Displaying publications 1 - 20 of 93 in total

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  1. Fulltext Exploring the potential of a highly compressible microcrystalline cellulose as novel tabletting excipient in the compaction of extended-release coated pellets containing an extremely water-soluble model drug
    Zeeshan F, Peh KK, Tan YT
    AAPS PharmSciTech, 2009;10(3):850-7.
    PMID: 19554454 DOI: 10.1208/s12249-009-9278-2
    Compaction of controlled-release coated pellets into tablets is challenging because of the fusion of pellets and the rupturing of coated film. The difficulty in compaction intensifies with the use of extremely water-soluble drugs. Therefore, the present study was conducted to prepare and compact pellets containing pseudoephedrine hydrochloride as an extremely water-soluble model drug. The pellets were produced using an extrusion-spheronization technique. The drug-loaded pellets were coated to extend the drug release up to 12-h employing various polymers, and then they were compressed into tablets using microcrystalline cellulose Ceolus KG-801 as a novel tabletting excipient. The in vitro drug release studies of coated pellets and tablets were undertaken using the USP basket method in dissolution test apparatus I. The amount of drug released was analyzed at a wavelength of 215 nm. The combined coatings of hydroxypropyl methylcellulose and Kollicoat SR-30D yielded 12-h extended-release pellets with drug release independent of pH of dissolution medium following zero-order kinetics. The drug release from the tablets prepared using inert Celous KG-801 granules as tabletting excipient was found faster than that of coated pellets. However, a modification in drug release rate occurred with the incorporation of inert Ceolus KG-801 pellets. The drug dissolution profile from tablets containing 40% w/w each of coated pellets and inert granules along with 20% w/w inert pellets was found to be closely similar to that of coated pellets. Furthermore, the friability, tensile strength, and disintegration time of the tablets were within the USP specifications.
    Matched MeSH terms: Microspheres
  2. Synthesis and characterization of carbon cryogel microspheres from lignin-furfural mixtures for biodiesel production
    Zainol MM, Amin NA, Asmadi M
    Bioresour Technol, 2015 Aug;190:44-50.
    PMID: 25919936 DOI: 10.1016/j.biortech.2015.04.067
    The aim of this work was to study the potential of biofuel and biomass processing industry side-products as acid catalyst. The synthesis of carbon cryogel from lignin-furfural mixture, prepared via sol-gel polycondensation at 90°C for 0.5h, has been investigated for biodiesel production. The effect of lignin to furfural (L/F) ratios, lignin to water (L/W) ratios and acid concentration on carbon cryogel synthesis was studied. The carbon cryogels were characterized and tested for oleic acid conversion. The thermally stable amorphous spherical carbon cryogel has a large total surface area with high acidity. Experimental results revealed the optimum FAME yield and oleic acid conversion of 91.3wt.% and 98.1wt.%, respectively were attained at 65°C for 5h with 5wt.% catalyst loading and 20:1 methanol to oleic acid molar ratio. Therefore, carbon cryogel is highly potential for heterogeneous esterification of free fatty acid to biodiesel.
    Matched MeSH terms: Microspheres
  3. Fulltext Microfluidic systems for dielectrophoretic separation of fluorescent particles
    Yunus, N.A.M., Jaafar, H., Halin, I.A., Green, N.G.
    ASM Science Journal, 2014;8(1):29-35.
    MyJurnal
    This paper presents a suitable and unique system for observing dielectrophoretic particle separation in a microfluidic device. Details presented on the experimental setup used will enable real time examination, monitoring and analysis of carboxylate-modified latex sphere particles in a colloidal mixture. Observations of the particles were made possible through an optical setup that illuminates the particles that went through the microelectrode array in the microchannel that was controlled by two analog signal generators. Through the setup, it was easily observed that the latex sphere particles move at a flow rate of 0.2 μl/s without colliding or overlapping on each other and successfully separated in two bands left and right. The new separation of one finest particles size for finest purification with respect to frequency was also observed, obtained and analysed.
    Matched MeSH terms: Microspheres
  4. Continuous separation of colloidal particles using dielectrophoresis
    Yunus NA, Nili H, Green NG
    Electrophoresis, 2013 Apr;34(7):969-78.
    PMID: 23436439 DOI: 10.1002/elps.201200466
    Dielectrophoresis is the movement of particles in nonuniform electric fields and has been of interest for application to manipulation and separation at and below the microscale. This technique has the advantages of being noninvasive, nondestructive, and noncontact, with the movement of particle achieved by means of electric fields generated by miniaturized electrodes and microfluidic systems. Although the majority of applications have been above the microscale, there is increasing interest in application to colloidal particles around a micron and smaller. This paper begins with a review of colloidal and nanoscale dielectrophoresis with specific attention paid to separation applications. An innovative design of integrated microelectrode array and its application to flow-through, continuous separation of colloidal particles is then presented. The details of the angled chevron microelectrode array and the test microfluidic system are then discussed. The variation in device operation with applied signal voltage is presented and discussed in terms of separation efficiency, demonstrating 99.9% separation of a mixture of colloidal latex spheres.
    Matched MeSH terms: Microspheres*
  5. Fulltext A Highly Sensitive Impedimetric DNA Biosensor Based on Hollow Silica Microspheres for Label-Free Determination of E. coli
    Yuhana Ariffin E, Heng LY, Tan LL, Abd Karim NH, Hasbullah SA
    Sensors (Basel), 2020 Feb 26;20(5).
    PMID: 32111092 DOI: 10.3390/s20051279
    A novel label-free electrochemical DNA biosensor was constructed for the determination of Escherichia coli bacteria in environmental water samples. The aminated DNA probe was immobilized onto hollow silica microspheres (HSMs) functionalized with 3-aminopropyltriethoxysilane and deposited onto a screen-printed electrode (SPE) carbon paste with supported gold nanoparticles (AuNPs). The biosensor was optimized for higher specificity and sensitivity. The label-free E. coli DNA biosensor exhibited a dynamic linear response range of 1 × 10-10 µM to 1 × 10-5 µM (R2 = 0.982), with a limit of detection at 1.95 × 10-15 µM, without a redox mediator. The sensitivity of the developed DNA biosensor was comparable to the non-complementary and single-base mismatched DNA. The DNA biosensor demonstrated a stable response up to 21 days of storage at 4 ℃ and pH 7. The DNA biosensor response was regenerable over three successive regeneration and rehybridization cycles.
    Matched MeSH terms: Microspheres*
  6. Fulltext Supramolecular Nested Microbeads as Building Blocks for Macroscopic Self-Healing Scaffolds
    Yu Z, Liu J, Tan CSY, Scherman OA, Abell C
    Angew Chem Int Ed Engl, 2018 03 12;57(12):3079-3083.
    PMID: 29377541 DOI: 10.1002/anie.201711522
    The ability to construct self-healing scaffolds that are injectable and capable of forming a designed morphology offers the possibility to engineer sustainable materials. Herein, we introduce supramolecular nested microbeads that can be used as building blocks to construct macroscopic self-healing scaffolds. The core-shell microbeads remain in an "inert" state owing to the isolation of a pair of complementary polymers in a form that can be stored as an aqueous suspension. An annealing process after injection effectively induces the re-construction of the microbead units, leading to supramolecular gelation in a preconfigured shape. The resulting macroscopic scaffold is dynamically stable, displaying self-recovery in a self-healing electronic conductor. This strategy of using the supramolecular assembled nested microbeads as building blocks represents an alternative to injectable hydrogel systems, and shows promise in the field of structural biomaterials and flexible electronics.
    Matched MeSH terms: Microspheres
  7. Anisotropic lanthanide-based nano-clusters for imaging applications
    Yang X, Wang S, King TL, Kerr CJ, Blanchet C, Svergun D, et al.
    Faraday Discuss, 2016 Jul 18.
    PMID: 27430046
    We have developed a new class of lanthanide nano-clusters that self-assemble using flexible Schiff base ligands. Cd-Ln and Ni-Ln clusters, [Ln8Cd24(L(1))12(OAc)39Cl7(OH)2] (Ln = Nd, Eu), [Eu8Cd24(L(1))12(OAc)44], [Ln8Cd24(L(2))12(OAc)44] (Ln = Nd, Yb, Sm) and [Nd2Ni4(L(3))2(acac)6(NO3)2(OH)2], were constructed using different types of flexible Schiff base ligands. These molecular nano-clusters exhibit anisotropic architectures that differ considerably depending upon the presence of Cd (nano-drum) or Ni (square-like nano-cluster). Structural characterization of the self-assembled particles has been undertaken using crystallography, transmission electron microscopy and small-angle X-ray scattering. Comparison of the metric dimensions of the nano-drums shows a consistency of size using these techniques, suggesting that these molecules may share similar structural features in both solid and solution states. Photophysical properties were studied by excitation of the ligand-centered absorption bands in the solid state and in solution, and using confocal microscopy of microspheres loaded with the compounds. The emissive properties of these compounds vary depending upon the combination of lanthanide and Cd or Ni present in these clusters. The results provide new insights into the construction of novel high-nuclearity nano-clusters and offer a promising foundation for the development of new functional nanomaterials.
    Matched MeSH terms: Microspheres
  8. Fulltext Preparation and In Vitro Evaluation of Neutron-Activated, Theranostic Samarium-153-Labeled Microspheres for Transarterial Radioembolization of Hepatocellular Carcinoma and Liver Metastasis
    Wong YH, Tan HY, Kasbollah A, Abdullah BJJ, Yeong CH
    Pharmaceutics, 2019 Nov 12;11(11).
    PMID: 31718079 DOI: 10.3390/pharmaceutics11110596
    INTRODUCTION: Transarterial radioembolization (TARE) has been proven as an effective treatment for unresectable liver tumor. In this study, neutron activated, 153Sm-labeled microspheres were developed as an alternative to 90Y-labeled microspheres for hepatic radioembolization. 153Sm has a theranostic advantage as it emits both therapeutic beta and diagnostic gamma radiations simultaneously, in comparison to the pure beta emitter, 90Y.

    METHODS: Negatively charged acrylic microspheres were labeled with 152Sm ions through electrostatic interactions. In another formulation, the Sm-labeled microsphere was treated with sodium carbonate solution to form the insoluble 152Sm carbonate (152SmC) salt within the porous structures of the microspheres. Both formulations were neutron-activated in a research reactor. Physicochemical characterization, gamma spectrometry, and radiolabel stability tests were carried out to study the performance and stability of the microspheres.

    RESULTS: The Sm- and SmC-labeled microspheres remained spherical and smooth, with a mean size of 35 µm before and after neutron activation. Fourier transform infrared (FTIR) spectroscopy indicated that the functional groups of the microspheres remained unaffected after neutron activation. The 153Sm- and 153SmC-labeled microspheres achieved activity of 2.53 ± 0.08 and 2.40 ± 0.13 GBq·g-1, respectively, immediate after 6 h neutron activation in the neutron flux of 2.0 × 1012 n·cm-2·s-1. Energy-dispersive X-ray (EDX) and gamma spectrometry showed that no elemental and radioactive impurities were present in the microspheres after neutron activation. The retention efficiency of 153Sm in the 153SmC-labeled microspheres was excellent (~99% in distilled water and saline; ~97% in human blood plasma), which was higher than the 153Sm-labeled microspheres (~95% and ~85%, respectively).

    CONCLUSION: 153SmC-labeled microspheres have demonstrated excellent properties for potential application as theranostic agents for hepatic radioembolization.

    Matched MeSH terms: Microspheres
  9. Fulltext Neutron-activated biodegradable samarium-153 acetylacetonate-poly-L-lactic acid microspheres for intraarterial radioembolization of hepatic tumors
    Wong YH, Tan HY, Kasbollah A, Abdullah BJJ, Acharya RU, Yeong CH
    World J Exp Med, 2020 Mar 30;10(2):10-25.
    PMID: 32266125 DOI: 10.5493/wjem.v10.i2.10
    BACKGROUND: Liver cancer is the 6th most common cancer in the world and the 4th most common death from cancer worldwide. Hepatic radioembolization is a minimally invasive treatment involving intraarterial administration of radioembolic microspheres.

    AIM: To develop a neutron-activated, biodegradable and theranostics samarium-153 acetylacetonate (153SmAcAc)-poly-L-lactic acid (PLLA) microsphere for intraarterial radioembolization of hepatic tumors.

    METHODS: Microspheres with different concentrations of 152SmAcAc (i.e., 100%, 150%, 175% and 200% w/w) were prepared by solvent evaporation method. The microspheres were then activated using a nuclear reactor in a neutron flux of 2 × 1012 n/cm2/s1, converting 152Sm to Samarium-153 (153Sm) via152Sm (n, γ) 153Sm reaction. The SmAcAc-PLLA microspheres before and after neutron activation were characterized using scanning electron microscope, energy dispersive X-ray spectroscopy, particle size analysis, Fourier transform infrared spectroscopy, thermo-gravimetric analysis and gamma spectroscopy. The in-vitro radiolabeling efficiency was also tested in both 0.9% sodium chloride solution and human blood plasma over a duration of 550 h.

    RESULTS: The SmAcAc-PLLA microspheres with different SmAcAc contents remained spherical before and after neutron activation. The mean diameter of the microspheres was about 35 µm. Specific activity achieved for 153SmAcAc-PLLA microspheres with 100%, 150%, 175% and 200% (w/w) SmAcAc after 3 h neutron activation were 1.7 ± 0.05, 2.5 ± 0.05, 2.7 ± 0.07, and 2.8 ± 0.09 GBq/g, respectively. The activity of per microspheres were determined as 48.36 ± 1.33, 74.10 ± 1.65, 97.87 ± 2.48, and 109.83 ± 3.71 Bq for 153SmAcAc-PLLA microspheres with 100%, 150%, 175% and 200% (w/w) SmAcAc. The energy dispersive X-ray and gamma spectrometry showed that no elemental and radioactive impurities present in the microspheres after neutron activation. Retention efficiency of 153Sm in the SmAcAc-PLLA microspheres was excellent (approximately 99%) in both 0.9% sodium chloride solution and human blood plasma over a duration of 550 h.

    CONCLUSION: The 153SmAcAc-PLLA microsphere is potentially useful for hepatic radioembolization due to their biodegradability, favorable physicochemical characteristics and excellent radiolabeling efficiency. The synthesis of the formulation does not involve ionizing radiation and hence reducing the complication and cost of production.

    Matched MeSH terms: Microspheres
  10. Aging and microwave effects on alginate/chitosan matrices
    Wong TW, Chan LW, Kho SB, Heng PW
    J Control Release, 2005 Jun 2;104(3):461-75.
    PMID: 15911046
    The influence of microwave irradiation on the drug release properties of freshly prepared and aged alginate, alginate-chitosan and chitosan beads was investigated. The beads were prepared by extrusion method with sulphathiazole as a model drug. The dried beads were subjected to microwave irradiation at 80 W for 10 min, 20 min or three consecutive cycles of 10 and 20 min, respectively. The profiles of drug dissolution, drug content, drug stability, drug polymorphism, drug-polymer interaction, polymer crosslinkage and complexation were determined by dissolution testing, drug content assay, differential scanning calorimetry and Fourier transform infra-red spectroscopy. The chemical stability of drug embedded in beads was unaffected by microwave conditions and length of storage time. The release property of drug was mainly governed by the extent of polymer interaction in beads. The aged alginate beads required intermittent cycles of microwave irradiation to induce drug release retarding effect in contrast to their freshly prepared samples. Unlike the alginate beads, the level of polymer interaction was higher in aged alginate-chitosan beads than the corresponding fresh beads. The drug release retarding property of aged alginate-chitosan beads could be significantly enhanced through subjecting the beads to microwave irradiation for 10 min. No further change in drug release from these beads was observed beyond 30 min of microwave irradiation. Unlike beads containing alginate, the rate and extent of drug released from the aged chitosan beads were higher upon treatment by microwave in spite of the higher degree of polymer interaction shown by the latter on prolonged storage. The observation suggested that the response of polymer matrix to microwave irradiation in induction of drug release retarding property was largely affected by the molecular arrangement of the polymer chains.
    Matched MeSH terms: Microspheres
  11. In vitro and in vivo evaluation of drug-eluting microspheres designed for transarterial chemoembolization therapy
    Wang Y, Molin DG, Sevrin C, Grandfils C, van den Akker NM, Gagliardi M, et al.
    Int J Pharm, 2016 Apr 30;503(1-2):150-62.
    PMID: 26965198 DOI: 10.1016/j.ijpharm.2016.03.002
    Poly(d,l-lactic acid) biodegradable microspheres, loaded with the drugs cisplatin and/or sorafenib tosylate, were prepared, characterized and studied. Degradation of the microspheres, and release of cisplatin and/or sorafenib tosylate from them, were investigated in detail. Incubation of the drug-carrying microspheres in phosphate buffered saline (pH=7.4) revealed slow degradation. Nevertheless, significant release of cisplatin and sorafenib tosylate from microspheres loaded with both drugs was apparent in vitro; this can be attributed to their porous structure. Supernatants from microspheres loaded with both drugs showed strong toxic effects on cells (i.e. endothelial cells, fibroblast cells and Renca tumor cells) and potent anti-angiogenic effect in the matrigel endothelial tube assay. In vivo anti-tumor effects of the microspheres were also observed, in a Renca tumor mouse model. The poly(d,l-lactic acid) microspheres containing both cisplatin and sorafenib tosylate revealed highest therapeutic efficacy, probably demonstrating that combined local administration of cisplatin and sorafenib tosylate synergistically inhibits tumor growth in situ. In conclusion, this study demonstrates the applicability of biodegradable poly(d,l-lactic acid) microspheres loaded with cisplatin and sorafenib tosylate for local drug delivery as well as the potential of these microspheres for future use in transarterial chemoembolization.
    Matched MeSH terms: Microspheres
  12. Equilibrium and kinetics studies of adsorption of copper (II) on chitosan and chitosan/PVA beads
    Wan Ngah WS, Kamari A, Koay YJ
    Int J Biol Macromol, 2004 Jun;34(3):155-61.
    PMID: 15225987
    The adsorption of Cu(II) ions from aqueous solution by chitosan and chitosan/PVA beads was studied in a batch adsorption system. Chitosan solution was blended with poly(vinyl alcohol) (PVA) in order to obtain sorbents that are insoluble in aqueous acidic and basic solution. The adsorption capacities and rates of Cu(II) ions onto chitosan and chitosan/PVA beads were evaluated. The Langmuir, Freundlich and BET adsorption models were applied to describe the isotherms and isotherm constants. Adsorption isothermal data could be well interpreted by the Langmuir model. The kinetic experimental data properly correlated with the second-order kinetic model, which indicates that the chemical sorption is the rate-limiting step. The Cu(II) ions can be removed from the chitosan and chitosan/PVA beads rapidly by treatment with an aqueous EDTA solution. Results also showed that chitosan and chitosan/PVA beads are favourable adsorbers.
    Matched MeSH terms: Microspheres
  13. Comparison of alginate and pectin based beads for production of poultry probiotic cells
    Voo WP, Ravindra P, Tey BT, Chan ES
    J Biosci Bioeng, 2011 Mar;111(3):294-9.
    PMID: 21216192 DOI: 10.1016/j.jbiosc.2010.11.010
    A comparative study on the stability and potential of alginate and pectin based beads for production of poultry probiotic cells using MRS medium in repeated batch fermentation was conducted. The bead cores, made of three types of materials, i.e., ca-alginate, ca-pectinate and ca-alginate/pectinate, were compared. The effect of single and double layer coatings using chitosan and core material, respectively, on the bead stability and cell production were also studied. The pectin based beads were found to be more stable than that of the alginate beads and their stability was further improved by coating with chitosan. The cell concentration in pectin based beads was comparable to that in the alginate beads. On the other hand, pectin based beads gave significantly lower cell concentration in the growth medium for the initial fermentation cycles when compared to the alginate beads. In conclusion, pectin was found to be potential encapsulation material for probiotic cell production owing to its stability and favourable microenvironment for cell growth.
    Matched MeSH terms: Microspheres*
  14. Microfluidic production of bioactive fibrin micro-beads embedded in crosslinked collagen used as an injectable bulking agent for urinary incontinence treatment
    Vardar E, Larsson HM, Allazetta S, Engelhardt EM, Pinnagoda K, Vythilingam G, et al.
    Acta Biomater, 2018 02;67:156-166.
    PMID: 29197579 DOI: 10.1016/j.actbio.2017.11.034
    Endoscopic injection of bulking agents has been widely used to treat urinary incontinence, often due to urethral sphincter complex insufficiency. The aim of the study was to develop a novel injectable bioactive collagen-fibrin bulking agent restoring long-term continence by functional muscle tissue regeneration. Fibrin micro-beads were engineered using a droplet microfluidic system. They had an average diameter of 140 μm and recombinant fibrin-binding insulin-like growth factor-1 (α2PI1-8-MMP-IGF-1) was covalently conjugated to the beads. A plasmin fibrin degradation assay showed that 72.5% of the initial amount of α2PI1-8-MMP-IGF-1 loaded into the micro-beads was retained within the fibrin micro-beads. In vitro, the growth factor modified fibrin micro-beads enhanced cell attachment and the migration of human urinary tract smooth muscle cells, however, no change of the cellular metabolic activity was seen. These bioactive micro-beads were mixed with genipin-crosslinked homogenized collagen, acting as a carrier. The collagen concentration, the degree of crosslinking, and the mechanical behavior of this bioactive collagen-fibrin injectable were comparable to reference samples. This novel injectable showed no burst release of the growth factor, had a positive effect on cell behavior and may therefore induce smooth muscle regeneration in vivo, necessary for the functional treatment of stress and other urinary incontinences.

    STATEMENT OF SIGNIFICANCE: Urinary incontinence is involuntary urine leakage, resulting from a deficient function of the sphincter muscle complex. Yet there is no functional cure for this devastating condition using current treatment options. Applied physical and surgical therapies have limited success. In this study, a novel bioactive injectable bulking agent, triggering new muscle regeneration at the injection site, has been evaluated. This injectable consists of cross-linked collagen and fibrin micro-beads, functionalized with bound insulin-like growth factor-1 (α2PI1-8-MMP-IGF-1). These bioactive fibrin micro-beads induced human smooth muscle cell migration in vitro. Thus, this injectable bulking agent is apt to be a good candidate for regeneration of urethral sphincter muscle, ensuring a long-lasting treatment for urinary incontinence.

    Matched MeSH terms: Microspheres*
  15. Fulltext Kinematics of mouthbrooding in Oreochromis niloticus (Cichlidae)
    Van Wassenbergh S, Joris I, Desclée M, Liew HJ, De Boeck G, Adriaens D, et al.
    J Exp Biol, 2016 05 15;219(Pt 10):1535-41.
    PMID: 27207955 DOI: 10.1242/jeb.131631
    Many species from several different families of fishes perform mouthbrooding, where one of the sexes protects and ventilates the eggs inside the mouth cavity. This ventilation behaviour differs from gill ventilation outside the brooding period, as the normal, small-amplitude suction-pump respiration cycles are alternated with actions including near-simultaneous closed-mouth protrusions and high-amplitude depressions of the hyoid. The latter is called churning, referring to its hypothetical function in moving around and repositioning the eggs by a presumed hydrodynamic effect of the marked shifts in volume along the mouth cavity. We tested the hypothesis that churning causes the eggs located posteriorly in the mouth cavity to move anteriorly away from the gill entrance. This would prevent or clear accumulations of brood at the branchial basket, which would otherwise hinder breathing by the parent. Dual-view videos of female Nile tilapias (Oreochromis niloticus) during mouthbrooding showed that churning involves a posterior-to-anterior wave of expansion and compression of the head volume. Flow visualisation with polyethylene microspheres revealed a significant inflow of water entering the gill slits at the zone above the pectoral fin base, followed by a predominantly ventral outflow passing the ventrolaterally flapping branchiostegal membranes. X-ray videos indicated that particularly the brood located close to the gills is moved anteriorly during churning. These data suggest that, in addition to mixing of the brood to aid its oxygenation, an important function of the anterior flow through the gills and buccal cavity during churning is to prevent clogging of the eggs near the gills.
    Matched MeSH terms: Microspheres
  16. Fabrication of alginate microspheres for drug delivery: A review
    Uyen NTT, Hamid ZAA, Tram NXT, Ahmad N
    Int J Biol Macromol, 2020 Jun 15;153:1035-1046.
    PMID: 31794824 DOI: 10.1016/j.ijbiomac.2019.10.233
    Alginate microspheres (AMs) have received much attention as a novel drug delivery system owing to various advantages of alginate such as inexpensiveness, nontoxicity, biocompatibility and biodegradability. The well-designed fabrication method is essential to achieve desired AMs suitable for specific drug delivery system. Reports on AMs preparation techniques have increased rapidly in the last decade. A number of synthesis parameters have been investigated for the improvement of physical, chemical and biological properties of AMs. Hence, this review summarizes the work to date on the fabrication techniques of AMs for drug delivery system, including spray-drying, extrusion and emulsification/gelation technique. Besides, the influence of various factors such as alginate concentration, oil phase, surfactant, cross-linker concentrations, cross-linking time, stirring speed, model drug and drug content on the morphologies, properties and encapsulation efficiency (EE) of AMs via extrusion and emulsification/gelation technique are summarized. Before embarking on the development of any drug delivery system, a thorough understanding of drug release mechanism and factors that impact the drug release profile are essential, which are also covered in this review.
    Matched MeSH terms: Microspheres
  17. Fulltext An electrochemical DNA microbiosensor based on succinimide-modified acrylic microspheres
    Ulianas A, Heng LY, Abu Hanifah S, Ling TL
    Sensors (Basel), 2012;12(5):5445-60.
    PMID: 22778594 DOI: 10.3390/s120505445
    An electrochemical microbiosensor for DNA has been fabricated based on new acrylic microspheres modified with reactive N-acryloxysuccinimide (NAS) functional groups. Hydrophobic poly(n-butylacrylate-N-acryloxysuccinimide) microspheres were synthesized in an emulsion form with a simple one-step photopolymerization technique. Aminated DNA probe was attached to the succinimde functional group of the acrylic microspheres via covalent bonding. The hybridization of the immobilized DNA probe with the complementary DNA was studied by differential pulse voltametry using anthraquninone-2-sulfonic acid monohydrate sodium salt (AQMS) as the electroactive hybridization label. The influences of many factors such as duration of DNA probe immobilization and hybridization, pH, type of ions, buffer concentrations, ionic strength, operational temperature and non-complementary DNA on the biosensor performance were evaluated. Under optimized conditions, the DNA microbiosensor demonstrated a linear response range to target DNA over a wide concentration range of 1.0 × 10(-16) and 1.0 × 10(-8) M with a lower limit of detection (LOD) of 9.46 × 10(-17) M (R(2) = 0.97). This DNA microbiosensor showed good reproducibility with 2.84% RSD (relative standard deviation) (n = 3). Application of the NAS-modified acrylic microspheres in the construction of DNA microbiosensor had improved the overall analytical performance of the resultant DNA microbiosensor when compared with other reported DNA biosensors using other nano-materials for membranes and microspheres as DNA immobilization matrices.
    Matched MeSH terms: Microspheres
  18. Fulltext A biosensor for urea from succinimide-modified acrylic microspheres based on reflectance transduction
    Ulianas A, Heng LY, Ahmad M
    Sensors (Basel), 2011;11(9):8323-38.
    PMID: 22164078 DOI: 10.3390/s110908323
    New acrylic microspheres were synthesised by photopolymerisation where the succinimide functional group was incorporated during the microsphere preparation. An optical biosensor for urea based on reflectance transduction with a large linear response range to urea was successfully developed using this material. The biosensor utilized succinimide-modified acrylic microspheres immobilized with a Nile blue chromoionophore (ETH 5294) for optical detection and urease enzyme was immobilized on the surface of the microspheres via the succinimide groups. No leaching of the enzyme or chromoionophore was observed. Hydrolysis of the urea by urease changes the pH and leads to a color change of the immobilized chromoionophore. When the color change was monitored by reflectance spectrophotometry, the linear response range of the biosensor to urea was from 0.01 to 1,000 mM (R2 = 0.97) with a limit of detection of 9.97 μM. The biosensor response showed good reproducibility (relative standard deviation = 1.43%, n = 5) with no interference by major cations such as Na+, K+, NH4+ and Mg2+. The use of reflectance as a transduction method led to a large linear response range that is better than that of many urea biosensors based on other optical transduction methods.
    Matched MeSH terms: Microspheres*
  19. Aluminium and radiation cross-linked carboxymethyl sago pulp beads for colon targeted delivery
    Thenapakiam S, Kumar DG, Pushpamalar J, Saravanan M
    Carbohydr Polym, 2013 Apr 15;94(1):356-63.
    PMID: 23544549 DOI: 10.1016/j.carbpol.2013.01.004
    The carboxymethyl sago pulp (CMSP) with a degree of substitution of 0.4% was synthesized from sago waste. The CMSP beads with an average diameter of 3.1-4.8 mm were formed by aluminium chloride gelation as well as further cross-linked by irradiation. To evaluate colon targeted release, a model drug, 5-aminosalicylic acid (5-ASA) was encapsulated in CMSP beads. Fourier-transform infrared spectroscopy and X-ray diffraction studies indicated intact and amorphous nature of entrapped drug. A pH dependent drug release was observed, and about 90% of the drug was released only at pH 7.4 over 9 h. Irradiated beads were resisted the drug release in an acidic environment at a higher extent than non-irradiated beads. The drug release from 6% (w/w) of 5-ASA loaded bead followed zero order, whereas, 15 and 22% loaded beads followed first order. The release exponent n value suggests non-fickian transport of 5-ASA from the beads.
    Matched MeSH terms: Microspheres
  20. Mixed polymer coating for modified release from coated spheroids
    Tan YT, Heng PW, Wan LS
    Pharm Dev Technol, 1999;4(4):561-70.
    PMID: 10578511
    Modified-release drug spheroids coated with an aqueous mixture of high-viscosity hydroxypropylmethylcellulose (HPMC) and sodium carboxymethylcellulose (NaCMC) were formulated. The preparation of core drug spheroids and the coating procedures were performed using the rotary processor and a bottom-spray fluidized bed, respectively. Dissolution studies indicated that incorporation of suitable additives, such as poly(vinylpyrrolidone) (PVP) and poly(ethylene glycol) 400 (PEG) improved the flexibility and integrity of the coat layer by retarding the drug release. An increase in coating levels applied generally retarded the release rate of the drug. However, the ratio of HPMC to NaCMC in the mixed, plasticized polymeric coat played a more dominant role in determining the dissolution T50% values. The optimal ratio of HPMC to NaCMC for prolonged drug release was found to be 3:1, whereas an increase in the amount of NaCMC in the mixed polymer coat only increased drug release. The synergistic viscosity effect of HPMC and NaCMC in retarding drug release rate was greater in distilled water than in dissolution media of pH 1 and 7.2. Cross-sectional view of the scanning electron micrograph showed that all of the coated spheroids exhibited a well-fused, continuous, and distinct layer of coating film. The drug release kinetics followed a biexponential first-order kinetic model.
    Matched MeSH terms: Microspheres*
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