Smart integrated biosensor system

Professor Tony Killard from the University of the West of England is leading a collaborative project to develop and implement smart integrated miniturised sensor systems

Disposable sensors

© 2017 Elsevier B.V. Device disposability is a critical feature of electrochemical sensor production, allowing complex measurements to be carried out in a low cost and efficient manner. Disposable sensors are increasing rapidly in their level of sophistication, supported by developments in materials and fabrication processing. This is, in turn, leading to greater levels of device integration and functionality and has the potential to significantly expand the number of people who can use them, where they can be deployed and how they can be used. As well as becoming more complex, there is also significant emphasis in making such disposable devices more environmentally sustainable. Current themes in the development of disposable sensors are explored here

Microfluidics in coagulation monitoring devices: A mini review

Diagnosis and monitoring of disorders of coagulation and disturbances in haemostasis has been around for many years. Thrombotic and bleeding disorders are amongst the leading causes of mortality in the developed world, thus driving research in this area. The simplicity with which miniaturised devices operate and their application to the study of coagulation and haemostasis offer potential advantages over traditional testing, such as improvements in clinical decision making and ultimately patient care. This review looks at progress in microfluidic device development in the field of haemostasis and coagulation biology

Creatinine biosensors: principles and designs

Creatinine biosensors, based on both potentiometric and amperometric devices, have been created. However, there are significant problems still to be addressed, including the balance between sensitivity and selectivity, interference rejection and sensor stability. In addition, many devices still rely on a dual-sensor approach for creatine and creatinine subtractive measurements. However, creatinine biosensors appear close to attaining the performance goals necessary for their widespread application. This article looks at the operating principle and design of both potentiometric and amperometric creatinine biosensors, and shows how the design of these devices affects their performance

Evaluation of Activated Partial Thromboplastin Time (aPTT) Reagents for Application in Biomedical Diagnostic Device Development

Introduction: The most commonly used test for monitoring heparin therapy is the activated partial thromboplastin time (aPTT). The response of available aPTT reagents to heparin varies significantly. The aim of this study was to highlight the differences between aPTT reagents stored in a dried format to select the most suitable formulations to be used for the development of point-of-care diagnostic devices used for monitoring of unfractionated heparin dose response. Methods: Ten reagents were analysed in terms of their performance in liquid and in dried form after storage for 24 h and 14 days. Performance was assessed by measurement of the clotting time (CT) as evidenced by the onset of thrombin formation using a chromogenic thrombin substrate in plasma samples activated with these formulations. Results: Reagents in all of the three forms tested (liquid, 24 h and 14 days) resulted in significant shortening of CTs in comparison with the nonactivated plasma CT. Liquids returned more rapid CTs in comparison with dried reagents. Most of the reagents were more sensitive to heparin in dried, rather than in liquid form. Dried reagents based on kaolin as a surface activator were notably more effective in achieving short CT than others, while dried reagents composed of silica and synthetic phospholipids were the most sensitive to heparin. Conclusion: Two reagents, namely aPTT-SP and SynthASIL both of which are based on synthetic phospholipids and silica, were identified as promising candidates for incorporation into point-of-care diagnostic device platforms as dried reagents

The production of antibodies to coumarin and its major human metabolites

Two strategies were applied to the production of antibodies to coumarin and its phase I metabolite, 7-hydroxycoumarin. One system was the production of Fab antibody fragments using the combinatorial phage display library, employing the phagemid vector, pComb3. Although a library of murine heavy and light chain genes was established following immunisations with coumarin and 7-hydroxycoumarin conjugates, preparation of the library in pComb3 was not possible due to associated problems with this vector. An alternative antibody library system was obtained. This was the naive semi-synthetic human scFv library of Nissim et al. (1994). The production of antibodies to both coumarin and 7-hydroxycoumarin was investigated. Various production and isolation techniques were explored. Best results were obtained by isolating correctly folded scFv protein from the periplasm or culture supernatants of E. coli. In the case of coumarin, three soluble antibody clones were isolated and characterised. These clones showed the characteristics of poor affinity for free coumarin, but did bind well to coumarin-protein conjugates. Isolated anti-7-hydroxycoumarin clones also showed the same characteristics of no binding to free drug. It was theorised that, due to the structural simplicity of these molecules, affinity selection and screening is biased against the detection of clones with high affinity for free drug. This conclusion was in broad agreement with other findings (Danilova, 1994). Recommendations are made as to how the selection and screening procedures can be improved to isolate antibodies to such molecules. Techniques for the in vitro production of the phase II metabolite 7-hydroxycoumaringlucuronide were developed. These were accompanied by the development of analytical methods (capillary electrophoresis and HPLC) for the glucuronide. Purification methodologies using 7-hydroxycoumarin present in these metabolic mixtures and in urine were also developed. The coupling of 7-hydroxycoumarin-glucuronide to proteins for the production of antibodies was also explored. A 7-hydroxycoumarin-glucuronide-bovine serum albumin conjugate was successfully synthesised for use in further antibody production strategies

Screen-printable silver nanoparticulate-based inks for the electrocatalysis of hydrogen peroxide

The detection of hydrogen peroxide has been shown to be very important in recent years due to its relevant role in many industrial applications as well as biological reactions. We are interested in it as a quantitative marker for oxidase-based biosensor applications where it is produced when substrate (e.g., glucose, cholesterol) is catalysed by its respective oxidase enzyme. Previously, a commercial silver flake-based screen-printing ink (PF-410, Acheson®), when treated with surfactant and salt (dodecylbenzenesulfonic acid (DBSA) and KCl) has shown to significantly enhance the electrochemical reduction of hydrogen peroxide up to 80-fold over non-treated inks. In this study, the silver morphology, size and silver supplier is investigated for its effect on the electrocatalysis of hydrogen peroxide. In order to do this, inks loaded with silver micron-sized flakes and silver nanopowders, from various suppliers, are prepared using the binder material extracted from the Acheson® PF-410 to formulate inks

A fully integrated microfluidic device for point of care monitoring of antithrombotics

© 2016 The Royal Society of Chemistry. The simplicity and efficiency of point of care diagnostics have revolutionised patient care. Current methods for measuring hypercoagulability often require trained technicians, large blood volumes, and result in long turnaround times. Standard testing for hypercoagulable disorders is performed in the central laboratory using automated coagulation analysers. However the trend is moving towards the development and implementation of point of care testing, as a result of the ever increasing number of patients on antithrombotic therapy. We present a novel microfluidic device and assay for monitoring the effect of two anticoagulants, unfractionated heparin (UFH) and low molecular weight heparin (LMWH). The assay is based on the anti-Xa assay principle but uses fluorescence detection. Our device is a disposable laminate microfluidic strip, fabricated from the cyclic polyolefin (COP), Zeonor®, which is extremely suitable for application to fluorescent device platforms. We present data on the execution of the anti-Xa assay in this microfluidic format, demonstrating that the assay can be used to measure both UFH and LMWH in human plasma samples from 0 to 1 U mL-1, with a rapid result obtained within 30-60 seconds

Elucidation of the mode of action of a conductive polymer-based electrochemical immunosensor.

An amperometric biosensor has been developed, incorporating the electroactive polymer, polyaniline (PANI), which undergoes redox cycling, and can couple electrons directly from the enzyme active site, to the electrode surface. Construction of this sensor was achieved by electropolymerisation of polyvinylsulphonate-doped aniline onto the surface of a screen-printed carbon-paste electrode. Biomolecules could then be doped onto the surface of the polymer by electrostatic interactions with the polymer backbone. A key component in a biosensor is the recognition molecule and its immobilisation. This study investigates this process of protein immobilisation using amperometric and colorimetric techniques. Immobilisation of protein (enzyme or antibody) onto the transducer is achieved by electrostatic interactions. By applying bovine serum albumin (BSA) electrostatically at the electrode, efficient blocking of the electrode surface from the bulk solution was achieved above approximately 0.75 mg/ml. When horseradish peroxidase was immobilised on the electrode surface at various concentrations, optimal amperometric responses were achieved at approximately the same protein concentration. Determination of the number of molecules of protein immobilised on the surface of the electrode at this concentration was done using a colorimetric enzyme assay. It was found that under optimal immobilisation conditions, a protein monolayer was formed at the electrode surface. In the case of enzymes such as horseradish peroxidase (HRP), this provides simultaneous blocking of the electrode surface from bulk solution interactions as well as yielding optimal electron transfer properties

Immunoelectrochemical methods immunoelectrochemical of hormone anaylsis

Over the last decade, there has been considerable interest in the development of immunoelectrochemical assays, mainly due to the advantages offered by the combination of the selectivity of immunoassays with the great sensitivity and simplicity of modern electroanalytical techniques. However, immunoelectrochemical assays have not yet been exploited commercially, as transitions from the laboratory bench to large-scale manufacturing has proved difficult. The system described is an amperometric peroxide biosensor prepared by electrochemical deposition of horseradish peroxidase on an electroactive polymer, polyaniline. Polyaniline brings about mediatorless redox coupling between the electrode and biomolecular components attached to the surface. This assay will be the stepping-stone to developing an immunoelectrochemical method for the analysis of human chorionic gonadotropin (hCG), and other female hormones. The assay initially utilises glassy carbon electrodes for preliminary data, before being replaced with a commercially available electrode Euroflash TM, produced by Inverness Medical Limited TM. This electrode was utilised with a view to producing an electrochemical assay that complies with manufacturing requirements