital her condition worsened and she suffered an electromechanical dissociation that needed cardiopulmonary resuscitation. Few hours later, energetic medical treatment could not improve her haemodynamic situation. Having no adequate organ available for emergency transplantation, a total orthotopic prosthesis (Jarvik-7-70) implantation was decided. Anesthesia was maintained with fentanyl (50 micrograms/kg), droperidol (0.23 mg/kg) and diazepam (0.25 mg/kg). There were no incidents during or after extracorporeal circulation bypass; despite the use of furosemide (100 mg) and mannitol (1 g/kg) diuresis was less than 40 ml/h. After by-pass, pulmonary hypertension was observed and treated with sodium nitroprusside (1 microgram/kg/min) and isoproterenol (5 micrograms/kg/min), as well as increasing the right ventricle working pressure of the device from 40 to 70 mmHg, obtaining haemodynamic stabilization and good tissular perfusion. After operation, the patient arrived to the Recovery Unit in a steady situation, with a cardiac index of 2.87 l/min/m2 and a diuresis of 150 ml/h. Some other aspects of the anaesthetic management are also discussed in this paper.

Ventilatory depression during and after infusion of alfentanil in man.

Sixteen fit young patients undergoing body surface surgery received an infusion of alfentanil 50 or 100 micrograms kg-1 h-1 to supplement nitrous oxide anaesthesia. The alfentanil infusion was continued for 2 h after operation at the slower rate of 20 micrograms kg-1 h-1. The intraoperative infusions provided satisfactory conditions for anaesthesia. The infusion after operation provided adequate analgesia at a cost of depression of carbon dioxide responsiveness to 50% of its value before operation, but only moderate effects on minute volume and PaCO2. Plasma alfentanil concentration during the postoperative infusion was 108 +/- 37 ng ml-1 (mean +/- SD).