Improvements in electrochemical glucose biosensors

Diabetes is one of the leading causes of death and disability in the world. Even though insulin was discovered in 1920, an intense research on diabetes has been conducted during the last five decades and this is because of the market size. The huge demand is creating the need for the development of new approaches. This project involved the research aimed at better understanding and improvements in performance of glucose biosensors. In general, high surface area electrodes are desired as the high surface area provides more active sites for electrochemical reactions, and hence higher kinetic rate capability. Therefore, the determination of the active electrochemical surface area of the electrode is very important. A study has been conducted to determine the real electrochemical surface area of the Pelikan screen printed electrodes (SPEs) and a method has been optimised and established by Pelikan for the evaluation of their SPEs. Another very important issue that most of the current blood glucose monitoring tests are facing is the haematocrit effect, since the haematocrit differences observed in the blood samples can significantly affect glucose measurements. Therefore a study has been conducted in order to observe the absorption of the blood samples into the working electrode paste according to the haematocrit level. The second part of the study included the characterisation of the novel conjugated polymer made of N-(N, N’ diethyldicarbamoyl ethyl amido ethyl) aniline (NDDEAEA), the optimization of the conditions for the electrochemical polymerization, their application in grafting and finally the development of NDDEAEA based glucose biosensor. The new conducting polymer, acted as a matrix for the biosensor fabrication in this study, possesses macroiniferter properties and is capable of initiation free radical initiated addition polymerisation after formation of the polyaniline (PANI) material while preserving or even enhancing some of the PANI’s electrochemical properties. This material can potentially be used in the construction of novel Pelikan electrodes with enhanced integration functionalities, e.g. grafting non adhesive polymer coatings to assure that the poor performance in sensors as a result of impact of blood components can be mitigated. The final study included the development and optimisation of the reaction conditions for grafting a hyperbranched polymer onto the surface of the multi walled carbon nanotubes (MWCNT), using the A3 and B2 approach (described below). The aim of this work was achieving further increase in the sensitivity of Pelikan sensors.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Paper as smart support for bioreceptor immobilization in electrochemical paper-based devices

The use of paper as a smart support in the field of electrochemical sensors has been largely improved over the last 15 years, driven by its outstanding features such as foldability and porosity, which enable the design of reagent and equipment-free multi-analysis devices. Furthermore, the easy surface engineering of paper has been used to immobilize different bioreceptors, through physical adsorption, covalent bonding, and electrochemical poly-merization, boosting the fine customization of the analytical performances of paper-based biosensors. In this review, we focused on the strategies to engineer the surface of the paper for the immobilization of (bio)recog-nition elements (eg., enzymes, antibodies, DNA, molecularly imprinted polymers) with the overriding goal to develop accurate and reliable paper-based electrochemical biosensors. Furthermore, we highlighted how to take advantage of paper for designing smart configurations by integrating different analytical processes in an eco-designed analytical tool, starting from the immobilization of the (bio)receptor and the reagents, through a designed sample flow along the device, until the analyte detection

Paper microfluidics for clinical diagnostics using colourimetric detection methods

Microfluidics is a technology currently aiming to advance the medical devices currently available in the developing and developed world through simultaneously creating point-of-care devices which are “as good” or better than current methods at a cheaper production cost. To be able to diagnose diseases and infections quickly and affordably remains the aim of many researchers and the use microfluidics has advantages which plug this difficulty. However, one main gap in the research is to train users for these devices which give accurate results when compared to current methods. Described herein are three point-of-care devices which would not require specialist users and give no significantly different results from hospital methods.The aim of this project was to design, fabricate and use a microfluidic device made from filter paper as a cheaper alternative to current microfluidic devices already available. The creation of channels to direct the movement of fluid within the paper matrix was established by modifying a photolithography method, thereby providing hydrophilic channels surrounded by a hydrophobic barrier.A three dimensional device was constructed entirely from filter paper to incorporate the simultaneous removal, reduction and detection of iron(II) via bathophenanthroline detection for the determination of iron(II) levels in a patient, indicative of the nutritional state of the patient e.g. does the pateitn suffer from anaemia. This method was deemed accurate by comparing the results to a conventional laboratory method (spectrophotometer analysis) completed in a hospital pathology laboratory. No significant difference was observed between results received from the hospital and results found using the paper microfluidic device, 15 μM ± 0.6% SEM versus 15.5 μM ± 0.8% SEM respectively.Two paper devices were developed to allow a quick and reliable measurement assessment of a patient’s renal function. The first for urea, as a simple colour change for a high or low readout of urea levels in serum samples, e.g. ≥ 150 μg/mL then an orange/red colour would be seen on the paper device, indicative of renal failure ≤ 150 ug mL¯¹. The second device used the Jaffe reaction on filter paper as a dipstick assay. No significant difference was observed between results received from the hospital and results found using the paper device 3.92 ± 1.2% versus 3.88 mg mL¯¹ ± 0.6% respectively.These three devices fulfil the aims of the project outline by remaining simplistic to use and are cost effective in both the developing and developed world, whilst maintaining accuracy as seen in the results received from hospital pathology laboratories

Review—Lab-in-a-Mouth and Advanced Point-of-Care Sensing Systems: Detecting Bioinformation from the Oral Cavity and Saliva

Cavitas sensors and point-of-need sensors capable of providing physical and biochemical information from the oral cavity and saliva have attracted great attention because they offer remarkable advantages for noninvasive sensing systems. Herein, we introduce the basic anatomy and physiology of important body cavities to understand their characteristics as it is a pivotal foundation for the successful development of in-mouth devices. Next, the advanced development in lab-in-a-mouth sensors and point-of-need sensors for analyzing saliva are explained. In addition, we discuss the integrations of artificial intelligence and electronic technologies in smart sensing networks for healthcare systems. This review ends with a discussion of the challenges, future research trends, and opportunities in relevant disciplines. Mouthguard-based sensors and conventional salivary sensing devices will continue to be significant for the progress in the next-generation sensing technologies and smart healthcare systems.ope

Nanofiber Based on Electrically Conductive Materials for Biosensor Applications

Biosensors are analytical tools that enable the transmission of different signals produced from the target analyte to a transducer for the production of real-time clinical diagnostic devices by obtaining meaningful results. Recent research demonstrates that the production of structured nanofiber through various methods has come to light as a potential platform for enhancing the functionality of biosensing devices. The general trend is towards the use of nanofibers for electrochemical biosensors. However, optical and mechanical biosensors are being developed by functionalization of nanofibers. Such nanofibers exhibit a high surface area to volume ratio, surface porosity, electroconductivity and variable morphology. In addition, nanosized structures have shown to be effective as membranes for immobilizing bioanalytes, offering physiologically active molecules a favorable microenvironment that improves the efficiency of biosensing. Cost effective, wearable biosensors are crucial for point of care diagnostics. This review aims to examine the electrically conductive materials, potential forming methods, and wide-ranging applications of nanofiber-based biosensing platforms, with an emphasis on transducers incorporating mechanical, electrochemical and optical and bioreceptors involving cancer biomarker, urea, DNA, microorganisms, primarily in the last decade. The appealing properties of nanofibers mats and the attributes of the biorecognition components are also stated and explored. Finally, consideration is given to the difficulties now affecting the design of nanofiber-based biosensing platforms as well as their future potential

Correlating the Effect of Dynamic Variability in the Sensor Environment on Sensor Design

This dissertation studies the effect of biofluid dynamics on the electrochemical response of a wearable sensor for monitoring of chronic wounds. The research investigates various dynamic in vivo parameters and correlates them with experimentally measured behavior with wound monitoring as a use case. Wearable electrochemical biosensors suffer from several unaddressed challenges, like stability and sensitivity, that need to be resolved for obtaining accurate data. One of the major challenges in the use of these sensors is continuous variation in biofluid composition. Wound healing is a dynamic process with wound composition changing continuously. This dissertation investigates the effects of several in vivo biochemical and environmental parameters on the sensor response to establish actionable correlations. Real-time assessment of wound healing was carried out through longitudinal monitoring of uric acid and other wound fluid characteristics. A textile sensor was designed using a simple fabrication approach combining conductive inks with a polymeric substrate, for conformal contact with the wound bed. A −1 cm−2, establishing the applicability of the sensor for measurements in the physiologically relevant range. The sensor was also found to be stable for a period of 3 days when subjected to physiological and elevated temperatures (37oC and 40oC) confirming its relevance for long-term monitoring. A direct correlation between sensor response and the dynamic parameters was seen, with the results showing a ~20% deviation from the accurate UA reading. The results confirmed that as a consequence of these parameters temporally changing in the wound environment, the sensor response will be altered. The work develops mathematical models correlating this effect on sensor response to allow for real-time sensor calibration. The clinical validation studies established the feasibility of UA measurement by the developed electrochemical sensor and derive correlations between the wound chronicity and UA levels. The protocols developed in this work for the design, fabrication, and calibration of the sensor to correct for the dynamic in vivo behavior can be extended to any wearable sensor for improved accuracy

Development of paper-based microfluidic devices for environmental and food quality analysis, The

Includes bibliographical references.2016 Fall.Providing safe and nutritious food and water, both domestically and internationally, has long been a goal for improving global health. Recent legislations enacted within the United States have enabled government agencies to further regulate agricultural and industry standards, necessitating the need for more preventative approaches with regards to food and beverage quality and safety. Increasing detection speed and enabling field and production detection of point-source contamination are crucial to maintaining food and beverage safety as well as preventing detrimental disease outbreaks, such as those caused by bacterial contamination. The development of simple, inexpensive, and portable methods for detecting contamination indicators are key to reaching this goal. Moreover, recent developments into microfluidic approaches for analysis have shown great promise as platforms for providing faster simplified methods for detection. The work conducted within this dissertation focuses on the development of simple, inexpensive and disposable platforms for colorimetric and electrochemical analysis of food and beverage quality. Aside from more commonly studied polymer-based devices, recent advances in paper-based diagnostics have demonstrated use as an analytical platform capable of self-pumping, reagent storage, mixing, and implementation of various detection motifs. Herein, the development of microfluidic paper-based analytical devices (μPADs) is presented as a platform for the colorimetric detection of bacteria in food and water samples. Initial work was conducted for the paper-based, colorimetric detection of Listeria monocytogenes, Salmonella Typhimurium, and E. coli O157:H7 bacteria species, all of which have been associated with fatal, multistate food- and waterborne outbreaks. Detection was performed on ready-to-eat meats using a swabbing technique to collect and quickly culture surface contamination of bacteria using enzymatic assays within paper-based microwells. A scanner was used for imaging followed by use of image analysis software for semi-quantitative measurement determination. This method was further applied to the detection of bacteria in irrigation water, a known source of foodborne contamination, using a 3D-printed filter for collection and culture of bacteria present in low concentrations within water. Although colorimetric detection offers a simple, visual detection method, electrochemistry is an alternative, sensitive and portable method for detection. Use of common office materials such as transparency film and copy paper, as well as laboratory filter papers were studied and developed for optimal electrochemical platform performance. The use of microwires as a simple fabrication method for incorporating metallic or modified metallic electrodes into electrochemical paper-based devices (ePADs) was also developed. Electrochemical behavior in both well-based and flow-based ePADs was studied and implemented for the nonenzymatic detection of sugars in beverages using copper oxide modified microwires, and for the in-line flow detection of enzymatic assays using gold and platinum microwire electrodes respectively. Furthermore, the fast, inexpensive, and simple fabrication of carbon stencil-printed electrodes (CSPEs) on transparency film were demonstrated for the electrochemical detection of E. coli and Enterococci bacteria species, both indicators of fecal contamination, in food and water samples using enzymatic assays. These same assays could also be determined colorimetrically and a more portable cell phone was used to image and wirelessly send paper-based well-plate results. This method was developed for use in place of a more bulky and expensive plate reader, and results were used for comparison to electrochemical detection of bacteria from a single assay

The development of novel electroanalytical interfaces for point of care diagnostics

Reduced sulphydryl thiols (RSH): cysteine, homocysteine and glutathione are fundamental cellular components having important biological functions, including roles within the pathogenesis of a variety of clinical conditions. Independent analysis of these species is problematic and analytical difficulties relating to instrumental selectivity and sensitivity need to be overcome. This thesis describes the work carried out on the development and characterisation of a range of systems that could be used to facilitate thiol detection, ideally at the point-of-care, focussing largely on electrochemical techniques. Silver-thiol interactions were studied as a route to assist the sample processing. Here a novel controlled silver release mechanism was assessed. Silver release was found to be dependent upon the thiol structure. This has possible future applications to the development of methods to prevent biofilm formation, although the full mechanism of silver-thiol release requires further understanding. The development of unique molecular imprinted polymers was attempted. These would facilitate the detection of amino acids and the relevant thiol species via the amine functionality

Working note-book for the practical classes on biochemistry

БИОХИМИ