Microfluidic-based Bacterial Molecular Computing on a Chip

Biocomputing systems based on engineered bacteria can lead to novel tools for environmental monitoring and detection of metabolic diseases. In this paper, we propose a Bacterial Molecular Computing on a Chip (BMCoC) using microfluidic and electrochemical sensing technologies. The computing can be flexibly integrated into the chip, but we focus on engineered bacterial AND Boolean logic gate and ON-OFF switch sensors that produces secondary signals to change the pH and dissolved oxygen concentrations. We present a prototype with experimental results that shows the electrochemical sensors can detect small pH and dissolved oxygen concentration changes created by the engineered bacterial populations’ molecular signals. Additionally, we present a theoretical model analysis of the BMCoC computation reliability when subjected to unwanted effects, i.e., molecular signal delays and noise, and electrochemical sensors threshold settings that are based on either standard or blind detectors. Our numerical analysis found that the variations in the production delay and the molecular output signal concentration can impact on the computation reliability for the AND logic gate and ON-OFF switch. The molecular communications of synthetic engineered cells for logic gates integrated with sensing systems can lead to a new breed of biochips that can be used for numerous diagnostic applications

Characteristics of Irish child sexual abuse victims attending a specialist centre

The present study aimed to build on the findings of other Irish studies by profiling a cohort of cases in which CSA had occurred or where there was a high probability that it had occurred on a wider range of variables than used in previous studies. Of particular interest was the status of the cohort on variables in the following domains: circumstances of referral, demographic characteristics, family adversity, characteristics of abusive experiences, perpetrator characteristics, strategies to achieve compliance and factors hindering disclosure, emotional and behavioural problems before and after disclosure, and factors supporting credibility of allegations. We also wished to examine the associations between variables in these domains

Portable Data Acquisition System for Nano and Ultra-Micro Scale Electrochemical Sensors

This work describes a flexible and portable data acquisition system that has been developed to interface to nano and ultra-micro scale electrochemical sensors at the point of use. It can perform a range of voltammetric tests, including Cyclic Voltammetry, Square Wave Voltammetry and Generator Collector Voltammetery. The data acquisition system interfaces to a smartphone, operates from a rechargeable battery and is of suitable form factor to ensure that it’s fully portable. By utilising commercially available components, this system has been developed to lower the barrier for entry for the development of emerging portable electrochemical sensing technologies at micro and nano scale. To show the full range of functionality of the system, a use case involving river water quality monitoring is presented through generation of a calibration curve, using a recently developed Tyndall National Institute ultra-microband electrochemical sensor, for the detection of dissolved oxygen in river water

Platinum Interdigitated Electrode Arrays for Reagent-Free Detection of Copper

Water is a precious resource that is under threat from a number of pressures, including release of toxic compounds that can have damaging effect on ecology and human health. The current methods of water quality monitoring are based on sample collection and analysis at dedicated laboratories. This can provide an incomplete picture of the status of the water body as pollution events can be missed. Recently, electrochemical based methods have attracted a lot of attention for environmental sensing owing to their versatility, sensitivity and compatible integration with cost effective, smart and portable readout systems. In the present work, we report on the fabrication and characterization of platinum interdigitated microband electrodes arrays, and their application for trace detection of copper. Using square wave voltammetry after acidification with mineral acids, a limit of detection of 0.8 μg/L was achieved. Copper detection was also under taken on river water samples and compared with standard analytical techniques. The possibility of controlling the pH at the surface of the sensors – thereby avoiding the necessity to add mineral acids – was investigated. By applying potentials driving the water splitting reaction at one comb on the sensors electrode (the protonator), it was possible to lower the pH in the vicinity of the sensing electrode. Detection of standard copper solutions down to 5 μg/L using this technique is reported. This reagent free method of detection opens the way for autonomous, in situ monitoring of pollutants in water bodies.</p

Madden, Julia; O\u27Mahony, Conor; Thompson, Michael; O\u27Riordan, Alan; Galvin, Paul

This article explores recent advances in the development of electrochemical biosensors on microneedle platforms towards on-device sensing of biomarkers present in dermal interstitial fluid. The integration of a biosensor with a microneedle platform opens the possibility for minimally invasive bio-chemical detection or continuous monitoring within the dermal interstitial fluid. An introduction to interstitial fluid is provided placing emphasis on sampling methods that have been employed to extract and/or sample tissue fluid for analysis. We look briefly at microneedle technologies used to extract dermal interstitial fluid for subsequent analysis. Successive content will focus on microneedle technologies which have been integrated with electrochemical biosensors for the quantification of various metabolites, electrolytes and other miscellaneous entities known to be present in the dermal interstitial fluid. The review concludes with some of the key challenges and opportunities faced by this next-generation wearable sensing technology

Elimination of Oxygen Interference in the Electrochemical Detection of Monochloramine, Using In-Situ pH Control at Interdigitated Electrodes

Disinfection by chloramination of water systems is an alternative to chlorination that is frequently used in North America. In such a case, monochloramine is used as the primary source of chlorine for disinfection. Regular monitoring of the residual concentrations of this species is crucial to ensure adequate disinfection. An amperometric sensor for monochloramine would provide fast, reagent free analysis, however the presence of dissolved oxygen in water complicates sensor development. In this work, we have explored the use of in-situ pH control as a method of eliminating oxygen as an interferent by conversion of monochloramine to dichloramine. The electrochemical reduction of dichloramine occurs outside the oxygen reduction window and is therefore not affected by oxygen concentration. Potential sweep methods were used to investigate the conversion of monochloramine to dichloramine at pH 3. The pH control method was used to calibrate monochloramine concentrations between 1 and 10 ppm, with a detection limit of 0.03 ppm. Tests were carried out in high alkalinity samples, wherein it was found that the sensitivity of this method effectively remained unchanged. Monochloramine was also quantified in the presence of common interferents (copper, phosphate and iron) which had no significant impact on the analysi

Electrochemical Detection of Free-Chlorine in Water Samples Facilitated by In-Situ pH Control Using Interdigitated Microelectrodes

Residual free-chlorine concentration in water supplies is a key metric studied to ensure disinfection. High residual chlorine concentrations lead to unpleasant odours and tastes, while low concentrations may lead to inadequate disinfection. The concentration is most commonly monitored using colorimetric techniques which require additional reagents. Electrochemical analysis offers the possibility for in-line analysis without the need for additional reagents. Electrochemical-based detection of chlorine is influenced by the solution pH, which defines the particular chlorine ionic species present in solution. As such, controlling the pH is essential to enable electrochemical based detection of residual chlorine in water. To this end, we explore the application of solid state interdigitated electrodes to tailor the in-situ pH of a solution while simultaneously detecting free-chlorine. Finite element simulations and subsequent electrochemical characterization, using gold interdigitated microelectrode arrays, were employed to explore the feasibility of an in-situ pH control approach. In practice, the approach converted residual chlorine from an initial mixture of two species (hypochlorous acid and hypochlorite ion), to one species (hypochlorous acid). Chlorine detection was shown in water samples using this exploratory method, resulting in a two-fold increase in signal response, compared to measurements without pH control. Finally, tap water samples were measured using the in-situ pH control method and the results showed excellent correlation (within experimental error) with a commercial instrument, demonstrating the efficacy of the developed technique. This work establishes the possibility of deploying an electrochemical based reagent-free, in-line chlorine sensor required for water distribution networks

Electrochemical-Based Serological Detection of Bovine Immunoglobulin G in Calves

Bovine antibodies, such as immunoglobulin G (IgG), cannot pass the placental barrier and as such are not transferred from the mother to the foetus, in utero. Instead a calf must absorb antibodies following ingestion of colostrum postpartum. Failure of Passive Transfer (FPT) is a condition that predisposes calves to development of disease and increases the risk of mortality. Thus, continuous early monitoring of IgG absorption in a calf, within the first 24 hours of life, is imperative to allow faster treatment and prevent FPT. In this paper, we present the development of a label-free impedimetric immunosensor device for bovine IgG in serum and demonstrate its suitability to determine early FPT in new-born calves. The developed sensors were challenged to discriminate between new born calf sera, both pre- and post-colostrum feeding, and demonstrated efficent detection of IgG in under 15 minutes. Such a device could enable rapid determination of FPT, thereby improving calves’ vitality and survival rat

Simultaneous Detection of Copper, Lead and Mercury in River Water with In-Situ pH Control Using Electrochemical Stripping Techniques

ABSTRACT: An electrochemical sensor for the detection of lead, mercury and copper in neutral solutions is described. The electrode is made of two distinct parallel gold interdigitated microband electrodes that can be polarized separately. Biasing one electrode “protonator” sufficiently positive to begin water electrolysis, results in the production of H+ ions which consequently drops the pH in the locality around the other second interdigitated “sensing” electrode. This decrease in pH permits the electodeposition (and consequent stripping) of metals at the sensing electrode without the need to acidify the whole test solution. In this work, the local pH can be adjusted from 1 to 7 in a stable and reproducible way by tailoring the applied potential to the protonator electrode. Using this approach, linear ranges for lead 10-100 ppb, copper 5-100 ppb and mercury 1-75 ppb, respectively were demonstrated which exhibit extremely high sensitivity. This technique allowed detection of these metals in a complex water matrix (river water) without sample pretreatment, with excellent results. The electrode reproducibility is high (RSD < 10%) and the metals can be co-detected when present all together. This is the first demonstration of the in-situ pH control for heavy metal detection using solid state sensors and will unable real time and in situ analysis of heavy metals by unskilled personnel in remote settings. </p

Near-infrared electroluminescent devices based on colloidal HgTe quantum dot arrays

Crystalline 4.6 nm HgTe quantum dots, stabilized by 1-thioglycerol ligands, were synthesized by wet chemical methods. Room-temperature photoluminescencespectra of the dots, both in solution and as solid arrays, exhibited near-infrared emission. Light-emitting devices were fabricated by deposition of quantum dot layers onto glass∕indium tin oxide (ITO)∕3,4-polyethylene-dioxythiophene-polystyrene sulfonate (PEDOT) substrates followed by top contacting with evaporated aluminum. Room-temperature near-infraredelectroluminescence from 1mm2 ITO∕PEDOT∕HgTe∕Al devices, centered at ∼1600nm, with an external quantum efficiency of 0.02% and brightness of 150nW/mm2 at 50 mA and 2.5 V was achieved