Displaying publications 61 - 75 of 75 in total

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  1. Reduction of hexavalent chromium using Aerva lanata L.: elucidation of reduction mechanism and identification of active principles
    Poonkuzhali K, Rajeswari V, Saravanakumar T, Viswanathamurthi P, Park SM, Govarthanan M, et al.
    J Hazard Mater, 2014 May 15;272:89-95.
    PMID: 24681590 DOI: 10.1016/j.jhazmat.2014.03.001
    The effluent discharge treatment for controlling the environment from non biodegradable metal contaminants using plant extract is an efficient technique. The reduction of hexavalent chromium by abundantly available weed, Aerva lanata L. was investigated using batch equilibrium technique. The variables studied were Cr(VI) concentration, Aerva lanata L. dose, contact time, pH, temperature and agitation speed. Cyclic voltammetry and ICP-MS analysis confirmed the reduction of Cr(VI) to Cr(III). Electrochemical analysis proved that, the chromium has not been degraded and the valency of the chromium has only been changed. ICP-MS analysis shows that 100ng/L of hexavalent chromium was reduced to 97.01ng/L trivalent chromium. These results suggest that components present in the Aerva lanata L. are responsible for the reduction of Cr(VI) to Cr(III). The prime components ferulic acid, kaempherol and β-carboline present in the Aerva lanata L. may be responsible for the reduction of Cr(VI) as evident from LC-MS analysis.
    Matched MeSH terms: Electrochemistry
  2. Metal ion removal from aqueous solution using physic seed hull
    Mohammad M, Maitra S, Ahmad N, Bustam A, Sen TK, Dutta BK
    J Hazard Mater, 2010 Jul 15;179(1-3):363-72.
    PMID: 20362390 DOI: 10.1016/j.jhazmat.2010.03.014
    The potential of physic seed hull (PSH), Jantropha curcas L. as an adsorbent for the removal of Cd(2+) and Zn(2+) metal ions from aqueous solution has been investigated. It has been found that the amount of adsorption for both Cd(2+) and Zn(2+) increased with the increase in initial metal ions concentration, contact time, temperature, adsorbent dosage and the solution pH (in acidic range), but decreased with the increase in the particle size of the adsorbent. The adsorption process for both metal ions on PSH consists of three stages-a rapid initial adsorption followed by a period of slower uptake of metal ions and virtually no uptake at the final stage. The kinetics of metal ions adsorption on PSH followed a pseudo-second-order model. The adsorption equilibrium data were fitted in the three adsorption isotherms-Freundlich, Langmuir and Dubinin-Radushkevich isotherms. The data best fit in the Langmuir isotherm indication monolayer chemisorption of the metal ions. The adsorption capacity of PSH for both Zn(2+) and Cd(2+) was found to be comparable with other available adsorbents. About 36-47% of the adsorbed metal could be leached out of the loaded PSH using 0.1M HCl as the eluting medium.
    Matched MeSH terms: Electrochemistry
  3. Electrochemical DNA biosensor for the detection of specific gene related to Trichoderma harzianum species
    Siddiquee S, Yusof NA, Salleh AB, Abu Bakar F, Heng LY
    Bioelectrochemistry, 2010 Aug;79(1):31-6.
    PMID: 19945357 DOI: 10.1016/j.bioelechem.2009.10.004
    A new electrochemical biosensor is described for voltammetric detection of gene sequence related to Trichoderma harzianum. The sensor involves immobilization of a 20 base single-stranded probe (ssDNA), which is complementary to a specific gene sequence related to T. harzianum on a gold electrode through specific adsorption. The DNA probe was used to determine the amount of target gene in solution using methylene blue (MB) as the electrochemical indicator. The covalently immobilized probe could selectively hybridize with the target DNA to form a hybrid on the surface despite the bases being attached to the electrode. The changes in the peak currents of methylene blue (MB), an electroactive label, were observed upon hybridization of probe with the target. Peak currents were found to increase in the following order: hybrid-modified AuE and the probe-modified AuE which localized to the affinity of MB. Control experiments with the non-complementary oligonucleotides were performed to assess whether the DNA biosensor responds selectively, via hybridization, to the target. DNA biosensor also able to detect microorganism at the species levels without nucleic acid amplification. The redox current was linearly related to the concentration of target oligonucleotide DNA, ranged from 1-20 ppm. Numerous factors, affecting the probe immobilization, target hybridization and indicator binding reactions are optimized to maximize the sensitivity and reduce the assay time.
    Matched MeSH terms: Electrochemistry
  4. Hydroxyapatite nanoparticles: electrospinning and calcination of hydroxyapatite/polyvinyl butyral nanofibers and growth kinetics
    Zakaria SM, Sharif Zein SH, Othman MR, Jansen JA
    J Biomed Mater Res A, 2013 Jul;101(7):1977-85.
    PMID: 23225849 DOI: 10.1002/jbm.a.34506
    Electrospinning of hydroxyapatite (HA)/polyvinyl butyral solution resulted in the formation of fibers with average diameter of 937-1440 nm. These fibers were converted into HA nanoparticles with size <100 nm after undergoing calcination treatment at 600°C. The diameter of the fiber was found to be influenced by applied voltage and spinning distance. The injection flowrate did not affect the diameter significantly. The electrospinning method successfully reduced the commercial HA particle size in the range of 400-1100 nm into <100 nm. The dispersion of the finally calcined HA nanoparticles was improved significantly after anionic sodium dodecyl sulfate surfactant was introduced. The experimental data of HA growth kinetics were subjected to the integral method of analysis, and the rate law of the reaction was found to follow the first order reaction.
    Matched MeSH terms: Electrochemistry
  5. Biosensors for phenolic compounds by immobilization of tyrosinase in photocurable methacrylic-acrylic membranes of varying hydrophilicities
    Hanifah SA, Heng LY, Ahmad M
    Anal Sci, 2009 Jun;25(6):779-84.
    PMID: 19531887
    Electrochemical biosensors for phenolic compound determination were developed by immobilization of tyrosinase enzyme in a series of methacrylic-acrylic based biosensor membranes deposited directly using a photocuring method. By modifying the hydrophilicity of the membranes using different proportions of 2-hydroxyethyl methacrylate (HEMA) and butyl acrylate (nBA), we developed biosensor membranes of different hydrophilic characters. The differences in hydrophilicity of these membranes led to changes in the sensitivity of the biosensors towards different phenolic compounds. In general biosensors constructed from the methacrylic-acrylic based membranes showed the poorest response to catechol relative to other phenolic compounds, which is in contrast to many other biosensors based on tyrosinase. The decrease in hydrophilicity of the membrane also allowed better selectivity towards chlorophenols. However, phenol biosensors constructed from the more hydrophilic membrane materials demonstrated better analytical performance towards phenol compared with those made from less hydrophilic ones. For the detection of phenols, these biosensors with different membranes gave detection limits of 0.13-0.25 microM and linear response range from 6.2-54.2 microM phenol. The phenol biosensors also showed good phenol recovery from landfill leachate samples (82-117%).
    Matched MeSH terms: Electrochemistry
  6. Extraction, preparation and application of pigments from Cordyline fruticosa and Hylocereus polyrhizus as sensitizers for dye-sensitized solar cells
    Al-Alwani MAM, Ludin NA, Mohamad AB, Kadhum AAH, Sopian K
    Spectrochim Acta A Mol Biomol Spectrosc, 2017 May 15;179:23-31.
    PMID: 28213142 DOI: 10.1016/j.saa.2017.02.026
    Current study employs mixture of chlorophyll-anthocyanin dye extracted from leaves of Cordyline fruticosa as new sensitizers for dye-sensitized solar cell (DSSCs), as well as betalains dye obtained from fruit of Hylocereus polyrhizus. Among ten pigments solvents, the ethanol and methanol extracts revealed higher absorption spectra of pigments extracted from C. fruticosa and H. polyrhizus respectively. A major effect of temperature increase was studied to increase the extraction yield. The results indicated that extraction temperature between 70 and 80°C exhibited a high dye concentration of each plant than other temperatures. The optimal temperature was around 80°C and there was a sharp decrease of dye concentration at temperatures higher than this temperature. According to experimental results, the conversion efficiency of DSSC fabricated by mixture of chlorophyll and anthocyanin dyes from C. fruticosa leaves is 0.5% with short-circuit current (Isc) of 1.3mA/cm-2, open-circuit voltage (Voc) of 0.62V and fill factor (FF) of 60.16%. The higher photoelectric conversion efficiency of the DSSC prepared from the extract of H. polyrhizus was 0.16%, with Voc of 0.5V, Isc of 0.4mA/cm-2 and FF of 79.16%. The DSSC based betalain dye extracted from fruit of H. polyrhizus shows higher maximum IPCE of 44% than that of the DSSCs sensitized with mixed chlorophyll-anthocyanin dye from C. fruticosa (42%).
    Matched MeSH terms: Electrochemistry
  7. A single step electrochemical integration of gold nanoparticles, cholesterol oxidase, cholesterol esterase and mediator with polypyrrole films for fabrication of free and total cholesterol nanobiosensors
    Rahim MZA, Govender-Hondros G, Adeloju SB
    Talanta, 2018 Nov 01;189:418-428.
    PMID: 30086941 DOI: 10.1016/j.talanta.2018.06.041
    The development of free and total cholesterol nanobiosensors based on a single step electrochemical integration of gold nanoparticles (AuNPs), cholesterol oxidase (COx), cholesterol esterase (CE) and a mediator with polypyrrole (PPy) films is described. The incorporation of the various components in the PPy films was confirmed by chronopotentiometry, cyclic voltammetry (CV), scanning electron microscopy, energy dispersive X-ray analysis (SEM-EDX), and Fourier transformed infrared (FTIR) spectroscopy. The free cholesterol, PPy-NO3--Fe(CN)64--AuNPs-COx, nanobiosensor achieved a minimum detectable concentration of 5 μM, a linear concentration range of 5-25 μM and a sensitivity of 1.6 µA cm-2 µM-1 in 0.05 M phosphate buffer (pH 7.00). For the total cholesterol, PPy-NO3--Fe(CN)64--AuNPs-COx-CE, nanobiosensor which also involved the co-incorporation of cholesterol esterase (CE) with the other components, the achieved performances include a minimum detectable total cholesterol concentration of 25 μM, a broader linear concentration range of 25-170 μM and a lower sensitivity of 0.1 µA µM-1 cm-2. Owing to its high selectivity, the presence of common interferants did not affect the total cholesterol measurement with the PPy-NO3--Fe(CN)64--AuNPs-COx-CE nanobiosensor. Both nanobiosensors were successfully used for direct and indirect determination of total cholesterol in human blood serum samples.
    Matched MeSH terms: Electrochemistry
  8. Application of dyes extracted from Alternanthera dentata leaves and Musa acuminata bracts as natural sensitizers for dye-sensitized solar cells
    Al-Alwani MAM, Ludin NA, Mohamad AB, Kadhum AAH, Mukhlus A
    Spectrochim Acta A Mol Biomol Spectrosc, 2018 Mar 05;192:487-498.
    PMID: 29133132 DOI: 10.1016/j.saa.2017.11.018
    The natural dyes anthocyanin and chlorophyll were extracted from Musa acuminata bracts and Alternanthera dentata leaves, respectively. The dyes were then applied as sensitizers in TiO2-based dye-sensitized solar cells (DSSCs). The ethanol extracts of the dyes had maximum absorbance. High dye yields were obtained under extraction temperatures of 70 to 80°C, and the optimal extraction temperature was approximately 80°C. Moreover, dye concentration sharply decreased under extraction temperatures that exceeded 80°C. High dye concentrations were obtained using acidic extraction solutions, particularly those with a pH value of 4. The DSSC fabricated with anthocyanin from M. acuminata bracts had a conversion efficiency of 0.31%, short-circuit current (Isc) of 0.9mA/cm2, open-circuit voltage (Voc) of 0.58V, and fill factor (FF) of 62.22%. The DSSC sensitized with chlorophyll from A. dentata leaves had a conversion efficiency of 0.13%, Isc of 0.4mA/cm-2,Voc of 0.54V, and FF of 67.5%. The DSSC sensitized with anthocyanin from M. acuminata bracts had a maximum incident photon-to-current conversion efficiency of 42%, which was higher than that of the DSSC sensitized with chlorophyll from A. dentata leaves (23%). Anthocyanin from M. acuminata bracts exhibited the best photosensitization effects.
    Matched MeSH terms: Electrochemistry
  9. Electro-transformation of mefenamic acid drug: a case study of kinetics, transformation products, and toxicity
    Mussa ZH, Al-Qaim FF, Yuzir A, Latip J
    Environ Sci Pollut Res Int, 2019 Apr;26(10):10044-10056.
    PMID: 30756352 DOI: 10.1007/s11356-019-04301-3
    Poor removal of many pharmaceuticals and personal care products in sewage treatment plants leads to their discharge into the receiving waters, where they may cause negative effects for aquatic environment and organisms. In this study, electrochemical removal process has been used as alternative method for removal of mefenamic acid (MEF). For our knowledge, removal of MEF using electrochemical process has not been reported yet. Effects of initial concentration of mefenamic acid, sodium chloride (NaCl), and applied voltage were evaluated for improvement of the efficiency of electrochemical treatment process and to understand how much electric energy was consumed in this process. Removal percentage (R%) was ranged between 44 and 97%, depending on the operating parameters except for 0.1 g NaCl which was 9.1%. Consumption energy was 0.224 Wh/mg after 50 min at 2 mg/L of mefenamic acid, 0.5 g NaCl, and 5 V. High consumption energy (0.433 Wh/mg) was observed using high applied voltage of 7 V. Investigation and elucidation of the transformation products were provided by Bruker software dataAnalysis using liquid chromatography-time of flight mass spectrometry. Seven chlorinated and two non-chlorinated transformation products were investigated after 20 min of electrochemical treatment. However, all transformation products (TPs) were eliminated after 140 min. For the assessment of the toxicity, it was impacted by the formation of transformation products especially between 20 and 60 min then the inhibition percentage of E. coli bacteria was decreased after 80 min to be the lowest value.
    Matched MeSH terms: Electrochemistry
  10. Fulltext A Highly Sensitive Impedimetric DNA Biosensor Based on Hollow Silica Microspheres for Label-Free Determination of E. coli
    Yuhana Ariffin E, Heng LY, Tan LL, Abd Karim NH, Hasbullah SA
    Sensors (Basel), 2020 Feb 26;20(5).
    PMID: 32111092 DOI: 10.3390/s20051279
    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 × 10-10 µM to 1 × 10-5 µM (R2 = 0.982), with a limit of detection at 1.95 × 10-15 µM, 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.
    Matched MeSH terms: Electrochemistry
  11. Neuraminidase treatment abrogates the binding abnormality of IgA1 from IgA nephropathy patients and the differential charge distribution of its alpha-heavy chains
    Hashim OH, Shuib AS, Chua CT
    Nephron, 2001 Dec;89(4):422-5.
    PMID: 11721160
    We have studied the interaction of the Gal-GalNAc-reactive champedak lectin-C with neuraminidase-treated and untreated IgA1 from IgA nephropathy patients. The binding ability of the lectin to untreated IgA1 from IgA nephropathy patients was significantly lower as compared to the untreated IgA1 from normal controls. This differential lectin-binding capacity was abrogated when the experiment was performed on neuraminidase-treated sera. Treatment of the serum IgA1 with neuraminidase also abrogated the differential charge distribution between the alpha-heavy chains of IgA nephropathy patients and normal controls.
    Matched MeSH terms: Electrochemistry
  12. Magnesium-zinc scaffold loaded with tetracycline for tissue engineering application: In vitro cell biology and antibacterial activity assessment
    Dayaghi E, Bakhsheshi-Rad HR, Hamzah E, Akhavan-Farid A, Ismail AF, Aziz M, et al.
    Mater Sci Eng C Mater Biol Appl, 2019 Sep;102:53-65.
    PMID: 31147024 DOI: 10.1016/j.msec.2019.04.010
    Recently, porous magnesium and its alloys are receiving great consideration as biocompatible and biodegradable scaffolds for bone tissue engineering application. However, they presented poor antibacterial performance and corrosion resistance which limited their clinical applications. In this study, Mg-Zn (MZ) scaffold containing different concentrations of tetracycline (MZ-xTC, x = 1, 5 and 10%) were fabricated by space holder technique to meet the desirable antibacterial activity and corrosion resistance properties. The MZ-TC contains total porosity of 63-65% with pore sizes in the range of 600-800 μm in order to accommodate bone cells. The MZ scaffold presented higher compressive strength and corrosion resistance compared to pure Mg scaffold. However, tetracycline incorporation has less significant effect on the mechanical and corrosion properties of the scaffolds. Moreover, MZ-xTC scaffolds drug release profiles show an initial immediate release which is followed by more stable release patterns. The bioactivity test reveals that the MZ-xTC scaffolds are capable of developing the formation of HA layers in simulated body fluid (SBF). Next, Staphylococcus aureus and Escherichia coli bacteria were utilized to assess the antimicrobial activity of the MZ-xTC scaffolds. The findings indicate that those scaffolds that incorporate a high level concentration of tetracycline are tougher against bacterial organization than MZ scaffolds. However, the MTT assay demonstrates that the MZ scaffolds containing 1 to 5% tetracycline are more effective to sustain cell viability, whereas MZ-10TC shows some toxicity. The alkaline phosphatase (ALP) activity of the MZ-(1-5)TC was considerably higher than that of MZ-10TC on the 3 and 7 days, implying higher osteoblastic differentiation. All the findings suggest that the MZ-xTC scaffolds containing 1 to 5% tetracycline is a promising candidate for bone tissue healing due to excellent antibacterial activity and biocompatibility.
    Matched MeSH terms: Electrochemistry
  13. Fabrication and preliminary in vitro evaluation of ultraviolet-crosslinked electrospun fish scale gelatin nanofibrous scaffolds
    Beishenaliev A, Lim SS, Tshai KY, Khiew PS, Moh'd Sghayyar HN, Loh HS
    J Mater Sci Mater Med, 2019 May 24;30(6):62.
    PMID: 31127374 DOI: 10.1007/s10856-019-6264-4
    This study aimed to explore a potential use of fish scale-derived gelatin nanofibrous scaffolds (GNS) in tissue engineering due to their biological and economical merits. Extraction of gelatin was achieved via decalcification, sonication and lyophilization of mixed fish scales. To fabricate nano-scale architecture of scaffolds analogous to natural extracellular matrix, gelatin was rendered into nanofibrous matrices through 6-h electrospinning, resulting in the average diameter of 48 ± 12 nm. In order to improve the water-resistant ability while retaining their biocompatibility, GNS were physically crosslinked with ultraviolet (UV) irradiation for 5 min (UGN5), 10 min (UGN10) and 20 min (UGN20). On average, the diameter of nanofibers increased by 3 folds after crosslinking, however, Fourier transform infrared spectroscopy analysis confirmed that no major alterations occurred in the functional groups of gelatin. A degradation assay showed that UGN5 and UGN10 scaffolds remained in minimum essential medium for 14 days, while UGN20 scaffolds degraded completely after 10 days. All UGN scaffolds promoted adhesion and proliferation of human keratinocytes, HaCaT, without causing an apparent cytotoxicity. UGN5 scaffolds were shown to stimulate a better growth of HaCaT cells compared to other scaffolds upon 1 day of incubation, whereas UGN20 had a long-term effect on cells exhibiting 25% higher cell proliferation than positive control after 7 days. In the wound scratch assay, UGN5 scaffolds induced a rapid cell migration closing up to 79% of an artificial wound within 24 h. The current findings provide a new insight of UGN scaffolds to serve as wound dressings in the future. In the wound scratch assay, UGN5 induced a rapid cell migration closing up to 79% of an artificial wound within 24 h.
    Matched MeSH terms: Electrochemistry
  14. Bio-corrosion behavior and mechanical characteristics of magnesium-titania-hydroxyapatite nanocomposites coated by magnesium-oxide flakes and silicon for use as resorbable bone fixation material
    Khalajabadi SZ, Abu ABH, Ahmad N, Yajid MAM, Hj Redzuan NB, Nasiri R, et al.
    J Mech Behav Biomed Mater, 2018 Jan;77:360-374.
    PMID: 28985616 DOI: 10.1016/j.jmbbm.2017.09.032
    This study was aimed to improve of the corrosion resistance and mechanical properties of Mg/15TiO2/5HA nanocomposite by silicon and magnesium oxide coatings prepared using a powder metallurgy method. The phase evolution, chemical composition, microstructure and mechanical properties of uncoated and coated samples were characterized. Electrochemical and immersion tests used to investigate the in vitro corrosion behavior of the fabricated samples. The adhesion strength of ~36MPa for MgO and ~32MPa for Si/MgO coatings to substrate was measured by adhesion test. Fabrication a homogenous double layer coating with uniform thicknesses consisting micro-sized particles of Si as outer layer and flake-like particles of MgO as the inner layer on the surface of Mg/15TiO2/5HA nanocomposite caused the corrosion resistance and ductility increased whereas the ultimate compressive stress decreased. However, after immersion in SBF solution, Si/MgO-coated sample indicates the best mechanical properties compared to those of the uncoated and MgO-coated samples. The increase of cell viability percentage of the normal human osteoblast (NHOst) cells indicates the improvement in biocompatibility of Mg/15TiO2/5HA nanocomposite by Si/MgO coating.
    Matched MeSH terms: Electrochemistry
  15. Fulltext Sudomotor dysfunction independently predicts incident cardiovascular-renal events and all-cause death in type 2 diabetes: the Joint Asia Diabetes Evaluation register
    Lim LL, Fu AWC, Lau ESH, Ozaki R, Cheung KKT, Ma RCW, et al.
    Nephrol Dial Transplant, 2019 Aug 01;34(8):1320-1328.
    PMID: 29939305 DOI: 10.1093/ndt/gfy154
    BACKGROUND: Early detection and risk factor control prevent chronic kidney disease (CKD) progression. Evaluation of peripheral autonomic dysfunction may detect incident cardiovascular-renal events in type 2 diabetes (T2D).

    METHODS: SUDOSCAN, a non-invasive tool, provides an age-adjusted electrochemical skin conductance (ESC) composite score incorporating hands/feet ESC measurements, with a score ≤53 indicating sudomotor dysfunction. A consecutive cohort of 2833 Chinese adults underwent structured diabetes assessment in 2012-13; 2028 participants without preexisting cardiovascular disease (CVD) and CKD were monitored for incident cardiovascular-renal events until 2015.

    RESULTS: In this prospective cohort {mean age 57.0 [standard deviation (SD) 10.0] years; median T2D duration 7.0 [interquartile range (IQR) 3.0-13.0] years; 56.1% men; 72.5% never-smokers; baseline ESC composite score 60.7 (SD 14.5)}, 163 (8.0%) and 25 (1.2%) participants developed incident CKD and CVD, respectively, after 2.3 years of follow-up. The adjusted hazard ratios (aHRs) per 1-unit decrease in the ESC composite score for incident CKD, CVD and all-cause death were 1.02 [95% confidence interval (CI) 1.01-1.04], 1.04 (1.00-1.07) and 1.04 (1.00-1.08), respectively. Compared with participants with an ESC composite score >53, those with a score ≤53 had an aHR of 1.56 (95% CI 1.09-2.23) for CKD and 3.11 (95% CI 1.27-7.62) for CVD, independent of common risk markers. When added to clinical variables (sex and duration of diabetes), the ESC composite score improved discrimination of all outcomes with appropriate reclassification of CKD risk.

    CONCLUSIONS: A low ESC composite score independently predicts incident cardiovascular-renal events and death in T2D, which may improve the screening strategy for early intervention.

    Matched MeSH terms: Electrochemistry
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