Direct replacement of antibodies with molecularly imprinted polymer (MIP) nanoparticles in ELISA - development of a novel assay for vancomycin

A simple and straightforward technique for coating microplate wells with molecularly imprinted polymer nanoparticles (nanoMIPs) to develop ELISA type assays is presented here for the first time. NanoMIPs were synthesized by a solid phase approach with immobilized vancomycin (template) and characterized using Biacore 3000, dynamic light scattering and electron microscopy. Immobilization, blocking and washing conditions were optimized in microplate format. The detection of vancomycin was achieved in competitive binding experiments with a HRP-vancomycin conjugate. The assay was capable of measuring vancomycin in buffer and in blood plasma within the range 0.001-70 nM with a detection limit of 0.0025 nM (2.5 pM). The sensitivity of the assay was three orders of magnitude better than a previously described ELISA based on antibodies. In these experiments nanoMIPs have shown high affinity and minimal interference from blood plasma components. Immobilized nanoMIPs were stored for 1 month at room temperature without any detrimental effects to their binding properties. The high affinity of nanoMIPs and the lack of a requirement for cold chain logistics make them an attractive alternative to traditional antibodies used in ELIS

Early warning pollution detection device for application in water quality

It has been well recognised that water is a valuable resource and the quality of our water systems require sampling at a higher temporal and spatial frequency than is currently taking place. The AQUAWARN project aims to meet this challenge through the development of commercially competitive water quality monitoring devices. These will be capable of performing analytical measurements in situ - primarily aimed at freshwater and wastewater systems. The analytes of interest are mainly phosphate, nitrite, nitrate, and pH. The initial focus of this project is the assessment and optimisation of appropriate colorimetric chemistries for each sensing target. These chemistries have been developed and optimised using bench-top instrumentation. Integration within microfluidic chips followed to reduce the per sample costs. Microfluidic technology uses minute amounts of reagent per sample measurement, allowing for a dramatic increase in the number of potential assays per unit volume of reagent. Moreover, the integration of LEDs and photodiodes as light sources and detectors, coupled with syringe pumps, opens the way to new generations of low-cost, portable, and autonomous devices, capable of performing multiple in-situ measurements.  For example, an analysis requiring 50 uL of reagent implies 2,000 measurements are possible per 100 mL of reagent

Early warning device for detection of pollutants in water

Due to a growing need to protect water resources from contamination, there is a requirement for the development of more reliable and cost effective devices for water quality monitoring. The aim of the AQUAWARN project is to develop and deploy a fully autonomous water quality monitoring device that can measure nitrite, nitrate, phosphate and pH colorimetrically in fresh water and wastewater, and communicate the information to stakeholders in real time

Introducing MINA-The Molecularly Imprinted Nanoparticles Assay

A new ELISA‐ (enzyme‐linked immunosorbent assay)‐like assay is demonstrated in which no elements of biological origin are used for molecular recognition or signaling. Composite imprinted nanoparticles that contain a catalytic core and which are synthesized by using a solid‐phase approach can simultaneously act as recognition/signaling elements, and be used with minimal modifications to standard assay protocols. This assay provides a new route towards replacement of unstable biomolecules in immunoassays

A new LED-LED portable CO2 gas sensor based on an interchangeable membrane system for industrial applications

CO2 monitoring is important for many areas of high economic relevance, like environmental monitoring, control of biotechnological processes in bio-pharmaceutical industries, and the food industry, particularly controlled atmosphere storage rooms and modified atmosphere packaging [ ]. CO2 sensing is not a trivial area of research, as is testified by the increasing numbers of publications regarding this topic over the past decade. The main reason is that CO2 chemically is relatively unreactive, and therefore finding a mechanism for signal generation is difficult. Most publications are based on its well-known acidic properties. In this communication, we present a portable optical sensor for gaseous CO2 detection based on the phosphorescence intensity variation of a platinum octaethylporphyrin (PtOEP) complex trapped in oxygen-insensitive poly(vinylidene chloride-co-vinyl chloride) (PVCD) membranes. The sensing mechanism arises from the increasing displacement of the α-naphtholphthalein acid–base equilibrium with rising CO2 concentrations [ ]. The low-power LED-based optical sensing instrumentation for monitoring CO2 is based on a pair of light emitting diodes (LEDs) arranged to face each other, wherein one LED functions as the light source and the other LED is reverse biased to function as a light detector [ ]. A transparent polymer substrate coated on both sides with the CO2 sensitive membrane placed between the two LEDs serves as a chemically responsive filter between the light source and the detector

LED-LED portable oxygen gas sensor

A portable instrument for oxygen determination, based on the quenching of phosphorescent octaethylporphyrin by gaseous O2, has been developed using the fluorimetric paired emitter–detector diode technique (FPEDD). The instrument configuration used consists of two light emitting diodes (LEDs) facing each other including an interchangeable support containing a phosphorescent membrane in between, in which one of the LEDs is used as the light source (emitter LED) and the other working in reverse bias mode as the light detector. In this report, we study the feasibility of using a LED as a luminescent detector and realising a sensing instrument whose small size possibles to embed it into a portable measurement system. A complete study of instrument was carried out in order to optimise the specifications of the portable instrument such as: range, sensitivity, short term and long term stability, dynamical behaviour, temperature influence, humidity influence and temporal drift. Keywords: Oxygen sensor, Gas sensor, Optical sensor, Paired emitter detector-diode sensor; Portable instrumentation

Autonomous reagent-based microfluidic pH sensor platform

A portable sensor has been developed for in situ measurements of pH within aqueous environments. The sensor design incorporates microfluidic technology, allowing for the use of low volume of samples and reagents, and an integrated low cost detection system that uses a light emitting diode as light source and a photodiode as the detector. Different combination of dyes has been studied in order to allow for a broader pH detection range, than can be obtained using a single dye. The optimum pH range for this particular dye combination was found to be between pH 4 and pH 9. The reagents developed for pH measurement were first tested using bench-top instrumentation and once optimised, the selected formulation was then implemented in the microfluidic system. The prototype system has been characterised in terms of pH response, linear range, reproducibility and stability. Results obtained using the prototype system are in good agreement with those obtained using reference instrumentation, i.e. a glass electrode/pH meter and analysis via spectrophotometer based assays. The reagent (mixture #3) is shown to be stable for over 8 months, which is important for long term deployments. A high reproducibility is reported with a global RSD of ≤1.8% across measurements of 90 samples, i.e. with respect to concentrations reported by a calibrated pH meter. A series of real water samples from multiple sources were also analysed using the portable sensor system, of which the global error found was 3.84% showing its feasibility for real-world applications

Optical portable instrument for the determination of CO2 in indoor environments

A portable device based on a colorimetric sensor to determine the atmospheric level of CO2 gas is presented in this work. The system is based on a low-cost, low-power System on a Chip (SoC) microcontroller with integrated Wi-Fi. A user-friendly application was developed to monitor and log the CO2 measurements when the system is connected to a Wi-Fi network. The sensing membrane is directly deposited on the surface of the colour detector, thus reducing the complexity of the system. This sensing membrane is formed by a pH indicator α-naphtholphthalein, tetramethylammonium hydroxide pentahydrate, 1-ethyl-3-methylimidazolium tetrafluoroborate, Tween 20 and hydroxypropyl methylcellulose as the hydrophilic polymer. The system has been fully characterized, obtaining response and recovery times of 1.3 and 2.5 s, respectively, a limit of detection of 51 ppm, and an average resolution of 6.3 ppm. This portable device was applied for the in-situ determination of CO2 gas in the atmosphere inside classrooms in several secondary schools. The measurements were taken during complete workdays and the results were statistically compared with the same measurements taken using a commercially available non-dispersive infra-red (NDIR) device. No significant statistical differences were found between the results obtained using both devices. A complete statistical treatment of the measurements made with the proposed portable device was carried out. The obtained results show that the concentration of CO2 gas in some schools was higher than the desired concentration, with regard to influencing the student's health, safety, productivity and comfort. This demonstrates the need to control this parameter to ensure appropriate indoor environmental quality (IEQ)

Localization of CO2 leakage from transportation pipelines through low frequency acoustic emission detection

Carbon Capture and Storage is a technology to reduce greenhouse gas emissions. CO2 leak from high pressure CO2 transportation pipelines can pose a significant threat to the safety and health of the people living in the vicinity of the pipelines. This paper presents a technique for the efficient localization of CO2 leakage in the transportation pipelines using acoustic emission method with low frequency and narrow band sensors. Experimental tests were carried out on a lab scale test rig releasing CO2 from a stainless steel pipe. Further, the characteristics of the acoustic emission signals are analyzed in both the time and the frequency domains. The impact of using the transverse wave speed and the longitudinal wave speed on the accuracy of the leak localization is investigated. Since the acoustic signals are expected to be attenuated and dispersed when propagating along the pipe, empirical mode decomposition, signal reconstruction and a data fusion method are employed in order to extract high quality data for accurate localization of the leak source. It is demonstrated that a localization error of approximately 5% is achievable with the proposed detecting system

Surface-modified multifunctional MIP nanoparticles

The synthesis of core–shell molecularly imprinted polymer nanoparticles (MIP NPs) has been performed using a novel solid-phase approach on immobilised templates. The same solid phase also acts as a protective functionality for high affinity binding sites during subsequent derivatisation/shell formation. This procedure allows for the rapid synthesis, controlled separation and purification of high-affinity materials, with each production cycle taking just 2 hours. The aim of this approach is to synthesise uniformly sized imprinted materials at the nanoscale which can be readily grafted with various polymers without affecting their affinity and specificity. For demonstration purposes we grafted anti-melamine MIP NPs with coatings which introduce the following surface characteristics: high polarity (PEG methacrylate); electro-activity (vinylferrocene); fluorescence (eosin acrylate); thiol groups (pentaerythritol tetrakis(3-mercaptopropionate)). The method has broad applicability and can be used to produce multifunctional imprinted nanoparticles with potential for further application in the biosensors, diagnostics and biomedical fields and as an alternative to natural receptors