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Fulltext Optical DNA Biosensor Based on Square-Planar Ethyl Piperidine Substituted Nickel(II) Salphen Complex for Dengue Virus Detection

Ariffin EY, Tan LL, Abd Karim NH, Yook Heng L

Sensors (Basel), 2018 Apr 12;18(4).
PMID: 29649118 DOI: 10.3390/s18041173

A sensitive and selective optical DNA biosensor was developed for dengue virus detection based on novel square-planar piperidine side chain-functionalized N,N'-bis-4-(hydroxysalicylidene)-phenylenediamine-nickel(II), which was able to intercalate via nucleobase stacking within DNA and be functionalized as an optical DNA hybridization marker. 3-Aminopropyltriethoxysilane (APTS)-modified porous silica nanospheres (PSiNs), was synthesized with a facile mini-emulsion method to act as a high capacity DNA carrier matrix. The Schiff base salphen complexes-labelled probe to target nucleic acid on the PSiNs renders a colour change of the DNA biosensor to a yellow background colour, which could be quantified via a reflectance transduction method. The reflectometric DNA biosensor demonstrated a wide linear response range to target DNA over the concentration range of 1.0 × 10-16-1.0 × 10-10 M (R² = 0.9879) with an ultralow limit of detection (LOD) at 0.2 aM. The optical DNA biosensor response was stable and maintainable at 92.8% of its initial response for up to seven days of storage duration with a response time of 90 min. The reflectance DNA biosensor obtained promising recovery values of close to 100% for the detection of spiked synthetic dengue virus serotypes 2 (DENV-2) DNA concentration in non-invasive human samples, indicating the high accuracy of the proposed DNA analytical method for early diagnosis of all potential infectious diseases or pathological genotypes.
Heterojunction engineering of graphitic carbon nitride (g-C3N4) via Pt loading with improved daylight-induced photocatalytic reduction of carbon dioxide to methane

Ong WJ, Tan LL, Chai SP, Yong ST

Dalton Trans, 2015 Jan 21;44(3):1249-57.
PMID: 25415620 DOI: 10.1039/c4dt02940b

In this paper, noble-metal Pt nanoparticles of around 2.5 nm were deposited on graphitic carbon nitride (g-C3N4) synthesized by a chemical reduction process in ethylene glycol. Compared with pure g-C3N4, the resulting Pt-loaded g-C3N4 (Pt/CN) exhibited a considerable improvement in the photoreduction of CO2 to CH4 in the presence of water vapor at ambient temperature and atmospheric pressure under visible light irradiation. 2 wt% Pt-loaded g-C3N4 (2Pt/CN) nanocomposites produced the highest CH4 yield of 13.02 μmol gcatalyst(-1) after 10 h of light irradiation, which was a 5.1-fold enhancement in comparison with pure g-C3N4 (2.55 μmol gcatalyst(-1)). The remarkable photocatalytic activity of Pt/CN nanostructures in the CH4 production was ascribed to the enhanced visible light absorption and efficient interfacial transfer of photogenerated electrons from g-C3N4 to Pt due to the lower Fermi level of Pt in the Pt/CN hybrid heterojunctions as evidenced by the UV-Vis and photoluminescence studies. The enriched electron density on Pt favored the reduction of CO2 to CH4via a multi-electron transfer process. This resulted in the inhibition of electron-hole pair recombination for effective spatial charge separation, thus enhancing the photocatalytic reactions. Based on the experimental results obtained, a plausible mechanism for improved photocatalytic performance associated with Pt/CN was proposed.
Graphene oxide as a structure-directing agent for the two-dimensional interface engineering of sandwich-like graphene-g-C3N4 hybrid nanostructures with enhanced visible-light photoreduction of CO2 to methane

Ong WJ, Tan LL, Chai SP, Yong ST

Chem Commun (Camb), 2015 Jan 18;51(5):858-61.
PMID: 25429376 DOI: 10.1039/c4cc08996k

A facile one-pot impregnation-thermal reduction strategy was employed to fabricate sandwich-like graphene-g-C3N4 (GCN) nanocomposites using urea and graphene oxide as precursors. The GCN sample exhibited a slight red shift of the absorption band edge attributed to the formation of a C-O-C bond as a covalent cross linker between graphene and g-C3N4. The GCN sample demonstrated high visible-light photoactivity towards CO2 reduction under ambient conditions, exhibiting a 2.3-fold enhancement over pure g-C3N4. This was ascribed to the inhibition of electron-hole pair recombination by graphene, which increased the charge transfer.
Rapid detection of porcine DNA in processed food samples using a streamlined DNA extraction method combined with the SYBR Green real-time PCR assay

Tan LL, Ahmed SA, Ng SK, Citartan M, Raabe CA, Rozhdestvensky TS, et al.

Food Chem, 2020 Mar 30;309:125654.
PMID: 31678669 DOI: 10.1016/j.foodchem.2019.125654

A specialized DNA extraction method and a SYBR Green quantitative polymerase chain reaction (SyG-qPCR) assay were combined to generate a ready-to-use kit for rapid detection of porcine admixtures in processed meat products. Our qPCR assay utilized repetitive LINE-1 elements specific to the genome of Sus scrofa domesticus (pig) as a target and incorporated internal controls. We improved the genomic DNA extraction method, and reduced extraction times to the minimum. The method was validated for specificity, sensitivity (0.001% w/w) and robustness, and values were compared with those of a commercially available kit. We also tested our method using 121 processed food products and consistently detected amplification only in samples containing pork. Due to its efficiency and cost-effectiveness, our method represents a valuable new method for detecting food adulteration with pork that is superior to existing quality control approaches.
Psychological well-being, quality of life and patient satisfaction among adults with chronic spontaneous urticaria in a multi-ethnic Asian population

Yong SS, Robinson S, Kwan Z, Khoo EM, Han WH, Tan LL, et al.

Psychol Health Med, 2023 Feb;28(2):324-335.
PMID: 35057684 DOI: 10.1080/13548506.2022.2029914

Patients with chronic spontaneous urticaria (CSU) have an increased risk of psychological distress. This cross-sectional study aimed to determine factors associated with psychological burden, quality of life (QoL) and patient satisfaction among adults living with CSU. Participants completed the self-administered Urticaria Activity Score-7 (UAS-7), Depression Anxiety Stress Scale (DASS 21), Dermatology Life Quality Index (DLQI), and Short Assessment Patient Satisfaction (SAPS) questionnaires. Multivariate logistic regression was used to determine the independent predictors of depression, anxiety, stress, QoL and patient satisfaction. From a total of 115 subjects with a median age of 42.6 years, range (19-89 years). 60.9% subjects reported moderate-to-severe CSU, 26.1% reported symptoms of depression, 54.8% had anxiety, 40.0% had stress, and 36.5% reported severely impaired QoL. The median UAS-7 score was 20 (IQR 11-27) while the median score of DLQI was 8 (IQR 4-13). The median score of SAPS was 20 (IQR 17-21). Low-income and severe disease were the significant predictors for depression while severe disease was predictive of impaired QoL and depression. Subjects who were diagnosed at older ages and those who required medical leave due to flares of CSU were less likely to be satisfied with their care. (192 words).
Fulltext Self-reported generalised pruritus among community-dwelling older adults in Malaysia

Yong SS, Kwan Z, Ch'ng CC, Yong ASW, Tan LL, Han WH, et al.

BMC Geriatr, 2020 06 24;20(1):223.
PMID: 32580764 DOI: 10.1186/s12877-020-01610-y

BACKGROUND: The ageing skin is more susceptible to pruritic dermatoses, which are associated with adverse psychosocial effects and reduced quality of life among older adults. This cross-sectional study aimed to identify the burden of pruritus and factors associated with its presence and severity among older adults recruited to the Malaysian Elders Longitudinal Research study.
METHODS: Seven hundred seventy individuals aged 55 years (lower age limit) and above were interviewed as to whether they experienced pruritus during the preceding week and the locations involved if present. The association between generalised pruritus, sleep quality, and major systemic risk factors were explored.
RESULTS: 5.97% of respondents reported generalised pruritus. Generalised pruritus was associated with poorer sleep quality, with Pittsburgh Sleep Quality Index score above 6. Mean haemoglobin level was lower in subjects with generalised pruritus (13.14 g/dL) but there was no significant difference in the frequency of generalised pruritus and severe generalized pruritus between subjects with clinically defined anaemia. Also, there were no significant associations between other major systemic risk factors and generalised pruritus in this population-based study. There was no association between generalised pruritus with depression, anxiety or stress.
CONCLUSION: The negative effect of pruritus on sleep quality suggests a possible deleterious effect of pruritus on health and quality of life. Further prospective research on the longer-term effects of pruritus on health status is now warranted. (222 words).
Fulltext Highly Sensitive Fluorescence Sensor for Carrageenan from a Composite Methylcellulose/Polyacrylate Membrane

Hassan RA, Heng LY, Tan LL

Sensors (Basel), 2020 Sep 04;20(18).
PMID: 32899886 DOI: 10.3390/s20185043

Carrageenans are linear sulphated polysaccharides that are commonly added into confectionery products but may exert a detrimental effect to human health. A new and simpler way of carrageenan determination based on an optical sensor utilizing a methylcellulose/poly(n-butyl acrylate) (Mc/PnBA) composite membrane with immobilized methylene blue (MB) was developed. The hydrophilic Mc polymer membrane was successfully modified with a more hydrophobic acrylic polymer. This was to produce an insoluble membrane at room temperature where MB reagent could be immobilized to build an optical sensor for carrageenan analysis. The fluorescence intensity of MB in the composite membrane was found to be proportional to the carrageenan concentrations in a linear manner (1.0-20.0 mg L-1, R2 = 0.992) and with a detection limit at 0.4 mg L-1. Recovery of spiked carrageenan into commercial fruit juice products showed percentage recoveries between 90% and 102%. The optical sensor has the advantages of improved sensitivity and better selectivity to carrageenan when compared to other types of hydrocolloids. Its sensitivity was comparable to most sophisticated techniques for carageenan analysis but better than other types of optical sensors. Thus, this sensor provides a simple, rapid, and sensitive means for carageenan analysis.
Fulltext Syringocystadenoma papilliferum arising in a naevus sebaceous

Faheem NAA, Kwan Z, Yong ASW, Ch'ng CC, Tan KK, Naicker M, et al.

Malays J Pathol, 2019 Apr;41(1):47-49.
PMID: 31025637

Naevus sebaceus is a cutaneous hamartoma with the potential of developing into benign or malignant neoplasms. Syringocystadenoma papilliferum (SCAP) have been reported to originate from naevus sebaceus. SCAP is a rare, benign adnexal skin tumour of apocrine or eccrine type of differentiation which typically presents as a nodule or a plaque on the scalp or face. We report a case of syringocystadenoma papilliferum arising in an undiagnosed pre-existing naevus sebaceus in a 56-year-old female.
Fulltext Novel DNA Biosensor for Direct Determination of Carrageenan

Hassan RA, Heng LY, Tan LL

Sci Rep, 2019 04 23;9(1):6379.
PMID: 31015498 DOI: 10.1038/s41598-019-42757-y

A novel disposable electrochemical biosensor based on immobilized calf thymus double-stranded DNA (dsDNA) on the carbon-based screen-printed electrode (SPE) is developed for rapid biorecognition of carrageenan by using methylene blue (MB) redox indicator. The biosensor protocol for the detection of carrageenan is based on the concept of competitive binding of positively charged MB to the negatively charged dsDNA and carrageenan. The decrement in the MB cathodic peak current (ipc) signal as a result of the released MB from the immobilized dsDNA, and attracted to the carrageenan can be monitored via differential pulse voltammetry (DPV). The biosensor showed high sensitivity and selectivity to carrageenan at low concentration without interference from other polyanions such as alginate, gum arabic and starch. Calibration of the biosensor with carrageenan exhibited an excellent linear dependence from 1-10 mg L-1 (R2 = 0.98) with a detection limit of 0.08 mg L-1. The DNA-based carrageenan biosensor showed satisfactory reproducibility with 5.6-6.9% (n = 3) relative standard deviations (RSD), and possessing several advantages such as simplicity, fast and direct application to real sample analysis without any prior extensive sample treatments, particularly for seaweeds and food analyses.
Optical enzymatic formaldehyde biosensor based on alcohol oxidase and pH-sensitive methacrylic-acrylic optode membrane

Nurlely, Ahmad M, Heng LY, Tan LL

Spectrochim Acta A Mol Biomol Spectrosc, 2022 Feb 15;267(Pt 2):120535.
PMID: 34749257 DOI: 10.1016/j.saa.2021.120535

Optical biosensor for the detection of formaldehyde has been developed based on the transparent enzymatic stacked membranes system on the glass substrate, and employing optical absorption transducer with H+ ion-selective Nile Blue chromoionophore (NBCM) dye-doped methacrylic acrylic (MB28) copolymer membrane as the optode membrane. Alcohol oxidase (AOx) enzymes were entrapped within the biocompatible sol-gel matrix and deposited on top of the pH optode membrane. As the uppermost catalytic membrane catalyzes the oxidative conversion of formaldehyde to formic acid and hydrogen peroxide, the immobilized NBCM undergoes protonation reaction and forms HNBCM+, the dark blue ion-chromoionophore complex via H+ ion transfer reaction within the soft and flexible MB28 polymeric membrane. This rendered the enzymatic optode membrane absorbed a high yellow light intensity from the light source and exhibited maximum absorption peaks at 610 and 660 nm. Optical evaluation of formaldehyde by means on UV-vis absorption transduction of the enzymatic stacked membranes demonstrated rapid response time of 10 min with high sensitivity, good linearity and high reproducibility across a wide formaldehyde concentration range of 1 × 10-3-1 × 103 mM (R2 = 0.9913), and limit of detection (LOD) at 1 × 10-3 mM, which could be useful for formaldehyde assay in industrial, agricultural, environmental, food and beverages as well as medical samples. The formaldehyde concentration in snapper fish, pomfret fish and threadfin fish samples determined by the proposed optical enzymatic biosensor were very much close to the formaldehyde concentration values determined by the UV-vis spectrophotometric NASH standard method based on the statistical t-test. This suggests that the optical biosensor can be used as a reliable method for quantitative determination of formaldehyde levels in food samples.
Fulltext Rapid determination of kappa-carrageenan using a biosensor from immobilized Pseudomonas carrageenovora cells

Hassan RA, Heng LY, Ahmad A, Tan LL

PLoS One, 2019;14(4):e0214580.
PMID: 30990847 DOI: 10.1371/journal.pone.0214580

A potentiometric whole cell biosensor based on immobilized marine bacterium, Pseudomonas carrageenovora producing κ-carrageenase and glycosulfatase enzymes for specific and direct determination of κ-carrageenan, is described. The bacterial cells were immobilized on the self-plasticized hydrogen ion (H+)-selective acrylic membrane electrode surface to form a catalytic layer. Hydrogen ionophore I was incorporated in the poly(n-butyl acrylate) [poly(nBA)] as a pH ionophore. Catalytic decomposition of κ-carrageenan by the bienzymatic cascade reaction produced neoagarobiose, an inorganic sulfate ion and a proton. The latter was detectable by H+ ion transducer for indirect potentiometric quantification of κ-carrageenan concentration. The use of a disposable screen-printed Ag/AgCl electrode (SPE) provided no cleaning requirement and enabled κ-carrageenan detection to be carried out conveniently without cross contamination in a complex food sample. The SPE-based microbial biosensor response was found to be reproducible with high reproducibility and relative standard deviation (RSD) at 2.6% (n = 3). The whole cell biosensor demonstrated a broad dynamic linear response range to κ-carrageenan from 0.2-100 ppm in 20 mM phosphate buffer saline (PBS) at pH 7.5 with a detection limit at 0.05 ppm and a Nernstian sensitivity of 58.78±0.87 mV/decade (R2 = 0.995). The biosensor showed excellent selectivity towards κ-carrageenan compared to other types of carrageenans tested e.g. ι-carrageenan and λ-carrageenan. No pretreatment to the food sample was necessary when the developed whole cell biosensor was employed for direct assay of κ-carrageenan in dairy product.
Electrochemical genosensor based on RNA-responsive human telomeric G-quadruplex DNA: A proof-of-concept with SARS-CoV-2 RNA

Ibrahim N, Gan KB, Mohd Yusof NY, Goh CT, Krupa B N, Tan LL

Talanta, 2024 Mar 18;274:125916.
PMID: 38547835 DOI: 10.1016/j.talanta.2024.125916

In this report, a facile and label-free electrochemical RNA biosensor is developed by exploiting methylene blue (MB) as an electroactive positive ligand of G-quadruplex. The electrochemical response mechanism of the nucleic acid assay was based on the change in differential pulse voltammetry (DPV) signal of adsorbed MB on the immobilized human telomeric G-quadruplex DNA with a loop that is complementary to the target RNA. Hybridization between synthetic positive control RNA and G-quadruplex DNA probe on the transducer platform rendered a conformational change of G-quadruplex to double-stranded DNA (dsDNA), and increased the redox current of cationic MB π planar ligand at the sensing interface, thereby the electrochemical signal of the MB-adsorbed duplex is proportional to the concentration of target RNA, with SARS-CoV-2 (COVID-19) RNA as the model. Under optimal conditions, the target RNA can be detected in a linear range from 1 zM to 1 μM with a limit of detection (LOD) obtained at 0.59 zM for synthetic target RNA and as low as 1.4 copy number for positive control plasmid. This genosensor exhibited high selectivity towards SARS-CoV-2 RNA over other RNA nucleotides, such as SARS-CoV and MERS-CoV. The electrochemical RNA biosensor showed DPV signal, which was proportional to the 2019-nCoV_N_positive control plasmid from 2 to 200000 copies (R2 = 0.978). A good correlation between the genosensor and qRT-PCR gold standard was attained for the detection of SARS-CoV-2 RNA in terms of viral copy number in clinical samples from upper respiratory specimens.
Acrylic microspheres-based optosensor for visual detection of nitrite

Noor NS, Tan LL, Heng LY, Chong KF, Tajuddin SN

Food Chem, 2016 Sep 15;207:132-8.
PMID: 27080889 DOI: 10.1016/j.foodchem.2016.03.088

A new optosensor for visual quantitation of nitrite (NO2(-)) ion has been fabricated by physically immobilizing Safranine O (SO) reagent onto a self-adhesive poly(n-butyl acrylate) [poly(nBA)] microspheres matrix, which was synthesized via facile microemulsion UV lithography technique. Evaluation and optimization of the optical NO2(-) ion sensor was performed with a fiber optic reflectance spectrophotometer. Scanning electron micrograph showed well-shaped and smooth spherical morphology of the poly(nBA) microspheres with a narrow particles size distribution from 0.6μm up to 1.8μm. The uniform size distribution of the acrylic microspheres promoted homogeneity of the immobilized SO reagent molecules on the microspheres' surfaces, thereby enhanced the sensing response reproducibility (<5% RSD) with a linear range obtained from 10 to 100ppm NO2(-) ion. The micro-sized acrylic immobilization matrix demonstrated no significant barrier for diffusion of reactant and product, and served as a good solid state ion transport medium for reflectometric nitrite determination in food samples.
Fulltext Sandwich-Type DNA Micro-Optode Based on Gold-Latex Spheres Label for Reflectance Dengue Virus Detection

Jeningsih, Tan LL, Ulianas A, Heng LY, Mazlan NF, Jamaluddin ND, et al.

Sensors (Basel), 2020 Mar 25;20(7).
PMID: 32218202 DOI: 10.3390/s20071820

A DNA micro-optode for dengue virus detection was developed based on the sandwich hybridization strategy of DNAs on succinimide-functionalized poly(n-butyl acrylate) (poly(nBA-NAS)) microspheres. Gold nanoparticles (AuNPs) with an average diameter of ~20 nm were synthesized using a centrifugation-based method and adsorbed on the submicrometer-sized polyelectrolyte-coated poly(styrene-co-acrylic acid) (PSA) latex particles via an electrostatic method. The AuNP-latex spheres were attached to the thiolated reporter probe (rDNA) by Au-thiol binding to functionalize as an optical gold-latex-rDNA label. The one-step sandwich hybridization recognition involved a pair of a DNA probe, i.e., capture probe (pDNA), and AuNP-PSA reporter label that flanked the target DNA (complementary DNA (cDNA)). The concentration of dengue virus cDNA was optically transduced by immobilized AuNP-PSA-rDNA conjugates as the DNA micro-optode exhibited a violet hue upon the DNA sandwich hybridization reaction, which could be monitored by a fiber-optic reflectance spectrophotometer at 637 nm. The optical genosensor showed a linear reflectance response over a wide cDNA concentration range from 1.0 × 10-21 M to 1.0 × 10-12 M cDNA (R2 = 0.9807) with a limit of detection (LOD) of 1 × 10-29 M. The DNA biosensor was reusable for three consecutive applications after regeneration with mild sodium hydroxide. The sandwich-type optical biosensor was well validated with a molecular reverse transcription polymerase chain reaction (RT-PCR) technique for screening of dengue virus in clinical samples, e.g., serum, urine, and saliva from dengue virus-infected patients under informed consent.
Fulltext The Association Between Bullous Pemphigoid and Neurological Disorders in A Selected Malaysian Population

Kwan Z, Lai YN, Ch'ng CC, Tan AH, Tan LL, Robinson S, et al.

Med J Malaysia, 2015 Apr;70(2):81-5.
PMID: 26162382 MyJurnal

BACKGROUND: An association of bullous pemphigoid with neurological disorders has been reported. The objectives of this study were to review the clinical characteristics of patients with bullous pemphigoid and compare the association between bullous pemphigoid and various neurological disorders and comorbidities.

METHODS: This was a retrospective case-control study involving 43 patients with bullous pemphigoid and 43 age-, sex- and ethnicity-matched controls.

RESULTS: There was a statistically significant association between bullous pemphigoid and neurological disorders [Odds Ratio (OR) = 3.5, 95% Confidence Interval (CI) 1.3 to 9.2, p=0.011 and adjusted OR=3.5, 95% CI 1.2-10.3, p=0.026], in particular for dementia (p=0.002). Although stroke was more common among patients with bullous pemphigoid, this association was not statistically significant with OR of 1.9 (95% CI 0.7 to 5.2) and adjusted OR of 2.1 (95% CI 0.6 to 7.2). Similarly both ischaemic stroke (OR 1.5, 95% CI 0.5 to 4.2) and haemorrhagic stroke (OR 1.5, 95% CI 0.2 to 9.7) were more common. Other neurological disorders more common among patients with bullous pemphigoid were Parkinson's disease and epilepsy. Dyslipidaemia was significantly less common among patients with bullous pemphigoid (OR 0.4, 95% CI 0.1 to 0.9, p=0.033).

CONCLUSION: A combination of an inflammatory process, prothrombotic state and endothelial activation leads to an increased frequency of neurological disorders among patients with bullous pemphigoid. Thus, a holistic approach to patient care, including screening for dementia and control of comorbidities, should be practised as bullous pemphigoid affects more than just the skin.
Fulltext Full-length sequence analysis of chloroquine resistance transporter gene in Plasmodium falciparum isolates from Sabah, Malaysia

Tan LL, Lau TY, Timothy W, Prabakaran D

ScientificWorldJournal, 2014;2014:935846.
PMID: 25574497 DOI: 10.1155/2014/935846

Chloroquine resistance (CQR) in falciparum malaria was identified to be associated with several mutations in the chloroquine resistance transporter gene (pfcrt) that encodes the transmembrane transporter in digestive vacuole membrane of the parasite. This study aimed to investigate the point mutations across the full-length pfcrt in Plasmodium falciparum isolates in Sabah, Malaysia. A total of 31 P. falciparum positive samples collected from Keningau, Kota Kinabalu, and Kudat, Sabah, were analyzed. pfcrt was PCR amplified and cloned prior to sequence analysis. This study showed that all the previously described 10 point mutations associated with CQR at codons 72, 74, 75, 76, 97, 220, 271, 326, 356, and 371 were found with different prevalence. Besides, two novel point mutations, I166V and H273N, were identified with 22.5% and 19.3%, respectively. Three haplotypes, namely, CVMNK (29%), CVIET (3.2%), and SVMNT (67.7%), were identified. High prevalence of SVMNT among P. falciparum isolates from Sabah showed that these isolates are closer to the P. falciparum isolates from Papua New Guinea rather than to the more proximal Southeast Asian CVIET haplotype. Full-length analysis of pfcrt showed that chloroquine resistant P. falciparum in Sabah is still prevalent despite the withdrawal of chloroquine usage since 1979.
Point-Defect Engineering: Leveraging Imperfections in Graphitic Carbon Nitride (g-C3 N4 ) Photocatalysts toward Artificial Photosynthesis

Yu X, Ng SF, Putri LK, Tan LL, Mohamed AR, Ong WJ

Small, 2021 12;17(48):e2006851.
PMID: 33909946 DOI: 10.1002/smll.202006851

Graphitic carbon nitride (g-C3 N4 ) is a kind of ideal metal-free photocatalysts for artificial photosynthesis. At present, pristine g-C3 N4 suffers from small specific surface area, poor light absorption at longer wavelengths, low charge migration rate, and a high recombination rate of photogenerated electron-hole pairs, which significantly limit its performance. Among a myriad of modification strategies, point-defect engineering, namely tunable vacancies and dopant introduction, is capable of harnessing the superb structural, textural, optical, and electronic properties of g-C3 N4 to acquire an ameliorated photocatalytic activity. In view of the burgeoning development in this pacey field, a timely review on the state-of-the-art advancement of point-defect engineering of g-C3 N4 is of vital significance to advance the solar energy conversion. Particularly, insights into the intriguing roles of point defects, the synthesis, characterizations, and the systematic control of point defects, as well as the versatile application of defective g-C3 N4 -based nanomaterials toward photocatalytic water splitting, carbon dioxide reduction and nitrogen fixation will be presented in detail. Lastly, this review will conclude with a balanced perspective on the technical and scientific hindrances and future prospects. Overall, it is envisioned that this review will open a new frontier to uncover novel functionalities of defective g-C3 N4 -based nanostructures in energy catalysis.
Prevalence of visual disorders in Chinese schoolchildren

Chung KM, Mohidin N, Yeow PT, Tan LL, O'Leary D

Optom Vis Sci, 1996 Nov;73(11):695-700.
PMID: 8950751

We performed a vision screening of 1883 Chinese schoolchildren from 4 schools around Kuala Lumpur in June 1990. The group contained 1083-males and 800 females. Visual acuity, refractive error, oculomotor balance, and axial length were measured. The prevalence of myopia in Chinese schoolchildren was found to be 37% in the 6- to 12-year age group and 50% in the 13- to 18-year age group. Approximately 63% of the sample had unaided visual acuity of 6/6 or better and 24% had unaided acuity of 6/12 or worse. Six hundred twenty-five students (33%) failed the vision screening test and were referred for further examinations. The group which failed the vision screening test and had the highest rate of referral (46%) was the 11- to 12-year-old age group. The most common visual disorder was uncorrected myopia, accounting for 38% of the referrals (235 students). Only 26% of the sample were wearing a spectacle correction.
Canine and feline cutaneous screw-worm myiasis in Malaysia: clinical aspects in 76 cases

Han HS, Toh PY, Yoong HB, Loh HM, Tan LL, Ng YY

Vet Dermatol, 2018 Oct;29(5):442-e148.
PMID: 30066413 DOI: 10.1111/vde.12672

BACKGROUND: Cutaneous screw-worm myiasis in companion animals either due to the New World screw-worm, Cochliomyia hominivorax or the Old World screw-worm, Chrysomya bezziana, has been reported particularly in tropical and subtropical regions of the world. Although treatment of screw-worm myiasis in dogs has been described, few studies have been conducted regarding its clinical and epidemiological aspects in companion animals.
OBJECTIVES: To describe clinical and epidemiological aspects of canine and feline screw-worm myiasis.
ANIMALS: Naturally infested dogs and cats, presented to five veterinary clinics in four Malaysian states from September 2017 to February 2018.
METHODS AND MATERIALS: Cutaneous screw-worm myiasis was diagnosed based on clinical signs and visual examination of burrowing larvae within lesion. Age, breed, gender, anatomical site of infestation and suspected underlying predisposing causes were investigated.
RESULTS: A total of 55 dogs and 21 cats were included in the study. Intact male mixed breed dogs (mean age 58 months) and intact male domestic short hair cats (mean age 24 months) with suspected fight-related wounds were most commonly presented with exudative and ulcerative lesions associated with screw-worm myiasis. The most common anatomical sites of infestation in the dogs were the external ear canals, followed by the perineum and medial canthus. For the cats, the most commonly affected areas were paws and tail. Five cats with screw-worm myiasis were concurrently infected with sporotrichosis.
CONCLUSION AND CLINICAL RELEVANCE: Aggression between unneutered animals is a likely underlying cause for cutaneous screw-worm myiasis in both cats and dogs. Sporotrichosis was also a potential predisposing cause for screw-worm myiasis in cats.
Contamination levels of selected organochlorine and organophosphate pesticides in the Selangor River, Malaysia between 2002 and 2003

Leong KH, Tan LL, Mustafa AM

Chemosphere, 2007 Jan;66(6):1153-9.
PMID: 17027062

In Malaysia, rivers are the main source of public water supplies. This study was conducted from 2002 to 2003 to determine the levels of selected organochlorine and organophosphate pesticides in the Selangor River in Malaysia. Surface water samples have been collected seasonally from nine sites along the river. A liquid-liquid extraction followed by gas chromatography-mass spectrometry technique was used to determine the trace levels of these pesticide residues. The organochlorine pesticides detected were lindane, heptachlor, endosulfan, dieldrin, endosulfan sulfate, o,p'-DDT, p,p'-DDT, o,p'-DDE and p,p'-DDE whereas for organophosphate pesticides, they were chlorpyrifos and diazinon. At the river upstream where a dam is located for public water supply, incidents of pesticide levels exceeding the European Economic Community Directive of water quality standards have occurred. Furthermore, the wetland ecosystems located at the downstream of the river which houses the fireflies community is being threatened by occasional pesticide levels above EPA limits for freshwater aquatic organisms. The occurrence of these residual pesticides in the Selangor River can be attributed to the intense agriculture and urban activity.

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