2 results for Abdul Rahman, Mohd Syaifudin Bin

  • Novel planar interdigital sensors for the detection of bacterial endotoxins : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philososphy in Electronics Engineering at Massey University, Palmerston North, New Zealand

    Abdul Rahman, Mohd Syaifudin Bin (2012)

    Doctoral thesis
    Massey University

    Food poisoning caused by endotoxins or Lipopolysaccharide (LPS) are associated with Gram-negative bacteria. Foodborne pathogens, Escherichia coli (E. coli) and Salmonella are examples of Gram-negative bacteria which could cause large food poisoning outbreaks. New types of planar interdigital sensors have been fabricated with different coating materials to assess their response to endotoxins. A carboxyl-funtional polymer, APTES (3-Aminopropyltriethoxysilane) and Thionine were chosen for coating the novel interdigital sensors. All coated sensors were immobilized with PmB (Polymyxin B) which has specific binding properties to LPS. The sensors were tested with different concentrations of LPS O111:B4, ranging from 0.1 μg/ml to 1000 μg/ml. Analyses of sensors’ performance were based on the Impedance Spectroscopy method. The impedance spectra were modelled using a Constant Phase-Element (CPE) equivalent circuit, and a Principal Component Analysis (PCA) was used for data classification. Sensors coated with APTES have shown better selectivity towards LPS detection. The experiments were repeated by coating APTES and immobilizing PmB to a newly improved design of silicon based interdigital sensor. Scanning electron microscope (SEM) and atomic force microscope (AFM) images were taken to analyse the APTES coating surface and PmB immobilization. The images of non-coated sensors and coated silicon sensors were studied and the thickness of a single layer coating was estimated ([approximately equal to] 268 nm). Analyses of results with LPS O111:B4 showed that these silicon sensors have higher sensitivity and selectivity to the target biomolecule LPS. The complex non-linear least squares (CNLS) fitting method was used to fit the measured impedance spectra based on chosen equivalent circuit model. PCA results were clustered, showing the parameters were related and have identified process which related to the diffusion, charge transfer and adsorption of molecules on sensors’ surface. It was also found that these sensors can detect the standard endotoxin as low as 0.01 EU/ml which is equivalent to 1 pg/ml. Selectivity, stability and sensitivity of different thickness of coated sensors were analysed. It was observed that the optimum thickness layer is 3-layers of coating which is equivalent to 800 nm. Analyses of results with food samples have shown the developed novel interdigital sensors can detect the presence of endotoxin in contaminated food samples.

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  • Novel sensor design for detection of dangerous contaminated marine biotoxins : a thesis submitted in fulfilment of the requirements for the degree of Master of Engineering in Information and Telecommunication Engineering, School of Engineering and Advanced Technology, Massey University, Palmerston North, New Zealand

    Abdul Rahman, Mohd Syaifudin Bin (2009)

    Masters thesis
    Massey University

    Planar electromagnetic sensing system has been used as one of the NDT methods to evaluate the material properties i.e., to evaluate near-surface properties such as conductivity, permeability and dielectric properties. The applications of planar electromagnetic sensors will depend on both the characteristic of the sensor type chosen and also the characteristic of material under test. Conventional planar interdigital sensors and novel planar interdigital sensors have been designed, fabricated and tested for detection of dangerous marine biotoxins in seafood. Our main objective is to sense the presence of dangerous contaminated acid in mussels and other seafoods. Initial studies were conducted with three peptide derivatives namely Sarcosine, Proline and Hydroxylproline. These three chemicals are structurally closely related to our target molecule (domoic acid). The initial results have shown that all sensors respond very well to the chemicals and it is possible to discriminate the different chemicals from the output of the sensor. Novel interdigital sensors have shown better sensitivity measurement compared to conventional interdigital sensors. The novel interdigital sensors were then being tested with three seafood products. Results from the analysis have shown that novel interdigital sensor with configuration #1 (Sensor_1) has better sensitivity compared to other sensors. Sensor_1 has been chosen for experiment using proline and mussels. The changes in sensor sensitivity were analysed with mussels before and after adding the proline. The presence of proline on the mussel surface and also injected proline to the mussel samples were clearly detected by Sensor_1. Further experiment was conducted with small amount of domoic acid (0.5 µg to 5.0 µg) injected to a mussel and it was found that Sensor_1 was able to detect small amount of domoic acid (1.0 µg) injected into the mussel sample. Sensor_1 was able to detect approximately 12.6 µg/g of domoic acid in mussel meat. Three threshold levels of particular sample thickness have been established for detection of domoic acid. The first prototype of a low cost sensing system known as SIT (Seafood Inspection Tool) has been developed. The outcomes from the experiments provide chances of opportunity for further research in developing a low cost miniature type of sensors for reliable sensing system for commercial use.

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