Papers by Author: Khalil Arshak

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Authors: Vijayalakshmi Velusamy, Khalil Arshak, Olga Korostynska, Ahmed Al-Shamma'a
Abstract: Detailed in this paper is the design of a novel handheld electrochemical analyzer system interfaced to a smart phone, which provides versatile and cost-effective solution for real-time sensing applications. It was characterised for electron transfer events associated with chemical and biological samples. The presented design is implemented based on the Arduino nanoopen source electronics prototyping platform. The versatility of the instrument is further demonstrated by employing the electrochemical analyser to a modified electrochemical cell which formed the basis of a DNA biosensor. Cyclic voltammetry technique was used to impose a triangular waveform on an electrochemical cell and the resulting current through the cell was then monitored. The DNA biosensor generated unique electrical signals in real-time between complementary and non-complementary oligonucleotides sequences of the Bacillus cereus DNA. The effects of hybridization and non-specific binding were compared when the probe DNA molecules were immobilized on a conducting polymer matrix. The results showed that the probe DNA immobilized using electrochemical adsorption yielded better hybridization signals compared to other immobilization methods. The performance of the DNA sensor proved to be effective in terms of selectivity, sensitivity and reproducibility of hybridization events. Analysis of these DNA probes showed that the minimum level of detection was 33.3 pg/ml.
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Authors: Olga Korostynska, Jun Jie Yan, Alex Mason, Khalil Arshak, Ahmed Al-Shamma'a
Abstract: This paper reports on the development of a flexible nanopatterning approach using the NanoeNablerTM to manufacture miniaturised sensor arrays platform for real-time water quality assessment. Traditionally biosensors are fabricated by lithography, screen printing, inkjet printing, spin-or deep-coating methods to immobilize the sensing element onto substrate pre-patterned with electrodes. NanoeNablerTM patterning method is benchmarked against other currently adapted approaches for cost-effective sensors arrays manufacture. Sensors measuring ~1 µm diameter or more can be patterned for further employment in molecularly imprinted polymer structures. Notably, the dimensions of the sensor depend on the fluid being patterned and on the interaction forces between the substrate and the patterning tool. Thus, careful selecting of patterning parameters is vital for repeatable and controlled manufacture of sensors to guarantee superior sensitivity. The reported nanopatterning method is capable of accurately placing attoliter to femtoliter volumes of liquids, including proteins and DNAs, onto any substrate, thus making it an ideal technology for biomedical sensors. A custom-made 1 cm2 silicon wafer with 48 interdigited electrodes sensor heads was used as a platform for the multi-sensor array with potential use in a wide range of real-time monitoring applications.
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Authors: Olga Korostynska, Khalil Arshak, Arousian Arshak, Edric Gill, Padraig Creedon, Shane Fitzpatrick
Abstract: Novel method of manufacturing micro sensors arrays for biomedical applications using BioForce NanoeNablerTM is reported. The operation of pH and glucose sensing elements is based on the properties of polymers, which exhibit a change in their electrical characteristics (such as resistance or capacitance) on exposure to solutions with different concentrations of pH or glucose. A sensor for glucose was successfully fabricated using the enzyme glucose oxidase immobilized within the polymer poly (o-phenylenediamine). This sensor was then successfully miniaturized utilizing immobilization for a dry process. The concentrations used for the microsensor were between 1 mM and 6 mM. Samples containing different concentrations of glucose were applied to the sensor while the system was being monitored for variances in either current or conductance. The resulting changes in the electrical characteristics of the sensor monitored in real time were found to be proportional to the different concentrations of glucose applied. Microscaled interdigitated electrodes were used for sensors array, with 48 sensors places on one chip. It is envisaged that findings of this work would form the basis for miniaturised point-of-care diagnostic system.
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Authors: Khalil Arshak, Olga Korostynska, John Henry
Abstract: This paper reports on the gamma radiation-induced changes in thin oxide films deposited by thermal vacuum technique. Structures of various oxides thin films, such as In2O3, SiO and TeO2 and their mixtures in different proportions were studied. The influence of gamma radiation on In2O3/SiO films has resulted in significant changes in the microstructure of this film. Some kind of agglomerations with variable sizes in the range 0.5-3 µm has occurred. After a dose of 8160 µSv an evidence of partial crystallisation was observed with X-ray diffraction. Structural changes in TeO2 thin film were explored by means of Raman spectroscopy. After they have been exposed to g- radiation, a strong peak appeared at 448.83 cm-1, indicating further transformation to g-TeO2 modification.
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