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Molecularly imprinted polymers as optical sensing receptors: correlation between analytical signals and binding isotherms

Ng SM, Narayanaswamy R

Anal Chim Acta, 2011 Oct 10;703(2):226-33.
PMID: 21889638 DOI: 10.1016/j.aca.2011.07.032

Despite the increasing number of usage of molecularly imprinted polymers (MIPs) in optical sensor application, the correlation between the analytical signals and the binding isotherms has yet to be fully understood. This work investigates the relationship between the signals generated from MIPs sensors to its respective binding affinity variables generated using binding isotherm models. Two different systems based on the imprinting of metal ion and organic compound have been selected for the study, which employed reflectance and fluorescence sensing schemes, respectively. Batch binding analysis using the standard binding isotherm models was employed to evaluate the affinity of the binding sites. Evaluation using the discrete bi-Langmuir isotherm model found both the MIPs studied have generally two classes of binding sites that was of low and high affinities, while the continuous Freundlich isotherm model has successfully generated a distribution of affinities within the investigated analytical window. When the MIPs were incorporated as sensing receptors, the changes in the analytical signal due to different analyte concentrations were found to have direct correlation with the binding isotherm variables. Further data analyses based on this observation have generated robust models representing the analytical performance of the optical sensors. The best constructed model describing the sensing trend for each of the sensor has been tested and demonstrated to give accurate prediction of concentration for a series of spiked analytes.
Synthesis of fluorescent carbon dots via simple acid hydrolysis of bovine serum albumin and its potential as sensitive sensing probe for lead (II) ions

Wee SS, Ng YH, Ng SM

Talanta, 2013 Nov 15;116:71-6.
PMID: 24148375 DOI: 10.1016/j.talanta.2013.04.081

Carbon dots have great potential to be utilised as an optical sensing probe due to its unique photoluminescence and less toxic properties. This work reports a simple and novel synthesis method of carbon dots via direct acid hydrolysis of bovine serum albumin protein in a one-pot approach. Optimisation of the important synthetic parameters has been performed which consists of temperature effect, acid to protein ratio and kinetics of reaction. Higher temperature has promoted better yield with shorter reaction time. The carbon dots obtained shows a strong emission at the wavelength of 400 nm with an optimum excitation of 305 nm. The potential of the carbon dots as optical sensing probe has been investigated on with different cations that are of environmental and health concern. The fluorescence of the carbon dots was significantly quenched particularly by lead (II) ions in a selective manner. Further analytical study has been performed to leverage the performance of the carbon dots for lead (II) ions sensing using the standard Stern-Volmer relationship. The sensing probe has a dynamic linear range up to 6.0 mM with a Stern-Volmer constant of 605.99 M(-1) and a limit of detection (LOD) of 5.05 μM. The probe performance was highly repeatable with a standard deviation below 3.0%. The probe suggested in this study demonstrates the potential of a more economical and greener approach that uses protein based carbon dots for sensing of heavy metal ions.
A unique "turn-on" fluorescence signalling strategy for highly specific detection of ascorbic acid using carbon dots as sensing probe

Fong JFY, Chin SF, Ng SM

Biosens Bioelectron, 2016 Nov 15;85:844-852.
PMID: 27290666 DOI: 10.1016/j.bios.2016.05.087

Carbon dots (CDs) that showed strong blue fluorescence were successfully synthesised from sodium alginate via furnace pyrolysis. The single step pyrolytic synthesis was simple to perform while yielded CDs with high photostability, good water solubility and minimum by-products. In order to design the probe with "turn-on" sensing capability, the CDs were screened against a series of metal cations to first "turn-off" the fluorescence. It was found that ferric ions (Fe(3+)) were most responsive and effective in quenching the fluorescence of CDs. Based on this observation, the conditioning of the probe was performed to ensure the fluorescence was completely quenched, while not overloading the system with Fe(3+). At the optimised condition, the CDs-Fe(3+) mixture served as a highly specific detection probe for ascorbic acid (AA). The analytical potential of the probe was evaluated and showed a good linear range of response for AA concentration of 24-40μg/mL. The selectivity study against other possible co-existing species was carried out and proved that our unique "turn-on" fluorescence signalling strategy was highly effective and selective towards AA as the target analyte. The probe was demonstrated for quantification of AA in real samples, which was the commercially available vitamin C supplement. The result showed good accuracy with minimum deviation from standard method adopted for validation purpose.
Fulltext Presenting features and treatment outcome of 78 Malaysian children with neuroblastoma

Ng SM, Abdullah WA, Lin HP, Chan LL

Southeast Asian J Trop Med Public Health, 1999 Mar;30(1):149-53.
PMID: 10695803

To study the distribution of presenting features and their prognostic significance in neuroblastoma treated in a single institution in Malaysia. A retrospective study was made of 78 neuroblastoma cases diagnosed and treated in the University Hospital, Kuala Lumpur, Malaysia between June 1982 and February 1997. Diagnosis was established by standard histological criteria. The presenting features were evaluated for their distribution and prognostic influence. Disease-free survival from diagnosis was the outcome variable of interest. The ages ranged from 0.1 to 11 years old (median: 3 years old). The tumor originated from the adrenal glands in 83% and the majority of cases presented in advanced stage (stage III 22%, stage IV 66%). Bone marrow was the commonest site of distant metastasis occurring in 45% of patients. The main presenting signs and symptoms in decreasing order were pallor, fever, abdominal mass, weight loss, and bone/joint pain. Univariate analysis conferred age, initial stage and Hb level as significant prognostic factors. No influence in disease-free survival was found for sex, race, primary site, urinary vanillylmandelic acid level, white cell count and platelet count. Overall 2-year disease-free survival was achieved in 27 (39%) patients. Four patients underwent bone marrow transplant, three of whom achieved 2-year disease-free survival. The results suggest that age, initial stage and hemoglobin level are significant prognostic factors based on univariate analysis. In addition, more Malaysian children presented with adrenal primary site and advanced disease compared to previous reported studies.
One-pot synthesis of carbon dots using two different acids and their respective unique photoluminescence property

Loi E, Ng RW, Chang MM, Fong JF, Ng YH, Ng SM

Luminescence, 2017 Feb;32(1):114-118.
PMID: 27166514 DOI: 10.1002/bio.3157

Carbon dots, a new class of nanomaterial with unique optical property and have great potential in various applications. This work demonstrated the possibility of tuning the emission wavelength of carbon dots by simply changing the acid type used during synthesis. In particular, sulfuric and phosphoric acids and a mixture of the two were used to carbonize the same starting precursor, sucrose. This resulted in the isolation of carbon dots with blue (440 nm) and green (515 nm) emission. Interestingly, the use of an acid mixture at various ratios did not shift the initial emission profile, but did obviously alter the fluorescence efficiency of the peaks. This clearly showed that acid type can be used as an alternative tool to produce carbon dots that have different emissions using the same starting precursor. Copyright © 2016 John Wiley & Sons, Ltd.
Integrated miniature fluorescent probe to leverage the sensing potential of ZnO quantum dots for the detection of copper (II) ions

Ng SM, Wong DS, Phung JH, Chin SF, Chua HS

Talanta, 2013 Nov 15;116:514-9.
PMID: 24148438 DOI: 10.1016/j.talanta.2013.07.031

Quantum dots are fluorescent semiconductor nanoparticles that can be utilised for sensing applications. This paper evaluates the ability to leverage their analytical potential using an integrated fluorescent sensing probe that is portable, cost effective and simple to handle. ZnO quantum dots were prepared using the simple sol-gel hydrolysis method at ambient conditions and found to be significantly and specifically quenched by copper (II) ions. This ZnO quantum dots system has been incorporated into an in-house developed miniature fluorescent probe for the detection of copper (II) ions in aqueous medium. The probe was developed using a low power handheld black light as excitation source and three photo-detectors as sensor. The sensing chamber placed between the light source and detectors was made of 4-sided clear quartz windows. The chamber was housed within a dark compartment to avoid stray light interference. The probe was operated using a microcontroller (Arduino Uno Revision 3) that has been programmed with the analytical response and the working algorithm of the electronics. The probe was sourced with a 12 V rechargeable battery pack and the analytical readouts were given directly using a LCD display panel. Analytical optimisations of the ZnO quantum dots system and the probe have been performed and further described. The probe was found to have a linear response range up to 0.45 mM (R(2)=0.9930) towards copper (II) ion with a limit of detection of 7.68×10(-7) M. The probe has high repeatable and reliable performance.
Age, sex, haemoglobin level, and white cell count at diagnosis are important prognostic factors in children with acute lymphoblastic leukemia treated with BFM-type protocol

Ng SM, Lin HP, Ariffin WA, Zainab AK, Lam SK, Chan LL

J Trop Pediatr, 2000 Dec;46(6):338-43.
PMID: 11191144

The presenting features and treatment outcome for 575 Malaysian children (< or = 12 years of age) with newly diagnosed acute lymphoblastic leukemia (ALL), admitted to the University Hospital, Kuala Lumpur, Malaysia between 1 January 1980 and 30 May 1995 were evaluated to determine their prognostic significance. Two-year overall survival was achieved in 67 per cent of all patients and 55 per cent of patients were relapse-free at 2 years. All except 10 patients, with identified French-American-British L3 morphology were treated with the modified Berlin-Frankfurt-Munster 78 treatment protocol. Univariate analyses of failure rate conferred age, sex, white cell count and hemoglobin level as potentially significant prognostic factors. All four presenting features retained their prognostic strength in a multivariate analysis. Race, platelet count, morphological subtype, liver/spleen size, lymphadenopathy, central nervous system and mediastinal mass involvement did not show any significant effect on treatment outcome. The 2-year survival rate was significantly different with regard to age, white cell count and hemoglobin level. However, sex was not significantly related to overall survival. These prognostic factors may have implications on future stratification of risk-adjusted initial treatment in the management of childhood ALL. Our analysis of Malaysian children is similar to what could be predicted based on previous studies in other populations.
Clinical features and treatment outcome of children with myeloid antigen coexpression in B-lineage acute lymphoblastic leukemia: a study of 151 Malaysian children

Ng SM, Ariffin WA, Lin HP, Chan LL, Chin YM

J Trop Pediatr, 2000 Apr;46(2):73-8.
PMID: 10822932

The purpose of the study was to evaluate the incidence of myeloid antigen coexpression and its prognostic significance in childhood acute lymphoblastic leukemia (ALL) in Malaysia. A retrospective study was conducted of all ALL cases (< or = 12 years old) diagnosed and treated in University Hospital, Kuala Lumpur, Malaysia between 1 January 1992 and 30 May 1995, with available immunophenotype data. Presenting features and treatment outcome of 39 B-lineage ALL patients with myeloid antigen coexpression (My+B) were compared with 112 B-lineage ALL patients without myeloid antigen coexpression (My-B) for similarity in demographic, clinical and laboratory features and their treatment outcome. My+B and My-B patients were treated with a uniform treatment protocol. Myeloid antigen coexpression was defined as more than 30% isolated leukemic cells positive for CD13 and/or CD33. The ages at diagnoses ranged from 2 months to 12 years. Median age was 4 years. The incidence of myeloid antigen coexpression was 23 per cent. Univariate analyses showed that presenting features were similar between My+B and My-B with regard to age, sex, race, FAB morphology, white cell count, hemoglobin level, platelet count, liver/spleen size, central nervous system or mediastinal involvement, presence of lymphadenopathy, and proportion of blast cells detected in the marrow. Treatment outcome were not significant between the two groups. The 2-year event free survival was achieved in 44 per cent of My+B and 57 per cent of My-B (p = 0.11). The 2-year overall survival rates were 62 per cent for My+B vs. 77 per cent for My-B (p = 0.08). This study demonstrates that myeloid antigen coexpression is fairly common and constitutes 23 per cent of childhood ALL within the Malaysian population and that it is not an adverse risk factor in childhood ALL.
Fulltext Closing the Type 1 Diabetes gap in South-East Asia through government partnership working with non-government organisations

Ng SM, Malene IV, Nilar M, Rassavong K, Dung Vu C, Hui Sieng Tan F, et al.

Diabetes Res Clin Pract, 2022 May;187:109868.
PMID: 35395247 DOI: 10.1016/j.diabres.2022.109868

This will be the first publication of Type 1 diabetes(T1D) outcomes in five low-middle-income countries (LMICs)-Laos, Malaysia, Vietnam, Cambodia and Myanmar in the Southeast Asia (SEA) region. The information obtained has been possible due to partnership programmes of non-government organisationAction4Diabetes (A4D) with defined local hospitalsthrough a Memorandum of Understandingsigned with the governments in SEAthat guarantees ongoing supplies of free insulin, blood glucose meter supplies, HbA1c tests and hospital emergency funds.
PARTICIPANTS: Between 2020 and 2021, 383 children and young people with T1D who were active in the A4D supported programmes were reviewed including information on health coverage, multidisciplinary team management, diabetic ketoacidosis (DKA) on admission and insulin regimen.
RESULTS: Mean HbA1c between 2020 and 2021 for patients in these LMICs arereported for the first time. The average glycaemic index in the five SEAcountries reviewed between 2020 and 2021 were high at 83 mmol/mol (9.7%).
CONCLUSIONS: Government partnership working with non-government organisationsto support T1D from diagnosis to adulthood are the first steps to closing thegaps in many LMICs. Further epidemiological studies are needed to identify the glycaemic outcomes and DKA rates on admission for many of these countries.
Fulltext A randomized single-dose, two-period crossover bioequivalence study of two fixed-dose Paracetamol/Orphenadrine combination preparations in healthy volunteers under fasted condition

Cheah KY, Mah KY, Pang LH, Ng SM, Wong JW, Tan SS, et al.

BMC Pharmacol Toxicol, 2020 06 23;21(1):45.
PMID: 32576287 DOI: 10.1186/s40360-020-00416-3

BACKGROUND: Paracetamol/Orphenadrine is a fixed dose combination containing 35 mg orphenadrine and 450 mg paracetamol. It has analgesic and muscle relaxant properties and is widely available as generics. This study is conducted to investigate the relative bioavailability and bioequivalence between one fixed dose paracetamol/orphenadrine combination test preparation and one fixed dose paracetamol/orphenadrine combination reference preparation in healthy volunteers under fasted condition for marketing authorization in Malaysia.
METHOD: This is a single-center, single-dose, open-label, randomized, 2-treatment, 2-sequence and 2-period crossover study with a washout period of 7 days. Paracetamol/Orphenadrine tablets were administered after a 10-h fast. Blood samples for pharmacokinetic analysis were collected at scheduled time intervals prior to and up to 72 h after dosing. Blood samples were centrifuged, and separated plasma were kept frozen (- 15 °C to - 25 °C) until analysis. Plasma concentrations of orphenadrine and paracetamol were quantified using liquid-chromatography-tandem mass spectrometer using diphenhydramine as internal standard. The pharmacokinetic parameters AUC0-∞, AUC0-t and Cmax were determined using plasma concentration time profile for both preparations. Bioequivalence was assessed according to the ASEAN guideline acceptance criteria for bioequivalence which is the 90% confidence intervals of AUC0-∞, AUC0-t and Cmax ratio must be within the range of 80.00-125.00%.
RESULTS: There were 28 healthy subjects enrolled, and 27 subjects completed this trial. There were no significant differences observed between the AUC0-∞, AUC0-t and Cmax of both test and reference preparations in fasted condition. The 90% confidence intervals for the ratio of AUC0-t (100.92-111.27%), AUC0-∞ (96.94-108.08%) and Cmax (100.11-112.50%) for orphenadrine (n = 25); and AUC0-t (94.29-101.83%), AUC0-∞ (94.77-101.68%) and Cmax (87.12-101.20%) for paracetamol (n = 27) for test preparation over reference preparation were all within acceptable bioequivalence range of 80.00-125.00%.
CONCLUSION: The test preparation is bioequivalent to the reference preparation and can be used interchangeably.
TRIAL REGISTRATION: NMRR- 17-1266-36,001; registered and approved on 12 September 2017.
Fulltext Comparative analysis of nucleus-encoded plastid-targeting proteins in Rafflesia cantleyi against photosynthetic and non-photosynthetic representatives reveals orthologous systems with potentially divergent functions

Ng SM, Lee XW, Mat-Isa MN, Aizat-Juhari MA, Adam JH, Mohamed R, et al.

Sci Rep, 2018 Nov 22;8(1):17258.
PMID: 30467394 DOI: 10.1038/s41598-018-35173-1

Parasitic plants are known to discard photosynthesis thus leading to the deletion or loss of the plastid genes. Despite plastid genome reduction in non-photosynthetic plants, some nucleus-encoded proteins are transported back to the plastid to carry out specific functions. In this work, we study such proteins in Rafflesia cantleyi, a member of the holoparasitic genus well-known for producing the largest single flower in the world. Our analyses of three transcriptome datasets, two holoparasites (R. cantleyi and Phelipanche aegyptiaca) and one photosynthetic plant (Arabidopsis thaliana), suggest that holoparasites, such as R. cantleyi, retain some common plastid associated processes such as biosynthesis of amino acids and lipids, but are missing photosynthesis components that can be extensions of these pathways. The reconstruction of two selected biosynthetic pathways involving plastids correlates the trend of plastid retention to pathway complexity - transcriptome evidence for R. cantleyi suggests alternate mechanisms in regulating the plastidial heme and terpenoid backbone biosynthesis pathways. The evolution to holoparasitism from autotrophy trends towards devolving the plastid genes to the nuclear genome despite the functional sites remaining in the plastid, or maintaining non-photosynthetic processes in the plastid, before the eventual loss of the plastid and any site dependent functions.
Internet analytics of an innovative digital educational resource of type 1 diabetes HelloType1 in local languages for people living with diabetes families and healthcare professionals in Southeast Asia

Ng SM, Malene IV, Nguyen TK, Le K, Lim YXL, Lek N, et al.

BMC Endocr Disord, 2023 Nov 16;23(1):249.
PMID: 37974071 DOI: 10.1186/s12902-023-01501-4

BACKGROUND: There is minimal data of health outcomes for Type 1 Diabetes (T1D) in Southeast Asia (SEA) where government funding of insulin and blood glucose monitoring either do not exist or is limited. The full impact of Covid-19 pandemic on the national economies of SEA remain unknown. In the midst of the pandemic, in 2021, HelloType1 was developed by Action4Diabetes (A4D), a non-government organisation charity in collaboration with Southeast Asia local healthcare professionals as an innovative digital educational resource platform of T1D in local languages. HelloType1 was launched in Cambodia, Vietnam, Thailand and Malaysia in 2021 to 2022 with Memorandums of Understandings (MOUs) signed between A4D and each country. Internet data analytics were undertaken between the 1st of January 2022 to 31st of December 2022.
AIMS: The aims of this study were to explore the usability and internet data analytics of the HelloType1 online educational platform within each country.
METHODS: The data analytics were extracted Google analytics that tracks data from the website hellotype1.com and Facebook analytics associated with the website.
RESULTS: There was a 147% increase in the number of HelloType1 users between the first 6 months versus the latter 6 months in 2022 and a 15% increase in the number of pages visited were noted. The majority of traffic source were coming from organic searches with a significant increase of 80% growth in 2022.
CONCLUSIONS: The results of the analytics provide important insights on how an innovative diabetes digital educational resource in local languages may be optimally delivered in low-middle income countries with limited resources.
Fulltext In silico-guided sequence modifications of K-ras epitopes improve immunological outcome against G12V and G13D mutant KRAS antigens

Ng AWR, Tan PJ, Hoo WPY, Liew DS, Teo MYM, Siak PY, et al.

PeerJ, 2018;6:e5056.
PMID: 30042874 DOI: 10.7717/peerj.5056

Background: Somatic point substitution mutations in the KRAS proto-oncogene primarily affect codons 12/13 where glycine is converted into other amino acids, and are highly prevalent in pancreatic, colorectal, and non-small cell lung cancers. These cohorts are non-responsive to anti-EGFR treatments, and are left with non-specific chemotherapy regimens as their sole treatment options. In the past, the development of peptide vaccines for cancer treatment was reported to have poor AT properties when inducing immune responses. Utilization of bioinformatics tools have since become an interesting approach in improving the design of peptide vaccines based on T- and B-cell epitope predictions.
Methods: In this study, the region spanning exon 2 from the 4th to 18th codon within the peptide sequence of wtKRAS was chosen for sequence manipulation. Mutated G12V and G13D K-ras controls were generated in silico, along with additional single amino acid substitutions flanking the original codon 12/13 mutations. IEDB was used for assessing human and mouse MHC class I/II epitope predictions, as well as linear B-cell epitopes predictions, while RNA secondary structure prediction was performed via CENTROIDFOLD. A scoring and ranking system was established in order to shortlist top mimotopes whereby normalized and reducing weighted scores were assigned to peptide sequences based on seven immunological parameters. Among the top 20 ranked peptide sequences, peptides of three mimotopes were synthesized and subjected to in vitro and in vivo immunoassays. Mice PBMCs were treated in vitro and subjected to cytokine assessment using CBA assay. Thereafter, mice were immunized and sera were subjected to IgG-based ELISA.
Results: In silico immunogenicity prediction using IEDB tools shortlisted one G12V mimotope (68-V) and two G13D mimotopes (164-D, 224-D) from a total of 1,680 candidates. Shortlisted mimotopes were predicted to promote high MHC-II and -I affinities with optimized B-cell epitopes. CBA assay indicated that: 224-D induced secretions of IL-4, IL-5, IL-10, IL-12p70, and IL-21; 164-D triggered IL-10 and TNF-α; while 68-V showed no immunological responses. Specific-IgG sera titers against mutated K-ras antigens from 164-D immunized Balb/c mice were also elevated post first and second boosters compared to wild-type and G12/G13 controls.
Discussion: In silico-guided predictions of mutated K-ras T- and B-cell epitopes were successful in identifying two immunogens with high predictive scores, Th-bias cytokine induction and IgG-specific stimulation. Developments of such immunogens are potentially useful for future immunotherapeutic and diagnostic applications against KRAS(+) malignancies, monoclonal antibody production, and various other research and development initiatives.

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