Combined Dielectrophoresis and Impedance Systems for Bacteria Analysis in Microfluidic On-Chip Platforms.

Bacteria concentration and detection is time-consuming in regular microbiology procedures aimed to facilitate the detection and analysis of these cells at very low concentrations. Traditional methods are effective but often require several days to complete. This scenario results in low bioanalytical and diagnostic methodologies with associated increased costs and complexity. In recent years, the exploitation of the intrinsic electrical properties of cells has emerged as an appealing alternative approach for concentrating and detecting bacteria. The combination of dielectrophoresis (DEP) and impedance analysis (IA) in microfluidic on-chip platforms could be key to develop rapid, accurate, portable, simple-to-use and cost-effective microfluidic devices with a promising impact in medicine, public health, agricultural, food control and environmental areas. The present document reviews recent DEP and IA combined approaches and the latest relevant improvements focusing on bacteria concentration and detection, including selectivity, sensitivity, detection time, and conductivity variation enhancements. Furthermore, this review analyses future trends and challenges which need to be addressed in order to successfully commercialize these platforms resulting in an adequate social return of public-funded investments.

Dielectrophoretic concentrator enhancement based on dielectric poles for continuously flowing samples.

We describe a novel continuous-flow cell concentrator microdevice based on dielectrophoresis, and its associated custom-made control unit. The performances of a classical interdigitated metal electrode-based dielectrophoresis microfluidic device and this enhanced version, that includes insulator-based pole structures, were compared using the same setup. Escherichia coli samples were concentrated at several continuous flows and the device's trapping efficiencies were evaluated by exhaustive cell counts. Our results show that pole structures enhance the retention up to 12.6%, obtaining significant differences for flow rates up to 20 µL/min, when compared to an equivalent classical interdigitated electrodes setup. In addition, we performed a subsequent proteomic analysis to evaluate the viability of the biological samples after the long exposure to the actuating electrical field. No Escherichia coli protein alteration in any of the two systems was observed.

Combined dielectrophoretic and impedance system for on-chip controlled bacteria concentration: Application to Escherichia coli.

The present paper reports a bacteria autonomous controlled concentrator prototype with a user-friendly interface for bench-top applications. It is based on a microfluidic lab-on-a-chip and its associated custom instrumentation, which consists of a dielectrophoretic actuator, to preconcentrate the sample, and an impedance analyzer, to measure concentrated bacteria levels. The system is composed of a single microfluidic chamber with interdigitated electrodes and an instrumentation with custom electronics. The prototype is supported by a real-time platform connected to a remote computer, which automatically controls the system and displays impedance data used to monitor the status of bacteria accumulation on-chip. The system automates the whole concentrating operation. Performance has been studied for controlled volumes of Escherichia coli samples injected into the microfluidic chip at constant flow rate of 10 µL/min. A media conductivity correcting protocol has been developed, as the preliminary results showed distortion of the impedance analyzer measurement produced by bacterial media conductivity variations through time. With the correcting protocol, the measured impedance values were related to the quantity of bacteria concentrated with a correlation of 0.988 and a coefficient of variation of 3.1%. Feasibility of E. coli on-chip automated concentration, using the miniaturized system, has been demonstrated. Furthermore, the impedance monitoring protocol had been adjusted and optimized, to handle changes in the electrical properties of the bacteria media over time.

Symptoms of anxiety on both sides of the US-Mexico border: the role of immigration.

Home to about 15 million people, the US-Mexico border area has suffered stresses from increased border security efforts and a costly drug war in Mexico. Whether immigration patterns add to increasing levels of anxiety for the Mexican population and the Mexican-origin individuals living in the US-Mexico border and near the border is unknown. We used the US-Mexico Study on Alcohol and Related Conditions (UMSARC), a cross-sectional survey (2011-2013) of individuals living in border and non-border cities of the US (n = 2336) and Mexico (n = 2460). In Mexico respondents were asked if they ever migrated to the US or have a family member living in the US (328) or not (2124), while in the US respondents were asked if they were born in Mexico (697), born in the US with no US-born parents (second generation, 702) or born in the US with at least one US-born parent (third generation, 932). The prevalence and risk factors for symptoms of anxiety using the Beck Anxiety Inventory (>=10) were obtained. Mexicans with no migrant experience had a prevalence of anxiety and adjusted prevalence ratio (PR) within the last month of 6.7% (PR = reference), followed by Mexicans with migration experience of 13.1% (PR = 1.8), Mexican-born respondents living in the US of 17.3% (PR = 2.6), US born Mexican-Americans of 2nd generation of 18.6% (PR = 3.3) and finally US born 3rd + generation of 25.9% (PR = 3.8). Results help to identify regions and migration patterns at high risk for anxiety and may help to unravel causal mechanisms that underlie this risk.

[Acute suppurative thyroiditis. Report of a pediatric case]. / Tiroiditis aguda supurada en un paciente pediátrico.

Acute suppurative thyroiditis (AST) is an uncommon condition because thyroid gland is remarkably resistant to infections. In children, anatomic defects such as a left pyriform sinus fistula or a thyroglossal duct remnant predispose to this infection. Once the diagnosis is confirmed by ultrasound or computed tomography, antimicrobial therapy based on the culture and Gram staining must be started. After two or three weeks of treatment, predisposing anatomic defects must be sought cautiously. We report a 13 year old girl presenting with cervical pain and fever. A cervical ultrasound showed an enlarged thyroid lobule with hypoecogenic zones that suggested a supurative collection. Cefotaxime and cloxacillin were started. A needle aspiration of the collection obtained a purulent material. The culture of this material yielded a Streptococcus Pneumoniae. The clinical condition of the patient improved and she was discharged in good conditions. Two months later a contrast esophagus X ray did not show predisposing anatomic defects.