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  1. Inhibitory effects of Sargassum polycystum on tyrosinase activity and melanin formation in B16F10 murine melanoma cells
    Chan YY, Kim KH, Cheah SH
    J Ethnopharmacol, 2011 Oct 11;137(3):1183-8.
    PMID: 21810462 DOI: 10.1016/j.jep.2011.07.050
    ETHNOPHARMACOLOGICAL RELEVANCE: Sargassum polycystum, a type of brown seaweed, has been used for the treatment of skin-related disorders in traditional medicine.

    AIM OF THE STUDY: The aim of the present study is to investigate the antimelanogenesis effect of Sargassum polycystum extracts by cell-free mushroom tyrosinase assay followed by cell viability assay, cellular tyrosinase assay and melanin content assay using B16F10 murine melanoma cells.

    MATERIALS AND METHODS: Sargassum polycystum was extracted with 95% ethanol and further fractionated with hexane, ethyl acetate and water. The ethanolic crude extract and its fractionated extracts were tested for their potential to act as antimelanogenesis or skin-whitening agents by their abilities to inhibit tyrosinase activity in the cell-free mushroom tyrosinase assay and cellular tyrosinase derived from melanin-forming B16F10 murine melanoma cells. The tyrosinase inhibitory activity was correlated to the inhibition of melanin production in α-MSH-stimulated and unstimulated B16F10 cells.

    RESULTS: Sargassum polycystum ethanolic extract and its fractions had little or no inhibitory effect on mushroom tyrosinase activity. However, when tested on cellular tyrosinase, the ethanolic extract and its non-polar fraction, hexane fraction (SPHF), showed significant inhibition of cellular tyrosinase activity. In parallel to its cellular tyrosinase inhibitory activity, SPHF was also able to inhibit basal and α-MSH-stimulated melanin production in B16F10 cells.

    CONCLUSIONS: Our findings showed that (i) cellular tyrosinase assay is more reliable than mushroom tyrosinase assay in the initial testing of potential antimelanogenesis agents and, (ii) SPHF inhibited melanogenesis by inhibiting cellular tyrosinase activity. SPHF may be useful for treating hyperpigmentation and as a skin-whitening agent in cosmetics industry.

  2. Electrochemical genosensor for specific detection of the food-borne pathogen, Vibrio cholerae
    Low KF, Chuenrangsikul K, Rijiravanich P, Surareungchai W, Chan YY
    World J Microbiol Biotechnol, 2012 Apr;28(4):1699-706.
    PMID: 22805952 DOI: 10.1007/s11274-011-0978-x
    A disposable horseradish peroxidase (HRP)-based electrochemical genosensor was developed for chronoamperometric detection of single-stranded asymmetric lolB gene PCR amplicon (118 bp in length) of the food-borne pathogen, Vibrio cholerae. A two-step sandwich-type hybridization strategy using two specific probes was employed for specific detection of the target single-stranded DNA (ssDNA). The analytical performances of the detection platform have been evaluated using a synthetic ssDNA (ST3) which was identical to the target single-stranded amplicon and a total of 19 bacterial strains. Under optimal condition, ST3 was calibrated with a dynamic range of 0.4883-15.6250 nM. By coupling asymmetric PCR amplification, the probe-based electrochemical genosensor was highly specific to the target organism (100% specificity) and able to detect as little as 0.85 ng/μl of V. cholerae genomic DNA.
  3. Assays to Study Hypoxia-Inducible Factor Prolyl Hydroxylase Domain 2 (PHD2), a Key Human Oxygen Sensing Protein
    Chan YY, Mbenza NM, Chan MC, Leung IKH
    Methods Mol Biol, 2023;2648:187-206.
    PMID: 37039992 DOI: 10.1007/978-1-0716-3080-8_12
    Molecular oxygen is essential for all multicellular life forms. In humans, the hypoxia-inducible factor (HIF) prolyl hydroxylase domain-containing enzymes (PHDs) serve as important oxygen sensors by regulating the activity of HIF, the master regulator that mediates cellular oxygen homeostasis, in an oxygen-dependent manner. In normoxia, PHDs catalyze the prolyl hydroxylation of HIF, which leads to its degradation and prevents cellular hypoxic response to be triggered. PHDs are current inhibition targets for the potential treatments of a number of diseases. In this chapter, we discuss in vitro and cell-based methods to study the modulation of PHD2, the most important human PHD isoform in normoxia and mild hypoxia. These include the production and purification of recombinant PHD2, the use of mass spectrometry to follow PHD2-catalyzed reactions and the studies of HIF stabilization in cells by immunoblotting.
  4. Pneumocystis pneumonia among HIV patients in Malaysia
    Asmal HS, Mustafa M, Abdullah S, Zaidah AR, Nurhaslindawati AR, Sarimah A, et al.
    Southeast Asian J. Trop. Med. Public Health, 2009 Nov;40(6):1293-7.
    PMID: 20578464
    Pneumocystis pneumonia (PCP) has become the most common opportunistic infection in HIV/AIDS patients with a CD4 count < or = 200. The incidence of PCP has declined as a result of prophylaxis and better highly active antiretroviral therapy (HAART). The objective of this study was to review the demographic data of HIV patients diagnosed clinically as having PCP at the Hospital Raja Perempuan Zainab II (HRPZ II) in Malaysia. This was a prospective study. All HIV patients admitted to HRPZ II with respiratory symptoms were enrolled in this study after giving informed consent. Their demographic data were collected. The total number of HIV patients reviewed in this study was 107. Nearly 60% of patients were clinically diagnosed as having pneumocystis pneumonia based on their signs, symptoms and chest x-ray findings. A CD4 count was available in 83 out of 107 patients. The fifty-three percent of patients(44) had a CD4 < 200 and were clinically diagnosed as having pneumocystis pneumonia. Thirty percent had a CD4 < 200 but did not have clinical pneumocystis pneumonia. Sixteen point nine percent had a CD4 > 200 and had clinical pneumocystis pneumonia, three of whom had received HAART, four patients had received prophylaxis. Overall, 94 patients (87.8%) received prophylaxis for pneumocystis pneumonia. Thirty-three patients (30.8%) received HAART. The occurrence of pneumocystis pneumonia was common before full implementation of HAART. Pneumocystis pneumonia can occur in patients with a CD4 >200.
  5. Detection of Cryptosporidium parvum in HIV-infected patients in Malaysia using a molecular approach
    Zaidah AR, Chan YY, Asma HS, Abdullah S, Nurhaslindawati AR, Salleh M, et al.
    Southeast Asian J. Trop. Med. Public Health, 2008 May;39(3):511-6.
    PMID: 18564692
    This cross-sectional study determined the prevalence of cryptosporidiosis in HIV-infected patients using polymerase chain reaction (PCR). Stool specimens were collected from HIV infected patients who were admitted to Hospital Raja Perempuan Zainab II, Kota Bharu, Malaysia, for various indications from December 2004 to December 2005. A modified acid-fast stain was performed on the direct stool smears, then the stool specimens were further tested using nested PCR targeting the 18S rRNA gene of Cryptosporidium parvum, with a built-in internal control (IC). Out of 59 samples, 11 were positives. Nested PCR identified a total of nine samples (16%) compared to microscopy, which identified only three samples. All PCR negative results showed IC amplicons, suggesting that these samples were true negatives and were not due to inhibition of PCR. This study highlights the importance of molecular diagnosis in determining the true prevalence and epidemiology of C. parvum.
  6. Enzymatic electrochemical detection of epidemic-causing Vibrio cholerae with a disposable oligonucleotide-modified screen-printed bisensor coupled to a dry-reagent-based nucleic acid amplification assay
    Yu CY, Ang GY, Chan KG, Banga Singh KK, Chan YY
    Biosens Bioelectron, 2015 Aug 15;70:282-8.
    PMID: 25835520 DOI: 10.1016/j.bios.2015.03.048
    In this study, we developed a nucleic acid-sensing platform in which a simple, dry-reagent-based nucleic acid amplification assay is combined with a portable multiplex electrochemical genosensor. Preparation of an amplification reaction mix targeting multiple DNA regions of interest is greatly simplified because the lyophilized reagents need only be reconstituted with ultrapure water before the DNA sample is added. The presence of single or multiple target DNAs causes the corresponding single-stranded DNA (ssDNA) amplicons to be generated and tagged with a fluorescein label. The fluorescein-labeled ssDNA amplicons are then analyzed using capture probe-modified screen-printed gold electrode bisensors. Enzymatic amplification of the hybridization event is achieved through the catalytic production of electroactive α-naphthol by anti-fluorescein-conjugated alkaline phosphatase. The applicability of this platform as a diagnostic tool is demonstrated with the detection of toxigenic Vibrio cholerae serogroups O1 and O139, which are associated with cholera epidemics and pandemics. The platform showed excellent diagnostic sensitivity and specificity (100%) when challenged with 168 spiked stool samples. The limit of detection was low (10 colony-forming units/ml) for both toxigenic V. cholerae serogroups. A heat stability assay revealed that the dry-reagent amplification reaction mix was stable at temperatures of 4-56 °C, with an estimated shelf life of seven months. The findings of this study highlight the potential of combining a dry-reagent-based nucleic acid amplification assay with an electrochemical genosensor in a more convenient, sensitive, and sequence-specific detection strategy for multiple target nucleic acids.
  7. Fulltext Food choices among Malaysian adults: Findings from Malaysian Adults Nutrition Survey (MANS) 2003 and MANS 2014
    Mohamad Kasim N, Ahmad MH, Shaharudin AB, Naidu BM, Chan YY, Aris T
    Malays J Nutr, 2018;24(1):63-75.
    MyJurnal
    Introduction: Changes in dietary habits are known to be associated with changes in health outcomes. This study determined food choices among Malaysian adults using secondary data of the Malaysian Adults Nutrition Survey (MANS) in 2003 and MANS in 2014.
    Methods: A total of 6,742 and 3,000 adults aged 18 to 59 years participated in MANS 2003 and MANS 2014, respectively. Both studies used a semi-quantitative food frequency questionnaire (FFQ) to assess habitual food intake.
    Results: Overall, the prevalence of adults consuming rice twice daily were 97.3% and 86.9% in 2003 and 2014, respectively. While the percentage of urban dwellers who consumed rice daily differed significantly between 2003 (96.7%) and 2014 (86.9%), the percentage remained quite similar among rural adults in 2003 (97.8%) and 2014 (96.3%). Other top ten food items consumed daily were sugar (2003, 58.5% vs 2014, 55.9%), marine fish (40.8% vs 29.4%), green leafy vegetables (39.9% vs 43.2%) and sweetened condensed milk (35.2% vs 29.3%). In both surveys, a higher percentage of men consumed rice, sugar and sweetened condensed milk on a daily basis compared to women, a higher proportion of whom daily consumed green leafy vegetables and marine fish. Majority of the adults reported drinking plain water daily. Other beverages taken daily were tea, coffee and chocolate-malt drinks.
    Conclusion: Rice, sugar and sweetened condensed milk were among the top food items consumed daily in 2003 and 2014. Educational efforts to improve dietary intake of Malaysian adults is recommended.
    Study name: Malaysian Adult Nutrition Survey (MANS-2003); Malaysian Adult Nutrition Survey (MANS-2014)
  8. Development of a thermostabilized, one-step, nested, tetraplex PCR assay for simultaneous identification and differentiation of Entamoeba species, Entamoeba histolytica and Entamoeba dispar from stool samples
    Foo PC, Chan YY, See Too WC, Tan ZN, Wong WK, Lalitha P, et al.
    J Med Microbiol, 2012 Sep;61(Pt 9):1219-1225.
    PMID: 22556327 DOI: 10.1099/jmm.0.044552-0
    Entamoeba histolytica is the only Entamoeba species that causes amoebiasis in humans. Approximately 50 million people are infected, with 100, 000 deaths annually in endemic countries. Molecular diagnosis of Entamoeba histolytica is important to differentiate it from the morphologically identical Entamoeba dispar to avoid unnecessary medication. Conventional molecular diagnostic tests require trained personnel, cold-chain transportation and/or are storage-dependent, which make them user-unfriendly. The aim of this study was to develop a thermostabilized, one-step, nested, tetraplex PCR assay for the detection of Entamoeba histolytica, Entamoeba dispar and Entamoeba species in cold-chain-free and ready-to-use form. The PCR test was designed based on the Entamoeba small subunit rRNA (SSU-rRNA) gene, which detects the presence of any Entamoeba species, and simultaneously can be used to differentiate Entamoeba histolytica from Entamoeba dispar. In addition, a pair of primers was designed to serve as an internal amplification control to help identify inhibitors in the samples. All PCR reagents together with the designed primers were thermostabilized by lyophilization and were stable at 24 °C for at least 6 months. The limit of detection of the tetraplex PCR was found to be 39 pg DNA or 1000 cells for Entamoeba histolytica and 78 pg DNA or 1000 cells for Entamoeba dispar, and the specificity was 100 %. In conclusion, this cold-chain-free, thermostabilized, one-step, nested, multiplex PCR assay was found to be efficacious in differentiating Entamoeba histolytica from other non-pathogenic Entamoeba species.
  9. Vision and Hearing Impairments Affecting Activities of Daily Living among Malaysian Older Adults by Gender
    Chan YM, Sahril N, Chan YY, Ab Wahab NA, Shamsuddin N, Ismail MZH
    Int J Environ Res Public Health, 2021 Jun 10;18(12).
    PMID: 34200564 DOI: 10.3390/ijerph18126271
    Vision and hearing impairments are common among older adults and can cause undesirable health effects. There are limited studies from low- and middle-income countries exploring gender differences between vision and hearing impairment with Activities of Daily Living (ADL) disability. Therefore, this study aimed to investigate gender differences between vision and hearing impairments with ADL disability among older adults in Malaysia. Cross-sectional data from 3977 respondents aged 60 and above from the Malaysian National Health and Morbidity Survey 2018 were used. We used logistic regression analysis to measure associations between vision and hearing impairments with ADL disability, adjusted for covariates. The prevalence of ADL disability was higher among females than males (p < 0.001). The adjusted associations between vision impairment and ADL disability were significant among males (aOR 3.79; 95%CI 2.26, 6.38) and females (aOR 2.66; 95%CI 1.36, 5.21). Similarly, significant adjusted associations were found between hearing impairment and ADL disability among males (aOR 5.76; 95%CI 3.52, 9.40) and females (aOR 3.30; 95%CI 1.17, 9.33). Vision and hearing impairments were significantly associated with ADL disability, with no gender differences identified. Early detection and effective management of vision and hearing impairments are important to prevent ADL disability and improve older adults' level of independence.
  10. Development of a thermostabilised triplex LAMP assay with dry-reagent four target lateral flow dipstick for detection of Entamoeba histolytica and non-pathogenic Entamoeba spp
    Foo PC, Chan YY, Mohamed M, Wong WK, Nurul Najian AB, Lim BH
    Anal Chim Acta, 2017 May 08;966:71-80.
    PMID: 28372729 DOI: 10.1016/j.aca.2017.02.019
    This study highlighted the development of a four target nitrocellulose-based nucleic acid lateral flow immunoassay biosensor in a dry-reagent strip format for interpretation of double-labelled double-stranded amplicons from thermostabilised triplex loop-mediated isothermal amplification assay. The DNA biosensor contained two test lines which captured biotin and texas red labelled amplicons; a LAMP internal amplification control line that captured digoxigenin labelled amplicon; and a chromatography control line that validated the functionality of the conjugated gold nanoparticles and membrane. The red lines on detection pad were generated when the gold nanoparticles conjugated antibody bound to the fluorescein labelled amplicons, and the capture agents bound to their specific hapten on the other 5' end of the double-stranded amplicon. The applicability of this DNA biosensor was demonstrated using amoebiasis-causing Entamoeba histolytica simultaneously with the non-pathogenic but morphologically identical Entamoeba dispar and Entamoeba moshkovskii. The biosensor detection limit was 10 E. histolytica trophozoites, and revealed 100% specificity when it was evaluated against 3 medically important Entamoeba species and 75 other pathogenic microorganisms. Heat stability test showed that the biosensor was stable for at least 181 days at ambient temperature. This ready-to-use and cold-chain-free biosensor facilitated the post-LAMP analysis based on visualisation of lines on strip instead of observation of amplicon patterns in agarose gel.
  11. Fulltext Iodine deficiency disorders among pregnant women in Sarawak, Malaysia
    Lim KK, Chan YY, Mahmud NA, Ismail H, Tan BC, Chua BK, et al.
    Int J Public Health Res, 2018;8(2):980-986.
    MyJurnal
    Introduction Iodine deficiency disorders (IDD) during pregnancy may impair the neurological development of the fetus. The aim of this study is to determine the iodine status among pregnant women (PW) in Sarawak after introduction of mandatory universal salt iodisation (USI) for seven years.
    Methods A total of 508 first trimester PW attending government Maternal and Child Health Care clinics in all 11 divisions in Sarawak between 1st April and 15th June 2015 were recruited. Urine samples were obtained and analysed for urinary iodine concentration (UIC) using the modified Sandell-Kolthoff reaction method. For pregnant women, an adequate iodine intake was defined as a median UIC between 150-249 µg/L according to the WHO/UNICEF/ICCIDD’s criterion. For further analyses, the 11 divisions were then combined into 3 regions, namely Northern (Miri, Bintulu, Limbang), Central (Kapit, Mukah, Sibu, Sarikei, Betong) and Southern (Kota Samarahan, Kuching, Sri Aman).
    Results TThe median UIC of the PW in Sarawak was 105.6 µg/L, indicating iodine deficiency. A total of 330 (65.0%) PW had UIC<150 µg/L. In terms of urinary iodine levels by region, the median UIC in Northern, Central and Southern regions were 136.3 µg/L, 85.5 µg/L and 97.4 µg/L respectively. The differences in median UIC between regions were significant. In addition, the Northern region (p = 0.001), Malay/Melanau ethnicity (p = 0.015) and parous parity (p = 0.014) were significantly associated with higher median UIC. No significant association was found for locality, age nor gravida.
    Conclusions This study indicates inadequate iodine status among PW in Sarawak despite seven years of mandatory USI. In fact, the majority of PW appear not to be protected against IDD and its consequences. In future, a comprehensive study should be carried out to determine the levels of iodine in salt at the retail outlets, villages and households in Sarawak.
    Keywords Iodine deficiency disorders - Pregnant women - Mandatory USI - Sarawak
  12. Complete immunization coverage and its determinants among children in Malaysia: findings from the National Health and Morbidity Survey (NHMS) 2016
    Lim KK, Chan YY, Noor Ani A, Rohani J, Siti Norfadhilah ZA, Santhi MR
    Public Health, 2017 Dec;153:52-57.
    PMID: 28915402 DOI: 10.1016/j.puhe.2017.08.001
    OBJECTIVES: The success of the Expanded Program on Immunization among children will greatly reduce the burden of illness and disability from vaccine preventable diseases. The aim of the study was to evaluate the complete immunization coverage and its determinants among children aged 12-23 months in Malaysia.
    STUDY DESIGN: Cross-sectional study.
    METHODS: Data on immunization were extracted from the 2016 National Health and Morbidity Survey. Complete immunization coverage was classified as received all recommended primary vaccine doses by the age of 12 months and verified by vaccination cards, and incompletely immunized if they received partially recommended vaccine dose or not received any recommended vaccine dose or had no vaccination card. The multiple logistic regression analyses were conducted to determine the sociodemographic factors associated with complete immunization coverage.
    RESULTS: The overall complete immunization coverage among children (verified by cards) was 86.4% (n = 8920, 95% confidence interval: 85.4-87.4). Multivariable logistic regression analyses model revealed that factors significantly associated with complete immunization coverage were ethnicity, occupation of the mother, head of household's education level, and head of household's occupation. While sex, citizenship, household income, mother's age, and marital status were not significantly associated with complete immunization coverage.
    CONCLUSIONS: According to the World Health Organization criteria, the present study demonstrated that the immunization coverage of 86.4% is still unsatisfactory. Thus, the current intervention program should be enhanced in order to achieve the 95% coverage for all antigens in the national vaccination program.
    Study name: National Health and Morbidity Survey (NHMS-2016)
  13. Distribution of sasX, qacA/B and mupA genes and determination of genetic relatedness of methicillin-resistant Staphylococcus aureus among clinical isolates and nasal swab samples from the same patients in a hospital in Malaysia
    Nurhafiza NNBA, Siti Asma H, Azian H, Foo PC, Yasmin KMI, Chan YY
    Singapore Med J, 2020 12 02.
    PMID: 33264563 DOI: 10.11622/smedj.2020166
    INTRODUCTION: This study determined the distribution of sasX, qacA/B and mupA genes from methicillin-resistant Staphylococcus aureus (MRSA) isolated from clinical samples and nasal swab samples of the same patients and analysed their genetic relatedness.

    METHODS: Polymerase chain reaction (PCR) was used to detect the presence of sasX, qacA/B and mupA genes from 47 paired MRSA isolates. A paired isolate was defined as one nasal swab (colonising) isolate and clinical isolate that caused infection in the same patient. 22 selected paired isolates were subjected to multilocus sequence typing (MLST). The genetic relatedness among the isolates and association between the putative genes with epidemic sequence types (STs) were investigated.

    RESULTS: 7 (14.9%, n = 14) paired isolates were positive for the sasX gene. qacA/B genes were positive in 7.4% (n = 7) of the isolates, from three paired isolates and one clinical isolate whose paired colonising isolate was negative. The paired sample of three patients were positive for both genes. The mupA gene was not detected in all the isolates. MLST revealed two epidemic STs, ST22 and ST239, and a novel ST4649. sasX and qacA/B genes were found in ST239 in 29.5% (n = 13) and 13.6% (n = 6) of cases, respectively. Gene co-existence occurred in 13.6% (n = 6) of MRSA ST239 and 2.3% (n = 1) of MRSA ST4649.

    CONCLUSION: sasX and qacA/B genes were present in the MRSA isolates, while the mupA gene was undetected. ST22 and ST239 were the major MRSA clones. The circulating MRSA genotypes conferred different virulence and resistance determinants in our healthcare settings.

  14. Enhanced photocatalytic degradation of methyl orange by coconut shell-derived biochar composites under visible LED light irradiation
    Pang YL, Law ZX, Lim S, Chan YY, Shuit SH, Chong WC, et al.
    Environ Sci Pollut Res Int, 2021 Jun;28(21):27457-27473.
    PMID: 33507503 DOI: 10.1007/s11356-020-12251-4
    The conversion of carbon-rich biomass into valuable material is an environmental-friendly approach for its reutilization. In this study, coconut shell-derived biochar, graphitic carbon nitride (g-C3N4), g-C3N4/biochar, titanium dioxide (TiO2)/biochar, zinc oxide (ZnO)/biochar, and ferric oxide (Fe2O3)/biochar were synthesized and characterized by using scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDX), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), surface area analysis, UV-Vis diffuse reflectance spectroscopy (DRS), and zeta potential analysis. The g-C3N4 or metal oxide particles were found to be well-distributed on the coconut shell-derived biochar with the improvement in thermal stability and enlargement of specific surface area. A great reduction in band gap energy was observed in the composite materials after incorporating with the biochar. Among different biochar composites, g-C3N4/biochar was found to have the highest photocatalytic activity. The interactive effect of parameters such as catalyst dosage, peroxymonosulfate (PMS) oxidant dosage, and solution pH on the photocatalytic degradation of methyl orange was investigated using the response surface methodology (RSM). The highest photocatalytic degradation efficiency (96.63%) was achieved at catalyst dosage of 0.75 g/L, oxidant dosage of 0.6 mM, and solution pH 3 after 30 min.
  15. Biosynthesized Fe- and Ag-doped ZnO nanoparticles using aqueous extract of Clitoria ternatea Linn for enhancement of sonocatalytic degradation of Congo red
    Chan YY, Pang YL, Lim S, Lai CW, Abdullah AZ, Chong WC
    Environ Sci Pollut Res Int, 2020 Oct;27(28):34675-34691.
    PMID: 31628641 DOI: 10.1007/s11356-019-06583-z
    Nowadays, the current synthesis techniques used in industrial production of nanoparticles have been generally regarded as nonenvironmentally friendly. Consequently, the biosynthesis approach has been proposed as an alternative to reduce the usage of hazardous chemical compounds and harsh reaction conditions in the production of nanoparticles. In this work, pure, iron (Fe)-doped and silver (Ag)-doped zinc oxide (ZnO) nanoparticles were successfully synthesized through the green route using Clitoria ternatea Linn. The optical, chemical, and physical properties of the biosynthesized ZnO nanoparticles were then analyzed by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDX), UV-Vis diffuse reflectance spectroscopy (DRS), zeta potential measurement, Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and surface analysis. The biosynthesized ZnO nanoparticles were crystallized with a hexagonal wurtzite structure and possessed smaller particle sizes than those of commercially or chemically produced samples. The existence of biomolecules to act as reducing and stabilizing agents from C. ternatea Linn aqueous extract was confirmed using FTIR analysis. The biosynthesized ZnO nanoparticles mainly comprised of negatively charged groups and responsible for moderately stable dispersion of the nanoparticles. All these properties were favorable for the sonocatalytic degradation of Congo red. Sonocatalytic activity of ZnO nanoparticles was studied through the degradation of 10 mg/L Congo red using ultrasonic irradiation at 45 kHz and 80 W. The results showed that the sonocatalytic degradation efficiency of Congo red in the presence of biosynthesized ZnO nanoparticles prepared at 50 °C for 1 h could achieve 88.76% after 1 h. The sonocatalytic degradation efficiency of Congo red in the presence of Ag-doped ZnO was accelerated to 94.42% after 10 min which might be related to the smallest band gap energy (3.02 eV) and the highest specific surface area (10.31 m2/g) as well as pore volume (0.0781 cm3/g). Lastly, the biosynthesized ZnO nanoparticles especially Ag-doped ZnO offered significant antibacterial potential against Escherichia coli which indicated its ability to inhibit the normal growth and replication of bacterial cells. These results affirmed that the biosynthesized ZnO nanoparticles could be used as an alternative to the current chemical compounds and showed a superior sonocatalytic activity toward degradation of Congo red.
  16. On the resistance of new lightweight block ciphers against differential cryptanalysis
    Chan YY, Khor CY, Khoo BT, Teh JS, Teng WJ, Jamil N
    Heliyon, 2023 Apr;9(4):e15257.
    PMID: 37095966 DOI: 10.1016/j.heliyon.2023.e15257
    Many recently proposed lightweight block ciphers lack security evaluation against generic cryptanalytic attacks such as differential cryptanalysis. In this paper, we contribute towards security evaluation efforts by investigating four lightweight Feistel-based block ciphers including SLIM, LBC-IoT, SCENERY, and LCB. SLIM claims resistance to differential cryptanalysis since, using a heuristic technique, its designers could only find a 7-round differential trail. Despite having no analysis of security against attacks such as differential cryptanalysis, the designers of LBC-IoT and LCB claimed that their ciphers are secure. Meanwhile, the designers of SCENERY claim that the best 11-round differential trail for the cipher has a probability of 2 - 66 . To substantiate these claims, we propose attacks on all four ciphers based on differential cryptanalysis. We presented practical key recovery attacks on SLIM which can retrieve the final round key for up to 14 rounds with a time complexity of 232. LBC-IoT was found to be weaker against differential cryptanalysis despite sharing many similarities with SLIM, whereby a key recovery attack of up to 19 rounds is possible with time complexity 231. For SCENERY, we found a differential trail of up to 12 rounds with probability 2 - 60 , which was used as the distinguisher for a 13-round key recovery attack. We also discovered that LCB's design lacks nonlinearity, allowing us to easily derive deterministic differential trails regardless of the number of rounds. This flaw allowed us to perform a trivial distinguishing attack using a single known ciphertext. By using a different S-box to address this flaw, LCB is now more resilient to differential cryptanalysis than SLIM and LBC-IoT when using the same number of rounds. Our paper presents new independent cryptanalysis results for these ciphers.
  17. Plant-mediated synthesis of silver-doped ZnO nanoparticles with high sonocatalytic activity: Sonocatalytic behavior, kinetic and thermodynamic study
    Chan YY, Pang YL, Lim S, Chong WC, Shuit SH
    Environ Sci Pollut Res Int, 2022 Nov 22.
    PMID: 36417069 DOI: 10.1007/s11356-022-24145-8
    Together with the rapid growth of technology, the discharge of wastewater from industry into environment had become a hot topic among society nowadays. More attention had been given to the development of water treatment techniques. In this study, sonocatalysis was proposed to degrade the organic pollutants using silver-doped zinc oxide (Ag-ZnO) nanoparticles which were synthesized via green synthesis process using Clitoria ternatea Linn (Asian Pigeonwings flower). The characterization results revealed that the incorporation of Ag into the ZnO lattice decreased the crystallite size and increased the specific surface area of ZnO nanoparticles. It is noteworthy that about 98% of sonocatalytic degradation efficiency of malachite green (MG) was successfully achieved within 30 min in the presence of 5 wt.% Ag-ZnO with 1.0 g/L of catalyst loading under 500 mg/L of initial dye concentration, 80 W of ultrasonic power, 45 kHz of ultrasound frequency, and 2.0 mM of oxidant concentration. The kinetic study showed that the sonocatalytic degradation of organic dye was fitted well into second-order kinetic model with high R2 value (0.9531). In the thermodynamic study, negative value of standard Gibbs free energy and low value of activation energy (+ 24.43 kJ/mol) were obtained in the sonocatalytic degradation of MG using the green-synthesized Ag-ZnO sample. HIGHLIGHTS: • Facile synthesis of silver-doped zinc oxide nanoparticles using plant extract which act as reducing and stabilizing agents • Optical, physical, and chemical characterization of green-synthesized nanomaterials were performed • Evaluation of sonocatalytic degradation of organic dye using green-synthesized nanomaterials • Sonocatalytic behavior, kinetic and thermodynamic studies of sonocatalytic reaction.
  18. Fulltext The Effect of Hydrocotyle sibthorpioides Lam. Extracts on In Vitro Dengue Replication
    Husin F, Chan YY, Gan SH, Sulaiman SA, Shueb RH
    Evid Based Complement Alternat Med, 2015;2015:596109.
    PMID: 25767554 DOI: 10.1155/2015/596109
    Objective. To investigate the potential effect of Hydrocotyle sibthorpioides Lam. (H. sibthorpioides) extracts against in vitro dengue viral replication. Methods. The cytotoxicity of H. sibthorpioides was evaluated using a cell viability assay. Cells were pre- and posttreated with water and methanol extracts of H. sibthorpioides, and the viral inhibitory effect was investigated by observing the morphological changes, which were further confirmed by plaque assay. Results. The methanolic extract cytotoxicity was higher in Vero and C6/36 cells than the cytotoxicity of the water extract. Preincubation of the cells with H. sibthorpioides extract showed nonexistent to mild prophylactic effects. The posttreatment of Vero cells with H. sibthorpioides methanolic extract presented higher antidengue activities when compared with the water extract. Surprisingly, posttreatment of C6/36 cells resulted in an enhancement of viral replication. Conclusion. H. sibthorpioides had variable effects on dengue viral replication, depending on the treatment, cell lines, and solvent types. This study provides important novel insights on the phytomedicinal properties of H. sibthorpioides extracts on dengue virus.
  19. Fulltext First isolation of Burkholderia tropica from a neonatal patient successfully treated with imipenem
    Deris ZZ, Van Rostenberghe H, Habsah H, Noraida R, Tan GC, Chan YY, et al.
    Int J Infect Dis, 2010 Jan;14(1):e73-4.
    PMID: 19482535 DOI: 10.1016/j.ijid.2009.03.005
    We report the first case of a human Burkholderia tropica infection. The patient was a premature neonate who had necrotizing enterocolitis with bowel perforation requiring surgical intervention. The stoma care and difficulties in feeding were a chronic problem. At the age of almost 4 months he developed septicemia due to B. tropica. Three consecutive blood cultures grew this organism. The organism was cleared from the blood after a course of imipenem and resolution of post-operative ileus. Our case suggests that environmental and plant pathogens can cause human infection especially in those in an immunocompromised condition.
  20. Analysis of lolB gene sequence and its use in the development of a PCR assay for the detection of Vibrio cholerae
    Lalitha P, Siti Suraiya MN, Lim KL, Lee SY, Nur Haslindawaty AR, Chan YY, et al.
    J Microbiol Methods, 2008 Sep;75(1):142-4.
    PMID: 18579241 DOI: 10.1016/j.mimet.2008.05.001
    A PCR assay has been developed based on a lolB (hemM) gene, which was found to be highly conserved among the Vibrio cholerae species but non-conserved among the other enteric bacteria. The lolB PCR detected all O1, O139 and non-O1/non-O139 serogroup and biotypes of V. cholerae. The analytical specificity of this assay was 100% while the analytical sensitivity was 10 pg/microL and 10(3) CFU/mL at DNA and bacterial level respectively. The diagnostic sensitivity and specificity was 98.5% and 100% respectively.
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