Displaying publications 1 - 20 of 28 in total

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  1. Ang QY, Low SC
    Anal Bioanal Chem, 2015 Sep;407(22):6747-58.
    PMID: 26163132 DOI: 10.1007/s00216-015-8841-9
    Molecular imprinting is an emerging technique to create imprinted polymers that can be applied in affinity-based separation, in particular, biomimetic sensors. In this study, the matrix of siloxane bonds prepared from the polycondensation of hydrolyzed tetraethoxysilane (TEOS) was employed as the inorganic monomer for the formation of a creatinine (Cre)-based molecularly imprinted polymer (MIP). Doped aluminium ion (Al(3+)) was used as the functional cross-linker that generated Lewis acid sites in the confined silica matrix to interact with Cre via sharing of lone pair electrons. Surface morphologies and pore characteristics of the synthesized MIP were determined by field emission scanning electron microscopy (FESEM) and Brunauer-Emmet-Teller (BET) analyses, respectively. The imprinting efficiency of MIPs was then evaluated through the adsorption of Cre with regard to molar ratios of Al(3+). A Cre adsorption capacity of up to 17.40 mg Cre g(-1) MIP was obtained and adsorption selectivity of Cre to its analogues creatine (Cr) and N-hydroxysuccinimide (N-hyd) were found to be 3.90 ± 0.61 and 4.17 ± 3.09, respectively. Of all the studied MIP systems, chemisorption was predicted as the rate-limiting step in the binding of Cre. The pseudo-second-order chemical reaction kinetic provides the best correlation of the experimental data. Furthermore, the equilibrium adsorption capacity of MIP fit well with a Freundlich isotherm (R (2) = 0.98) in which the heterogeneous surface was defined.
  2. Chin JY, Ahmad AL, Low SC
    J Environ Manage, 2023 Oct 01;343:118231.
    PMID: 37247545 DOI: 10.1016/j.jenvman.2023.118231
    The surge in the use of antibiotics, especially in aquaculture, has led to development of antibiotic resistance genes, which will harm environmental and public health. One of the most commonly used antibiotics in aquaculture is oxytetracycline (OTC). Employing photocatalysis, this study compared OTC degradation efficiency of two different types of common photocatalysts, TiO2 and graphitic carbon nitride (GCN) in terms of their photochemical properties and underlying photocatalytic mechanism. For reference purpose, self-synthesized GCN from urea precursor (GCN-Urea) and commercial GCN (GCN-Commercial) were both examined. OTC adsorption-photocatalysis removal rates in pure OTC solution by TiO2, GCN-Urea and GCN-Commercial were attained at 95%, 60% and 40% respectively. Photochemical properties evaluated included light absorption, band gap, valence and conduction band positions, photoluminescence, cyclic voltammetry, BET surface area and adsorption capability of the photocatalysts. Through the evaluations, this study provides novel insights towards current state-of-the-art heterogeneous photocatalytic processes. The electron-hole recombination examined by photoluminescence is not the key factor influencing the photocatalytic efficacies as commonly discussed. On the contrary, the dominating factors governing the higher OTC degradation efficiency of TiO2 compared to GCN are the high mobility of electrons that leads to high redox capability and the high pollutant-photocatalyst affinity. These claims are proven by 86% and 40% more intense anodic and cathodic cyclic voltammetry curve peaks of TiO2 as compared to both GCNs. OTC also demonstrated 1.7 and 2.3 times higher affinity towards TiO2 than GCN-Urea and GCN-Commercial. OTC removal by TiO2 in real aquaculture wastewater only achieved 50%, due to significant inhibition effect by dissolved solids, dissolved organic matters and high ionic contents in the wastewater.
  3. Lim J, Yeap SP, Che HX, Low SC
    Nanoscale Res Lett, 2013;8(1):381.
    PMID: 24011350 DOI: 10.1186/1556-276X-8-381
    Here we provide a complete review on the use of dynamic light scattering (DLS) to study the size distribution and colloidal stability of magnetic nanoparticles (MNPs). The mathematical analysis involved in obtaining size information from the correlation function and the calculation of Z-average are introduced. Contributions from various variables, such as surface coating, size differences, and concentration of particles, are elaborated within the context of measurement data. Comparison with other sizing techniques, such as transmission electron microscopy and dark-field microscopy, revealed both the advantages and disadvantages of DLS in measuring the size of magnetic nanoparticles. The self-assembly process of MNP with anisotropic structure can also be monitored effectively by DLS.
  4. Low SC, Shaimi R, Thandaithabany Y, Lim JK, Ahmad AL, Ismail A
    Colloids Surf B Biointerfaces, 2013 Oct 1;110:248-53.
    PMID: 23732801 DOI: 10.1016/j.colsurfb.2013.05.001
    Protein adsorption onto membrane surfaces is important in fields related to separation science and biomedical research. This study explored the molecular interactions between protein, bovine serum albumin (BSA), and nitrocellulose films (NC) using electrokinetic phenomena and the effects of these interactions on the streaming potential measurements for different membrane pore morphologies and pH conditions. The data were used to calculate the streaming ratios of membranes-to-proteins and to compare these values to the electrostatic or hydrophobic attachment of the protein molecules onto the NC membranes. The results showed that different pH and membrane pore morphologies contributes to different protein adsorption mechanisms. The protein adsorption was significantly reduced under conditions where the membrane and protein have like-charges due to electrostatic repulsion. At the isoelectric point (IEP) of the protein, the repulsion between the BSA and the NC membrane was at the lowest; thus, the BSA could be easily attached onto the membrane/solution interface. In this case, the protein was considered to be in a compact layer without intermolecular protein repulsions.
  5. Ahmad AL, Low SC, Shukor SR, Ismail A
    J Immunoassay Immunochem, 2012 Jan;33(1):48-58.
    PMID: 22181820 DOI: 10.1080/15321819.2011.591479
    This study was aimed at gaining a quantitative understanding of the effect of protein quantity and membrane pore structure on protein immobilization. The concentration of immobilized protein was measured by staining with Ponceau S and measuring its color intensity. In this study, both membrane morphology and the quantity of deposited protein significantly influenced the quantity of protein immobilization on the membrane surface. The sharpness and intensity of the red protein spots varied depending on the membrane pore structure, indicating a dependence of protein immobilization on this factor. Membranes with smaller pores resulted in a higher color density, corresponding to enhanced protein immobilization and an increased assay sensitivity level. An increased of immobilized volume has a significant jagged outline on the protein spot but, conversely, no difference in binding capacity.
  6. Low SC, Ahmad AL, Ideris N, Ng QH
    Bioresour Technol, 2012 Jun;113:219-24.
    PMID: 22153291 DOI: 10.1016/j.biortech.2011.11.048
    The aim of this study was to explore the utilization of polymeric membrane for bio-sensing application in most efficient and rapid way. Customization of membrane formulation via phase separation study to modify its morphologies and properties enable the detection of different pathogens in a specific manner. Experimental findings (FESEM, through-pore distribution, porosity, capillary flow test and protein binding test) verified the predictions of faster capillary flow time and higher membrane's protein binding by the addition of cellulose acetate and nitrocellulose to the membrane casting dope, respectively. Throughout the phase separation study, the potential phase behavior was investigated, which was correlating various membrane structures to its performances for potential pathogens detection in water.
  7. Ahmad AL, Ideris N, Ooi BS, Low SC, Ismail A
    J Immunoassay Immunochem, 2016;37(4):421-37.
    PMID: 27088961 DOI: 10.1080/15321819.2016.1157489
    Statistical experimental design was employed to optimize the preparation conditions of polyvinylidenefluoride (PVDF) membranes. Three variables considered were polymer concentration, dissolving temperature, and casting thickness, whereby the response variable was membrane-protein binding. The optimum preparation for the PVDF membrane was a polymer concentration of 16.55 wt%, a dissolving temperature of 27.5°C, and a casting thickness of 450 µm. The statistical model exhibits a deviation between the predicted and actual responses of less than 5%. Further characterization of the formed PVDF membrane showed that the morphology of the membrane was in line with the membrane-protein binding performance.
  8. Chin JY, Teoh GH, Ahmad AL, Low SC
    Water Sci Technol, 2020 Dec;82(12):2948-2961.
    PMID: 33341784 DOI: 10.2166/wst.2020.528
    Membrane distillation (MD) is an advantageous separation process compared with pressure-driven technologies and was subsequently introduced to treat aquaculture wastewater. Harnessing a superhydrophobic membrane in an MD process is of extreme importance to prevent membrane wetting. In this work, the electrospun polypropylene (PP) membrane was surface modified by depositing an additional coating of PP via the solvent-exchange method, thereby improving the membrane's superhydrophobicity. Layer-by-layer deposition of PP caused the formation of uniform polymer spherulites on the membrane surface, which levelled up the membrane's surface roughness. A superhydrophobic surface was achieved by applying a single-layered PP coating, with static water contact angle of 152.2° and sliding angle of 12.5°. While all membranes achieved almost perfect salt rejection (up to 99.99%), the MD permeate flux improved by 30%, average of 13.0 kg/m2h, when the single-layered PP-coated membrane was used to treat the high salinity water in both 2 and 60 hr MD processes. Further layers of coating resulted in larger size of PP spherulites with higher sliding angle, followed by lowered flux in MD. The evenness of the surface coating and the size of the aggregate PP spherulites (nano-scaled) are two predominant factors contributing to the superhydrophobicity character of a membrane.
  9. Chin JY, Teoh GH, Ahmad AL, Low SC
    Sci Total Environ, 2021 Nov 10;794:148657.
    PMID: 34198076 DOI: 10.1016/j.scitotenv.2021.148657
    Surging growth of aquaculture industry has alarmed the public when the wastewater discharged had an adverse effect on the environment. This current study is a pioneer in the use of membrane distillation (MD) to treat real aquaculture wastewater. In addition to excellent hydrophobicity, the slippery surface of membrane used for MD is another key factor that enhances the performance of MD. The slippery surface of the membrane was tuned by layering high-viscosity and low-viscosity polypropylene (PP) polymers on the electrospun membrane by solvent-exchanged method. While the high-viscosity PP coating (PP/HV) rendered the membrane surface slippery, the low-viscosity PP coating (PP/LV) caused the fish farm wastewater to have stick-slip movement on the membrane surface. In the long-term 70-hour direct contact membrane distillation (DCMD) separation, PP/HV and PP/LV membranes can perfectly eliminate the undesirable components in the fish farm wastewater. The PP/HV membrane has registered a flux of 19.1 kg/m2·h, while the flux of PP/LV membrane was only 7.3 kg/m2·h. The PP/HV membrane also showed excellent anti-scaling properties in relative to the PP/LV membrane. This is because the PP/HV membrane promotes effortless gliding of the feed water along the surface of the membrane, while the surface of the PP/LV membrane has a static water boundary. Therefore, it can be concluded that the application of MD using the membrane coated with high-viscosity PP polymer is a feasible technology for the treatment of aquaculture wastewater.
  10. Abdul Latif AA, Lau KK, Low SC, Azeem B
    Membranes (Basel), 2021 Aug 26;11(9).
    PMID: 34564471 DOI: 10.3390/membranes11090654
    A spiral wound membrane (SWM) is employed to separate acid gases (mainly CO2) from natural gas due to its robustness, lower manufacturing cost, and moderate packing density compared to hollow fiber membranes. Various mathematical models are available to describe the separation performance of SWMs under different operating conditions. Nevertheless, most of the mathematical models deal with only binary gas mixtures (CO2 and CH4) that may lead to an inaccurate assessment of separation performance of multicomponent natural gas mixtures. This work is aimed to develop an SWM separation model for multicomponent natural gas mixtures. The succession stage method is employed to discretize the separation process within the multicomponent SWM module for evaluating the product purity, hydrocarbon loss, stage cut, and permeate acid gas composition. Our results suggest that multicomponent systems tend to generate higher product purity, lower hydrocarbon loss, and augmented permeate acid gas composition compared to the binary system. Furthermore, different multicomponent systems yield varied separation performances depending on the component of the acid gas. The developed multicomponent SWM separation model has the potential to design and optimize the spiral wound membrane system for industrial application.
  11. Lim J, Yeap SP, Leow CH, Toh PY, Low SC
    J Colloid Interface Sci, 2014 May 1;421:170-7.
    PMID: 24594047 DOI: 10.1016/j.jcis.2014.01.044
    Magnetophoresis of iron oxide magnetic nanoparticle (IOMNP) under low magnetic field gradient (<100 T/m) is significantly enhanced by particle shape anisotropy. This unique feature of magnetophoresis is influenced by the particle concentration and applied magnetic field gradient. By comparing the nanosphere and nanorod magnetophoresis at different concentration, we revealed the ability for these two species of particles to achieve the same separation rate by adjusting the field gradient. Under cooperative magnetophoresis, the nanorods would first go through self- and magnetic field induced aggregation followed by the alignment of the particle clusters formed with magnetic field. Time scale associated to these two processes is investigated to understand the kinetic behavior of nanorod separation under low field gradient. Surface functionalization of nanoparticles can be employed as an effective strategy to vary the temporal evolution of these two aggregation processes which subsequently influence the magnetophoretic separation time and rate.
  12. Abosadiya HM, Hasbullah SA, Mackeen MM, Low SC, Ibrahim N, Koketsu M, et al.
    Molecules, 2013;18(11):13369-84.
    PMID: 24172244 DOI: 10.3390/molecules181113369
    C-5-bromo-2-hydroxyphenylcalix[4]-2-methylresorcinarene (I) was synthesized by cyclocondensation of 5-bromo-2-hydroxybenzaldehyde and 2-methylresorcinol in the presence of concentrated HCl. Compound I was characterized by infrared and nuclear magnetic resonance spectroscopic data. X-ray analysis showed that this compound crystallized in a triclinic system with space group of Pī, a = 15.9592(16)Å, b = 16.9417(17)Å, c = 17.0974(17)Å, α = 68.656(3)°, β = 85.689(3)°, γ = 81.631(3)°, Z = 2 and V = 4258.6(7)Å3. The molecule adopts a chair (C2h) conformation. The thermal properties and antioxidant activity were also investigated. It was strongly antiviral against HSV-1 and weakly antibacterial against Gram-positive bacteria. Cytotoxicity testing on Vero cells showed that it is non-toxic, with a CC50 of more than 0.4 mg/mL.
  13. Wong GW, Lim KH, Wan WK, Low SC, Kong SC
    Med J Malaysia, 2015 08;70(4):232-7.
    PMID: 26358020
    BACKGROUND: Eosinophilic gastroenteritis (EG) can mimic symptoms of common gastrointestinal (GI) disorders but responds well to appropriate treatment. Accurate diagnosis is central to effective management. Data on EG in Southeast Asia is lacking. We aim to describe the clinical profiles and treatment outcomes of adult patients with EG in a Singapore Tertiary Hospital.

    MATERIALS AND METHODS: This retrospective study involved archival search of patients with GI biopsies that showed eosinophilic infiltration from January 2004 to December 2012. Patients' clinical data from computerised hospital records and clinical notes was reviewed. Diagnostic criteria for EG included presence of GI symptoms with more than 30 eosinophils/high power field on GI biopsies. Patients with secondary causes for eosinophilia were excluded.

    RESULTS: Eighteen patients with EG were identified (mean age 52 years; male/female: 11/7). Fifteen patients (83%) had peripheral blood eosinophilia. Seven patients (39%) had atopic conditions. Most common symptoms were diarrhoea and abdominal pain. Small intestine was the most common site involved. Endoscopic finding was non-specific. Ten patients were treated with corticosteroids (nine prednisolone, one budesonide): eight patients (89%) responded clinically to prednisolone but four patients (50%) relapsed following tapering-off of prednisolone and required maintenance dose. One patient each responded to diet elimination and montelukast respectively. Half of the remaining six patients who were treated with proton-pump inhibitors, antispasmodic or antidiarrheal agents still remained symptomatic.

    CONCLUSION: Prednisolone is an effective treatment though relapses are common. Small intestine is most commonly involved. EG should be considered in the evaluation of unexplained chronic recurrent GI symptoms.

  14. Leong SS, Ahmad Z, Low SC, Camacho J, Faraudo J, Lim J
    Langmuir, 2020 07 21;36(28):8033-8055.
    PMID: 32551702 DOI: 10.1021/acs.langmuir.0c00839
    The migration process of magnetic nanoparticles and colloids in solution under the influence of magnetic field gradients, which is also known as magnetophoresis, is an essential step in the separation technology used in various biomedical and engineering applications. Many works have demonstrated that in specific situations, separation can be performed easily with the weak magnetic field gradients created by permanent magnets, a process known as low-gradient magnetic separation (LGMS). Due to the level of complexity involved, it is not possible to understand the observed kinetics of LGMS within the classical view of magnetophoresis. Our experimental and theoretical investigations in the last years unravelled the existence of two novel physical effects that speed up the magnetophoresis kinetics and explain the observed feasibility of LGMS. Those two effects are (i) cooperative magnetophoresis (due to the cooperative motion of strongly interacting particles) and (ii) magnetophoresis-induced convection (fluid dynamics instability originating from inhomogeneous magnetic gradients). In this feature article, we present a unified view of magnetophoresis based on the extensive research done on these effects. We present the physical basis of each effect and also propose a classification of magnetophoresis into four distinct regimes. This classification is based on the range of values of two dimensionless quantities, namely, aggregation parameter N* and magnetic Grashof number Grm, which include all of the dependency of LGMS on various physical parameters (such as particle properties, thermodynamic parameters, fluid properties, and magnetic field properties). This analysis provides a holistic view of the classification of transport mechanisms in LGMS, which could be particularly useful in the design of magnetic separators for engineering applications.
  15. Tham FK, Ng WM, Leong SS, Yeap SP, Low SC, Lee HL, et al.
    Langmuir, 2021 Jan 26.
    PMID: 33496594 DOI: 10.1021/acs.langmuir.0c03153
    Monodispersed iron oxide nanoparticles (IONPs) coated with polystyrenesulfonate (PSS) and cetrimonium bromide (CTAB) have been used to stabilize magnetic Pickering emulsions (MPEs). Magnetophoresis of MPEs under the influence of a low gradient magnetic field (∇B < 100 T/m) was investigated at the macroscopic and microscopic scale. At the macroscopic scale, for the case of pH 7, the MPE achieved a magnetophoretic velocity of 70.9 μm/s under the influence of ∇B at 93.8 T/m. The magnetic separation efficiency of the MPE at 90% was achieved within 30 min for pH 3, 7, and 10. At pH 10, the colloidal stability of the MPE was the lowest compared to that for pH 3 and 7. Thus, MPE at pH 10 required the shortest time for achieving the highest separation efficiency, as the MPE experienced cooperative magnetophoresis at alkaline pH. The creaming rate of the MPE at all conditions was still lower compared to magnetophoresis and was negligible in influencing its separation kinetics profiles. At the microscopic scale, the migration pathways of the MPEs (with diameters between 2.5 and 7.5 μm) undergoing magnetophoresis at ∇B ∼ 13.0 T/m were recorded by an optical microscope. From these experiments, and taking into consideration the MPE size distribution from the dynamic light scattering (DLS) measurement, we determined the averaged microscopic magnetophoretic velocity to be 7.8 ± 5.5 μm/s. By making noncooperative magnetophoresis assumptions (with negligible interactions between the MPEs along their migration pathways), the calculated velocity of individual MPEs was 9.8 μm/s. Such a value was within the percentage error of the experimental result of 7.8 ± 5.5 μm/s. This finding allows for an easy and quick estimation of the magnetophoretic velocity of MPEs at the microscale by using macroscopic separation kinetics data.
  16. Tan AH, Low SC, Tan CY, Lim KS, Tan CT, Lim SY
    Parkinsonism Relat Disord, 2016 11;32:137-139.
    PMID: 27688197 DOI: 10.1016/j.parkreldis.2016.09.019
  17. Lim SY, Tan AH, Fox SH, Evans AH, Low SC
    Curr Neurol Neurosci Rep, 2017 01;17(1):3.
    PMID: 28102483 DOI: 10.1007/s11910-017-0717-2
    Parkinson's disease (PD) is a complex motor and non-motor disorder and management is often challenging. In this review, we explore emerging approaches to improve the care of patients, drawing from the literature regarding patient-centred care, patient and caregiver perspectives and priorities, gaps in knowledge among patients and caregivers and the need for accurate information, individual variability in disease manifestations, prognostication of disease course, new developments in health technologies and personalized medicine, specialty care, pharmacological and non-pharmacological management, financial burden, lifestyle and work-related issues, support groups and palliative care.
  18. Gasim MF, Lim JW, Low SC, Lin KA, Oh WD
    Chemosphere, 2022 Jan;287(Pt 4):132458.
    PMID: 34610377 DOI: 10.1016/j.chemosphere.2021.132458
    Over the past decade, there has been a surge of interest in using char (hydrochar or biochar) derived from biomass as persulfate (PS, either peroxymonosulfate or peroxydisulfate) activator for anthropogenic pollutants removal. While extensive investigation showed that char could be used as a PS activator, its sustainability over prolonged application is equivocal. This review provides an assessment of the knowledge gap related to the sustainability of char as a PS activator. The desirable char properties for PS activation are identified, include the high specific surface area and favorable surface chemistry. Various synthesis strategies to obtain the desirable properties during biomass pre-treatment, hydrochar and biochar synthesis, and char post-treatment are discussed. Thereafter, factors related to the sustainability of employing char as a PS activator for anthropogenic pollutants removal are critically evaluated. Among the critical factors include performance uncertainty, competing adsorption process, char stability during PS activation, biomass precursor variation, scalability, and toxic components in char. Finally, some potential research directions are provided. Fulfilling the sustainability factors will provide opportunity to employ char as an economical and efficient catalyst for sustainable environmental remediation.
  19. Gasim MF, Veksha A, Lisak G, Low SC, Hamidon TS, Hussin MH, et al.
    J Colloid Interface Sci, 2023 Mar 15;634:586-600.
    PMID: 36549207 DOI: 10.1016/j.jcis.2022.12.072
    Herein, five N, S-co-doped carbocatalysts were prepared from different carbonaceous precursors, namely sawdust (SD), biochar (BC), carbon-nanotubes (CNTs), graphite (GP), and graphene oxide (GO) and compared. Generally, as the graphitization degree increased, the extent of N and S doping decreased, graphitic N configuration is preferred, and S configuration is unaltered. As peroxymonosulfate (PMS) activator for ciprofloxacin (CIP) removal, the catalytic performance was in order: NS-CNTs (0.037 min-1) > NS-BC (0.032 min-1) > NS-rGO (0.024 min-1) > NS-SD (0.010 min-1) > NS-GP (0.006 min-1), with the carbonaceous properties, rather than the heteroatoms content and textural properties, being the major factor affecting the catalytic performance. NS-CNTs was found to have the supreme catalytic activity due to its remarkable conductivity (3.38 S m-1) and defective sites (ID/IG = 1.28) with high anti-interference effect against organic and inorganic matter and varying water matrixes. The PMS activation pathway was dominated by singlet oxygen (1O2) generation and electron transfer regime between CIP and PMS activated complexes. The CIP degradation intermediates were identified, and a degradation pathway is proposed. Overall, this study provides a better understanding of the importance of selecting a suitable carbonaceous platform for heteroatoms doping to produce superior PMS activator for antibiotics decontamination.
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