449 results on '"Lee Yook Heng"'
Search Results
52. An ultrasensitive hollow-silica-based biosensor for pathogenic Escherichia coli DNA detection
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Ariffin, Eda Yuhana, Lee, Yook Heng, Futra, Dedi, Tan, Ling Ling, Karim, Nurul Huda Abd, Ibrahim, Nik Nuraznida Nik, and Ahmad, Asmat
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- 2018
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53. Ion-selective acrylic polymer matrices
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Lee, Yook Heng
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660.6 - Published
- 1998
54. Electrochemical genosensor assay using lyophilized gold nanoparticles/latex microsphere label for detection of Vibrio cholerae
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Liew, Pei Sheng, Lertanantawong, Benchaporn, Lee, Su Yin, Manickam, Ravichandran, Lee, Yook Heng, and Surareungchai, Werasak
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- 2015
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55. A Quinoline-Based Fluorescent Labelling for Zinc Detection and DFT Calculations
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Mohamad, Nur Syamimi, primary, Tan, Ling Ling, additional, Goh, Choo Ta, additional, Lee, Yook Heng, additional, Mobarak, Nadhratun Naiim, additional, Mat Lazim, Azwan, additional, Sapari, Suhaila, additional, Abdul Razak, Fazira Ilyana, additional, and Hassan, Nurul Izzaty, additional
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- 2022
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56. Biosensor DNA Voltametrik Berasaskan Nanozarah Emas Bersalut Elektrod Bercetak Skrin Karbon untuk Pengesanan DNA Organisma Terubahsuai Genetik (GMO)
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Nahdya Khairani, Nahdya Khairani, primary, Lau, Han Yih, additional, Ishak, Zamri, additional, Lee, Yook Heng, additional, and Tan, Ling Ling, additional
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- 2022
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57. A Simple Potentiometric Biosensor based on Carboxylesterase for the Analysis of Aspartame
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Ramli, Noor Izaanin, primary, Lee, Yook Heng, additional, and Tan, Ling Ling, additional
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- 2022
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58. Study of Histamine Detection using Liquid Chromatography and Gas Chromatography
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Lee Yook Heng, Muhammad Abdurrahman Munir, Khairiah Haji Badri, and Muhammad Mukram Mohamed Mackeen
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chemistry.chemical_compound ,Multidisciplinary ,Chromatography ,chemistry ,Gas chromatography ,Histamine - Abstract
Histamine is a heterocyclic amine shaped by decarboxylation of the histidine. It is a compound that lack chromophore and involatile. However, the detection of histamine is imperative due to the characteristic of histamine has given several disadvantages in food industry. This paper describes methods for histamine detection by employing high performance liquid chromatography and gas chromatography. The derivatization techniques required for both methods in order to increase the sensitivity of chromatography analysis. Two derivatizing agents were applied in this study such as 9-flourenilmethyl chloroformate (FMOC – Cl) for HPLC analysis whereas for GC analysis a N,O-bis (trimethylsilyl)acetamide (BSA) was used. Method validation was in accordance to Commission Decision 657/2002/CE. The validation of specificity, linearity, precision, accuracy, detection limit and quantitation limit results indicate that the methods were acceptable. The linear range for both methods were at 0.16 – 5.00 µg∙mL-1. The determination of histamine using GC showed the superiority of this instrument compared to HPLC. Method applicability was also checked on real sample namely mackerel in order to acquire a satisfactory recovery for both methods.
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- 2021
59. Effect of the big flood events on the water quality of the Muar River, Malaysia
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Ching, Yun Chen, Lee, Yook Heng, Toriman, Mohd Ekhwan, Abdullah, Maimon, and Yatim, Baharudin Bin
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- 2015
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60. Electrochemical Sunset Yellow Biosensor Based on Photocured Polyacrylamide Membrane for Food Dye Monitoring.
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Normazida Rozi, Amalina Ahmad, Lee Yook Heng, Loh Kee Shyuan, and Sharina Abu Hanifah
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- 2018
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61. A Potentiometric Formaldehyde Biosensor Based on Immobilization of Alcohol Oxidase on Acryloxysuccinimide-modified Acrylic Microspheres.
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Yew Pei Ling and Lee Yook Heng
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- 2010
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62. Determination of histamine using chemical sensor based on amperometric technique using screen-printed polyurethane electrode (SPPE) compared to HPLC equipped fluorescence detector
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Muhammad Abdurrahman Munir, Khairiah Haji Badri, Lee Yook Heng, Nurul Kusumawardani, and Rizal Fauzi
- Published
- 2022
63. The Application of Polyurethane-LiClO
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Muhammad Abdurrahman, Munir, Khairiah Haji, Badri, Lee Yook, Heng, Ahlam, Inayatullah, Eva, Nurinda, Daru, Estiningsih, Annisa, Fatmawati, Veriani, Aprilia, and Nur, Syafitri
- Abstract
Histamine is an important substance that can be applied as a parameter for allergic reactions and food freshness. This study develops a method to produce a histamine sensor based on electrodes modified using polyurethane-LiClO
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- 2021
64. Optical enzymatic formaldehyde biosensor based on alcohol oxidase and pH-sensitive methacrylic-acrylic optode membrane
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Ling Ling Tan, Musa Ahmad, Nurlely, and Lee Yook Heng
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Detection limit ,Chemistry ,Formic acid ,Formaldehyde ,Reproducibility of Results ,Biosensing Techniques ,Hydrogen-Ion Concentration ,Nile blue ,Enzymes, Immobilized ,Atomic and Molecular Physics, and Optics ,Analytical Chemistry ,chemistry.chemical_compound ,Light intensity ,Alcohol Oxidoreductases ,Membrane ,Animals ,Optode ,Instrumentation ,Biosensor ,Spectroscopy ,Nuclear chemistry - Abstract
Optical biosensor for the detection of formaldehyde has been developed based on the transparent enzymatic stacked membranes system on the glass substrate, and employing optical absorption transducer with H+ ion-selective Nile Blue chromoionophore (NBCM) dye-doped methacrylic acrylic (MB28) copolymer membrane as the optode membrane. Alcohol oxidase (AOx) enzymes were entrapped within the biocompatible sol–gel matrix and deposited on top of the pH optode membrane. As the uppermost catalytic membrane catalyzes the oxidative conversion of formaldehyde to formic acid and hydrogen peroxide, the immobilized NBCM undergoes protonation reaction and forms HNBCM+, the dark blue ion-chromoionophore complex via H+ ion transfer reaction within the soft and flexible MB28 polymeric membrane. This rendered the enzymatic optode membrane absorbed a high yellow light intensity from the light source and exhibited maximum absorption peaks at 610 and 660 nm. Optical evaluation of formaldehyde by means on UV–vis absorption transduction of the enzymatic stacked membranes demonstrated rapid response time of 10 min with high sensitivity, good linearity and high reproducibility across a wide formaldehyde concentration range of 1 × 10−3–1 × 103 mM (R2 = 0.9913), and limit of detection (LOD) at 1 × 10−3 mM, which could be useful for formaldehyde assay in industrial, agricultural, environmental, food and beverages as well as medical samples. The formaldehyde concentration in snapper fish, pomfret fish and threadfin fish samples determined by the proposed optical enzymatic biosensor were very much close to the formaldehyde concentration values determined by the UV–vis spectrophotometric NASH standard method based on the statistical t-test. This suggests that the optical biosensor can be used as a reliable method for quantitative determination of formaldehyde levels in food samples.
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- 2021
65. Comparison of sPLA2IIA performance with high-sensitive CRP neutrophil percentage PCT and lactate to identify bacterial infection
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Swee Thian Tan, Kok Beng Gan, D N Nasuruddin, Toh Leong Tan, Nurul Izzaty Hassan, Hui Min Neoh, Kai Shen Ooi, Khaizurin Tajul Arifin, Christabel Wan-li Kang, Nurul Saadah Ahmad, Lee Yook Heng, and Azlin Ithnin
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0301 basic medicine ,Adult ,Male ,medicine.medical_specialty ,Neutrophils ,Science ,Single measurement ,Gastroenterology ,Secretory Phospholipase A2 ,Procalcitonin ,Article ,Patient arrival ,03 medical and health sciences ,0302 clinical medicine ,Medical research ,Internal medicine ,medicine ,Humans ,Prospective cohort study ,Phospholipases A2, Secretory ,Aged ,Multidisciplinary ,Receiver operating characteristic ,Molecular medicine ,business.industry ,Bacterial Infections ,Middle Aged ,030104 developmental biology ,C-Reactive Protein ,030220 oncology & carcinogenesis ,Medicine ,Female ,business ,High sensitive crp ,Biomarkers - Abstract
Early bacterial infection (BI) identification in resource-limiting Emergency Departments (ED) is challenging, especially in low- and middle-income counties (LMIC). Misdiagnosis predisposes to antibiotic overuse and propagates antimicrobial resistance. This study evaluates new emerging biomarkers, secretory phospholipase A2 group IIA (sPLA2-IIA) and compares with other biomarkers on their performance characteristic of BI detection in Malaysia, an LMIC. A prospective cohort study was conducted involving 151 consecutive patients admitted to the ED. A single measurement was taken upon patient arrival in ED and was analysed for serum levels of sPLA2-IIA, high-sensitive C-reactive protein (CRP), procalcitonin (PCT), neutrophil percentage (N%), and lactate. All biomarkers’ performance was compared for the outcomes using area under the receiver operating characteristic curve (AUROC), sensitivity, and specificity. The performance of sPLA2-IIA (AUROC 0.93 [95% CI: 0.89–0.97]; Sn 80% [95% CI: 72–87]; Sp 94% [95% CI: 81–89]) was the highest among all. It was comparable with high-sensitive CRP (AUROC 0.93 [95% CI: 0.88–0.97]; Sn 75% [95% CI: 66–83]; Sp 91 [95% CI: 77–98]) but had a higher Sn and Sp. The sPLA2-IIA was also found superior to N%, PCT, and lactate. This finding suggested sPLA2-IIA was recommended biomarkers for BI detection in LMIC.
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- 2021
66. Acrylic-based genosensor utilizing metal salphen labeling approach for reflectometric dengue virus detection
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Nurul Huda Abd Karim, Lee Yook Heng, Nur Diyana Jamaluddin, Doris Huai Xia Quay, Ling Ling Tan, Bahariah Khalid, Nurul Yuziana Mohd Yusof, and Nur-Fadhilah Mazlan
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Base pair ,Acrylic Resins ,02 engineering and technology ,Phenylenediamines ,Dengue virus ,medicine.disease_cause ,01 natural sciences ,DNA sequencing ,Analytical Chemistry ,chemistry.chemical_compound ,medicine ,Detection limit ,Chromatography ,Hybridization probe ,Optical Imaging ,010401 analytical chemistry ,Dengue Virus ,021001 nanoscience & nanotechnology ,Microspheres ,0104 chemical sciences ,Reverse transcription polymerase chain reaction ,Zinc ,chemistry ,DNA Probes ,0210 nano-technology ,Biosensor ,DNA - Abstract
An optical genosensor based on Schiff base complex (Zn2+ salphen) DNA label and acrylic microspheres (AMs) as polymer support of the capturing DNA probe (cpDNA) was developed for dengue virus serotype 2 (DEN-2) detection via reflectance spectrophotometric method. The solid-state optical DNA biosensor showed high selectivity and specificity up to one-base mismatch in the target DNA sequence owing to the salphen chemical structure that is rich in localized electrons, and allowed π-π stacking interaction between stacked base pairs of double-stranded DNA (dsDNA). The reflectometric DNA microsensor demonstrated a broad linear detection range towards DEN-2 DNA from 1 × 10–15 M to 1 × 10−3 M with a low limit of detection (LOD) obtained at 1.21 × 10–16 M. The DNA biosensor gave reproducible optical response with a satisfactory relative standard deviation (RSD) at 3.1%, (n = 3), and the reflectance response was stable even after four regeneration cycles of the DNA biosensor. The optical genosensor was proven comparable with standard reverse transcription polymerase chain reaction (RT-PCR) in detecting DEN-2 genome acquired from clinical samples of serum, urine and saliva of dengue virus infected patients under informed consent. The developed reflectometric DNA biosensor is advantageous in offering an early DEN-2 diagnosis, when fever symptom started to manifest in patient.
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- 2019
67. Optical enzymatic biosensor membrane for rapid in situ detection of organohalide in water samples
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Lee Yook Heng, Ling Ling Tan, Hidayah Shahar, and Goh Choo Ta
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Detection limit ,Chromatography ,medicine.diagnostic_test ,Chemistry ,010401 analytical chemistry ,Halide ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Analytical Chemistry ,Dichloroethane ,chemistry.chemical_compound ,Tap water ,pH indicator ,Spectrophotometry ,medicine ,0210 nano-technology ,Biosensor ,Spectroscopy ,Haloalkane dehalogenase - Abstract
An optical biosensor employing immobilized haloalkane dehalogenase (HLD), the halide degrading enzyme for the detection of halogenated organic in environmental water and drinking water samples was developed. The enzymatic biosensor was fabricated by incorporating H+ ion selective chromoionophore ETH5294 and HLD enzyme in a stacked chitosan films system on a glass slide. Hydrolytic dehalogenation of dichloroethane (DCA) by the carbon-halide degrading HLD enzyme resulting in the release of a halogen, a proton and a primary alcohol. The halocarbon concentration was optically transduced by the pH transducer layer as a result of protonation reaction of the chromoionophore pH indicator dye embedded in the underneath layer. The resulting colour change of the protonated chromoionophore was measured by fiber optic reflectance spectrophotometry method. Under optimized conditions the detection limit of the proposed reflectance-based enzymatic biosensor membrane was estimated to be 1 mg L−1 with a wide dynamic linear concentration range of 5–60 mg L−1 DCA (R2 = 0.9792) and satisfactory reproducibility within the relative standard deviation (RSD) range of 3.4–4.3%. Validation test demonstrated that the optical halocarbon biosensor could be a promising tool for rapid (6 min) in situ and direct evaluation of organohalide in river water, tap water and bottled water samples without any sample pre-treatment or extraction steps.
- Published
- 2019
68. A quantification strategy for DNA hybridization via measurement of adsorbed anthraquinone monosulphonic acid on silica nanospheres
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Hui Yee Chee, Lee Yook Heng, and Yew Pei Ling
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Chemistry ,Applied Mathematics ,Sonication ,Hybridization probe ,Condensed Matter Physics ,Combinatorial chemistry ,Anthraquinone ,Amperometry ,chemistry.chemical_compound ,Adsorption ,Colloidal gold ,Electrical and Electronic Engineering ,Instrumentation ,Biosensor ,DNA - Abstract
An amperometric DNA biosensor was developed based on a DNA quantification concept involving the adsorption behavior of anthraquinone monosulphonic acid (AQMS). The biosensor was built from a carbon pasted screen-printed electrode coated with silica nanospheres and gold nanoparticles. Silica nanospheres of 65–84 nm were synthesized via sonication and its surface further modified with amine group. Aminated silica nanospheres immobilize amine-functionalized DNA probe covalently via glutaraldehyde linkers while gold nanoparticles used as an effective electron transfer agent. Anionic AQMS can physically adsorb onto cationic aminated silica nanospheres, and the total AQMS adsorption will be reduced if hybridization occurs. Hence, an increasing amount of hybridized DNA cause a declination in differential pulse voltammetric current signal of AQMS at −0.50 V. The biosensor yielded a linear response range of 10−9–0.5 μM (R2 = 0.97) towards DNA target and showed negligible response to mismatched and noncomplemetary DNA. The fabricated DNA biosensor as an early detection and possible noninvasive method for clinical and medical use was successfully performed; with the detection of synthetic DNA target and cDNA that were reverse-transcripted from dengue virus RNA.
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- 2019
69. Detection of halogenated hydrocarbon pollutants using enzymatic reflectance biosensor
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Hidayah Shahar, Goh Choo Ta, Ling Ling Tan, and Lee Yook Heng
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Detection limit ,Chromatography ,Metals and Alloys ,Substrate (chemistry) ,02 engineering and technology ,Halocarbon ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Nile blue ,01 natural sciences ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Matrix (chemical analysis) ,chemistry.chemical_compound ,chemistry ,Succinimide ,Materials Chemistry ,Electrical and Electronic Engineering ,0210 nano-technology ,Instrumentation ,Biosensor ,Haloalkane dehalogenase - Abstract
A reflectometric biosensor for enzymatic determination of halogenated organic pollutant in environmental water sample was developed. Polyacrylate microspheres modified with succinimide functional groups were employed as the substrate matrix for covalent immobilization of haloalkane dehalogenase (DhlA) enzyme, and ETH5294 Nile Blue chromoionophore (NBC) pH dye was physically immobilized on the acrylic micromatrix to function as an optical proton sensor. The hydrolytic dehalogenation of halocarbon catalyzed by the immobilized DhlA resulting in the release of a halogen and a proton, which protonated the immobilized NBC proton indicator, and a colour change of the biosensor from violet to blue was measured with a reflectance spectrophotometer for indirect quantification of the halogenated hydrocarbon concentration. The enzymatic halocarbon reflectance biosensor exhibited a dynamic linear response range of 1–30 mg L−1 1,2-dichloroethane (DCA) (R2 = 0.9762) with a detection limit of 0.3 mg L−1. The proposed enzymatic biosensor gave rapid response, within 2 min, towards the detection of 50 mg L−1 DCA at 662 nm, and demonstrated stable response up to 6 days of storage period at 4 °C and pH 8.0. Validation between the developed biosensor with standard gas chromatography–electron capture detector (GC-ECD) showed that both methods have a comparable accuracy in detecting halocarbon species.
- Published
- 2019
70. Hexaferrocenium tri[hexa(isothiocyanato)iron(III)] trihydroxonium complex as a new DNA intercalator for electrochemical DNA biosensor
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Bohari Mohd. Yamin, Muhammad Kassim, Siti Aishah Hasbullah, Farah Bt Ruslin, Lee Yook Heng, Eda Yuhana Ariffin, and Emma Izzati Zakariah
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Swine ,Science ,Iron ,Intercalation (chemistry) ,Metal Nanoparticles ,02 engineering and technology ,Biosensing Techniques ,010402 general chemistry ,01 natural sciences ,Article ,chemistry.chemical_compound ,Animals ,Electrodes ,Multidisciplinary ,DNA ,Electrochemical Techniques ,021001 nanoscience & nanotechnology ,HEXA ,Binding constant ,Materials science ,0104 chemical sciences ,Chemistry ,chemistry ,Ferrocene ,Medicine ,Titration ,Differential pulse voltammetry ,0210 nano-technology ,Biosensor ,Nuclear chemistry - Abstract
Ferrocene or ferrocenium has been widely studied in the field of organometallic complexes because of its stable thermodynamic, kinetic and redox properties. Novel hexaferrocenium tri[hexa(isothiocyanato)iron(III)]trihydroxonium (HexaFc) complex was the product from the reaction of ferrocene, maleic acid and ammonium thiocyanate and was confirmed by elemental analysis CHNS, FTIR and single crystal X-ray crystallography. In this study, HexaFc was used for the first time as an electroactive indicator for porcine DNA biosensor. The UV–Vis DNA titrations with this compound showed hypochromism and redshift at 250 nm with increasing DNA concentrations. The binding constant (Kb) for HexaFc complex towards CT-DNA (calf-thymus DNA) was 3.1 × 104 M−1, indicated intercalator behaviour of the complex. To test the usefulness of this complex for DNA biosensor application, a porcine DNA biosensor was constructed. The recognition probes were covalently immobilised onto silica nanospheres (SiNSs) via glutaraldehyde linker on a screen-printed electrode (SPE). After intercalation with the HexaFc complex, the response of the biosensor to the complementary porcine DNA was measured using differential pulse voltammetry. The DNA biosensor demonstrated a linear response range to the complementary porcine DNA from 1 × 10−6 to 1 × 10−3 µM (R2 = 0.9642) with a limit detection of 4.83 × 10−8 µM and the response was stable up to 23 days of storage at 4 °C with 86% of its initial response. The results indicated that HexaFc complex is a feasible indicator for the DNA hybridisation without the use of a chemical label for the detection of porcine DNA.
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- 2021
71. The Mineral Content of Food Plants of the Sumatran Rhinoceros (Dicerorhinus sumatrensis) in Danum Valley, Sabah, Malaysia
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Lee, Yook Heng, Stuebing, Robert B., and Ahmad, Abdul Hamid
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- 1993
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72. A Comparative Study of Microwave-Assisted and Conventional Heating Methods of the Synthesis of 1-(Naphthalene-1-Yl)-3-(O, M, P-Tolyl)Thioureas, DFT Analysis, Antibacterial Evaluation and Drug-Likeness Assessment
- Author
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SAPARI, SUHAILA, primary, ZAKARIAH, EMMA IZZATI, additional, ABDUL RAZAK, NURUL HIDAYAH, additional, RAMZAN, INSYIRAH, additional, NUMIN, MOHD SOFI, additional, LEE, YOOK HENG, additional, and HASBULLAH, SITI AISHAH, additional
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- 2021
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73. COMPARISON OF sPLA2-IIA PERFORMANCE WITH HIGH-SENSITIVE CRP, NEUTROPHIL PERCENTAGE, PCT AND LACTATE TO IDENTIFY BACTERIAL INFECTION: A PROSPECTIVE STUDY
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Tan, Toh Leong, primary, Kang, Christabel Wan-li, additional, Ooi, Kai Shen, additional, Tan, Swee Thian, additional, Ahmad, Nurul Saadah, additional, Nasuruddin, Dian Nasriana, additional, Ithnin, Azlin, additional, Arifin, Khaizurin Tajul, additional, Lee, Yook Heng, additional, Hassan, Nurul Izzaty, additional, Gan, Kok Beng, additional, and Neoh, Hui-min, additional
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- 2021
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74. Investigating the Potential of 8-Amidoquinoline Derivatives as a Fluorescent Probe for Zinc Detection: A Systematic Literature Review
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Ling Ling Tan, Nurul Izzaty Hassan, Nurulhaidah Daud, Nur Hanis Zakaria, Lee Yook Heng, Nur Syamimi Mohamad, and Goh Choo Ta
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analytical_chemistry ,Systematic review ,Chemistry ,chemistry.chemical_element ,Zinc ,Fluorescence ,Combinatorial chemistry - Abstract
Abundant of preparatory works have recognized that fluorescent sensors based on 8-aminoquinoline are popular tools to detect Zn2+ ions in environmental and biological applications. Along with these studies, researchers started to introduce a variety of carboxamido group into an 8-aminoquinoline molecule in forming 8-amidoquinoline derivatives. Therefore, this systematic review aims to introduce a general overview of the fluorophore 8-aminoquinoline as Zn2+ receptors and to provide comparisons of collected studies that related to 8-amidoquinoline derivatives as fluorophore probe of the sensor. According to PRISMA systematic searches strategy, 13 articles were analyzed for trends, research designs, results and discussion, subject samples, and remarks or conclusions. We found cross-sectional studies with four aspects in zinc sensing that have been targeted; binding studies via titration, detection's limit, interferences studies, and validation of the study. Hence, this paper also included assessments of those criteria and the trends of development of 8-amidoquinoline derivatives based-zinc fluorescent chemosensor. It also showed that most of the researches conducted in China. In conclusion, this study identified various research designs of fluorescent chemosensors based on 8-amidoquinoline prolong with the effectiveness and potential as a recognition probe to assist the detection of zinc. Hence, elucidation of those derivatives essential to be explored because more studies are needed to improve the sensing criteria of the zinc sensor
- Published
- 2020
75. Highly Sensitive Fluorescence Sensor for Carrageenan from a Composite Methylcellulose/Polyacrylate Membrane
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Ling Ling Tan, Riyadh Abdulmalek Hassan, and Lee Yook Heng
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Letter ,02 engineering and technology ,010402 general chemistry ,lcsh:Chemical technology ,01 natural sciences ,Biochemistry ,Analytical Chemistry ,fluorescence sensor ,chemistry.chemical_compound ,lcsh:TP1-1185 ,Electrical and Electronic Engineering ,Instrumentation ,chemistry.chemical_classification ,Detection limit ,Acrylate ,Chromatography ,Polymer ,polymer blend ,021001 nanoscience & nanotechnology ,Atomic and Molecular Physics, and Optics ,0104 chemical sciences ,Carrageenan ,Membrane ,chemistry ,Reagent ,carrageenan ,methylene blue ,Polymer blend ,0210 nano-technology ,Methylene blue - Abstract
Carrageenans are linear sulphated polysaccharides that are commonly added into confectionery products but may exert a detrimental effect to human health. A new and simpler way of carrageenan determination based on an optical sensor utilizing a methylcellulose/poly(n-butyl acrylate) (Mc/PnBA) composite membrane with immobilized methylene blue (MB) was developed. The hydrophilic Mc polymer membrane was successfully modified with a more hydrophobic acrylic polymer. This was to produce an insoluble membrane at room temperature where MB reagent could be immobilized to build an optical sensor for carrageenan analysis. The fluorescence intensity of MB in the composite membrane was found to be proportional to the carrageenan concentrations in a linear manner (1.0–20.0 mg L−1, R2 = 0.992) and with a detection limit at 0.4 mg L−1. Recovery of spiked carrageenan into commercial fruit juice products showed percentage recoveries between 90% and 102%. The optical sensor has the advantages of improved sensitivity and better selectivity to carrageenan when compared to other types of hydrocolloids. Its sensitivity was comparable to most sophisticated techniques for carageenan analysis but better than other types of optical sensors. Thus, this sensor provides a simple, rapid, and sensitive means for carageenan analysis.
- Published
- 2020
76. An electrochemical DNA biosensor fabricated from graphene decorated with graphitic nanospheres
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Ling Ling Tan, Kwok Feng Chong, Lee Yook Heng, and Raja Zaidatul Akhmar Raja Jamaluddin
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Materials science ,Immobilized Nucleic Acids ,Bioengineering ,02 engineering and technology ,Biosensing Techniques ,010402 general chemistry ,01 natural sciences ,Nanomaterials ,law.invention ,chemistry.chemical_compound ,law ,Limit of Detection ,General Materials Science ,Electrical and Electronic Engineering ,Electrodes ,Detection limit ,Pyrenes ,Graphene ,Mechanical Engineering ,General Chemistry ,DNA ,Electrochemical Techniques ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,Potassium ferricyanide ,chemistry ,Mechanics of Materials ,Electrode ,Graphite ,Differential pulse voltammetry ,Cyclic voltammetry ,0210 nano-technology ,DNA Probes ,Biosensor ,Nanospheres ,Nuclear chemistry - Abstract
Graphene decorated with graphitic nanospheres functionalized with pyrene butyric acid (PBA) is used for the first time to fabricate a DNA biosensor. The electrode was formed by attaching a DNA probe onto PBA, which had been stacked onto a graphene material decorated with graphene nanospheres (GNSs). The nanomaterial was drop-coated onto a carbon screen-printed electrode (SPE) to create the GNS-PBA modified electrode (GNS-PBA/SPE). A simple method was used to produce GNS by annealing graphene oxide (GO) solution at high temperature. Field emission scanning electron micrographs confirmed the presence of a spherical shape of GNS with a diameter range of 40–80 nm. A stable and uniform PBA-modified GNS (GNS-PBA) was obtained with a facile ultrasonication step. Thus allowing aminated DNA probes of genetically modified (GM) soybean to be attached to the nanomaterials to form the DNA biosensor. The GNS-PBA/SPE exhibited excellent electrical conductivity via cyclic voltammetry (CV) and differential pulse voltammetry (DPV) tests using potassium ferricyanide (K3[Fe(CN)6]) as the electroactive probe. By employing an anthraquinone monosulfonic acid (AQMS) redox intercalator as the DNA hybridization indicator, the biosensor response was evaluated using the DPV electrochemical method. A good linear relationship between AQMS oxidation peak current and target DNA concentrations from 1.0 × 10−16 to 1.0 × 10−8 M with a limit of detection (LOD) of less than 1.0 × 10−16 M was obtained. Selectivity experiments revealed that the voltammetric GM DNA biosensor could discriminate complementary sequences of GM soybean from non-complementary sequences and hence good recoveries were obtained for real GM soybean sample analysis. The main advantage of using GNS is an improvement of the DNA biosensor analytical performance.
- Published
- 2020
77. Sandwich-Type DNA Micro-Optode Based on Gold–Latex Spheres Label for Reflectance Dengue Virus Detection
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Nur-Fadhilah Mazlan, Nurul Yuziana Mohd Yusof, Goh Choo Ta, Nur Diyana Jamaluddin, Alizar Ulianas, Jeningsih, Ling Ling Tan, Bahariah Khalid, and Lee Yook Heng
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reflectance ,Polymers ,Metal Nanoparticles ,Succinimides ,02 engineering and technology ,Biosensing Techniques ,Dengue virus ,lcsh:Chemical technology ,medicine.disease_cause ,01 natural sciences ,Biochemistry ,Article ,Analytical Chemistry ,Dengue ,chemistry.chemical_compound ,Complementary DNA ,medicine ,sandwich hybridization ,Humans ,lcsh:TP1-1185 ,A-DNA ,Electrical and Electronic Engineering ,Instrumentation ,Detection limit ,Chromatography ,optical biosensor ,latex particles ,010401 analytical chemistry ,Dengue Virus ,021001 nanoscience & nanotechnology ,Atomic and Molecular Physics, and Optics ,Microspheres ,0104 chemical sciences ,Reverse transcription polymerase chain reaction ,chemistry ,Acrylates ,Colloidal gold ,gold nanoparticles ,DNA, Viral ,Gold ,0210 nano-technology ,Biosensor ,DNA - Abstract
A DNA micro-optode for dengue virus detection was developed based on the sandwich hybridization strategy of DNAs on succinimide-functionalized poly(n-butyl acrylate) (poly(nBA-NAS)) microspheres. Gold nanoparticles (AuNPs) with an average diameter of ~20 nm were synthesized using a centrifugation-based method and adsorbed on the submicrometer-sized polyelectrolyte-coated poly(styrene-co-acrylic acid) (PSA) latex particles via an electrostatic method. The AuNP&ndash, latex spheres were attached to the thiolated reporter probe (rDNA) by Au&ndash, thiol binding to functionalize as an optical gold&ndash, latex&ndash, rDNA label. The one-step sandwich hybridization recognition involved a pair of a DNA probe, i.e., capture probe (pDNA), and AuNP&ndash, PSA reporter label that flanked the target DNA (complementary DNA (cDNA)). The concentration of dengue virus cDNA was optically transduced by immobilized AuNP&ndash, PSA&ndash, rDNA conjugates as the DNA micro-optode exhibited a violet hue upon the DNA sandwich hybridization reaction, which could be monitored by a fiber-optic reflectance spectrophotometer at 637 nm. The optical genosensor showed a linear reflectance response over a wide cDNA concentration range from 1.0 ×, 10&minus, 21 M to 1.0 ×, 12 M cDNA (R2 = 0.9807) with a limit of detection (LOD) of 1 ×, 29 M. The DNA biosensor was reusable for three consecutive applications after regeneration with mild sodium hydroxide. The sandwich-type optical biosensor was well validated with a molecular reverse transcription polymerase chain reaction (RT-PCR) technique for screening of dengue virus in clinical samples, e.g., serum, urine, and saliva from dengue virus-infected patients under informed consent.
- Published
- 2020
- Full Text
- View/download PDF
78. A Highly Sensitive Impedimetric DNA Biosensor Based on Hollow Silica Microspheres for Label-Free Determination of E. coli
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Lee Yook Heng, Siti Aishah Hasbullah, Nurul Huda Abd Karim, Ling Ling Tan, and Eda Yuhana Ariffin
- Subjects
Metal Nanoparticles ,Biosensing Techniques ,02 engineering and technology ,macromolecular substances ,e. coli detection ,Buffers ,Electrochemistry ,medicine.disease_cause ,lcsh:Chemical technology ,01 natural sciences ,Biochemistry ,Article ,Analytical Chemistry ,chemistry.chemical_compound ,impedimetric dna sensor ,Limit of Detection ,label-free dna biosensor ,Spectroscopy, Fourier Transform Infrared ,Escherichia coli ,medicine ,E. coli detection ,lcsh:TP1-1185 ,Electrical and Electronic Engineering ,Electrodes ,Instrumentation ,Detection limit ,Chromatography ,Staining and Labeling ,Chemistry ,Hybridization probe ,010401 analytical chemistry ,technology, industry, and agriculture ,dna biosensor ,DNA ,Silicon Dioxide ,021001 nanoscience & nanotechnology ,Microspheres ,Atomic and Molecular Physics, and Optics ,0104 chemical sciences ,Colloidal gold ,Electrode ,Gold ,0210 nano-technology ,Biosensor - Abstract
A novel label-free electrochemical DNA biosensor was constructed for the determination of Escherichia coli bacteria in environmental water samples. The aminated DNA probe was immobilized onto hollow silica microspheres (HSMs) functionalized with 3-aminopropyltriethoxysilane and deposited onto a screen-printed electrode (SPE) carbon paste with supported gold nanoparticles (AuNPs). The biosensor was optimized for higher specificity and sensitivity. The label-free E. coli DNA biosensor exhibited a dynamic linear response range of 1 ×, 10&minus, 10 µ, M to 1 ×, 5 µ, M (R2 = 0.982), with a limit of detection at 1.95 ×, 15 µ, M, without a redox mediator. The sensitivity of the developed DNA biosensor was comparable to the non-complementary and single-base mismatched DNA. The DNA biosensor demonstrated a stable response up to 21 days of storage at 4 ℃ and pH 7. The DNA biosensor response was regenerable over three successive regeneration and rehybridization cycles.
- Published
- 2020
79. Biosensor Nitrit Optik Berasaskan Hemoglobin Terpegun pada Mikrosfera Poliakrilat
- Author
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Syamimi Haslan, Goh Choo Ta, Lee Yook Heng, and Ling Ling Tan
- Subjects
Multidisciplinary ,Chemistry ,Nuclear chemistry - Abstract
Biosensor optik berasaskan hemoglobin (Hb) terpegun pada mikrosfera poli(n-butil akrilat-co-N-akriloksisuksinimida) [poli(nBA-NAS)] telah dibangunkan bagi mengesan kepekatan ion nitrit (NO2-). Kompleks HEM ferum dalam Hb memangkinkan tindak balas penurunan ion NO2- kepada nitrik oksida (NO) lalu bergabung dengan deoksihemoglobin (HbFe2+) membentuk kompleks ferum-nitrosil-hemoglobin (HbFe2+-NO) yang berwarna hijau kekuningan. Spektrofotometer pantulan gentian optik digunakan untuk memantau kepekatan ion NO2- secara kuantitatif berdasarkan perubahan warna Hb terpegun pada mikrosfera poliakrilat daripada perang kemerahan ke hijau kekuningan pada panjang gelombang pantulan maksimum 668 nm. Pencirian terhadap biosensor nitrit reflektometrik melibatkan ujian kesan pH, kesan kepekatan Hb, julat rangsangan linear, kebolehasilan, jangka hayat dan kesan gangguan ion telah dijalankan. Biosensor ion NO2- optik terbangun memaparkan julat linear dinamik daripada 5 hingga 50 mg mL-1 (R2=0.9894) pada pH7.0 dengan had pengesanan (LOD) sebanyak 3.3 mg mL-1 dan nilai sisihan piawai relatif (RSD) kebolehasilan biosensor sebanyak 5.8%. Jangka hayat biosensor optik nitrit tersebut adalah selama 36 hari dan majoriti ion asing yang sering wujud bersama ion NO2- dalam sampel air semula jadi tidak menunjukkan kesan gangguan yang bererti terhadap penentuan ion NO2- menggunakan biosensor optik terbangun kecuali ion Hg2+, Ag+, Br- dan S2-.
- Published
- 2018
80. An Electrochemical DNA Biosensor for Carcinogenicity of Anticancer Compounds Based on Competition between Methylene Blue and Oligonucleotides
- Author
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Siti Aishah Hasbullah, Jalifah Latip, Lee Yook Heng, Wong Sheryn, Mohd Asyraf Shamsuddin, Nurul Izzaty Hassan, Eda Yuhana Ariffin, and Nor Diyana Md. Sani
- Subjects
Guanine ,Carcinogenesis ,Oligonucleotides ,DNA, Single-Stranded ,Metal Nanoparticles ,02 engineering and technology ,macromolecular substances ,Biosensing Techniques ,Cadmium chloride ,lcsh:Chemical technology ,01 natural sciences ,Biochemistry ,Article ,Analytical Chemistry ,chemistry.chemical_compound ,Electrochemistry ,Humans ,lcsh:TP1-1185 ,Electrical and Electronic Engineering ,Instrumentation ,Electrodes ,Detection limit ,010405 organic chemistry ,Oligonucleotide ,technology, industry, and agriculture ,toxicity ,electrochemical ,DNA ,Electrochemical Techniques ,021001 nanoscience & nanotechnology ,Silicon Dioxide ,Atomic and Molecular Physics, and Optics ,Carbon ,0104 chemical sciences ,carcinogen ,Methylene Blue ,chemistry ,Carcinogens ,Differential pulse voltammetry ,Gold ,0210 nano-technology ,Biosensor ,Methylene blue ,DNA biosensor ,Nuclear chemistry - Abstract
A toxicity electrochemical DNA biosensor has been constructed for the detection of carcinogens using 24 base guanine DNA rich single stranded DNA, and methylene blue (MB) as the electroactive indicator. This amine terminated ssDNA was immobilized onto silica nanospheres and deposited on gold nanoparticle modified carbon-paste screen printed electrodes (SPEs). The modified SPE was initially exposed to a carcinogen, followed by immersion in methylene blue for an optimized duration. The biosensor response was measured using differential pulse voltammetry. The performance of the biosensor was identified on several anti-cancer compounds. The toxicity DNA biosensor demonstrated a linear response range to the cadmium chloride from 0.0005 ppm to 0.01 ppm (R2 = 0.928) with a limit of detection at 0.0004 ppm. The biosensor also exhibited its versatility to screen the carcinogenicity of potential anti-cancer compounds.
- Published
- 2019
81. Carcinogens: Tracing a Potential Murderer Using DNA Biosensors
- Author
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Diyana Sani, Lee Yook Heng, and Azwan Mat Lazim
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chemistry.chemical_compound ,Biochemistry ,chemistry ,Electrical and Electronic Engineering ,Tracing ,Biosensor ,Atomic and Molecular Physics, and Optics ,DNA ,Carcinogen - Published
- 2018
82. A whole cell bio-optode based on immobilized nitrite-degrading microorganism on the acrylic microspheres for visual quantitation of nitrite ion
- Author
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Nina Suhaity Azmi, Lee Yook Heng, Siti Nur Syazni Mohd Zuki, Kwok Feng Chong, Ling Ling Tan, and Saiful Nizam Tajuddin
- Subjects
Detection limit ,Chromatography ,010401 analytical chemistry ,Ion chromatography ,Metals and Alloys ,Substrate (chemistry) ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Nitrite reductase ,Nile blue ,01 natural sciences ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Matrix (chemical analysis) ,chemistry.chemical_compound ,chemistry ,Materials Chemistry ,Electrical and Electronic Engineering ,Nitrite ,Optode ,0210 nano-technology ,Instrumentation - Abstract
A microspheres-based microbial optosensor for NO 2 − ion quantitation was constructed by using immobilized Raoutella planticola ( R. planticola ), the bacterium expressing NAD(P)H nitrite reductase (NiR) enzyme, which was isolated from local edible bird’s nest (EBN) via microbial technique. The whole cells and the lipophilic Nile Blue chromoionophore (NBC) were physically adsorbed on the self-adhesive photocurable poly( n -butyl acrylate-co- N -acryloxysuccinimide) [poly(nBA-NAS)] microspheres, whilst the reduced co-enzyme NAD(P)H was covalently immobilized on the succinimide-functionalized acrylic microspheres via peptide link to produce a reagentless nitrite biosensing system. As the microbial bio-optode responded to nitrite through colour change from blue to pink, a facile reflectometric approach was adopted to measure reflectance intensity at 639 nm, before and after reaction with nitrite at optimum pH 8. The optosensor could quantify NO 2 − ion concentration within a dynamic linear response range of 0.5–400 mg L −1 with a limit of detection (LOD) of 0.2 mg L −1 . The large surface area to volume ratio of the acrylic microspheres allowed solid-state diffusional mass transfer of the substrate to occur at micro-bio-optode surface, and an equilibrium response was achieved within 5 min. The practical feasibility of using the bio-optode for nitrite assay in food matrix sample showed good agreement with standard ion chromatography method.
- Published
- 2018
83. A Biosensor for Genetic Modified Soybean DNA Determination via Adsorption of Anthraquinone-2-sulphonic Acid in Reduced Graphene Oxide
- Author
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Lee Yook Heng, Ling Ling Tan, Raja Zaidatul Akhmar Raja Jamaluddin, and Kwok Feng Chong
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Detection limit ,Graphene ,Chemistry ,Hybridization probe ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Analytical Chemistry ,law.invention ,chemistry.chemical_compound ,Covalent bond ,law ,Electrochemistry ,A-DNA ,Differential pulse voltammetry ,0210 nano-technology ,Biosensor ,DNA ,Nuclear chemistry - Abstract
An electrochemical DNA biosensor for DNA determination of genetically modified (GM) soybean (CaMV 35S target genes) was developed utilizing a new detection concept based on the adsoption of anthraquinone‐2‐sulphonic acid (AQMS) on the reduced graphene oxide nano‐particles (rGO) during DNA hybridization events. The aminated DNA probe for CaMV 35S was immobilized onto poly(n‐butyl acrylate) film modified with succinimide functional groups [poly(nBA‐NAS)] via peptide covalent bond. Nanosheets of rGO were entrapped in the poly(nBA‐NAS) film to form a conducting [poly(nBA‐NAS)‐rGO] film of the DNA biosensor. Besides facilitating the electron transfer reactions, the rGO also functioned as an adsorbent for AQMS. The sensing mechanism of the proposed DNA biosensor involved measuring the oxidation current of the AQMS adsorbed on the electrode surface at −0.50 V using differential pulse voltammetry (DPV) before and after a DNA hybridization event. Under optimum conditions, the DNA biosensor demonstrated a linear proportionality between AQMS oxidation signal and logarithm cDNA concentration from 1.0×10−15 M to 1.0×10−8 M target DNA with a detection limit of 6.3×10−16 M. The electrochemical DNA biosensor possessed good selectivity and a shelf life of about 40 days with relative standard deviation of reproducibility obtained in the range of 3.7–4.6% (n=5). Evaluation of the DNA biosensor using GM soybean DNA extracts showed excellent recovery percentages of 97.2–104.0.
- Published
- 2017
84. The Use of Artificial Neural Network to Optimize The pH Response Range of Chlorophenol Red
- Author
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Lee Yook Heng, F. Wong, and Musa Ahmad
- Subjects
Atmospheric Science ,Artificial neural network ,Computer science ,Computer Science::Neural and Evolutionary Computation ,Back propagation algorithm ,Management, Monitoring, Policy and Law ,Oceanography ,equipment and supplies ,Artificial neural Networks ,body regions ,chemistry.chemical_compound ,chemistry ,pH indikator ,lcsh:Technology (General) ,Range (statistics) ,lcsh:T1-995 ,chlorophenol red ,Chlorophenol red ,Biological system ,lcsh:Science (General) ,Waste Management and Disposal ,back-propagation algorithm ,lcsh:Q1-390 - Abstract
Artificial Neural Network (ANN) had been used in this study to extend the response range of the pH indicator. The input from absorbance values of the absorbance spectra of chlorophenol red at different pH was used to train the ANN. During the training process, the coefficient values of the ANN will be adjusted to obtain the desire output. In this research, back propagation algorithm had been used for optimizing the response range of the pH indicator chlorophenol red in solution. The result indicates that the use of ANN enable the pH response range to be extended from 4.8-6.8 to 1.0-10.0.
- Published
- 2017
85. A DNA biosensor based on gold nanoparticle decorated on carboxylated multi-walled carbon nanotubes for gender determination of Arowana fish
- Author
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Lee Yook Heng, Kasra Saeedfar, and Chew Poh Chiang
- Subjects
Male ,Sex Determination Analysis ,Time Factors ,Ultraviolet Rays ,Carboxylic Acids ,Biophysics ,DNA, Single-Stranded ,Metal Nanoparticles ,Nanoparticle ,chemistry.chemical_element ,Nanotechnology ,Biosensing Techniques ,02 engineering and technology ,Carbon nanotube ,01 natural sciences ,law.invention ,Redox indicator ,Sonication ,law ,Electrochemistry ,Animals ,Physical and Theoretical Chemistry ,Electrodes ,Detection limit ,Nanotubes, Carbon ,Chemistry ,010401 analytical chemistry ,Fishes ,Nucleic Acid Hybridization ,DNA ,General Medicine ,Hydrogen-Ion Concentration ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,Ruthenium ,Colloidal gold ,Female ,Gold ,Differential pulse voltammetry ,0210 nano-technology ,Biosensor ,Nuclear chemistry - Abstract
Multi-wall carbon nanotubes (MWCNTs) were modified to design a new DNA biosensor. Functionalized MWCNTs were equipped with gold nanoparticles (GNPs) (~15nm) (GNP-MWCNTCOOH) to construct DNA biosensors based on carbon-paste screen-printed (SPE) electrodes. GNP attachment onto functionalized MWCNTs was carried out by microwave irradiation and was confirmed by spectroscopic studies and surface analysis. DNA biosensors based on differential pulse voltammetry (DPV) were constructed by immobilizing thiolated single-stranded DNA probes onto GNP-MWCNTCOOH. Ruthenium (III) chloride hexaammoniate [Ru(NH3)6,2Cl-] (RuHex) was used as hybridization redox indicator. RuHex and MWCNT interaction was low in compared to other organic redox hybridization indicators. The linear response range for DNA determination was 1×10-21 to 1×10-9M with a lower detection limit of 1.55×10-21M. Thus, the attachment of GNPs onto functionalized MWCNTs yielded sensitive DNA biosensor with low detection limit and stability more than 30days. Constructed electrode was used to determine gender of arowana fish.
- Published
- 2017
86. Managing Dengue Disaster: Uncovering Paramount Community Elements for DNA Sensory Tool Accessibility in Malaysia
- Author
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Mazlan, Nur-Fadhilah, primary, Tan, Ling Ling, additional, Hasan Reza, Mohammad Imam, additional, Goh, Choo Ta, additional, Abd. Karim, Nurul Huda, additional, and Lee, Yook Heng, additional
- Published
- 2020
- Full Text
- View/download PDF
87. Kajian Pengkompleksan Sebatian Bis-Tiourea dengan Ion Aluminium sebagai Ionofor dalam Pembangunan Sensor Ion Potensiometri
- Author
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Kook, Shih Ying, primary, Awang Ngah, Fatimatul Akma, additional, Sapari, Suhaila, additional, Lee, Yook Heng, additional, and Hasbullah, Siti Aishah, additional
- Published
- 2019
- Full Text
- View/download PDF
88. Potentiometric Urea Biosensor Based on Immobilization of Urease in Kappa-Carrageenan Biopolymer
- Author
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Lee Yook Heng, Chakavak Esmaeili, Tan Ling Ling, Yew Pei Ling, and Parviz Norouzi
- Subjects
Chromatography ,Urease ,biology ,Kappa-Carrageenan ,Chemistry ,020209 energy ,Potentiometric titration ,Urea biosensor ,02 engineering and technology ,engineering.material ,Atomic and Molecular Physics, and Optics ,0202 electrical engineering, electronic engineering, information engineering ,biology.protein ,engineering ,Biopolymer ,Electrical and Electronic Engineering - Published
- 2017
89. Crystal structure of 4-methoxy-N-(piperidine-1-carbonothioyl)benzamide
- Author
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Musa Ahmad, Lee Yook Heng, Khairi Suhud, Mohammad B. Kassim, and Siti Aishah Hasbullah
- Subjects
crystal structure ,benzamide ,Cyclohexane conformation ,pyrrolidine ,Thio ,benzoylthiourea ,Crystal structure ,Dihedral angle ,010402 general chemistry ,010403 inorganic & nuclear chemistry ,Ring (chemistry) ,01 natural sciences ,Crystal ,chemistry.chemical_compound ,C—H...π interactions ,General Materials Science ,anti-cancer ,Crystallography ,Chemistry ,Hydrogen bond ,General Chemistry ,Condensed Matter Physics ,piperidine ,hydrogen bonding ,0104 chemical sciences ,offset π–π interactions ,QD901-999 ,Piperidine - Abstract
In the title compound, C14H18N2O2S, the piperidine ring has a chair conformation. Its mean plane is twisted with respect to the 4-methoxybenzoyl ring, with a dihedral angle of 63.0 (3)°. The central N—C(=S)—N(H)—C(=O) bridge is twisted with an N—C—N—C torsion angle of 74.8 (6)°. In the crystal, molecules are linked by N—H...O and C—H...O hydrogen bonds, forming chains along thec-axis direction. Adjacent chains are linked by C—H...π interactions, forming layers parallel to theacplane. The layers are linked by offset π–π interactions [intercentroid distance = 3.927 (3) Å], forming a supramolecular three-dimensional structure.
- Published
- 2017
90. A New Hydrogen Peroxide Biosensor Using Hemoglobin Conjugated Titanium Dioxide for Milk Analysis
- Author
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Nur Hamidah Abdul Halim, Radha Swathe Priya Malon Marugan, Uda Hashim, and Lee Yook Heng
- Subjects
chemistry.chemical_compound ,chemistry ,Titanium dioxide ,Hemoglobin ,Electrical and Electronic Engineering ,Conjugated system ,Hydrogen peroxide ,Biosensor ,Atomic and Molecular Physics, and Optics ,Nuclear chemistry - Published
- 2017
91. Ultrasensitive Biosensor for the Detection of Vibrio cholerae DNA with Polystyrene-co-acrylic Acid Composite Nanospheres
- Author
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Dedi Futra, Lee Yook Heng, Mahbubur Rahman, and Tan Ling Ling
- Subjects
Materials science ,Analytical chemistry ,02 engineering and technology ,medicine.disease_cause ,01 natural sciences ,Matrix (chemical analysis) ,medicine ,Polystyrene co-acrylic acid (PSA) particles ,lcsh:TA401-492 ,General Materials Science ,Vibrio cholerae ,Detection limit ,Chromatography ,Nano Express ,Oligonucleotide ,Faradaic current ,010401 analytical chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,0104 chemical sciences ,Electrochemical determination ,Biosensors ,Colloidal gold ,Latex-gold nanosphere ,lcsh:Materials of engineering and construction. Mechanics of materials ,Differential pulse voltammetry ,0210 nano-technology ,Biosensor ,EDC/NHS chemistry - Abstract
An ultrasensitive electrochemical biosensor for the determination of pathogenic Vibrio cholerae (V. cholerae) DNA was developed based on polystyrene-co-acrylic acid (PSA) latex nanospheres-gold nanoparticles composite (PSA-AuNPs) DNA carrier matrix. Differential pulse voltammetry (DPV) using an electroactive anthraquninone oligonucleotide label was used for measuring the biosensor response. Loading of gold nanoparticles (AuNPs) on the DNA-latex particle electrode has significantly amplified the faradaic current of DNA hybridisation. Together with the use of a reported probe, the biosensor has demonstrated high sensitivity. The DNA biosensor yielded a reproducible and wide linear response range to target DNA from 1.0 × 10−21 to 1.0 × 10−8 M (relative standard deviation, RSD = 4.5%, n = 5) with a limit of detection (LOD) of 1.0 × 10−21 M (R 2 = 0.99). The biosensor obtained satisfactory recovery values between 91 and 109% (n = 3) for the detection of V. cholerae DNA in spiked samples and could be reused for six consecutive DNA assays with a repeatability RSD value of 5% (n = 5). The electrochemical biosensor response was stable and maintainable at 95% of its original response up to 58 days of storage period.
- Published
- 2017
92. Recent developments in microfluidic paper-, cloth-, and thread-based electrochemical devices for analytical chemistry
- Author
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Lee Yook Heng, Radha S. P. Malon, and Emma P. Córcoles
- Subjects
Polymer science ,fabric ,paper ,010401 analytical chemistry ,Microfluidics ,microfluidics ,02 engineering and technology ,Thread (computing) ,electrochemical ,021001 nanoscience & nanotechnology ,Electrochemistry ,biosensor ,01 natural sciences ,0104 chemical sciences ,Analytical Chemistry ,Chemistry ,Hardware_INTEGRATEDCIRCUITS ,0210 nano-technology ,Biosensor ,QD1-999 - Abstract
The attractive structural and mechanical properties of cellulose substrates (paper, cloth, and thread), including passive fluid transport, biocompatibility, durability, and flexibility, have attracted researchers in the past few decades to explore them as alternative microfluidic platforms. The incorporation of electrochemical (EC) sensing broadened their use for applications such as clinical diagnosis, pharmaceutical chemical analyses, food quality, and environmental monitoring. This article provides a review on the microfluidic devices constructed on paper, cloth, and thread substrates. It begins with an overview on paper-based microfluidic devices, followed by an in-depth review on the various applications of EC detection incorporated on paper-based microfluidic devices reported to date. The review on paper-based microfluidic devices attempts to convey a few perspective directions that cloth- and thread-based microfluidic devices may take in its development. Finally, the research efforts on the development and evaluation, as well as current limitations of cloth- and thread-based microfluidic devices are discussed. Microfluidic devices constructed on paper, cloth, and thread substrates are still at an early development stage (prototype) requiring several improvements in terms of fabrication, analytical techniques, and performance to become mature platforms that can be adapted and commercialized as real world products. However, they hold a promising potential as wearable devices.
- Published
- 2017
93. Optical biosensing using newly synthesized metal salphen complexes: A potential DNA diagnostic tool
- Author
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Mohammad Imam Hasan Reza, Lee Yook Heng, Ling Ling Tan, Nur-Fadhilah Mazlan, and Nurul Huda Abd Karim
- Subjects
Intercalation (chemistry) ,Stacking ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,Nucleobase ,chemistry.chemical_compound ,Complementary DNA ,Materials Chemistry ,Organic chemistry ,Electrical and Electronic Engineering ,Instrumentation ,Chemistry ,Oligonucleotide ,technology, industry, and agriculture ,Metals and Alloys ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Combinatorial chemistry ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Optode ,0210 nano-technology ,Biosensor ,DNA - Abstract
A solid-state DNA optode sensor has been developed based on the employment of glutaraldehyde (GD)-activated aminated silica nanoparticles (SiO2NPs-NH2) DNA carrier matrix, and the newly synthesized yellowish N,N’-bis-5-(hydroxysalicylidene)phenylene-diamine-zinc(II) (i.e. the Zn salphen complex) oligonucleotide label. Some three Schiff base complexes with three different transition metal ions (Zn2+, Ni2+, Cu2+) were synthesized through a simple one-pot reaction (5 h), and characterized by their physical and chemical properties based on FTIR, NMR and ESI–MS analyses. Due to the square planar geometry and aromatic ring structured characteristics of the metal complex intercalators, they could intercalate between DNA bases via π-π stacking interaction, and rendered a yellowish pink hue on the DNA biosensor surface. Reflectometric optimization revealed high selectivity of the nanosilica-based DNA biosensor in the detection of dengue serotype 2 DNA, which capable of discriminating even a single nucleotide mismatch. The optical DNA biosensor demonstrated a linear reflectance response between 1.0 × 10−15 M and 1.0 × 10−11 M cDNA (R2 = 0.9975) with a fast DNA hybridization time of 30 min and a limit of detectable (LOD) DNA concentration as low as 1 zM. In addition, this biosensor showed high shelf life stability with a 20-day operational duration and reusable for five consecutive DNA testings. The proposed optical DNA biosensor offers biosensing performance far superior to that of previously reported electrochemical DNA biosensor for early diagnosis of dengue infection with respect to dynamic linear range, LOD and response time.
- Published
- 2017
94. A DNA biosensor based on kappa-carrageenan-polypyrrole-gold nanoparticles composite for gender determination of Arowana fish (Scleropages formosus)
- Author
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Chew Poh Chiang, Lee Yook Heng, Eka Safitri, Radha Swathe Priya Malon Marugan, Chakavak Esmaeili, and Zulkafli A. Rashid
- Subjects
02 engineering and technology ,01 natural sciences ,chemistry.chemical_compound ,Arowana ,Materials Chemistry ,Electrical and Electronic Engineering ,Instrumentation ,Detection limit ,Chromatography ,biology ,DNA–DNA hybridization ,010401 analytical chemistry ,Metals and Alloys ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,biology.organism_classification ,Molecular biology ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,chemistry ,Colloidal gold ,Differential pulse voltammetry ,0210 nano-technology ,Biosensor ,Scleropages formosus ,DNA - Abstract
The preparation and characterization of a DNA biosensor based on kappa-carrageenan-polypyrrole-gold nanoparticles (KC-PPy-AuNPs) nano-biocomposite is reported to demonstrate an application for gender classification of Arowana fish. Immobilization of the thiol modified Arowana fish ssDNA probe sequence was successfully carried out via covalent attachment to the gold (Au) on the surface of the nano-biocomposite membrane. Under optimum conditions, the DNA biosensor showed a short immobilization and hybridization time with high sensitivity for monitoring the target DNA sequence. The hybridization with the target DNA was determined by monitoring the redox current of anthraquinone-2-sulfonic acid monohydrate sodium salt (AQMS) using differential pulse voltammetry (DPV). The DNA hybridization response gradually increased with increasing concentrations of target DNA from 5 × 10 −18 to 5 × 10 −12 M and the limit of detection was below 5 × 10 −18 M. The application of the DNA biosensor for gender classification of Arowana fish was demonstrated.
- Published
- 2017
95. Amperometric capsaicin biosensor based on covalent immobilization of horseradish peroxidase (HRP) on acrylic microspheres for chilli hotness determination
- Author
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Rosmawani Mohammad, Lee Yook Heng, and Musa Ahmad
- Subjects
02 engineering and technology ,01 natural sciences ,Horseradish peroxidase ,chemistry.chemical_compound ,Succinimide ,Materials Chemistry ,Electrical and Electronic Engineering ,Hydrogen peroxide ,Instrumentation ,Detection limit ,Pungency ,Chromatography ,biology ,010401 analytical chemistry ,Metals and Alloys ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Amperometry ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,chemistry ,Covalent bond ,biology.protein ,0210 nano-technology ,Biosensor - Abstract
The evaluation of chilli hotness using amperometric capsaicin biosensor-based enzyme that was immobilized covalently to the surface of modified acrylic microspheres is the first of its kind presented in this work. The immobilization of enzyme covalently to the surface of microspheres via succinimide groups prevented the leaching of the enzyme. The enzymatic reaction between horseradish peroxidase-capsaicin in the presence of hydrogen peroxide, which was mediated by vinyl ferrocene, enabled the current measurement at a low potential (0.22 V). Besides, the pungency level of the chilli that was proportional to the capsaicin concentration was measured using this method. This biosensor gave a linear response range towards capsaicin from 0.75–24.94 μM (R2 = 0.992) with a detection limit at 0.39 μM. Moreover, the relative standard deviation (RSD) for reproducibility study was 8.2% (n = 7). Therefore, this biosensor was successfully applied for evaluation of chilli hotness in chilli sample, as well as in comparison with a standard method that employed the HPLC method.
- Published
- 2017
96. Fluorescence bioanalytical method for urea determination based on water soluble ZnS quantum dots
- Author
-
Lee Yook Heng, Eka Safitri, Musa Ahmad, and Tan Ling Ling
- Subjects
Urease ,Inorganic chemistry ,02 engineering and technology ,01 natural sciences ,chemistry.chemical_compound ,Enzymatic hydrolysis ,Materials Chemistry ,Electrical and Electronic Engineering ,Instrumentation ,Detection limit ,Bioconjugation ,biology ,Chemistry ,010401 analytical chemistry ,technology, industry, and agriculture ,Metals and Alloys ,equipment and supplies ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Fluorescence ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Covalent bond ,biology.protein ,Urea ,0210 nano-technology ,Luminescence - Abstract
A new bioanalytical method for urea determination by using the immobilized urease on the highly luminescent ZnS quantum dots (QDs), which functioned as the pH fluorescent label has been developed. Bioconjugation of ZnS QDs to urease via amide bond was performed to obtain the ZnS QDs-urease bioconjugate. Upon enzymatic hydrolysis of urea by the immobilized urease, a pH change to a more alkaline condition has led to the deprotonation of ZnS QDs, and an increase in the fluorescence intensity can be observed. The fluorescence intensity of the urease conjugated ZnS QDs changed linearly with the urea concentrations between 4 × 10 −9 M and 4 × 10 −3 M (R 2 = 0.992) at pH 6 with a calibration sensitivity of 179.46 intensity/decade. No noticeable influence by the Ca 2+ , Mg 2+ , K + and Na + ions on the response of the fluorescent pH bioprobe. Urea determination in soil sample by using the urea bioprobe was in good agreement with the standard DMAB (p-dimethylaminobenzaldehyde) UV–vis spectrophotometric method. By employing the strategy of ZnS QDs-urease bioconjugation, the stable covalent link between the two substances has appeared to widen the dynamic range and lower the detection limit for urea compared to free enzyme and QDs in solution for bioassay of urea concentration.
- Published
- 2017
97. Pahang Flood Disaster : The Potential Flood Drivers
- Author
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Khairul Nizam Ahmad Maulud, Mohd Ekhwan Toriman, Maizurah Maizan, Mazlin Mokhtar, Syamimi Halimshah, Nurlina Mohamad Ramzan, Ahmad Fuad Embi, Lee Yook Heng, Syafinaz Salleh, Rahmah Elfithri, Maimon Abdullah, and Pauzi Abdullah
- Subjects
lcsh:Geology ,Geography ,Flood Potential Analysis (FPAn) Multi-Criteria Evaluation (MCE) Sabah ,Flood myth ,lcsh:QE1-996.5 ,Malaysia ,Water resource management - Abstract
The northeast monsoon which occurs from November to March carries heavy rainfall which always result in flood especially to the east coast of Peninsular Malaysia. Pahang was one of the state that severely affected by this flood. Although the heavy rain is the main driver of the flood but human being cannot ignore the other flood drivers especially the river and its nearby environment circumstance which regard the flood event. The objective of this study was to determine the other flood drivers especially the river and its nearby environment circumstance which regard the flood event. The methodologies used in this study involved data collection through literature reviews and flood reports from Drainage and Irrigation Department (DID) and districts and interview to gather more information and verify the issues and other related drivers. The possible drivers of flooding in Pahang that occurred are as follows : 1) High rain intensity (>60 mm/hour, 200 – 450 mm/day) at the upstream that increases the quantity of water in the river and causes it to overflow 2) Water from area that has no drainage connection with the river (lowland, recessed and swamp area) was also flowing out and contributed to the flood 3) The size of the irrigation system is insufficient to bear the water flow rate and the tributary network is unable to withstand the large runoff 4) Increased reclaim of wetland area for development that causes irrigation system to be narrowed and obstructed for the water to flowing in to the tributaries 5) Prevalent forest clearing and logging activity increased the water non-absorbent area 6) Ground cutting for development purpose decreased the rain water absorption into the ground and increased surface water runoff, thus causes the watershed area decrease in its ability to hold water 7) Shallow estuary caused by high sedimentation from various activities leads to slow water conduction flowing from flood area to the sea 8) Most residential area are located at lowland and flood plain region coupled with bad irrigation system especially in big residential area, thus increased the flood risk. Each possible driver of flooding in Pahang that occurred in 2014 has to be discussed further in term of the responsible stakeholders who should involve in the management and maintenance. The heavy rainfall from northeast monsoon which was the main flood driver cannot be avoided but some flood drivers especially the river and its nearby environment that may contribute to higher magnitude of flood can be fixed and controlled by human
- Published
- 2017
98. Fabricating Long Shelf Life Potentiometric Urea Biosensors Using Modified MWCNTs on Screen Printed Electrodes
- Author
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Lee Yook Heng, Kasra Saeedfar, and Majid Rezayi
- Subjects
Materials science ,Screen printed electrode ,020208 electrical & electronic engineering ,Potentiometric titration ,Nanotechnology ,02 engineering and technology ,Carbon nanotube ,021001 nanoscience & nanotechnology ,Shelf life ,Atomic and Molecular Physics, and Optics ,law.invention ,chemistry.chemical_compound ,chemistry ,law ,Electrode ,0202 electrical engineering, electronic engineering, information engineering ,Electroanalytical method ,Urea ,Electrical and Electronic Engineering ,0210 nano-technology ,Biosensor - Published
- 2017
99. STAKEHOLDERS’ RESPONSE AND PERSPECTIVES ON FLOOD DISASTER OF PAHANG RIVER BASIN
- Author
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Pauzi Abdullah, Maizura Maizan, Lee Yook Heng, Syamimi Halimshah, Ahmad Fuad Embi, Mazlin Mokhtar, Syafinaz Salleh, Rahmah Elfithri, Mohd Ekhwan Toriman, Maimon Abdullah, Khairul Nizam Abdul Maulud, and Nurlina Mohamad Ramzan
- Subjects
geography ,geography.geographical_feature_category ,workshop ,Flood myth ,business.industry ,Environmental resource management ,lcsh:QE1-996.5 ,Drainage basin ,Pahang river basin ,stakeholders ,lcsh:Geology ,catchment area ,Environmental science ,business ,flood disaster - Abstract
The Pahang river basin is the largest river basin in the Pahang State, with total catchment area covering 29300km2. Floods of Pahang river basin have become an annual natural disaster event where all the stakeholders have their own responsibility and parts to take care of it. This study has focused on stakeholders’ response and perspectives to verify the issues on flood disaster of Pahang river basin. The methodology used in this study is the stakeholders’ consultation workshop. This workshop was conducted by involving the stakeholders’ representatives from various agencies. The result from this workshop has revealed the response and perspectives based on the important parts of each stakeholder to face the flood event that occurred in Pahang river basin. Besides, the issues aroused from this workshop have shown the stakeholders’ response and their perspectives on how to reduce the impacts on flood disaster of Pahang river basin. According to the workshop, there are two factors contribute to flood event which are the heavy rainfall and the arising of water level. The causes of these two factors are the reason that we need to involve all aspects in order to reduce the impact of flood disaster. The aspects are to identify the frequent problems to arise during flood event, to improvise the operating systems such as flood forecasting systems, telemetric systems and hydrology system, the plans of each stakeholder on how to cooperate and reduce the impact as one team, to provide the proper flood maps at the study level and to review and verify what are the communities’ complaints and perspectives as they also one of the victims. This study had discussed the proposed actions need to be taken according to the stakeholders’ response and perspectives. The overflow of river water had caused by the low absorption of rainfall from forest which due to deforestation and loggings. The high water level also caused by the high sedimentations which contributed by these activities. The law enforcement with more stringent need to be done on these matters. Besides, the operating systems need to be improvised and added as these approaches can help in reducing the impact of flood events. The flood maps should be provided at study level to identify and produce a valuable case study. Stakeholders’ consultations and involvement are the keys to improvise the weakness on how to cope with the floods event from the early stage. The proposal and implementations of the development should be done by involving the stakeholders’ response and perspectives in any disaster
- Published
- 2017
100. Histamine Detection in Mackerel (Scomberomorus Sp.) and its Products Derivatized with 9-Flourenilmethylchloroformate.
- Author
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Munir, Muhammad Abdurrahman, Lee Yook Heng, Sage, Edison Eukun, Mackeen, Muhammad MukramMohamed, and Badri, Khairiah Haji
- Subjects
- *
HIGH performance liquid chromatography , *MACKERELS , *HISTAMINE , *HISTAMINE receptors - Abstract
Histamine is commonly present in food containing proteins, like in mackerel. Consuming fish is imperative for the improvement of human muscles. Nevertheless, some studies reported ingesting fish containing histamine more than 50 mg·kg-1 can cause toxicity. This study analyzed and determined the composition of histamine in mackerel and its products commonly consumed in Malaysia, especially on the East Coast of Malaysia. These included processed mackerel such as canned products, satay (skewed fish) and keropok lekor (fish cake/ cracker). Histamine analysis was performed using High Performance Liquid Chromatography (HPLC) equipped with a fluorescence detector. A derivatizing reaction was applied to increase the sensitivity of HPLC to histamine using 9-flourenilmethylchloroformate (FMOC-Cl). The chromatographic separation was achieved in 15 min. Method validation was in accordance to Commission Decision 657/2002/CE. The linear range was at 0.16 – 5.00 μg·mL-1 (histamine) with the LOD at 0.10 μg·mL-1 and LOQ at 0.30 μg·mL-1. Method applicability was checked on seven real samples involving raw, cooked, and dry products, yielding acceptable recovery. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
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