CO2 sensor for food application

The carbon dioxide levels inside meat packages can be used as indicator of freshness. If the CO2 concentration changes during storage it is a clear indicator that bacteria are growing inside the container and / or the package is not well sealed and the modified atmosphere has been compromised. However, a non-destructive method for determining the CO2 concentration within the package has not, as yet, been reported. To this end, the objective of the SmartPack project is to exploit the development and integration of a CO2 sensor in meat packages using the imaging and communications capabilities of Smartphones for freshness detection. Optical CO2 sensors based on the acidity of this molecule, are normally solvent-based sensors, the drawback of this approach in the food packaging industry is due to the long-term instability of the sensors, arising from the quaternary ammonium hydroxides decomposition. However, in this project we avoid the use of these compounds. Water based sensors are prepared using meta cresol purple sodium salt as indicator, glycerol as plasticizer and sodium bicarbonate as buffer in a matrix of hydroxyethyl cellulose. In this way, the lifetime is increased and also this composition creates an easily printable ink. Moreover, ionic liquids have been included in the matrix making the sensor more selective to CO2 than other gases due to its higher solubility. This new water-based sensor has been characterised in terms of carbon dioxide sensitivity, dynamic response, and stability under different conditions. The sensor responds up to 100% of carbon dioxide. In Figure 1 can be observed the change in colour from 0 to 100% of CO2. Moreover, it has been demonstrated that the stability is much higher than the solvent-based sensors making them suitable for smart packaging application. The sensitive ink has been optimised and characterized using bench-top instrumentation. Moreover, the RGB and HSV readout of standard digital photographic cameras have been used as a simple imaging techniqu

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

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

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

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

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

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

Direct Replacement of Antibodies with Molecularly Imprinted Polymer 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 assays similar to the enzyme-linked immunosorbent assay (ELISA) is presented here for the first time. NanoMIPs were synthesized by a solid-phase approach with an 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 horseradish peroxidase–vancomycin conjugate. The assay was capable of measuring vancomycin in buffer and in blood plasma within the range of 0.001–70 nM with a detection limit of 0.0025 nM (2.5 pM). The sensitivity of the assay was 3 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 ELISA