Effect of Unsaturation on the Stability of C₁₈ Polyunsaturated Fatty Acids Vesicles Suspension in Aqueous Solution

Teo, Yin Yin,Misran, Misni,Low, Kah Hin,Zain, Sharifuddin Md. Korean Chemical Society 2011 Bulletin of the Korean Chemical Society Vol.32 No.1

Degree of unsaturation in fatty acid molecules plays an important role in the formation of vesicles. Vesicle formation from C18 fatty acids with different amount of double bonds such as oleic acid, linoleic acid and linolenic acid with the incorporation of 1,2-dipalmitoyl-sn-glycerol-3-phosphoethanolamine-N-[methoxy(polyethylene glycol)-2000] (DPPE-PEG2000) have been examined by TEM. Critical vesicular concentrations (CVC) of the vesicle suspension are determined by turbidity and surface tension methods. The CVC of fatty acids increases when the amount of unsaturation in the alkyl chain increases. On the other hand, stability of vesicle suspension has been examined by using particle size and zeta potential at $30^{\circ}C$. There was a dramatic decrease in particle size measurement from mono-unsaturation to tri-unsaturation which could be due to the effect of fluidity in the membrane bilayer caused by different degree of unsaturation. The values of zeta potential for vesicles that were formed without the incorporation of DPPE-PEG2000 were in the range of -70 mV to -100 mV. It has been observed that the incorporation of DPPEPEG2000 to the vesicle reduces the magnitude of zeta potential. However, this phenomenon does not obviously seen in fatty acid vesicles formed by linoleate-linoleic acid and linolenate-linolenic acid. We therefore conclude that the addition of DPPE-PEG2000 does not effectively improve the stability of the linoleate-linoleic acid and linolenatelinolenic acid vesicle at pH 9.0 after the evaluation of their particle size and zeta potential over a period of 30 days. Although the vesicles formed were not stable for more than 10 days, they have displayed the potential in encapsulating the active ingredients such as vitamin E and calcein. The results show that the loading efficiencies of vitamin E are of encouraging value.

Effect of Unsaturation on the Stability of C_18 Polyunsaturated Fatty Acids Vesicles Suspension in Aqueous Solution

Yin Yin Teo,Misni Misran,Kah Hin Low,Sharifuddin Md. Zain 대한화학회 2011 Bulletin of the Korean Chemical Society Vol.32 No.1

Degree of unsaturation in fatty acid molecules plays an important role in the formation of vesicles. Vesicle formation from C18 fatty acids with different amount of double bonds such as oleic acid, linoleic acid and linolenic acid with the incorporation of 1,2-dipalmitoyl-sn-glycerol-3-phosphoethanolamine-N-[methoxy(polyethylene glycol)-2000](DPPE-PEG2000) have been examined by TEM. Critical vesicular concentrations (CVC) of the vesicle suspension are determined by turbidity and surface tension methods. The CVC of fatty acids increases when the amount of unsaturation in the alkyl chain increases. On the other hand, stability of vesicle suspension has been examined by using particle size and zeta potential at 30 ^oC. There was a dramatic decrease in particle size measurement from mono-unsaturation to tri-unsaturation which could be due to the effect of fluidity in the membrane bilayer caused by different degree of unsaturation. The values of zeta potential for vesicles that were formed without the incorporation of DPPE-PEG2000 were in the range of ‒70 mV to ‒100 mV. It has been observed that the incorporation of DPPEPEG2000to the vesicle reduces the magnitude of zeta potential. However, this phenomenon does not obviously seen in fatty acid vesicles formed by linoleate-linoleic acid and linolenate-linolenic acid. We therefore conclude that the addition of DPPE-PEG2000 does not effectively improve the stability of the linoleate-linoleic acid and linolenatelinolenic acid vesicle at pH 9.0 after the evaluation of their particle size and zeta potential over a period of 30 days. Although the vesicles formed were not stable for more than 10 days, they have displayed the potential in encapsulating the active ingredients such as vitamin E and calcein. The results show that the loading efficiencies of vitamin E are of encouraging value.

APMP.QM-K111-propane in nitrogen

Lin, Tsai-Yin,Liu, Hsin-Wang,Huang, Chiung-Kun,Kang, Namgoo,Bae, Hyun Kil,Woo, Jin Chun,Bi, Zhe,Zhou, Zeyi,Sinweeruthai, Ratirat,Wongjuk, Arnuttachai,Li, Hou,Keat, Teo Beng,Hui, Liu,Wu, Thomas,Ann, Ch BUREAU INTERNATIONAL DES POIDS ET MESURES 2018 METROLOGIA -BERLIN- Vol.55 No.1

Arabic Gum Grafted PEGDMA Hydrogels: Synthesis, Physico-Chemical Characterization and In-vitro Release of Hydrophobic Drug

Sani Mamman Ibrahim,Teo Yin Yin,Misni Misran 한국고분자학회 2020 Macromolecular Research Vol.28 No.13

Hydrogel development using natural and synthetic polymers for biomedical applications have shown promising properties for drug delivery due to virtuous stimuli response and improvement in mechanical strength. Biomaterial hydrogel was synthesized using combination of arabic gum (AG), a natural polymer and polyethylene glycol dimethacrylate (PEGDMA), a synthetic polymer. The synthesis process follows chemical cross linking by free radical polymerization. Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM) and differential scanning calorimetry (DSC) were used to characterize the hydrogels. Product yield, gel content and gelation time depends solely on the variable reacting concentrations and the mechanical properties of hydrogel depends on its compositions. Swelling studies reveal high swelling ratio in buffer solution pH 1.2 compare to buffer solution pH 7.4, and deionized water at pH 6.7. Swelling ratio raises with increase in PEGDMA concentration, but the presences of salt/ions solutions decreases the swelling ratio significantly and it depends on the charge of the ions. The kinetics of the swelling follows a second order non-linear rate equation. The rate of degradation revealed significant degradation in acidic medium and insignificant degradation was observed in basic medium. The encapsulation efficiency of quercetin introduced directly in the hydrogels during synthesis was found in the range of 85-94%. The release profile indicates the dependence of arabic gum grafted PEGDMA hydrogels on pH and compositions. The characteristic properties exhibited by the formulated hydrogels suggest the suitability of them to be applied as drug carriers.

Applying the OMOP Common Data Model to Facilitate Benefit-Risk Assessments of Medicinal Products Using Real-World Data from Singapore and South Korea

Hui Xing Tan,Desmond Chun Hwee Teo,이동윤,김청수,Jing Wei Neo,Cynthia Sung,Haroun Chahed,Pei San Ang,Doreen Su Yin Tan,박래웅,Sreemanee Raaj Dorajoo 대한의료정보학회 2022 Healthcare Informatics Research Vol.28 No.2

Objectives: The aim of this study was to characterize the benefits of converting Electronic Medical Records (EMRs) to acommon data model (CDM) and to assess the potential of CDM-converted data to rapidly generate insights for benefitriskassessments in post-market regulatory evaluation and decisions. Methods: EMRs from January 2013 to December 2016were mapped onto the Observational Medical Outcomes Partnership-CDM (OMOP-CDM) schema. Vocabulary mappingswere applied to convert source data values into OMOP-CDM-endorsed terminologies. Existing analytic codes used in a priorOMOP-CDM drug utilization study were modified to conduct an illustrative analysis of oral anticoagulants used for atrialfibrillation in Singapore and South Korea, resembling a typical benefit-risk assessment. A novel visualization is proposed torepresent the comparative effectiveness, safety and utilization of the drugs. Results: Over 90% of records were mapped ontothe OMOP-CDM. The CDM data structures and analytic code templates simplified the querying of data for the analysis. Intotal, 2,419 patients from Singapore and South Korea fulfilled the study criteria, the majority of whom were warfarin users. After 3 months of follow-up, differences in cumulative incidence of bleeding and thromboembolic events were observable viathe proposed visualization, surfacing insights as to the agent of preference in a given clinical setting, which may meaningfullyinform regulatory decision-making. Conclusions: While the structure of the OMOP-CDM and its accessory tools facilitatereal-world data analysis, extending them to fulfil regulatory analytic purposes in the post-market setting, such as benefit-riskassessments, may require layering on additional analytic tools and visualization techniques.

Risk for ACPA-positive rheumatoid arthritis is driven by shared HLA amino acid polymorphisms in Asian and European populations

Okada, Yukinori,Kim, Kwangwoo,Han, Buhm,Pillai, Nisha E.,Ong, Rick T.-H.,Saw, Woei-Yuh,Luo, Ma,Jiang, Lei,Yin, Jian,Bang, So-Young,Lee, Hye-Soon,Brown, Matthew A.,Bae, Sang-Cheol,Xu, Huji,Teo, Yik-Yin Oxford University Press 2014 Human Molecular Genetics Vol.23 No.25

<P>Previous studies have emphasized ethnically heterogeneous human leukocyte antigen (HLA) classical allele associations to rheumatoid arthritis (RA) risk. We fine-mapped RA risk alleles within the major histocompatibility complex (MHC) in 2782 seropositive RA cases and 4315 controls of Asian descent. We applied imputation to determine genotypes for eight class I and II HLA genes to Asian populations for the first time using a newly constructed pan-Asian reference panel. First, we empirically measured high imputation accuracy in Asian samples. Then we observed the most significant association in HLA-DRβ1 at amino acid position 13, located outside the classical shared epitope (<I>P</I><SUB>omnibus</SUB> = 6.9 × 10<SUP>−135</SUP>). The individual residues at position 13 have relative effects that are consistent with published effects in European populations (His > Phe > Arg > Tyr ≅ Gly > Ser)—but the observed effects in Asians are generally smaller. Applying stepwise conditional analysis, we identified additional independent associations at positions 57 (conditional <I>P</I><SUB>omnibus</SUB> = 2.2 × 10<SUP>−33</SUP>) and 74 (conditional <I>P</I><SUB>omnibus</SUB> = 1.1 × 10<SUP>−8</SUP>). Outside of HLA-DRβ1, we observed independent effects for amino acid polymorphisms within HLA-B (Asp9, conditional <I>P</I> = 3.8 × 10<SUP>−6</SUP>) and HLA-DPβ1 (Phe9, conditional <I>P</I> = 3.0 × 10<SUP>−5</SUP>) concordant with European populations. Our trans-ethnic HLA fine-mapping study reveals that (i) a common set of amino acid residues confer shared effects in European and Asian populations and (ii) these same effects can explain ethnically heterogeneous classical allelic associations (e.g. <I>HLA-DRB1*09:01</I>) due to allele frequency differences between populations. Our study illustrates the value of high-resolution imputation for fine-mapping causal variants in the MHC.</P>