Displaying publications 1 - 20 of 25 in total

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  1. Chay SY, Tan WK, Saari N
    J Microencapsul, 2015;32(5):488-95.
    PMID: 26079597 DOI: 10.3109/02652048.2015.1057250
    The aim of this study was to produce and characterise nanosize liposomes containing bioactive peptides with antioxidative and ACE-inhibitory properties, derived from winged bean seeds (WBS) protein. WBS powder was papain-proteolysed, at 70 °C and pH 6.5 for six hours, followed by encapsulation via a solvent-free heating method. The results showed that the WBS proteolysate was successfully incorporated into spherical, unilamellar liposomal particles, with particle diameter, polydispersity index, zeta potential and encapsulation efficiency of 193.3 ± 0.12 nm, 0.4 ± 0.02 (unit less), -70.5 ± 0.30 mV and 27.6 ± 1.17%, respectively. It also demonstrated good storage stability over eight weeks at 4 °C, indicated by slight increment (15.1%) in particle size and a zeta potential only weaker by 17.2% at the end of the study period. These results suggested the feasibility of entrapping water soluble peptides in hydrophobic liposomal system that, upon optimisation, has the potential to act as bioactive food ingredient.
  2. Tan WK, Teh SY, Koh HL
    Environ Sci Pollut Res Int, 2017 Jul;24(19):15976-15994.
    PMID: 28343360 DOI: 10.1007/s11356-017-8698-x
    Submarine landslides, also known as submarine mass failures (SMFs), are major natural marine disasters that could critically damage coastal facilities such as nuclear power plants and oil and gas platforms. It is therefore essential to investigate submarine landslides for potential tsunami hazard assessment. Three-dimensional seismic data from offshore Brunei have revealed a giant seabed mass deposited by a previous SMF. The submarine mass extends over 120 km from the continental slope of the Baram Canyon at 200 m water depth to the deep basin floor of the Northwest Borneo Trough. A suite of in-house two-dimensional depth-averaged tsunami simulation model TUNA (Tsunami-tracking Utilities and Application) is developed to assess the vulnerability of coastal communities in Sabah and Sarawak subject to potential SMF tsunami. The submarine slide is modeled as a rigid body moving along a planar slope with the center of mass motion parallel to the planar slope and subject to external forces due to added mass, gravity, and dissipation. The nonlinear shallow water equations are utilized to simulate tsunami propagation from deepwater up to the shallow offshore areas. A wetting-drying algorithm is used when a tsunami wave reaches the shoreline to compute run up of tsunami along the shoreline. Run-up wave height and inundation maps are provided for seven densely populated locations in Sabah and Sarawak to highlight potential risks at each location, subject to two scenarios of slide slopes: 2° and 4°. The first wave may arrive at Kudat as early as 0.4 h after the SMF, giving local communities little time to evacuate. Over a small area, maximum inundated depths reaching 20.3 m at Kudat, 26.1 m at Kota Kinabalu, and 15.5 m at Miri are projected, while the maximum inundation distance of 4.86 km is expected at Miri due to its low-lying coast. In view of the vulnerability of some locations to the SMF tsunami, it is important to develop and implement community resilience program to reduce the potential damage that could be inflicted by SMF tsunamis.
  3. Tan WK, Tan MY, Tan HM, Pathmanathan R, Tan WP
    Urology, 2016 Apr;90:e7-8.
    PMID: 26773348 DOI: 10.1016/j.urology.2015.12.046
    A 39-year-old man presented with painless scrotal swelling for 2 months. He denied any asbestos exposure but worked with wall and ceiling plaster. Physical exam revealed a large right scrotum which transilluminated. Scrotal ultrasonography revealed a large right hydrocele and a polypoidal mass along the anterior wall of the scrotum. Magnetic resonance imaging of the abdomen and computed tomography of the chest showed no metastases. He underwent a right inguinal scrotal exploration and wide excision of tunica vaginalis and a partial epididymectomy. Pathology revealed well-differentiated papillary mesothelioma of the tunica vaginalis. The patient had an uneventful recovery.
  4. Nyein N, Tan WK, Kawamura G, Matsuda A, Lockman Z
    Nanotechnology, 2016 Sep 02;27(35):355605.
    PMID: 27456036 DOI: 10.1088/0957-4484/27/35/355605
    Self-organized, 23 μm-thick anodic TiO2 nanotube (TNT) arrays were formed in sodium hydroxide/fluoride/ethylene glycol (EG) electrolyte at 60 V for 60 min. The presence of sodium hydroxide (NaOH) in the fluoride/EG electrolyte accelerates the formation of the TiO2 nanotube arrays. The anodic film was then decorated with silver nanoparticles (Ag NPs) by the photodeposition process and used as a photoanode in a rear-side-illuminated dye-sensitized solar cell. The Ag NPs decorated TNT arrays, with the former having diameters of 10-30 nm formed from 0.2 M of Ag-precursor solution and exhibiting the highest photoconversion efficiency (η) of 3.7% and a short-circuit current density of 12.2 mA cm(-2) compared to η = 3% and short-circuit current density of 9.1 mA cm(-2) for a sample without Ag NPs. The increase in η is thought to be due to the surface plasmon resonance and excess electrons from the nanoparticles.
  5. Chidan Kumar CS, Loh WS, Chandraju S, Win YF, Tan WK, Quah CK, et al.
    PLoS One, 2015;10(3):e0119440.
    PMID: 25742494 DOI: 10.1371/journal.pone.0119440
    A series of N-ethyl phthalimide esters 4(a-n) were synthesized and characterized by spectroscopic studies. Further, the molecular structure of majority of compounds were analysed by single crystal X-ray diffraction studies. The X-ray analysis revealed the importance of substituents on the crystal stability and molecular packing. All the synthesized compounds were tested for in vitro antioxidant activity by DPPH radical scavenging, FRAP and CUPRAC methods. Few of them have shown good antioxidant activity.
  6. Ho CC, Tan WP, Pathmanathan R, Tan WK, Tan HM
    Asian Pac J Cancer Prev, 2013;14(7):4057-9.
    PMID: 23991952
    BACKGROUND: Fluorescence in situ hybridization (FISH) testing may be useful to screen for bladder carcinoma or dysplasia by detecting aneuploidy chromosomes 3, 7, 17 and deletion of the chromosome 9p21 locus in urine specimens. This study aimed to assess the sensitivity, specificity, positive and negative predictive value of FISH in a multi-ethnic population in Asia.

    MATERIALS AND METHODS: Patients with haematuria and/or past history of urothelial cancer on follow-up had their voided urine tested with FISH. Patients then underwent cystoscopy/ ureteroscopy and any lesions seen were biopsied. The histopathological reports of the bladder or ureteroscopic mucosal biopsies were then compared with the FISH test results.

    RESULTS: Two hundred sixty patients were recruited. The sensitivity and specificity of the FISH test was 89.2% and 83.4% respectively. The positive (PPV) and negative predictive values (NPV) were 47.1% and 97.9%. By excluding patients who had positive deletion of chromosome 9, the overall results of the screening test improved: sensitivity 84.6%; specificity 96.4%; PPV 75.9% and NPV 97.9%.

    CONCLUSIONS: UroVysion FISH has a high specificity of detecting urothelial cancer or dysplasia when deletion of chromosome 9 is excluded. Negative UroVysion FISH-tests may allow us to conserve health resources and minimize trauma by deferring cystoscopic or ureteroscopic examination.

  7. Tan WK, Cheah SC, Parthasarathy S, Rajesh RP, Pang CH, Manickam S
    Chemosphere, 2021 Jul;274:129702.
    PMID: 33529956 DOI: 10.1016/j.chemosphere.2021.129702
    This investigation explores the efficacy of employing ultrasonic cavitation and coupling it with advanced oxidation processes (hydrogen peroxide and Fenton's reagent) for reducing the levels of total ammonia nitrogen in fish pond water containing Tilapia fishes. Ultrasonic cavitation is a phenomenon where the formation, growth and collapse of vaporous bubbles occur in a liquid medium producing highly reactive free radicals. Ultrasonic probe system (20 kHz with 750 W and 1000 W) was used to induce cavitation. Besides, to intensify the process, ultrasonic cavitation was coupled with hydrogen peroxide and Fenton's reagent. Using SERA colour indicator test kits, the levels of ammonium, nitrite and carbonate hardness were measured. The results obtained from this study clearly show that the advanced oxidation processes are more efficient in reducing the ammonium and nitrite levels in fish pond water than using ultrasound alone. The pH and carbonate hardness levels were not affected significantly by ultrasonic cavitation. The optimal treatment time and ultrasound power to treat the water samples were also established. Energy efficiency and cost analysis of this treatment have also been presented, indicating that ultrasonic cavitation coupled with hydrogen peroxide appears to be a promising technique for reducing total ammonia nitrogen levels in the fish pond water.
  8. Tan WK, Muto H, Ito T, Kawamura G, Lockman Z, Matsuda A
    J Nanosci Nanotechnol, 2020 Jan 01;20(1):359-366.
    PMID: 31383179 DOI: 10.1166/jnn.2020.17223
    Novel decoration of high aspect ratio zinc oxide nanowires (ZnO NWs) with noble metals such as Ag and Au nanoparticles (NPs) was demonstrated in this work. A facile method of chemical deposition with good controllability, as well as good homogeneity would be a huge advantage towards large scale fabrication. The highlight of this work is the feasibility of multiple component decoration such as a hybrid (co-exist) Ag-Au NPs decorated ZnO NWs formation that could be beneficial towards the development of nanoarchitectured materials with the most desired properties. The local surface plasmon effect (LSPR) of Ag and Au NPs were confirmed using extinction spectra and significant photoelectrochemical conversion efficiency (PCE) enhancement of dye-sensitized solar cells (DSSCs) was achieved. The Ag-NPs and hybrid Ag-Au NPs decorated ZnO NWs marked an impressive 125 and 240% efficiency improvement against pure ZnO NWs. The improved dye light extinction resulted from the LSPR effect that had enabled greater electron generation leading to improved PCE. As the complex design of oxides' nanoarchitectures have reached a point of saturation, this novel method would enable further enhancement in their photoelectrochemical properties through decoration with noble metals via a simple chemical deposition route.
  9. Alias N, Hussain Z, Tan WK, Kawamura G, Muto H, Matsuda A, et al.
    Chemosphere, 2021 Nov;283:131231.
    PMID: 34144283 DOI: 10.1016/j.chemosphere.2021.131231
    An anodic film with a nanoporous structure was formed by anodizing niobium at 60 V in fluorinated ethylene glycol (fluoride-EG). After 30 min of anodization, the anodic film exhibited a "pore-in-pore" structure; that is, there were smaller pores growing inside larger pores. The as-anodized film was weakly crystalline and became orthorhombic Nb2O5 after heat treatment. The energy band gap of the annealed nanoporous Nb2O5 film was 2.9 eV. A photocatalytic reduction experiment was performed on Cr(VI) under ultraviolet (UV) radiation by immersing the nanoporous Nb2O5 photocatalyst in a Cr(VI) solution at pH 2. The reduction process was observed to be very slow; hence, ethylenediaminetetraacetic acid (EDTA) was added as an organic hole scavenger, which resulted in 100% reduction after 45 min of irradiation. The photocatalytic reduction experiment was also performed under visible light, and findings showed that complete reduction achieved after 120 min of visible light exposure.
  10. Yau XH, Khe CS, Mohamed Saheed MS, Lai CW, You KY, Tan WK
    PLoS One, 2020;15(4):e0232490.
    PMID: 32353051 DOI: 10.1371/journal.pone.0232490
    Oily wastewater, especially water-oil emulsion has become serious environmental issue and received global attention. Chemical demulsifiers are widely used to treat oil-water emulsion, but the toxicity, non-recyclable and non-environmental friendly characteristic of chemical demulsifiers had limited their practical application in oil-water separation. Therefore, it is imperative to develop an efficient, simple, eco-friendly and recyclable demulsifiers for breaking up the emulsions from the oily wastewater. In this study, a magnetic demulsifier, magnetite-reduced graphene oxide (M-rGO) nanocomposites were proposed as a recyclable demulsifier to break up the surfactant stabilized crude oil-in-water (O/W) emulsion. M-rGO nanocomposites were prepared via in situ chemical synthesis by using only one type Fe salt and GO solid as precursor at room temperature. The prepared composites were fully characterized by various techniques. The effect of demulsifier dosage and pH of emulsion on demulsification efficiency (ED) has been studied in detailed. The demulsification mechanism was also proposed in this study. Results showed that M-rGO nanocomposites were able to demulsify crude O/W emulsion. The ED reaches 99.48% when 0.050 wt.% of M-rGO nanocomposites were added to crude O/W emulsion (pH = 4). Besides, M-rGO nanocomposites can be recycled up to 7 cycles without showing a significant change in terms of ED. Thus, M-rGO nanocomposite is a promising demulsifier for surfactant stabilized crude O/W emulsion.
  11. Budiman F, Tan WK, Kawamura G, Muto H, Matsuda A, Abdul Razak K, et al.
    ACS Omega, 2021 Oct 26;6(42):28203-28214.
    PMID: 34723018 DOI: 10.1021/acsomega.1c04280
    Coral-like and nanowire (NW) iron oxide nanostructures were produced at 700 and 800 °C, respectively, through thermal oxidation of iron foils in air- and water vapor-assisted conditions. Water vapor-assisted thermal oxidation at 800 °C for 2 h resulted in the formation of highly crystalline α-Fe2O3 NWs with good foil surface coverage, and we propose that their formation was due to a stress-driven surface diffusion mechanism. The Cr(VI) adsorption property of an aqueous solution on α-Fe2O3 NWs was also evaluated after a contact time of 90 min. The NWs had a removal efficiency of 97% in a 225 mg/L Cr(VI) solution (pH 2, 25 °C). The kinetic characteristic of the adsorption was fitted to a pseudo-second-order kinetic model, and isothermal studies indicated that the α-Fe2O3 NWs exhibited an adsorption capacity of 66.26 mg/g. We also investigated and postulated a mechanism of the Cr(VI) adsorption in an aqueous solution of α-Fe2O3 NWs.
  12. Xuan L, Hui D, Cheng W, Wong AHH, Han G, Tan WK, et al.
    Materials (Basel), 2017 Jul 12;10(7).
    PMID: 28773150 DOI: 10.3390/ma10070789
    The effects of alkaline copper quaternary (ACQ) and zinc borate (ZB) on the resistance of corn stalk fiber (CSF)-reinforced high-density polyethylene (HDPE) composites to biodegradation were examined. Both biocides could inhibit termites, mold fungi, and wood-decay fungi, even at high CSF formulations (i.e., 60%). Additionally, ACQ enhanced the resistance of the composite materials to certain biotic stresses better than ZB. The CSF/HDPE composites treated with ACQ at the 3.0% level exhibited a superior performance against termites, white rot fungi, and brown rot fungi. ACQ treatment at the 1% level was optimal for inhibiting soft rot fungi. Furthermore, mold growth was not observed on ACQ-treated CSF/HDPE samples. The untreated CSF/HDPE composites were more susceptible to mold infections and decay than the untreated poplar/HDPE composites, likely because of an incomplete removal of the pith. The chemical features of the corn stalk may also have influenced these differences, but this possibility will need to be explored in future investigations. Furthermore, the CSF component of CSF/HDPE composites is highly susceptible to fungal attacks, with the soft rot fungus inducing the largest mass losses, followed by the white rot fungus, and then the brown rot fungus.
  13. Zainudin NF, Sam ST, Wong YS, Ismail H, Walli S, Inoue K, et al.
    Polymers (Basel), 2023 Jan 03;15(1).
    PMID: 36616587 DOI: 10.3390/polym15010237
    The ability of poly-ferric-silicate-sulphate (PFSS) synthesized via a co-polymerization process has been applied for the removal of diazo Congo red dye. A novel degradation pathway of diazo Congo red dye by using PFSS is proposed based on LC-MS analysis. Diazo Congo red dye was successfully removed using synthesized PFSS at lower coagulant dosages and a wider pH range, i.e., 9 mg/L from pH 5 to 7, 11 mg/L at pH 9, and 50 mg/L at pH 11. The azo bond cleavage was verified by the UV-Vis spectra of diazo Congo red-loaded PFSS and FTIR spectra which showed disappearance of the peak at 1584 cm-1 for -N=N- stretching vibrations. The synchronized results of UV-Vis spectra, FTIR, and the LC-MS analysis in this study confirmed the significance of the Si and Fe bond in PFSS towards the degradation of diazo Congo red dye. The successfully synthesized PFSS coagulant was characterized by FTIR, SEM, TEM, and HRTEM analysis. From this analysis, it was proven that PFSS is a polycrystalline material which is favorable for the coagulation-flocculation process. Based on all these findings, it was established that synthesized PFSS can be employed as a highly efficient polymeric coagulant for the removal of dye from wastewater.
  14. Agatonovic-Kustrin S, Wong S, Dolzhenko AV, Gegechkori V, Ku H, Tan WK, et al.
    J Pharm Biomed Anal, 2023 Apr 01;227:115308.
    PMID: 36827737 DOI: 10.1016/j.jpba.2023.115308
    Extracts of two Salvia species, Salvia apiana (white sage) and Salvia officinalis (common sage) were screened for phytoconstituents with the ability to act as antidiabetic, cognitive enhancing, or antimicrobial agents, by hyphenation of high-performance thin-layer chromatography with enzymatic and microbial effect directed assays. Two bioactive zones with α-amylase inhibition (zone 1 and zone 2), 3 zones for acetylcholinesterase inhibition (zones 3, 4 and 5), and two zones for antimicrobial activity (zones 4 and 5) were detected. The compounds from the five bioactive zones were initially identified by coelution with standards and comparing the RF values of standards to the bioautograms. Identity was confirmed with ATR-FTIR spectra of the isolated compounds from the bioactive zones. A significantly higher α-amylase and acetylcholinesterase inhibition of S. apiana leaf extract was associated with a higher flavonoid and diterpenoid content. Fermented S. officinalis extract exhibited a significantly higher ability to inhibit α-amylase compared to other non-fermented extracts from this species, due to increased extraction of flavonoids. The ATR-FTIR spectra of 2 zones with α-amylase inhibition, indicated that flavonoids and phenolic acids were responsible for α-amylase inhibition. Multiple zones of acetylcholinesterase inhibition were related to the presence of phenolic abietane diterpenoids and triterpenoid acids. The presence of abietane diterpenoids and triterpenoid acids was also found responsible for the mild antimicrobial activity. Flash chromatography was used to isolate sufficient amounts of bioactive compounds for further characterisation via NMR and MS spectroscopy. Five compounds were assigned to the zones where bioactivity was observed: cirsimaritin (zone 1), a caffeic acid polymer (zone 2), 16-hydroxyrosmanol (zone 3), 16-hydroxycarnosic acid (zone 4), oleanolic and ursolic acids (zone 5).
  15. Majib NM, Sam ST, Yaacob ND, Rohaizad NM, Tan WK
    Polymers (Basel), 2023 Feb 10;15(4).
    PMID: 36850157 DOI: 10.3390/polym15040873
    Agricultural wastes and leaves, which are classified as lignocellulosic biomass, have been used as substrates in the production of fungal foams due to the significant growth of the mushroom industry in recent years. Foam derived from fungi can be utilized in a variety of industrial applications, including the production of packaging materials. Here, white oyster mushrooms (Pleurotus florida) and yellow oyster mushrooms (Pleurotus citrinopileatus) were cultivated on rice husk, sawdust, sugarcane bagasse, and teak leaves. Fungal foams were produced after 30 days of incubation, which were then analyzed using scanning electron microscopy (SEM), thermal analysis (TGA), and chemical structure using Fourier-transform infrared spectroscopy. Mechanical testing examined the material's hardness, resilience, and springiness, and water absorption tests were used to determine the durability of the fungal foams. Our findings demonstrated that fungal foams made from rice husk and teak leaves in both mycelium species showed better mechanical properties, thermal stability, and minimal water absorption compared to the other substrates, and can thus have great potential as efficient packaging materials.
  16. Alias N, Hussain Z, Tan WK, Kawamura G, Muto H, Matsuda A, et al.
    Environ Sci Pollut Res Int, 2022 Aug;29(40):60600-60615.
    PMID: 35426025 DOI: 10.1007/s11356-022-20005-7
    In this study, nanoporous anodic film was produced by anodization of niobium, Nb in a fluoride ethylene glycol electrolyte. The effect of anodization voltage and electrolyte temperature was studied to find an optimum condition for circular, ordered, and uniform pore formation. The diameter of the pores was found to be larger when the applied voltage was increased from 20 to 80 V. The as-anodized porous film was also observed to comprise of nanocrystallites which formed due to high field-induced crystallization. The nanocrystallites grew into orthorhombic Nb2O5 after post-annealing treatment. The Cr(VI) photoreduction property of both the as-anodized and annealed Nb2O5 samples obtained using an optimized condition (anodization voltage: 60 V, electrolyte temperature: 70 °C) was compared. Interestingly, the as-anodized Nb2O5 film was found to display better photoreduction of Cr(VI) than annealed Nb2O5. However, in terms of stability, the annealed Nb2O5 presented high photocatalytic efficiency for each cycle whereas the as-anodized Nb2O5 showed degradation in photocatalytic performance when used continually.
  17. Kawamura G, Ohmi H, Tan WK, Lockman Z, Muto H, Matsuda A
    Nanoscale Res Lett, 2015;10:219.
    PMID: 26019696 DOI: 10.1186/s11671-015-0924-1
    ABSTRACT: Dye-sensitized solar cells composed of a photoanode of Ag nanoparticle (NP)-deposited TiO2 nanotube (TNT) arrays were fabricated. The TNT arrays were prepared by anodizing Ti films on fluorine-doped tin oxide (FTO)-coated glass substrates. Efficient charge transportation through the ordered nanostructure of TNT arrays should be carried out compared to conventional particulate TiO2 electrodes. However, it has been a big challenge to grow TNT arrays on FTO glass substrates with the lengths needed for sufficient light-harvesting (tens of micrometers). In this work, we deposited Ag nanoparticles (NPs) on the wall of TNT arrays to enhance light-harvesting property. Dye-sensitized solar cells with these Ag NP-deposited TNT arrays yielded a higher power conversion efficiency (2.03 %) than those without Ag NPs (1.39 %).

    PACS CODES: 06.60.Ei Sample preparation, 81.05.Bx Metals, Semimetals, Alloys, 81.07.De Nanotubes.

  18. Ng CC, Sybil Shah MHB, Chaw SH, Mansor MB, Tan WK, Koong JK, et al.
    Expert Rev Med Devices, 2021 Feb;18(2):203-210.
    PMID: 33322949 DOI: 10.1080/17434440.2021.1865796
    Background: Supraglottic airway devices have increasingly been used as the airway technique of choice in laparoscopic surgeries. This study compared the efficacy and safety of the Baska Mask with endotracheal tube (ETT) in patients undergoing elective laparoscopic cholecystectomy.Research design and methods: This single-center, prospective, randomized controlled trial recruited 60 patients aged 18-75 years with American Society of Anesthesiologists' classifications I to III. The time taken to achieve effective airway, number of attempts, ease of insertion, ventilation parameters, hemodynamics data, and pharyngolaryngeal complications were recorded.Results: The time taken to achieve effective airway was shorter for the Baska group (26.6 ± 4.7 vs. 47.2 ± 11.8 s; p
  19. Taib MAA, Alias N, Jaafar M, Razak KA, Tan WK, Shahbudin IP, et al.
    Nanotechnology, 2020 Oct 23;31(43):435605.
    PMID: 32640434 DOI: 10.1088/1361-6528/aba3d8
    Arrays of TiO2 nanotubes (TiO2 NTs) with grassy surfaces were observed on titanium foil anodised at 60 V in fluorinated ethylene glycol (EG) with added hydrogen peroxide (H2O2). The grassy surface was generated by the chemical etching and dissolution of the surface of the TiO2 NTs walls, which was accelerated by the temperature increase on the addition of H2O2 . Upon annealing at 600 °C, the grassy part of the TiO2 NTs was found to consist of mostly anatase TiO2 whereas the bottom part of the anodic oxide comprised a mixture of anatase and rutile TiO2. The TiO2 NTs were then used to reduce hexavalent chromium (Cr(VI)) under ultraviolet radiation. They exhibited a rather efficient photocatalytic effect, with 100% removal of Cr(VI) after 30 min of irradiation. The fast removal of Cr(VI) was due to the anatase dominance at the grassy part of the TiO2 NTs as well as the higher surface area the structure may have. This work provides a novel insight into the photocatalytic reduction of Cr(VI) on grassy anatase TiO2 NTs.
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