Displaying publications 1 - 20 of 36 in total

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  1. Teoh JY, Cho CL, Wei Y, Isotani S, Tiong HY, Ong TA, et al.
    World J Urol, 2019 Sep;37(9):1879-1887.
    PMID: 30560297 DOI: 10.1007/s00345-018-2602-2
    PURPOSE: The Asian Urological Surgery Training & Education Group (AUSTEG) has been established to provide training and education to young urologists in Asia. We developed and validated a porcine bladder training model for transurethral resection of bladder tumour (TURBT).

    METHODS: Urology residents and specialists were invited to test the training model. They were asked to complete a pre-task questionnaire, to perform piecemeal and en bloc resection of 'bladder tumours' within the training model, and to complete a post-task questionnaire afterwards. Their performances were assessed by faculty members of the AUSTEG. For the face validity, a pre-task questionnaire consisting of six statements on TURBT and the training model were set. For the content validity, a post-task questionnaire consisting of 14 items on the details of the training model were set. For the construct validity, a Global Rating Scale was used to assess the participants' performances. The participants were stratified into two groups (junior surgeons and senior surgeons groups) according to their duration of urology training.

    RESULTS: For the pre-task questionnaire, a mean score of ≥ 4.0 out of 5.0 was achieved in 5 out of 6 statements. For the post-task questionnaire, a mean score of ≥ 4.5 out of 5.0 was achieved in every item. For the Global Rating Scale, the senior surgeons group had higher scores than the junior surgeons group in 8 out of 11 items as well as the total score.

    CONCLUSION: A porcine TURBT training model has been developed, and its face, content and construct validity has been established.

  2. Chan ES, Lee PP, Ravindra P, Krishnaiah K, Voo WP
    Appl Microbiol Biotechnol, 2010 Mar;86(1):385-91.
    PMID: 20033402 DOI: 10.1007/s00253-009-2384-y
    The aim of this work was to develop a standard quantitative method to measure the acid tolerance of probiotic cells when exposed to a simulated gastric fluid. Three model strains of different cell concentrations were exposed to a standard simulated gastric fluid of fixed volume. The fluid pH ranged from pH 1.5 to 2.5. In general, the death kinetics followed an exponential trend. The overall death constant, k (d), for all strains was found to be in a power relationship with the pH value and the initial cell concentration, and it can be expressed as k(d)=k(AII) (pH(-9.0)N(0)(-0.19)) where k (AII) is defined as the acid intolerance indicator and N (0) is the initial cell concentration (CFU/ml). This equation was validated with the experimental data with an average R (2) of 0.98. The acid intolerance of cells can be quantitatively expressed by the k (AII) values, where higher value indicates higher intolerance. In conclusion, a standard quantitative method has been developed to measure the acid tolerance of probiotic cells. This could facilitate the selection of probiotic strains and processing technologies.
  3. Ong WD, Tey BT, Quek SY, Tang SY, Chan ES
    J Food Sci, 2015 Jan;80(1):E93-E100.
    PMID: 25529579 DOI: 10.1111/1750-3841.12729
    Oil-in-water (O/W) emulsion-gel systems containing high oil payloads are of increasing interest for food applications because of the reduction in encapsulation cost, consumption frequency or volume of food products. This study shows a facile approach to prepare stable alginate-based O/W emulsions at high oil loading using a mixture of nonionic surfactants (Tween 80 and Span 20) as a template to form gelled-emulsions. The synergistic effects of alginate and surfactants on the O/W emulsion properties were evaluated in terms of oil droplet size and emulsion stability. At 2% (w/v) of alginate and 1% (w/v) of surfactants, the size distribution of oil droplets was narrow and monomodal, even at an oil loading of 70% (v/v). The emulsions formed were stable against phase separation. The oil droplet size could be further reduced to below 1 μm using a high-shear homogenizer. The emulsions formed could be easily molded and gelled into solids of different shapes via ionic gelation. The findings of this study create possible avenues for applications in food industries.
  4. Oh KS, Poh PE, Chong MN, Chan ES, Lau EV, Saint CP
    Carbohydr Polym, 2016 Sep 05;148:161-70.
    PMID: 27185127 DOI: 10.1016/j.carbpol.2016.04.039
    Polyelectrolyte-complex bilayer membrane (PCBM) was fabricated using biodegradable chitosan and alginate polymers for subsequent application in the treatment of bathroom greywater. In this study, the properties of PCBMs were studied and it was found that the formation of polyelectrolyte network reduced the molecular weight cut-off (MWCO) from 242kDa in chitosan membrane to 2.71kDa in PCBM. The decrease in MWCO of PCBM results in better greywater treatment efficiency, subsequently demonstrated in a greywater filtration study where treated greywater effluent met the household reclaimed water standard of <2 NTU turbidity and <30ppm total suspended solids (TSS). In addition, a further 20% improvement in chemical oxygen demand (COD) removal was achieved as compared to a single layer chitosan membrane. Results from this study show that the biodegradable PCBM is a potential membrane material in producing clean treated greywater for non-potable applications.
  5. Abdulla R, Chan ES, Ravindra P
    Crit Rev Biotechnol, 2011 Mar;31(1):53-64.
    PMID: 20572796 DOI: 10.3109/07388551.2010.487185
    The fuel crisis and environmental concerns, mainly due to global warming, have led researchers to consider the importance of biofuels such as biodiesel. Vegetable oils, which are too viscous to be used directly in engines, are converted into their corresponding methyl or ethyl esters by a process called transesterification. With the recent debates on "food versus fuel," non-edible oils, such as Jatropha curcas, are emerging as one of the main contenders for biodiesel production. Much research is still needed to explore and realize the full potential of a green fuel from J. curcas. Upcoming projects and plantations of Jatropha in countries such as India, Malaysia, and Indonesia suggest a promising future for this plant as a potential biodiesel feedstock. Many of the drawbacks associated with chemical catalysts can be overcome by using lipases for enzymatic transesterification. The high cost of lipases can be overcome, to a certain extent, by immobilization techniques. This article reviews the importance of the J. curcas plant and describes existing research conducted on Jatropha biodiesel production. The article highlights areas where further research is required and relevance of designing an immobilized lipase for biodiesel production is discussed.
  6. Maneeton N, Suttajit S, Maneeton B, Likhitsathian S, Eurviyanukul K, Udomratn P, et al.
    Nord J Psychiatry, 2017 Oct;71(7):503-508.
    PMID: 28632428 DOI: 10.1080/08039488.2017.1335344
    BACKGROUND: Anxious distress in major depressive disorder (MDD) is common and associated with poor outcomes and management difficulties.

    AIMS: This post hoc analysis aimed to examine the socio-demographic and clinical correlates of anxiety distress in Asian outpatients with MDD.

    METHODS: Instead of two out of five specifiers defined by the Diagnostic and Statistical Manual Version-5, anxious distress defined in this study was operationalized as the presence of at least two out of four proxy items drawn from the 90-item Symptom Checklist, Revised (SCL-90-R). Other measures included the Montgomery-Asberg Depression Rating Scale (MADRS), the Fatigue Severity Scale, the Sheehan Disability Scale and the Multidimensional Scale of Perceived Social Support.

    RESULTS: The data of 496 patients with MDD were included. Anxious distress was found in 371 participants (74.8%). The binary logistic regression analysis found that anxious distress was independently and significantly correlated with working status, higher MADRS scores, severe insomnia and functional impairment.

    CONCLUSIONS: Three-fourths of Asian patients with MDD in tertiary care settings may have DSM-5 anxious distress of at least moderate distress. Its prevalence may vary among working groups. The specifier was associated with greater depressive symptom severity, severe insomnia and functional impairment.

    Study site: n tertiary care
    settings in China, Korea, Malaysia, Singapore, Taiwan and
    Thailand
  7. Voo WP, Ravindra P, Tey BT, Chan ES
    J Biosci Bioeng, 2011 Mar;111(3):294-9.
    PMID: 21216192 DOI: 10.1016/j.jbiosc.2010.11.010
    A comparative study on the stability and potential of alginate and pectin based beads for production of poultry probiotic cells using MRS medium in repeated batch fermentation was conducted. The bead cores, made of three types of materials, i.e., ca-alginate, ca-pectinate and ca-alginate/pectinate, were compared. The effect of single and double layer coatings using chitosan and core material, respectively, on the bead stability and cell production were also studied. The pectin based beads were found to be more stable than that of the alginate beads and their stability was further improved by coating with chitosan. The cell concentration in pectin based beads was comparable to that in the alginate beads. On the other hand, pectin based beads gave significantly lower cell concentration in the growth medium for the initial fermentation cycles when compared to the alginate beads. In conclusion, pectin was found to be potential encapsulation material for probiotic cell production owing to its stability and favourable microenvironment for cell growth.
  8. Lim HP, Ng SD, Dasa DB, Adnan SA, Tey BT, Chan ES, et al.
    Int J Biol Macromol, 2023 Mar 31;232:123461.
    PMID: 36720328 DOI: 10.1016/j.ijbiomac.2023.123461
    Formulation of water-in-oil (W/O) Pickering emulsion (PE) for food applications has been largely restricted by the limited choices of food-grade Pickering emulsifiers. In this study, composite microgels made of chitosan and carrageenan were explored as a dual (pH and thermal) stimuli-responsive Pickering emulsifier for the stabilization of W/O PE. The chitosan-carrageenan (CS-CRG) composite microgels not only exhibited pH- and thermo-responsiveness, but also displayed enhanced lipophilicity as compared to the discrete polymers. The stability of the CS-CRG-stabilized W/O PE system (CS-CRG PE) was governed by CS:CRG mass ratio and oil fractions used. The CS-CRG PE remained stable at acidic pH and at temperatures below 40 °C. The instability of CS-CRG composite microgels at alkaline pH and at temperatures above 40 °C rendered the demulsification of CS-CRG PE. This stimuli-responsive W/O PE could unlock new opportunities for the development of stimuli-responsive W/O PE using food-grade materials.
  9. Ravindra P, Chan ES, Reddy KU
    Int J Food Sci Nutr, 2007 Nov;58(7):542-7.
    PMID: 17852467
    Extensive studies have been carried out on the effect of temperature and salt concentration on the theological behavior of whey proteins and different starches individually, but not on mixed dispersions of whey protein isolates and starches. In the present studies, the rheological behavior of cross-linked waxy maize starch and whey protein isolate mixed dispersions during heating at 60-85 degrees C was investigated. Further, the effect of CaCl2 (25-100 mM ionic strengths) on the gelatinization of these dispersions was determined. It was found that at a 2:3 ratio and a 3:2 ratio of cross-linked waxy maize starch to whey protein isolate mixed gels form a compatible networkmM concentration the solution viscosity was higher.
  10. Tan PY, Tan TB, Chang HW, Tey BT, Chan ES, Lai OM, et al.
    J Agric Food Chem, 2017 Dec 06;65(48):10651-10657.
    PMID: 29124932 DOI: 10.1021/acs.jafc.7b03521
    Considering the health benefits of tocotrienols, continuous works have been done on the encapsulation and delivery of these compounds. In this study, we encapsulated tocotrienols in chitosan-alginate microcapsules and evaluated their release profile. Generally, these tocotrienols microcapsules (TM) displayed high thermal stability. When subjected to pH adjustments (pH 1-9), we observed that the release of tocotrienols was the highest (33.78 ± 0.18%) under basic conditions. The TM were also unstable against the effect of ionic strength, with a high release (70.73 ± 0.04%) of tocotrienols even at a low sodium chloride concentration (50 mM). As for the individual isomers, δ-tocotrienol was the most sensitive to pH and ionic strength. In contrast, β-/γ-tocotrienols were the most ionic-stable isomers but more responsive toward thermal treatment. Simulated gastrointestinal model showed that the chitosan-alginate-based TM could be used to retain tocotrienols in the gastric and subsequently release them in the intestines for possible absorption.
  11. Tan PY, Tan TB, Chang HW, Tey BT, Chan ES, Lai OM, et al.
    Food Chem, 2018 Feb 15;241:79-85.
    PMID: 28958562 DOI: 10.1016/j.foodchem.2017.08.075
    Tocotrienol microcapsules (TM) were formed by firstly preparing Pickering emulsion containing tocotrienols, which was then gelled into microcapsules using alginate and chitosan. In this study, we examined the stability of TM during storage and when applied into a model food system, i.e. yogurt. During storage at 40°C, TM displayed remarkably lower tocotrienols loss (50.8%) as compared to non-encapsulated tocotrienols in bulk oil (87.5%). When the tocotrienols were incorporated into yogurt, the TM and bulk oil forms showed a loss of 23.5% and 81.0%, respectively. Generally, the tocotrienols were stable in the TM form and showed highest stability when these TM were added into yogurt. δ-Tocotrienol was the most stable isomer in both forms during storage and when incorporated into yogurt. The addition of TM into yogurt caused minimal changes in the yogurt's color and texture but slightly altered the yogurt's viscosity.
  12. Hia IL, Pasbakhsh P, Chan ES, Chai SP
    Sci Rep, 2016 10 03;6:34674.
    PMID: 27694922 DOI: 10.1038/srep34674
    Alginate microcapsules containing epoxy resin were developed through electrospraying method and embedded into epoxy matrix to produce a capsule-based self-healing composite system. These formaldehyde free alginate/epoxy microcapsules were characterized via light microscope, field emission scanning electron microscope, fourier transform infrared spectroscopy and thermogravimetric analysis. Results showed that epoxy resin was successfully encapsulated within alginate matrix to form porous (multi-core) microcapsules with pore size ranged from 5-100 μm. The microcapsules had an average size of 320 ± 20 μm with decomposition temperature at 220 °C. The loading capacity of these capsules was estimated to be 79%. Under in situ healing test, impact specimens showed healing efficiency as high as 86% and the ability to heal up to 3 times due to the multi-core capsule structure and the high impact energy test that triggered the released of epoxy especially in the second and third healings. TDCB specimens showed one-time healing only with the highest healing efficiency of 76%. The single healing event was attributed by the constant crack propagation rate of TDCB fracture test. For the first time, a cost effective, environmentally benign and sustainable capsule-based self-healing system with multiple healing capabilities and high healing performance was developed.
  13. Ong YY, Tan WS, Rosfarizan M, Chan ES, Tey BT
    J Food Sci, 2012 Oct;77(10):M560-4.
    PMID: 22924854 DOI: 10.1111/j.1750-3841.2012.02894.x
    Red dragon fruit or red pitaya is rich in potassium, fiber, and antioxidants. Its nutritional properties and unique flesh color have made it an attractive raw material of various types of food products and beverages including fermented beverages or enzyme drinks. In this study, phenotypic and genotypic methods were used to confirm the identity of lactic acid bacteria (LAB) appeared in fermented red dragon fruit (Hylocereus polyrhizus) beverages. A total of 21 isolates of LAB were isolated and characterized. They belonged to the genus of Enterococcus based on their biochemical characteristics. The isolates can be clustered into two groups by using the randomly amplified polymorphic DNA method. Nucleotide sequencing and restriction fragment length polymorphism of the 16S rRNA region suggested that they were either Enterococcus faecalis or Enterococcus durans.
  14. Lee YY, Tang TK, Chan ES, Phuah ET, Lai OM, Tan CP, et al.
    PMID: 33480262 DOI: 10.1080/10408398.2021.1873729
    Structured lipid is a type of modified form of lipid that is "fabricated" with the purpose to improve the nutritional and functional properties of conventional fats and oils derived from animal and plant sources. Such healthier choice of lipid received escalating attention from the public for its capability to manage the rising prevalence of metabolic syndrome. Of which, medium-chain triacylglycerol (MCT) and medium-and long-chain triacylglycerol (MLCT) are the few examples of the "new generation" custom-made healthful lipids which are mainly composed of medium chain fatty acid (MCFA). MCT is made up exclusively of MCFA whereas MLCT contains a mixture of MCFA and long chain fatty acid (LCFA), respectively. Attributed by the unique metabolism of MCFA which is rapidly metabolized by the body, MCFA and MCT showed to acquire multiple physiological and functional properties in managing and reversing certain health disorders. Several chemically or enzymatically oils and fats modification processes catalyzed by a biological or chemical catalyst such as acidolysis, interesterification and esterification are adopted to synthesis MCT and MLCT. With their purported health benefits, MCT and MLCT are widely being used as nutraceutical in food and pharmaceutical sectors. This article aims to provide a comprehensive review on MCT and MLCT, with an emphasis on the basic understanding of its structures, properties, unique metabolism; the current status of the touted health benefits; latest routes of production; its up-to-date applications in the different food systems; relevant patents filed and its drawbacks.
  15. Zhu T, Chong MN, Chan ES
    ChemSusChem, 2014 Nov;7(11):2974-97.
    PMID: 25274424 DOI: 10.1002/cssc.201402089
    The recent developments of nanostructured WO3 thin films synthesized through the electrochemical route of electrochemical anodization and cathodic electrodeposition for the application in photoelectrochemical (PEC) water splitting are reviewed. The key fundamental reaction mechanisms of electrochemical anodization and cathodic electrodeposition methods for synthesizing nanostructured WO3 thin films are explained. In addition, the effects of metal oxide precursors, electrode substrates, applied potentials and current densities, and annealing temperatures on size, composition, and thickness of the electrochemically synthesized nanostructured WO3 thin films are elucidated in detail. Finally, a summary is given for the general evaluation practices used to calculate the energy conversion efficiency of nanostructured WO3 thin films and a recommendation is provided to standardize the presentation of research results in the field to allow for easy comparison of reported PEC efficiencies in the near future.
  16. Lee MF, Chan ES, Tan WS, Tam KC, Tey BT
    J Chromatogr A, 2016 May 6;1445:1-9.
    PMID: 27059397 DOI: 10.1016/j.chroma.2016.03.066
    Purification of virus-like particles (VLPs) in bind-and-elute mode has reached a bottleneck. Negative chromatography has emerged as the alternative solution; however, benchmark of negative chromatography media and their respective optimized conditions are absent. Hence, this study was carried out to compare the performance of different negative chromatography media for the purification of hepatitis B VLPs (HB-VLPs) from clarified Escherichia coli feedstock. The modified anion exchange media, core-shell adsorbents (InertShell and InertLayer 1000) and polymer grafted adsorbents (SQ) were compared. The results of chromatography from packed bed column of core-shell adsorbents showed that there is a trade-off between the purity and recovery of HB-VLPs in the flowthrough fraction due to the shell thickness. Atomic force microscopic analysis revealed funnel-shaped pore channels in the shell layer which may contribute to the entrapment of HB-VLPs. A longer residence time at a lower feed flow rate (0.5ml/min) improved slightly the HB-VLPs purity in all modified adsorbents, but the recovery in InertShell reduced substantially. The preheat-treatment is not recommended for the negative chromatography as the thermal-induced co-aggregation of HCPs and HB-VLPs would flow along with HB-VLPs and thus reduced the HB-VLPs purity in the flowthrough. Further reduction in the feedstock concentration enhanced the purity of HB-VLPs especially in InertLayer 1000 but reduced substantially the recovery of HB-VLPs. In general, the polymer grafted adsorbent, SQ, performed better than the core-shell adsorbents in handling a higher feedstock concentration.
  17. Lee MF, Chan ES, Tan WS, Tam KC, Tey BT
    J Chromatogr A, 2015 Oct 9;1415:161-5.
    PMID: 26358561 DOI: 10.1016/j.chroma.2015.08.056
    Poly(oligo(ethylene glycol) methacrylate) (POEGMA), an inert polymer was grafted onto an anion exchange adsorbent for the exclusion of relatively larger hepatitis B virus-like particles (HB-VLPs) from the anion exchange ligand (Q) and at the same time this process allowed the selective adsorption of smaller size Escherichia coli host cell proteins (HCPs). The chain lengths of the POEGMA grafted were modulated by varying the amount of monomers used in the polymer grafting. The purification factor and yield of the HB-VLPs obtained from the flow-through of negative chromatography were 2.3 and 66.0±3.1%, respectively, when shorter chain length of POEGMA (SQ) was grafted. Adsorbent grafted with longer chain of POEGMA (LQ) excluded some HCPs that are larger in size together with the HB-VLPs, reducing the purity of the recovered HB-VLPs. Further heat-treatment of the flow-through pool from SQ followed by centrifugation increased the purity of heat stable HB-VLPs to 87.5±1.1%. Heat-treatment of the flow through sample resulted in thermal denaturation and aggregation of HCPs, while the heat stable HB-VLPs still remained intact as observed under a transmission electron microscope. The performance of the negative chromatography together with heat treatment in the purification of HB-VLPs is far better than the reported bind-and-elute techniques.
  18. Leong JY, Tey BT, Tan CP, Chan ES
    ACS Appl Mater Interfaces, 2015 Aug 5;7(30):16169-76.
    PMID: 26148344 DOI: 10.1021/acsami.5b04486
    Ionotropic gelation has been an attractive method for the fabrication of biopolymeric oil-core microcapsules due to its safe and mild processing conditions. However, the mandatory use of a nozzle system to form the microcapsules restricts the process scalability and the production of small microcapsules (<100 μm). We report, for the first time, a nozzleless and surfactant-free approach to fabricate oil-core biopolymeric microcapsules through ionotropic gelation at the interface of an O/W Pickering emulsion. This approach involves the self-assembly of calcium carbonate (CaCO3) nanoparticles at the interface of O/W emulsion droplets followed by the addition of a polyanionic biopolymer into the aqueous phase. Subsequently, CaCO3 nanoparticles are dissolved by pH reduction, thus liberating Ca(2+) ions to cross-link the surrounding polyanionic biopolymer to form a shell that encapsulates the oil droplet. We demonstrate the versatility of this method by fabricating microcapsules from different types of polyanionic biopolymers (i.e., alginate, pectin, and gellan gum) and water-immiscible liquid cores (i.e., palm olein, cyclohexane, dichloromethane, and toluene). In addition, small microcapsules with a mean size smaller than 100 μm can be produced by selecting the appropriate conventional emulsification methods available to prepare the Pickering emulsion. The simplicity and versatility of this method allows biopolymeric microcapsules to be fabricated with ease by ionotropic gelation for numerous applications.
  19. Tee LH, Yang B, Nagendra KP, Ramanan RN, Sun J, Chan ES, et al.
    Food Chem, 2014 Dec 15;165:247-55.
    PMID: 25038673 DOI: 10.1016/j.foodchem.2014.05.084
    Dacryodes species are evergreen, perennial trees with fleshy fruits and belong to the family Buseraseae. Many Dacryodes species are underutilized but are widely applied in traditional folk medicine to treat malaria, fever and skin diseases. The nutritional compositions, phytochemicals and biological activities of Dacryodes edulis, Dacryodes rostrata, Dacryodes buettneri, Dacryodes klaineana and Dacryodes hexandra are presented. The edible fruits of D. edulis are rich in lipids, proteins, vitamins, fatty acids and amino acids. Its extracts (leaf, fruit and resin) exhibit antioxidant, anti-microbial, anti-carcinogenic and other bioactivities. D. rostrata fruit has significant nutrient content, and is rich in proteins, lipids and minerals. These fruits are also highly rich in polyphenols, anthocyanins and antioxidant activities. This comprehensive review will assist the reader in understanding the nutritional benefits of Dacryodes species and in identifying current research needs.
  20. Liew JC, Tan WS, Alitheen NB, Chan ES, Tey BT
    J Biosci Bioeng, 2010 Sep;110(3):338-44.
    PMID: 20547346 DOI: 10.1016/j.jbiosc.2010.02.017
    Serum deprivation inhibits cell growth and initiates apoptosis cell death in mammalian cell cultures. Since apoptosis is a genetically controlled cell death pathway, over-expression of anti-apoptotic proteins may provide a way to delay apoptosis. This study investigated the ability of the X-linked inhibitor of apoptosis protein (XIAP) to inhibit apoptosis induced by serum deprivation. Study includes evaluation of the ability of XIAP to prolong culture period and its effect on cell proliferation in serum-deprived media. The full length human XIAP was introduced into CHO-K1 cell lines and the effects of XIAP over-expression on the inhibition of apoptosis induced by serum-deprived conditions were examined. In batch cultures, cells over-expressing XIAP showed decreased levels of apoptosis and a higher number of viable cell under serum-deprived conditions compared to the control cell lines. The viability of control cells dropped to 40% after 2days of serum deprivation, the XIAP expressing cells still maintained at a viability higher than 90%. Further investigation revealed that the caspase-3 activity of the CHO-K1 cell line was inhibited as a result of XIAP expression.
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