Displaying publications 1481 - 1500 of 10377 in total

Abstract:
Sort:
  1. Biologically active indole and bisindole alkaloids from Tabernaemontana divaricata
    Kam TS, Pang HS, Lim TM
    Org Biomol Chem, 2003 Apr 21;1(8):1292-7.
    PMID: 12929658
    The ethanol extract of the leaves of Tabernaemontana divaricata (double flower variety) provided a total of 23 alkaloids, including the new aspidosperma alkaloids, taberhanine, voafinine, N-methylvoafinine, voafinidine, voalenine and the new bisindole alkaloid, conophyllinine in addition to the previously known, biologically active bisindole, conophylline and its congener, conofoline. The structures of the new alkaloids were established by spectroscopic methods. The preparation and characterization of the corresponding quinones of the biologically active bisindoles are also described in relation to a structure-activity study of these compounds with respect to their action in stimulating insulin expression.
    Matched MeSH terms: Indoles/chemistry*; Indole Alkaloids/chemistry*; Tabernaemontana/chemistry*
  2. Stephanotic acid, a novel cyclic pentapeptide from the stem of Stephanotis floribunda
    Yoshikawa K, Tao S, Arihara S
    J Nat Prod, 2000 Apr;63(4):540-2.
    PMID: 10785436
    The stem of Stephanotis floribunda afforded a new cyclic pentapeptide stephanotic acid (1), possessing a novel 6-(leucin-3'-yl) tryptophan skeleton. The structure of 1 was assigned on the basis of extensive NMR experiments and a chemical reaction and shown to be closely related to the bicyclic octapeptide moroidin (3), a toxin from Laportea moroides.
    Matched MeSH terms: Peptides, Cyclic/chemistry*; Plants, Medicinal/chemistry*; Plant Stems/chemistry
  3. Effects of buffer properties on cyclodextrin glucanotransferase reactions and cyclodextrin production from raw sago (Cycas revoluta) starch
    Kamaruddin K, Illias RM, Aziz SA, Said M, Hassan O
    Biotechnol Appl Biochem, 2005 Apr;41(Pt 2):117-25.
    PMID: 15202937
    Results from the present study have shown that the ionic species of buffers, pH values and reaction temperature can affect the enzyme unit activities and product specificity of Toruzyme (Novo Nordisk A/S Bagsvaerd, Denmark) CGTase (cyclodextrin glucanotransferase). Applying a similar reaction environment (acetate buffer, pH 6.0; temperature, 60 degrees C), the CGTase was found to be capable of producing pre dominantly beta-cyclodextrin from either raw or gelatinized sago (Cycas revoluta) starch. Changing the buffer from acetate to phosphate reduced the yield of beta-cyclodextrin from 2.48 to 1.42 mg/ml and also affected the product specificity, where production of both alpha- and beta-cyclodextrins were more pronounced. The decrease in the production of cyclodextrins in phosphate buffer was significant at both pH 6.0 and 7.0. However, changing the buffer to Tris/HCl (pH 7.0) showed a significant increase in beta-cyclodextrin production. Increasing the ionic strength of sodium acetate and Tris/HCl buffers at pH 6.0 and 7.0 to equivalent ionic strength of phosphate buffers showed no significant effects on cyclodextrin production. Higher yield of cyclodextrins at pH 7.0 when Tris/HCl was used might be due to the binding of chloride ions at the calcium-binding sites of the CGTase, resulting in the shift of the optimum pH close to physiological environment, leading to an increase in the activities and specificity.
    Matched MeSH terms: Glucosyltransferases/chemistry; Starch/chemistry; Cycas/chemistry*
  4. Fulltext Tailoring the surface area and the acid-base properties of ZrO2 for biodiesel production from Nannochloropsis sp
    Rahman NJA, Ramli A, Jumbri K, Uemura Y
    Sci Rep, 2019 11 07;9(1):16223.
    PMID: 31700157 DOI: 10.1038/s41598-019-52771-9
    Bifunctional heterogeneous catalysts have a great potential to overcome the shortcomings of homogeneous and enzymatic catalysts and simplify the biodiesel production processes using low-grade, high-free-fatty-acid feedstock. In this study, we developed ZrO2-based bifunctional heterogeneous catalysts for simultaneous esterification and transesterification of microalgae to biodiesel. To avoid the disadvantage of the low surface area of ZrO2, the catalysts were prepared via a surfactant-assisted sol-gel method, followed by hydrothermal treatments. The response surface methodology central composite design was employed to investigate various factors, like the surfactant/Zr molar ratio, pH, aging time, and temperature on the ZrO2 surface area. The data were statistically analyzed to predict the optimal combination of factors, and further experiments were conducted for verification. Bi2O3 was supported on ZrO2 via the incipient wetness impregnation method. The catalysts were characterized by a variety of techniques, which disclosed that the surfactant-assisted ZrO2 nanoparticles possess higher surface area, better acid-base properties, and well-formed pore structures than bare ZrO2. The highest yield of fatty acid methyl esters (73.21%) was achieved using Bi2O3/ZrO2(CTAB), and the catalytic activity of the developed catalysts was linearly correlated with the total densities of the acidic and basic sites. The mechanism of the simultaneous reactions was also discussed.
    Matched MeSH terms: Bismuth/chemistry; Zirconium/chemistry*; Nanoparticles/chemistry
  5. Polymer Conjugated Gold Nanoparticles in Biomedical Applications
    Anniebell S, Gopinath SCB
    Curr Med Chem, 2018;25(12):1433-1445.
    PMID: 28093984 DOI: 10.2174/0929867324666170116123633
    BACKGROUND: Research interest on the properties of polymer conjugated gold nanoparticle (GNP) in biomedicine is rapidly rising because of the extensive evidences for their unique properties. In the field of biomedicine, GNPs have been widely used because of their inertness and low levels of cytotoxicity. Therefore, when exposed to cells, they are less prone to exert damaging effects. GNPs are capable of being functionalized as desired and are ideal as they do not encourage undesired side reactions that might counter react with the intention of the functionalization. Biofouling is an occurrence that takes place at cellular and biological molecular level, binds non-specifically on the detection surface and forms a wrong output. This undesired incidence can be avoided by conjugating the surface of biomolecules with polymers. Densely packed repeating chains of polymers such as polyethylene glycol are capable of decreasing non-specific reactions. Applications of polymer conjugated GNPs in the field of biomedicine are as biosensors, delivery and therapeutic agents.

    CONCLUSION: Therefore, the properties and applications of polymer conjugated GNPs are studied widely as overviewed here.

    Matched MeSH terms: Gold/chemistry*; Polyethylene Glycols/chemistry*; Metal Nanoparticles/chemistry*
  6. Influence of chloride ions on the reduction of mercury species in the presence of dissolved organic matter
    Lee S, Roh Y, Kim KW
    Environ Geochem Health, 2019 Feb;41(1):71-79.
    PMID: 29761243 DOI: 10.1007/s10653-018-0121-0
    Mercuric species, Hg(II), interacts strongly with dissolved organic matter (DOM) through the oxidation, reduction, and complexation that affect the fate, bioavailability, and cycling of mercury, Hg, in aquatic environments. Despite its importance, the reactions between Hg(II) and DOM have rarely been studied in the presence of different concentrations of chloride ions (Cl-) under anoxic conditions. Here, we report that the extent of Hg(II) reduction in the presence of the reduced DOM decreases with increasing Cl- concentrations. The rate constants of Hg(II) reduction ranged from 0.14 to 1.73 h-1 in the presence of Cl- and were lower than the rate constant (2.41 h-1) in the absence of Cl-. Using a thermodynamic model, we showed that stable Hg(II)-chloride complexes were formed in the presence of Cl-. We further examined that H(0) was oxidized to Hg(II) in the presence of the reduced DOM and Cl- under anoxic conditions, indicating that Hg(II) reduction is inhibited by the Hg(0) oxidation. Therefore, the Hg(II) reduction by the reduced DOM can be offset due to the Hg(II)-chloride complexation and Hg(0) oxidation in chloride-rich environments. These processes can significantly influence the speciation of Hg and have an important implication for the behavior of Hg under environmentally relevant concentrations.
    Matched MeSH terms: Chlorides/chemistry*; Mercury/chemistry*; Water Pollutants, Chemical/chemistry*
  7. Fabrication and characterization of porous scaffolds for bone replacements using gum tragacanth
    Anita Lett J, Sundareswari M, Ravichandran K, Latha B, Sagadevan S
    Mater Sci Eng C Mater Biol Appl, 2019 Mar;96:487-495.
    PMID: 30606558 DOI: 10.1016/j.msec.2018.11.082
    The practice of bone implants is the standard procedure for the treatment of skeletal fissures, or to substitute and re-establish lost bone. A perfect scaffold ought to be made of biomaterials that duplicate the structure and properties of natural bone. However, the production of living tissue constructs that are architecturally, functionally and mechanically comparable to natural bone is the major challenge in the treatment and regeneration of bone tissue in orthopaedics and in dentistry. In this work, we have employed a polymeric replication method to fabricate hydroxyapatite (HAP) scaffolds using gum tragacanth (GT) as a natural binder. GT is a natural gum collected from the dried sap of several species of Middle Eastern legumes of the genus Astragalus, possessing antibacterial and wound healing properties. The synthesized porous HAP scaffolds were analyzed structurally and characterized for their phase purity and mechanical properties. The biocompatibility of the porous HAP scaffold was confirmed by seeding the scaffold with Vero cells, and its bioactivity assessed by immersing the scaffold in simulated body fluid (SBF). Our characterization data showed that the biocompatible porous HAP scaffolds were composed of highly interconnecting pores with compressive strength ranging from 0.036 MPa to 2.954 MPa, comparable to that of spongy bone. These can be prepared in a controlled manner by using an appropriate binder concentration and sintering temperature. These HAP scaffolds have properties consistent with normal bone and should be further developed for potential application in bone implants.
    Matched MeSH terms: Tragacanth/chemistry*; Durapatite/chemistry*; Tissue Scaffolds/chemistry*
  8. Heteroatom-doped magnetic hydrochar to remove post-transition and transition metals from water: Synthesis, characterization, and adsorption studies
    Khan MA, Alqadami AA, Otero M, Siddiqui MR, Alothman ZA, Alsohaimi I, et al.
    Chemosphere, 2019 Mar;218:1089-1099.
    PMID: 30609488 DOI: 10.1016/j.chemosphere.2018.11.210
    Efforts to improve water quality have led to the development of green and sustainable water treatment approaches. Herein, nitrogen-doped magnetized hydrochar (mSBHC-N) was synthesized, characterized, and used for the removal of post-transition and transition heavy metals, viz. Pb2+ and Cd2+ from aqueous environment. mSBHC-N was found to be mesoporous (BET surface area - 62.5 m2/g) and paramagnetic (saturation magnetization - 44 emu/g). Both, FT-IR (with peaks at 577, 1065, 1609 and 3440 cm-1 corresponding to Fe - O stretching vibrations, C - N stretching, N - H in-plane deformation and stretching) and XPS analyses (with peaks at 284.4, 400, 530, 710 eV due to C 1s, N 1s, O 1s, and Fe 2p) confirmed the presence of oxygen and nitrogen containing functional groups on mSBHC-N. The adsorption of Pb2+ and Cd2+ was governed by oxygen and nitrogen functionalities through electrostatic and co-ordination forces. 75-80% of Pb2+ and Cd2+ adsorption at Co: 25 mg/L, either from deionized water or humic acid solution was accomplished within 15 min. The data was fitted to pseudo-second-order kinetic and Langmuir isotherm models, with maximum monolayer adsorption capacities being 323 and 357 mg/g for Cd2+and Pb2+ at 318 K, respectively. Maximum Cd2+ (82.6%) and Pb2+ (78.7%) were eluted with 0.01 M HCl, simultaneously allowing minimum iron leaching (2.73%) from mSBHC-N. In conclusion, the study may provide a novel, economical, and clean route to utilize agro-waste, such as sugarcane bagasse (SB), for aquatic environment remediation.
    Matched MeSH terms: Water/chemistry*; Water Pollutants, Chemical/chemistry*; Metals, Heavy/chemistry*
  9. Fulltext Artificial Neural Network Approach for Modelling of Mercury Ions Removal from Water Using Functionalized CNTs with Deep Eutectic Solvent
    Fiyadh SS, AlOmar MK, Binti Jaafar WZ, AlSaadi MA, Fayaed SS, Binti Koting S, et al.
    Int J Mol Sci, 2019 Aug 28;20(17).
    PMID: 31466219 DOI: 10.3390/ijms20174206
    Multi-walled carbon nanotubes (CNTs) functionalized with a deep eutectic solvent (DES) were utilized to remove mercury ions from water. An artificial neural network (ANN) technique was used for modelling the functionalized CNTs adsorption capacity. The amount of adsorbent dosage, contact time, mercury ions concentration and pH were varied, and the effect of parameters on the functionalized CNT adsorption capacity is observed. The (NARX) network, (FFNN) network and layer recurrent (LR) neural network were used. The model performance was compared using different indicators, including the root mean square error (RMSE), relative root mean square error (RRMSE), mean absolute percentage error (MAPE), mean square error (MSE), correlation coefficient (R2) and relative error (RE). Three kinetic models were applied to the experimental and predicted data; the pseudo second-order model was the best at describing the data. The maximum RE, R2 and MSE were 9.79%, 0.9701 and 1.15 × 10-3, respectively, for the NARX model; 15.02%, 0.9304 and 2.2 × 10-3 for the LR model; and 16.4%, 0.9313 and 2.27 × 10-3 for the FFNN model. The NARX model accurately predicted the adsorption capacity with better performance than the FFNN and LR models.
    Matched MeSH terms: Mercury/chemistry*; Solvents/chemistry; Nanotubes, Carbon/chemistry*
  10. Characterization of raw and alkali treated new natural cellulosic fibers from Tridax procumbens
    Vijay R, Lenin Singaravelu D, Vinod A, Sanjay MR, Siengchin S, Jawaid M, et al.
    Int J Biol Macromol, 2019 Mar 15;125:99-108.
    PMID: 30528990 DOI: 10.1016/j.ijbiomac.2018.12.056
    The aim of this study is to investigate natural cellulosic fibers extracted from Tridax procumbens plants. The obtained fibers were alkali treated for their effective usage as reinforcement in composites. The physical, chemical, crystallinity, thermal, wettability and surface characteristics were analyzed for raw, and alkali treated Tridax procumbens fibers (TPFs). The test results conclude that there was an increase in cellulose content with a reduction in hemicellulose, lignin, and wax upon alkali treatment. This enhanced the thermal stability, tensile strength, crystallinity, and surface roughness characteristics. The contact angle was also lesser for treated TPFs which prove its better wettability with the liquid phase. The Weibull distribution analysis was adopted for the analysis of the fiber diameter and tensile properties. Thus the considerable improvement in the properties of alkali treated TPFs would be worth for developing high-performance polymer composites.
    Matched MeSH terms: Alkalies/chemistry*; Cellulose/chemistry*; Asteraceae/chemistry*
  11. Investigation into mechanical, absorption and swelling behaviour of hemp/sisal fibre reinforced bioepoxy hybrid composites: Effects of stacking sequences
    Thiagamani SMK, Krishnasamy S, Muthukumar C, Tengsuthiwat J, Nagarajan R, Siengchin S, et al.
    Int J Biol Macromol, 2019 Nov 01;140:637-646.
    PMID: 31437507 DOI: 10.1016/j.ijbiomac.2019.08.166
    This work focuses on the fabrication of hybrid bio-composites using green epoxy as the matrix material, hemp (H) and sisal (S) fibre mats as the reinforcements. The hybrid composite with sisal/hemp fibres were fabricated by cost effective hand lay-up technique, followed by hot press with different stacking sequences. Static properties of the composites such as tensile, compressive, inter-laminar shear strengths (ILSS) and hardness were examined. The physical properties such as density, void content, water absorption and thickness swelling were also analyzed. The experimental results indicate that hybrid composites exhibited minor variation in tensile strength when the stacking sequence was altered. The hybrid composite with the intercalated arrangement (HSHS) exhibited the highest tensile modulus when compared with the other hybrid counterparts. Hybrid composites (SHHS and HSSH) offered 40% higher values of compressive strength than the other layering arrangements. HHHH sample exhibited the highest ILSS value of 4.08 MPa. Typical failure characteristics of the short beam test such as inter-laminar shear cracks in the transverse direction, micro-buckling and fibre rupture were also observed.
    Matched MeSH terms: Cannabis/chemistry*; Epoxy Resins/chemistry*; Water/chemistry
  12. Fulltext Structural, Impedance, and EDLC Characteristics of Proton Conducting Chitosan-Based Polymer Blend Electrolytes with High Electrochemical Stability
    Aziz SB, Abdulwahid RT, Hamsan MH, Brza MA, Abdullah RM, Kadir MFZ, et al.
    Molecules, 2019 Sep 27;24(19).
    PMID: 31569650 DOI: 10.3390/molecules24193508
    In this report, a facile solution casting technique was used to fabricate polymer blend electrolytes of chitosan (CS):poly (ethylene oxide) (PEO):NH4SCN with high electrochemical stability (2.43V). Fourier transform infrared (FTIR) spectroscopy was used to investigate the polymer electrolyte formation. For the electrochemical property analysis, cyclic voltammetry (CV), linear sweep voltammetry (LSV), and electrochemical impedance spectroscopy (EIS) techniques were carried out. Referring to the FTIR spectra, a complex formation between the added salt and CS:PEO was deduced by considering the decreasing and shifting of FTIR bands intensity in terms of functional groups. The CS:PEO:NH4SCN electrolyte was found to be electrochemically stable as the applied voltage linearly swept up to 2.43V. The cyclic voltammogram has presented a wide potential window without showing any sign of redox peaks on the electrode surface. The proved mechanisms of charge storage in these fabricated systems were found to be double layer charging. The EIS analysis showed the existence of bulk resistance, wherein the semicircle diameter decreased with increasing salt concentration. The calculated maximum DC conductivity value was observed to be 2.11 × 10-4 S/cm for CS:PEO incorporated with 40 wt% of NH4SCN salt. The charged species in CS:PEO:NH4SCN electrolytes were considered to be predominantly ionic in nature. This was verified from transference number analysis (TNM), in which ion and electron transference numbers were found to be tion = 0.954 and tel = 0.045, respectively. The results obtained for both ion transference number and DC conductivity implied the possibility of fabricating electrolytes for electrochemical double layer capacitor (EDLC) device application. The specific capacitance of the fabricated EDLC was obtained from the area under the curve of the CV plot.
    Matched MeSH terms: Electrochemistry*; Electrolytes/chemistry*; Polymers/chemistry*; Chitosan/chemistry*
  13. Essential oil composition of Alseodaphne perakensis (Gamble) Kosterm from Malaysia
    Anuar MZA, Salleh WMNHW, Khamis S, Nafiah MA, Mat Said Z
    Nat Prod Res, 2021 Feb;35(3):508-511.
    PMID: 31266357 DOI: 10.1080/14786419.2019.1636245
    The chemical composition of the essential oil from the leaves of Alseodaphne perakensis (Gamble) Kosterm (Lauraceae) growing in Perak, Malaysia was investigated for the first time. The essential oil was obtained by hydrodistillation and fully characterized by gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). A total of 37 components (90.9 ± 2.5%) were successfully identified in the essential oil which were characterized by high proportions of bicyclogermacrene (15.8 ± 0.5%), δ-cadinene (11.7 ± 0.2%), γ-cadinene (6.3 ± 0.4%), and aromadendrene (5.6 ± 0.5%).
    Matched MeSH terms: Oils, Volatile/chemistry*; Plant Leaves/chemistry; Lauraceae/chemistry*
  14. Evaluation of the thermomechanical properties and biodegradation of brown rice starch-based chitosan biodegradable composite films
    Hasan M, Gopakumar DA, Olaiya NG, Zarlaida F, Alfian A, Aprinasari C, et al.
    Int J Biol Macromol, 2020 Aug 01;156:896-905.
    PMID: 32289410 DOI: 10.1016/j.ijbiomac.2020.04.039
    Biodegradable films composed of starch and chitosan plasticized by palm oil were fabricated via a solvent casting technique. In this study, the influence of the ratio of brown rice starch and chitosan on the mechanical, thermal, antimicrobial, and morphological properties of the films was investigated. Antimicrobial films with a smooth surface and a compact structure of brown rice starch were obtained. The results showed that a higher proportion of chitosan in the polymer blends resulted in a substantial enhancement in the tensile strength (TS) and thermal stability of the film. The TS values for BRS100, BRS30CH70, BRS50CH50, BRS70CH30, and CH100 were 3.7, 15.2, 10.2, 9.3, and 8.8 MPa, respectively, and the elongation at break (EB) values of the BRS100, BRS30CH70, BRS50CH50, BRS70CH30, and CH100 samples were 39.5%, 34.7%, 7.3%, 11.5%, and 6.9%, respectively. The addition of chitosan to the brown rice starch samples resulted in a reduced water uptake of the film. The film with a balanced ratio of brown rice starch and chitosan exhibited excellent water resistance, with its water absorption being the lowest among all of the studied compositions.
    Matched MeSH terms: Oryza/chemistry*; Starch/chemistry*; Chitosan/chemistry*
  15. Cellulose nanofibril-based aerogel derived from sago pith waste and its application on methylene blue removal
    Beh JH, Lim TH, Lew JH, Lai JC
    Int J Biol Macromol, 2020 Oct 01;160:836-845.
    PMID: 32485260 DOI: 10.1016/j.ijbiomac.2020.05.227
    Sago pith cellulose nanofibril (SPCNF) aerogel derived from sago pith waste (SPW) was successfully produced through three consecutive steps, namely dewaxing and delignification, ultra-sonication and homogenization and freeze drying. The aerogel was characterized using field emission scanning electron microscopy (FE-SEM), Fourier-transform infra-red spectroscopy (FTIR), X-ray diffraction (XRD) and thermogravimetric analysis (TGA). Results of the analyses collectively showed that lignin & hemicellulose were absent in the SPCNF aerogel product which has a high crystallinity index of 88%. The diameters of individual nanofibril constituents of the SPCNF were between 15 and 30 nm and aspect ratios >1000 were observed. The SPCNF aerogel, with a density measured at 2.1 mg/cm3, was efficient in methylene blue (MB) removal with a maximum MB adsorption of 222.2 mg/g at 20 °C. The adsorption of MB onto the SPCNF aerogel was rapid and found to follow a pseudo-second-order kinetic model with the adsorption isotherm being in congruence with the Langmuir model. The SPCNF aerogel exhibited outstanding MB removal efficacies with 5 mg and 20 mg of SPCNF capable of removing over 90% and almost 99% MB, respectively. The optimized pH value and temperature for MB adsorption were determined as pH 7 and 20 °C.
    Matched MeSH terms: Cellulose/chemistry*; Methylene Blue/chemistry*; Water Pollutants, Chemical/chemistry
  16. Fulltext Microwave radiation-induced grafting of 2-methacryloyloxyethyl trimethyl ammonium chloride onto lentil extract (LE-g-DMC) as an emerging high-performance plant-based grafted coagulant
    Chua SC, Chong FK, Ul Mustafa MR, Mohamed Kutty SR, Sujarwo W, Abdul Malek M, et al.
    Sci Rep, 2020 03 03;10(1):3959.
    PMID: 32127558 DOI: 10.1038/s41598-020-60119-x
    The importance of graft copolymerization in the field of polymer science is analogous to the importance of alloying in the field of metals. This is attribute to the ability of the grafting method to regulate the properties of polymer 'tailor-made' according to specific needs. This paper described a novel plant-based coagulant, LE-g-DMC that synthesized through grafting of 2-methacryloyloxyethyl trimethyl ammonium chloride (DMC) onto the backbone of the lentil extract. The grafting process was optimized through the response surface methodology (RSM) using three-level Box-Behnken Design (BBD). Under optimum conditions, a promising grafting percentage of 120% was achieved. Besides, characterization study including SEM, zeta potential, TGA, FTIR and EDX were used to confirm the grafting of the DMC monomer chain onto the backbone of lentil extract. The grafted coagulant, LE-g-DMC outperformed lentil extract and alum in turbidity reduction and effective across a wide range of pH from pH 4 to pH 10. Besides, the use of LE-g-DMC as coagulant produced flocs with excellent settling ability (5.09 mL/g) and produced the least amount of sludge. Therefore, from an application and economic point of views, LE-g-DMC was superior to native lentil extract coagulant and commercial chemical coagulant, alum.
    Matched MeSH terms: Plant Extracts/chemistry*; Lens Plant/chemistry*; Trimethyl Ammonium Compounds/chemistry*
  17. Microfluidic formation of highly monodispersed multiple cored droplets using needle-based system in parallel mode
    Lian Z, Chan Y, Luo Y, Yang X, Koh KS, Wang J, et al.
    Electrophoresis, 2020 06;41(10-11):891-901.
    PMID: 31998972 DOI: 10.1002/elps.201900403
    Scale-up in droplet microfluidics achieved by increasing the number of devices running in parallel or increasing the droplet makers in the same device can compromise the narrow droplet-size distribution, or requires high fabrication cost, when glass- or polymer-based microdevices are used. This paper reports a novel way using parallelization of needle-based microfluidic systems to form highly monodispersed droplets with enhanced production rates yet in cost-effective way, even when forming higher order emulsions with complex inner structure. Parallelization of multiple needle-based devices could be realized by applying commercially available two-way connecters and 3D-printed four-way connectors. The production rates of droplets could be enhanced around fourfold (over 660 droplets/min) to eightfold (over 1300 droplets/min) by two-way connecters and four-way connectors, respectively, for the production of the same kind of droplets than a single droplet maker (160 droplets/min). Additionally, parallelization of four-needle sets with each needle specification ranging from 34G to 20G allows for simultaneous generation of four groups of PDMS microdroplets with each group having distinct size yet high monodispersity (CV < 3%). Up to six cores can be encapsulated in double emulsion using two parallelly connected devices via tuning the capillary number of middle phase in a range of 1.31 × 10-4 to 4.64 × 10-4 . This study leads to enhanced production yields of droplets and enables the formation of groups of droplets simultaneously to meet extensive needs of biomedical and environmental applications, such as microcapsules with variable dosages for drug delivery or drug screening, or microcapsules with wide range of absorbent loadings for water treatment.
    Matched MeSH terms: Dimethylpolysiloxanes/chemistry; Emulsions/chemistry; Nylons/chemistry
  18. Fulltext Rheology Impact of Various Hydrophilic-Hydrophobic Balance (HLB) Index Non-Ionic Surfactants on Cyclopentane Hydrates
    Foo KS, Bavoh CB, Lal B, Mohd Shariff A
    Molecules, 2020 Aug 15;25(16).
    PMID: 32824121 DOI: 10.3390/molecules25163725
    In this study, series of non-ionic surfactants from Span and Tween are evaluated for their ability to affect the viscosity profile of cyclopentane hydrate slurry. The surfactants; Span 20, Span 40, Span 80, Tween 20, Tween 40 and Tween 80 were selected and tested to provide different hydrophilic-hydrophobic balance values and allow evaluation their solubility impact on hydrate formation and growth time. The study was performed by using a HAAKE ViscotesterTM 500 at 2 °C and a surfactant concentration ranging from 0.1 wt%-1 wt%. The solubility characteristic of the non-ionic surfactants changed the hydrate slurry in different ways with surfactants type and varying concentration. The rheological measurement suggested that oil-soluble Span surfactants was generally inhibitive to hydrate formation by extending the hydrate induction time. However, an opposite effect was observed for the Tween surfactants. On the other hand, both Span and Tween demonstrated promoting effect to accelerate hydrate growth time of cyclopentane hydrate formation. The average hydrate crystallization growth time of the blank sample was reduced by 86% and 68% by Tween and Span surfactants at 1 wt%, respectively. The findings in this study are useful to understand the rheological behavior of surfactants in hydrate slurry.
    Matched MeSH terms: Cyclopentanes/chemistry*; Surface-Active Agents/chemistry*; Water/chemistry*
  19. Adsorption and desorption of malachite green by using chitosan-deep eutectic solvents beads
    Sadiq AC, Rahim NY, Suah FBM
    Int J Biol Macromol, 2020 Dec 01;164:3965-3973.
    PMID: 32910963 DOI: 10.1016/j.ijbiomac.2020.09.029
    Chitosan-deep eutectic solvent (DES) beads were prepared from chitosan and DESs. The DESs used were choline chloride-urea (DES A) and choline chloride-glycerol (DES B). Both chitosan-DES beads were used to remove malachite green (MG) dye from an aqueous solution. The optimum pH for chitosan-DES A was recorded at pH 8.0 while optimum pH for chitosan-DES B was pH 9.0. The maximum adsorption capacity obtained for chitosan-DES A and chitosan-DES B were 6.54 mg/g and 8.64 mg/g, respectively. The optimum conditions for both chitosan-DES beads to remove MG were 0.08 g of adsorbent and 20 min of agitation time. Five kinetic models were applied to analyse the data and the results showed that the pseudo-second-order and intraparticle diffusion model fitted best with R2 > 0.999. For the adsorption capacity, results show that the Freundlich and Langmuir adsorption isotherms fitted well with chitosan-DES A and chitosan-DES B, respectively. The maximum adsorption capacities (qmax) obtained from chitosan-DES A and chitosan-DES B were 1.43 mg/g and 17.86 mg/g, respectively. Desorption indicated good performance in practical applications.
    Matched MeSH terms: Rosaniline Dyes/chemistry*; Solvents/chemistry*; Chitosan/chemistry*
  20. Fulltext Kinetic Investigation for in-situ Epoxidation of Unsaturated Fatty Acid Based on the Pseudo-steady-state-hypothesis (PSSH)
    Sawitri DR, Mulyono P, Rochmadi, Hisyam A, Budiman A
    J Oleo Sci, 2020 Oct 07;69(10):1297-1305.
    PMID: 32908088 DOI: 10.5650/jos.ess20034
    Oleic acid is a mono-unsaturated fatty acid that can be found abundantly in various vegetable oils and potentially attractive to be used as raw material for epoxide chemical. In-situ epoxidation of oleic acid was conducted in batch reactor using peroxy-formic at 30-60°C. Pseudo-steady-state-hypothesis (PSSH) was applied to develop the kinetic model. Heterogeneous liquid-liquid system was chosen and four models which emphasized on the ring opening agent (ROA) and reversibility of the epoxidation reaction were proposed. It has been suggested that reversible model is well suited to represent the experimental data. Activation energy obtained from Arrhenius equation is in the range of 40-195 kJ/mol.
    Matched MeSH terms: Fatty Acids, Unsaturated/chemistry*; Plant Oils/chemistry; Oleic Acid/chemistry
Related Terms
Filters
Contact Us

Please provide feedback to Administrator (afdal@afpm.org.my)

External Links