Displaying publications 1 - 20 of 46 in total

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  1. Patterns of linkage disequilibrium at PARK16 may explain variances in genetic association studies
    Li H, Teo YY, Tan EK
    Mov Disord, 2015 Sep;30(10):1335-42.
    PMID: 25758099 DOI: 10.1002/mds.26176
    Reproducing genomewide association studies findings in different populations is challenging, because the reproducibility fundamentally relies on the similar patterns of linkage disequilibrium between the unknown causal variants and the genotyped single-nucleotide polymorphisms (SNPs).
  2. Effect of PEGylated lipid and Lecinol S-10 on physico-chemical properties and encapsulation efficiency of palmitoleate-palmitoleic acid vesicles
    Teo YY, Misran M, Low KH
    J Liposome Res, 2014 Sep;24(3):241-8.
    PMID: 24597523 DOI: 10.3109/08982104.2014.891234
    A vesicle is a microscopic particle composed of a lipid bilayer membrane that separates the inner aqueous compartment from the outer aqueous environment. Palmitoleate-palmitoleic acid vesicles were prepared and their physico-chemical properties were investigated. Moreover, mixed vesicles composed of palmitoleic acid and PEGylated lipid and/or a mixture of phospholipids were also prepared. The stabilizing effects of these double-chain lipids on the formation of palmitoleate-palmitoleic acid vesicles were studied. Stability of the vesicle suspension was examined using particle size and zeta potential at 30 °C. The magnitude of the zeta potential was relatively lower in the vesicle suspension with the presence of phospholipid. Although some of the mixed vesicles that were formed were not very stable, they displayed potential for encapsulating the active ingredient calcein and the encapsulation efficiencies of calcein were encouraging. The palmitoleate-palmitoleic acid-DPPE-PEG2000 vesicle showed the most promising stability and encapsulation efficiency.
  3. Fulltext Dicyclo-hexyl-ammonium bis-(chloro-difluoro-acetato-κO)cyclo-hexyl-diphenyl-stannate(IV)
    Teo YY, Lo KM, Ng SW
    Acta Crystallogr Sect E Struct Rep Online, 2008;64(Pt 5):m726-7.
    PMID: 21202250 DOI: 10.1107/S1600536808011057
    In the title mixed-organyl stannate, (C(12)H(24)N)[Sn(C(6)H(5))(2)(C(6)H(11))(CClF(2)O(2))(2)], there are two cations and two anions in the asymmetric unit. Each five-coordinate Sn atom shows trans-C(3)SnO(2) trigonal bipyramidal coordination. The four Sn-O distances are approximately equal in the two independent anions. Each ammonium cation serves as a hydrogen-bond donor to two stannates, the hydrogen-bonding inter-actions giving rise to linear hydrogen-bonded chains.
  4. Fulltext [μ-1,4-Bis(diphenyl-phosphino-yl)butane-κO:O']bis-[cyclo-pentyl-diphen-yl(trifluoro-acetato-κO)tin(IV)]
    Teo YY, Lo KM, Ng SW
    Acta Crystallogr Sect E Struct Rep Online, 2008;64(Pt 6):m790.
    PMID: 21202479 DOI: 10.1107/S1600536808013202
    The mol-ecule of the dinuclear title compound, [Sn(2)(C(5)H(9))(2)(C(6)H(5))(4)(C(2)F(3)O(2))(2)(C(28)H(28)O(2)P(2))], lies on a center of inversion at the mid-point of the central C-C bond of the bridging phosphine oxide ligand. The Sn atom is five-coordinate in a trans-C(3)SnO(2) trigonal-bipyramidal geometry.
  5. Fulltext Bis[1,3-bis-(diphenyl-phosphino)propane-κP:P']silver(I) bis-(chloro-difluoro-acetato-κO)triphenyl-stannate(IV)
    Teo YY, Lo KM, Ng SW
    Acta Crystallogr Sect E Struct Rep Online, 2008;64(Pt 5):m703.
    PMID: 21202235 DOI: 10.1107/S1600536808010763
    In the title salt, [Ag(C(27)H(26)P(2))(2)][Sn(C(6)H(5))(3)(C(2)ClF(2)O(2))], the Ag(I) atom exists in a tetra-hedral coordination geometry formed by four P atoms [Ag-P = 2.460 (1)-2.501 (1) Å], whereas the Sn(IV) atom exists in a trans-trigonal-bipyramidal coordination geometry formed by two O [Sn-O = 2.208 (3) and 2.233 (3) Å] and three C atoms [Sn-C = 2.115 (4)-2.128 (4) Å;(Σ C-Sn-C)= 360.0 (6)°].
  6. Fulltext Dicyclo-hexyl-ammonium bis-(chloro-difluoro-acetato-κO)cyclo-pentyl-diphenyl-stannate(IV)
    Teo YY, Lo KM, Ng SW
    Acta Crystallogr Sect E Struct Rep Online, 2008;64(Pt 5):m700.
    PMID: 21202233 DOI: 10.1107/S1600536808010775
    The five-coordinate Sn atom in the title mixed organyl stannate compound, (C(12)H(24)N)[Sn(C(5)H(9))(C(6)H(5))(2)(C(2)ClF(2)O(2))], is in a trans-C(3)SnO(2) trigonal-bipyramidal coordination environment. The NH(2) groups of the cations act as hydrogen-bond donors to two symmetry-related anions, resulting in the formation of linear chains. One of the phenyl rings is disordered over two sites with equal occupancies.
  7. Fulltext Bis[1,2-bis-(diphenyl-phosphino)ethane-κP:P']silver(I) bis-(chloro-difluoro-acetato-κO)(4-chloro-phen-yl)diphenyl-stannate(IV)
    Teo YY, Lo KM, Ng SW
    Acta Crystallogr Sect E Struct Rep Online, 2008;64(Pt 6):m819.
    PMID: 21202502 DOI: 10.1107/S1600536808014128
    In the title salt, [Ag(C(26)H(24)P(2))(2)][Sn(C(2)ClF(2)O(2))(2)(C(6)H(5))(2)(C(6)H(4)Cl)], the Ag(I) atom has a tetra-hedral and the Sn(IV) atom a trans-trigonal-bipyramidal coordination geometry. In the anion, the chloro substituent is disordered over two rings (occupancy ratio 0.81:0.19); the two chloro-difluoro-methyl groups are also disordered over two sites for their halogen atoms (occupancy ratios 0.72:0.28 and 0.70:0.30).
  8. Fulltext pH responsive N-succinyl chitosan/Poly (acrylamide-co-acrylic acid) hydrogels and in vitro release of 5-fluorouracil
    Bashir S, Teo YY, Naeem S, Ramesh S, Ramesh K
    PLoS One, 2017;12(7):e0179250.
    PMID: 28678803 DOI: 10.1371/journal.pone.0179250
    There has been significant progress in the last few decades in addressing the biomedical applications of polymer hydrogels. Particularly, stimuli responsive hydrogels have been inspected as elegant drug delivery systems capable to deliver at the appropriate site of action within the specific time. The present work describes the synthesis of pH responsive semi-interpenetrating network (semi-IPN) hydrogels of N-succinyl-chitosan (NSC) via Schiff base mechanism using glutaraldehyde as a crosslinking agent and Poly (acrylamide-co-acrylic acid)(Poly (AAm-co-AA)) was embedded within the N-succinyl chitosan network. The physico-chemical interactions were characterized by Fourier transform infrared (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and field emission scanning electron microscope (FESEM). The synthesized hydrogels constitute porous structure. The swelling ability was analyzed in physiological mediums of pH 7.4 and pH 1.2 at 37°C. Swelling properties of formulations with various amounts of NSC/ Poly (AAm-co-AA) and crosslinking agent at pH 7.4 and pH 1.2 were investigated. Hydrogels showed higher swelling ratios at pH 7.4 while lower at pH 1.2. Swelling kinetics and diffusion parameters were also determined. Drug loading, encapsulation efficiency, and in vitro release of 5-fluorouracil (5-FU) from the synthesized hydrogels were observed. In vitro release profile revealed the significant influence of pH, amount of NSC, Poly (AAm-co-AA), and crosslinking agent on the release of 5-FU. Accordingly, rapid and large release of drug was observed at pH 7.4 than at pH 1.2. The maximum encapsulation efficiency and release of 5-FU from SP2 were found to be 72.45% and 85.99%, respectively. Kinetics of drug release suggested controlled release mechanism of 5-FU is according to trend of non-Fickian. From the above results, it can be concluded that the synthesized hydrogels have capability to adapt their potential exploitation as targeted oral drug delivery carriers.
  9. Interethnic comparisons of important pharmacology genes using SNP databases: potential application to drug regulatory assessments
    Chen J, Teo YY, Toh DS, Sung C
    Pharmacogenomics, 2010 Aug;11(8):1077-94.
    PMID: 20712526 DOI: 10.2217/pgs.10.79
    The frequencies of alleles implicated in drug-response variability provide vital information for public health management. Differences in frequencies between genetically diverse groups of individuals can hamper drug assessments, particularly in populations where clinical data are not readily available.
  10. Fulltext Post-implantation Deformation of Titanium Rod and Cobalt Chrome Rod in Adolescent Idiopathic Scoliosis
    Sia U, Tan BB, Teo YY, Wong CC
    Malays Orthop J, 2019 Mar;13(1):14-19.
    PMID: 31001378 DOI: 10.5704/MOJ.1903.002
    Introduction: Post-implantation rod deformation is anticipated in scoliosis surgery but the difference in rod deformation between titanium and cobalt chrome rod has not been elucidated. This study aims to compare the difference in rod deformation between two groups. Materials and Methods: Twenty-one adolescent idiopathic scoliosis (AIS) patients were recruited from a single center. The over-contoured concave rods were traced prior to insertion. Post-operative sagittal rod shape was determined from lateral radiographs. Rod deformation was determined using maximal rod deflection and angle of the tangents to rod end points. The differences between pre- and post-operative rod contour were analysed statistically. Rod deformation and thoracic kyphosis between two types of implants were analysed. Results: Both rods exhibited significant change of rod angle and deflection post-operatively. Curvature of the titanium rod and cobalt chrome rod decreased from 60.5° to 37°, and 51° to 28° respectively. Deflection of titanium rod and cobalt chrome rod reduced from 28mm to 23.5mm and 30mm to 17mm respectively. There was no significant difference between titanium and cobalt chrome groups with regard to rod angle (p=0.173) and deflection (p=0.654). Thoracic kyphosis was increased from 20° to 26° in titanium group but a reduction from 25° to 23° was noticed in cobalt chrome group, but these findings were not statistically significant. Conclusion: There was no statistical difference in rod deformation between the two groups. Thus, the use of titanium rod in correction of sagittal profile is not inferior in outcome compared with cobalt chrome but with lower cost.
  11. Fulltext Development of nanostructured lipid carrier (NLC) assisted with polysorbate nonionic surfactants as a carrier for l-ascorbic acid and Gold Tri.E 30
    Eh Suk VR, Mohd Latif F, Teo YY, Misran M
    J Food Sci Technol, 2020 Sep;57(9):3259-3266.
    PMID: 32728274 DOI: 10.1007/s13197-020-04357-x
    Lipid nanocarrier displays the advantages over conventional drug carriers as they are formulated with biodegradable and non-irritant lipids. However, the main drawbacks are the agglomeration of lipid particles, instability over storage, low drug loading, and the burst release of active ingredients. In this study, we investigated the effects of various polysorbate nonionic surfactants namely Tween 20, 40, 60, or 80 on the nanostructured lipid carrier (NLC). NLC incorporated with polysorbate nonionic surfactant was prepared by using high-pressure homogenization technique. The average size was reduced to 139.9 ± 15.8 nm in the presence of Tween 80 and remained stable in nano-size even incubated for 28 days. Encapsulation of l-ascorbic acid or Gold Tri.E 30 showed a high encapsulation efficiency of more than 75%, where the highest was Gold Tri.E in the presence of Tween 60 at 99.7%. In vitro release study showed that the release of both l-ascorbic acid and Gold Tri.E was significantly reduced in NLC with Tween as compared to bare active ingredients and NLC without Tween. In conclusion, the incorporation of Tween successfully produced a lipid nanocarrier that has the potential to be developed as a carrier of various active ingredients such as nutrients, extracts, and drugs.
  12. Fulltext A Rare Incidence of Breakage of tip of Micropituitary Forceps during Percutaneous Discectomy - How to Remove it: A Case Report
    Sureisen M, Tan BB, Teo YY, Wong CC
    Malays Orthop J, 2015 Nov;9(3):58-60.
    PMID: 28611913 MyJurnal DOI: 10.5704/MOJ.1511.009
    Breakage of the tip of the micropituitary forceps during spine surgery is a rare occurrence. Retrieval of the broken tip could be a challenge in minimally invasive surgeries due to limitation of access and retrieval instruments. We describe our experience in handling such a situation during percutaneous radiofrequency discectomy. The removal was attempted, without converting into open surgery, by utilising percutaneous endoscopic lumbar discectomy working cannula and guided by image intensifier. We were able to remove the fragment without any significant morbidity to the patient. This technique for removal has not been reported previously in the literature.
  13. Rheological behavior of biodegradable N-succinyl chitosan-g-poly (acrylic acid) hydrogels and their applications as drug carrier and in vitro theophylline release
    Bashir S, Teo YY, Ramesh S, Ramesh K, Mushtaq MW
    Int J Biol Macromol, 2018 Oct 01;117:454-466.
    PMID: 29807081 DOI: 10.1016/j.ijbiomac.2018.05.182
    Novel pH sensitive N-succinyl chitosan-g-poly (acrylic acid) hydrogels were synthesized through free radical mechanism. Rheometer was used to observe the mechanical strength of the hydrogels. In vitro degradation was conducted in SIF (pH 7.4). The effect of concentration of monomers, initiator, and crosslinking agent and pH and ionic strength of NaCl, CaCl2, and AlCl3 on swelling of the hydrogels was observed. The results showed that equilibrium swelling ratio was highly influenced by concentration of monomers, initiator, and crosslinking agent concentration, and pH and salt solutions of NaCl, CaCl2, and AlCl3. The swelling kinetics revealed that swelling followed non-Fickian anomalous transport. Furthermore, theophylline loading (DL %) and encapsulation efficiency (EE %) of the hydrogels was in the range of 15.5 ± 0.15-22.8 ± 0.06% and 62 ± 0.15-91 ± 0.26%, respectively. The release of theophylline in physiological mediums was strongly influenced by the pH. The theophylline release was in the range of 51 ± 0.20-92 ± 0.12% in SIF and 7.4 ± 0.02-14.9 ± 0.03% in SGF (pH 1.2), respectively. The release data fitted well to Korsmeyer-Peppas model. The chemical activity of the theophylline suggested that drug maintained its chemical activity after release in vitro. The results suggest that synthesized hydrogels are excellent drug carriers.
  14. Fulltext Single Entry Posterior Parasagittal Approach Radiofrequency Neurotomy of Cervical Medial Branch: A Feasible Alternative to Conventional Approaches in the Treatment of Cervical Facet Pain
    Chen CK, Wong CC, Teo YY, Phui VE
    Int J Spine Surg, 2021 Dec;15(6):1180-1188.
    PMID: 35078892 DOI: 10.14444/8151
    BACKGROUND: Cervical facet joint pain is an important cause of chronic neck pain. The recommended treatment for this condition is radiofrequency (RF) neurotomy of the medial branch of dorsal rami. There have been attempts to find safe and effective ways to perform this procedure. The objective of this study is to describe the single entry posterior parasagittal approach and to evaluate the efficacy and safety of this approach compared to the conventional posterolateral approach of RF neurotomy of cervical medial branch.

    METHODS: The record of all patients with cervical facet pain who were treated with RF neurotomy medial branch of dorsal rami between January 2016 and December 2019 were reviewed retrospectively. Comparisons were made between patients who underwent RF neurotomy with multiple skin entry posterolateral approach and those who underwent RF neurotomy with single entry posterior parasagittal approach. The primary outcome was measured as the mean changes in numerical rating scale (NRS), and the secondary outcomes were duration and complications related to both approaches.

    RESULTS: Thirty-one patients who underwent RF neurotomy via posterolateral approach were compared with 40 patients who underwent the procedure via posterior parasagittal approach. Both approaches showed a significant decrease in the NRS from baseline values. However, the differences in the NRS lowering effect at 3 and 12 months between these 2 approaches were not statistically significant. The duration of the procedure was significantly shorter with posterior parasagittal approach (44.13 ± 4.72 minutes vs 54.68 ± 7.39 minutes; P < 0.001). There were no serious complications encountered in both approaches.

    CONCLUSIONS: With comparable efficacy and safety profile between the posterior parasagittal and the conventional posterolateral approaches, the former single skin entry approach offers the added advantage of being less time-consuming. Further randomized prospective studies are necessary to validate these findings.

  15. Fulltext Recent development of biodegradable synthetic rubbers and bio-based rubbers using sustainable materials from biological sources
    Boon ZH, Teo YY, Ang DT
    RSC Adv, 2022 Nov 22;12(52):34028-34052.
    PMID: 36545000 DOI: 10.1039/d2ra06602e
    Rubber is an amorphous hyperelastic polymer which is widely used in this modern era. Natural rubber is considered the ultimate rubber in terms of mechanical performance, but over the years, some limitations and challenges in natural rubber cultivation that could result in serious shortages in the supply chain had been identified. Since then, the search for alternatives including new natural and synthetic rubbers has been rather intense. The initiative to explore new sources of natural rubber which started during the 1940s has been reignited recently due to the increasing demand for natural rubber. The commercialization of natural rubber from the Parthenium argentatum and Taraxacum kok-saghyz species, with the cooperation from rubber product manufacturing companies, has somewhat improved the sustainability of the natural rubber supply chain. Meanwhile, the high demand for synthetic rubber drastically increases the rate of depletion of fossil fuels and amplifies the adverse environmental effect of overexploitation of fossil fuels. Moreover, rubber and plastic products disposal have been a major issue for many decades, causing environmental pollution and the expansion of landfills. Sustainable synthetic rubber products could be realized through the incorporation of materials from biological sources. They are renewable, low cost, and most importantly, biodegradable in nature. In this review, brief introduction to natural and synthetic rubbers, challenges in the rubber industry, alternatives to conventional natural rubber, and recent advances in biodegradable and/or bio-based synthetic rubbers are discussed. The effect of incorporating various types of biologically sourced materials in the synthetic rubbers are also elaborated in detail.
  16. Distribution and health risk assessment of trace metals in freshwater tilapia from three different aquaculture sites in Jelebu Region (Malaysia)
    Low KH, Zain SM, Abas MR, Md Salleh K, Teo YY
    Food Chem, 2015 Jun 15;177:390-6.
    PMID: 25660902 DOI: 10.1016/j.foodchem.2015.01.059
    The trace metal concentrations in edible muscle of red tilapia (Oreochromis spp.) sampled from a former tin mining pool, concrete tank and earthen pond in Jelebu were analysed with microwave assisted digestion-inductively coupled plasma-mass spectrometry. Results were compared with established legal limits and the daily ingestion exposures simulated using the Monte Carlo algorithm for potential health risks. Among the metals investigated, arsenic was found to be the key contaminant, which may have arisen from the use of formulated feeding pellets. Although the risks of toxicity associated with consumption of red tilapia from the sites investigated were found to be within the tolerable range, the preliminary probabilistic estimation of As cancer risk shows that the 95th percentile risk level surpassed the benchmark level of 10(-5). In general, the probabilistic health risks associated with ingestion of red tilapia can be ranked as follows: former tin mining pool > concrete tank > earthen pond.
  17. Fulltext Evaluating the possibility of detecting evidence of positive selection across Asia with sparse genotype data from the HUGO Pan-Asian SNP Consortium
    Liu X, Saw WY, Ali M, Ong RT, Teo YY
    BMC Genomics, 2014;15:332.
    PMID: 24885517 DOI: 10.1186/1471-2164-15-332
    The HUGO Pan-Asian SNP Consortium (PASNP) has generated a genetic resource of almost 55,000 autosomal single nucleotide polymorphisms (SNPs) across more than 1,800 individuals from 73 urban and indigenous populations in Asia. This has offered valuable insights into the correlation between the genetic ancestry of these populations with major linguistic systems and geography. Here, we attempt to understand whether adaptation to local climate, diet and environment partly explains the genetic variation present in these populations by investigating the genomic signatures of positive selection.
  18. Translational aspects of genetic factors in the prediction of drug response variability: a case study of warfarin pharmacogenomics in a multi-ethnic cohort from Asia
    Chan SL, Suo C, Lee SC, Goh BC, Chia KS, Teo YY
    Pharmacogenomics J, 2012 Aug;12(4):312-8.
    PMID: 21383771 DOI: 10.1038/tpj.2011.7
    Genetic markers displaying highly significant statistical associations with complex phenotypes may not necessarily possess sufficient clinical validity to be useful. Understanding the contribution of these markers beyond readily available clinical biomarkers is particularly important in pharmacogenetics. We demonstrate the utility of genetic testing using the example of warfarin in a multi-ethnic setting comprising of three Asian populations that are broadly representative of the genetic diversity for half of the population in the world, especially as distinct interethnic differences in warfarin dose requirements have been previously established. We confirmed the roles of three well-established loci (CYP2C9, VKORC1 and CYP4F2) in explaining warfarin dosage variation in the three Asian populations. In addition, we assessed the relationship between ethnicity and the genotypes of these loci, observing strong correlations at VKORC1 and CYP4F2. Subsequently, we established the additional utility of these genetic factors in predicting warfarin dose beyond ethnicity and clinical biomarkers through performing a series of systematic cross-validation analyses of the relative predictive accuracies of various fixed-dose regimen, clinical and genetic models. Through a pharmacogenetics model for warfarin, we show the importance of genetic testing beyond readily available clinical biomarkers in predicting dose requirements, confirming the role of genetic profiling in personalized medicine.
  19. Fulltext Three Level Thoracolumbar Spondylectomy for Recurrent Giant Cell Tumour of the Spine: A Case Report
    Faruk NA, Mohd-Amin MZ, Awang-Ojep DN, Teo YY, Wong CC
    Malays Orthop J, 2018 Nov;12(3):50-52.
    PMID: 30555648 MyJurnal DOI: 10.5704/MOJ.1811.013
    Giant cell tumour (GCT) is a benign tumour but can be locally aggressive and with the potential to metastasise especially to the lungs. Successful treatments have been reported for long bone lesions; however, optimal surgical and medical treatment for spinal and sacral lesions are not well established. In treating spinal GCTs, the aim is to achieve complete tumour excision, restore spinal stability and decompress the neural tissues. The ideal surgical procedure is an en bloc spondylectomy or vertebrectomy, where all tumour cells are removed as recurrence is closely related to the extent of initial surgical excision. However, such a surgery has a high complication rate, such as dura tear and massive blood loss. We report a patient with a missed pathological fracture of T12 treated initially with a posterior subtraction osteotomy, who had recurrence three years after the index surgery and subsequently underwent a three level vertebrectomy and posterior spinal fusion.
  20. Ethnic differences in pain perception and patient-controlled analgesia usage for postoperative pain
    Tan EC, Lim Y, Teo YY, Goh R, Law HY, Sia AT
    J Pain, 2008 Sep;9(9):849-55.
    PMID: 18550441 DOI: 10.1016/j.jpain.2008.04.004
    There are reports suggesting that sensitivity to and tolerance of both clinical and experimental pain differ among ethnic groups. We examined self-rated pain score and morphine usage in 1034 women who underwent elective lower cesarian section (LSCS) for their deliveries. Data on pain scores and amount of total morphine use according to patient-controlled analgesia were collected every 4 hours. Overall, lowest pain scores were recorded 12 hours after surgery and highest at 24 hours. Morphine consumption was highest within the first 4 hours and lowest between 12 and 16 hours. There were statistically significant ethnic group differences in pain scores (P = 1.7 x 10(-7)) and morphine usage (P = 2.8 x 10(-15)) between ethnic groups, with Indians having the highest mean pain score and using the highest amount of morphine. The ethnic differences in pain score and morphine self-administration persisted after controlling for age, body mass index, and duration of operation.
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