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microsphere
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, M.Sc. Thesis Sharif University of Technology ; Bahrampour, Alireza (Supervisor)
Abstract
By employing the image theory the Er doped microsphere coupled to an external cavity made by a metallic mirror is simulated by a bimicrosphere laser. The symmetric structure causes the formation of odd and even modes corresponding to the TE and TM mode of the microsphere and splitting the oscillation frequencies. The oscillation frequencies are dependent on the coupling coefficient. The coupling coefficient is obtained near the mirror-microsphere distance. The ohmic mirror loss also is determined as a function of the mirror distance. The total optical loss experienced in these resonators is exceptionally low. In fact,quality factor as high as 108 − 1011 have already been demonstrated for...
Fabrication and Characterization of PVA/PLA Composites
, M.Sc. Thesis Sharif University of Technology ; Frounchi, Masoud (Supervisor) ; Dadbin, Susan (Supervisor)
Abstract
Poly (vinyl alcohol) (PVA) hydrogel is a biocompatible material, which has been widely applied in drug delivery applications. Microspheres, nanospheres, and other types of particle-based drug delivery vehicles have proven capacity for long-term release. There is growing interest to overcoming the inherent pharmacological limitations of hydrogels by formulating particulate systems into the hydrogel matrix to form new delivery platforms. We here describe a simple composite system based on poly (vinyl alcohol) (PVA) hydrogels containing entrapped drug-loaded poly (lactic acid) (PLA) microspheres for controlled delivery over extended period of time. Gamma-Irradiation and freeze-thawing was...
Study and Synthesis of Biocompatible Polymer and Loading of Peptide Drug for using in Drug Delivery
, M.Sc. Thesis Sharif University of Technology ; Vosoughi, Manouchehr (Supervisor) ; Alemzadeh, Iran (Co-Advisor)
Abstract
With the rapid development of biotechnology, peptide and protein drugs are now playing an increasingly important role in therapeutics. Compared with chemical drugs, peptide and protein drugs have some limitations such as low stability and rapid deactivation. Biodegradable and biocompatible polymeric micro carriers have been shown to have a high potential for the delivery of peptides and proteins. Among these polymers, alginate has been widely investigated as a biomaterial. Alginates are natural polysaccharide polymers isolated from brown seaweed. Bovine serum albumin (BSA) loaded calcium alginate microspheres produced in this study by a modified w/o emulsification method. The influence of...
Magnetic Nanocomposites Based on Bio-Degradable Polylactic Acid
, M.Sc. Thesis Sharif University of Technology ; Frounchi, Masoud (Supervisor)
Abstract
In this work, magnetite (Fe3O4) nanoparticles with an average siz21.9nm
modified by oleic acid were prepared by the coprecipitation method, which can linked well with organic molecules because of the presence of C-O-C on their surface. Then magnetic poly(lactic acid) (PLA)/ poly(ethylene glycol) (PEG) microspheres were prepared by the single emulsion solvent evaporation technology. The incorporation of magnetit nanoparticles and dox into the PLA matrix was confirmed by FTIR. XRD and VSM confirmed the existence of MNPs in the microspheres which maintained superparamagnetic behavior with a saturation magnetization of 50.69 emu/g.Electron microscopy SEM showed that the magnetic microspheres...
modified by oleic acid were prepared by the coprecipitation method, which can linked well with organic molecules because of the presence of C-O-C on their surface. Then magnetic poly(lactic acid) (PLA)/ poly(ethylene glycol) (PEG) microspheres were prepared by the single emulsion solvent evaporation technology. The incorporation of magnetit nanoparticles and dox into the PLA matrix was confirmed by FTIR. XRD and VSM confirmed the existence of MNPs in the microspheres which maintained superparamagnetic behavior with a saturation magnetization of 50.69 emu/g.Electron microscopy SEM showed that the magnetic microspheres...
Design and Development of a Compound Skin Scaffold Capable of Drug Delivery for Skin Wound Healing
, M.Sc. Thesis Sharif University of Technology ; Shamloo, Amir (Supervisor) ; Firoozbakhsh, Keykhosrow (Supervisor)
Abstract
Skin tissue as the first protective barrier to the body is always exposed to the most injuries. The purpose of this project is to design an optimum skin scaffold capable of drug delivery for skin wounds healing. To this end, the skin scaffold has been considered as a combination of a hydrogel structure containing polymer microspheres carrying growth factor. Polyvinyl alcohol and sodium alginate polymers were utilized to make the hydrogel substrate. The hydrogel structure was optimized from the viewpoint of the percentage of gelation, water absorption, porosity, mechanical properties, biodegradability, biocompatibility and considering the volume percent of utilized polymers and the...
Fabrication of Biodegradable Micro/Nano Beads for the Pharmaceutical Applications
, M.Sc. Thesis Sharif University of Technology ; Shamloo, Amir (Supervisor) ; Asghari, Mohsen (Supervisor)
Abstract
Polymeric microspheres which can load biomolecules, proteins and growth factors play an important role in tissue engineering and drug delivery systems. The size of the microspheres and encapsulation efficiency exert a considerable impact on the usability of them. In this study double emulsion method is used for fabrication of microspheres. Effect of different parameters namely the speed of homogenization, time of homogenization, the amount of polymer in oil phase, the surfactant concentration in different phases on the size and surface morphology of the microspheres are investigated. Moreover, a release test for BSA loaded microspheres is conducted. Results indicate that by increasing the...
Design and Manufacture of a Scaffold with a Drug Delivery System for a Better Tissue Wound Healing Process
, M.Sc. Thesis Sharif University of Technology ; Shamloo, Amir (Supervisor) ; Aryanpour, Masoud (Supervisor)
Abstract
Articular cartilage is devoid of blood vessels, lymphatics, and nerves which gives it a very limited intrinsic healing and repair capabilities. Being under constant harsh biomechanical environment, makes maintaining the health of articular cartilage a vital principle in having healthy joints. Tissue engineering as a method for regeneration of damaged tissue have attracted a lot of attention. Articular cartilage engineered scaffolds act as a macro scale drug delivery system which in addition to having a good mechanical properties similar to that of cartilage tissue, have to provide a highly porous environment for cell migration and proliferation. The aim of this study is to fabricate a drug...
Magnetic nanoparticles-loaded PLA/PEG microspheres as drug carriers
, Article Journal of Biomedical Materials Research - Part A ; Vol. 103, issue. 5 , SEP , 2014 , p. 1893-1898 ; Shamshiri, S ; Sharif University of Technology
Abstract
Surface-modified magnetite (Fe3O4) nanoparticles with an average size of 22 nm were prepared. The nanoparticles had a saturation magnetization of 50.7 emu g-1. Then magnetite and drug-loaded microspheres of poly (lactic acid)/poly (ethylene glycol) were prepared at various compositions. The microspheres were spherical in shape and had smooth surface. The diameter size of the microspheres ranged between about 0.2 and 4 μm. Doxorubicin hydrochloride for cancer treatment was the drug that loaded into the microspheres. The prepared microspheres were characterized by FTIR, XRD, VSM, SEM and drug-release measurements. It was found that the drug cumulative release percentage was proportional to...
Controlled growth of hollow polyaniline structures: From nanotubes to microspheres
, Article Polymer (United Kingdom) ; Volume 54, Issue 21 , 2013 , Pages 5586-5594 ; 00323861 (ISSN) ; Ghorbani, M ; Shojaei, A ; Sharif University of Technology
2013
Abstract
Homogeneous and fairly monosized microspherical structures of polyaniline has been synthesized using a simple soft template method with β-naphthalene sulfonic acid (β-NSA) as both the surfactant and dopant, and ammonium persulfate (APS) as the oxidant at 2-5 C. The morphology of PANI-NSA was successfully controlled from nanotubes to microsphere, by changing the synthesis conditions (i.e. pH, the concentration of surfactant and monomer, and temperature). Some mechanistic aspects of the formation of nanotubes and hollow spheres have been discussed precisely based on SEM, TEM, DLS, FTIR and UV-visible results. Moreover, synthesis was performed under acidic environment to obtain further...
Axial potential mapping of optical tweezers for biopolymer stretching: The bead size matters
, Article Optics Letters ; Volume 38, Issue 5 , 2013 , Pages 685-687 ; 01469592 (ISSN) ; Reihani, S. N. S ; Sharif University of Technology
2013
Abstract
Optical tweezers (OT) are widely used for pico (and femto)-Newton range force measurements. The appropriate choice of the bead size is not well understood for biopolymer stretching applications of OT. We have shown, both by theory and experiment, that wrong choice of the bead size could cause errors as large as 295% in the measured force. We provide a simple map for correct choice of the bead size and the direction of pulling for such applications. There is a good agreement between our theoretical and experimental results
Freestanding light scattering hollow silver spheres prepared by a facile sacrificial templating method and their application in dye-sensitized solar cells
, Article Journal of Power Sources ; Volume 225 , 2013 , Pages 46-50 ; 03787753 (ISSN) ; Dadgostar, S ; Taghavinia, N ; Iraji Zad, A ; Sharif University of Technology
2013
Abstract
Hollow silver microspheres are synthesized in an easy and environmentally friendly process by a sacrificial templating method. Carbonaceous microspheres (CMSs) are used as hard templates, which have been synthesized previously by a hydrothermal carbonization process. Hollow silver spheres (HSSs) are synthesized by thermal removal of the core carbon component. The thickness of shell could be controlled by the concentration of precursors. Depending on the thickness, uniform or discontinuous shells are formed. The spheres are coated with SiO 2, and then added into the electrolyte of a dye solar cell. The enhancement of 50% is achieved in short-circuit current density (JSC) due to the scattering...
PLA microspheres-embedded pva hydrogels prepared by gamma-irradiation and freeze-thaw methods as drug release carriers
, Article International Journal of Polymeric Materials and Polymeric Biomaterials ; Volume 62, Issue 1 , 2013 , Pages 28-33 ; 00914037 (ISSN) ; Dadbin, S ; Frounchi, M ; Sharif University of Technology
2013
Abstract
A drug delivery system based on poly (vinyl alcohol) (PVA) hydrogels containing ibuprofen-loaded poly (lactic acid) (PLA) microspheres was developed to improve the release kinetics of this model drug. Gamma-irradiation and freeze-thawing were applied to prepare poly (vinyl alcohol) hydrogels. Properties and morphology of these composite hydrogels were investigated using FTIR, DSC, and SEM. In vitro release indicated that entrapment of the microspheres into the PVA hydrogels causes a reduction in both the release rate and the initial burst effect. PLA microspheres entrapped into the PVA hydrogels showed more suitable controlled release kinetics for drug delivery
Development of a non-invasive micron sized blood glucose sensor based on microsphere stimulated raman spectroscopy
, Article Sensors and Transducers ; Volume 147, Issue 12 , 2012 , Pages 129-142 ; 17265479 (ISSN) ; Jahangiri, N ; Taraz, M ; Sharif University of Technology
2012
Abstract
We proposed a new method for Non-invasive measuring of blood glucose levels by using micro sphere Stimulated Raman scattering. We show that this method can be used to measure biological glucose levels with low power lasers. The field enhancement due to the resonance condition of high quality factor microsphere causes to reduce stimulated Raman scattering thresholds of its surrounding media (glucose) and hence observing stimulated Raman scattering with low power. The results from theoretical studies indicate that the stimulated Raman signal amplitude levels produced from the very low Glucose concentrations. By measuring the changes of the signal intensity in output of fiber, we can determine...
Human cardiac troponin i sensor based on silver nanoparticle doped microsphere resonator
, Article Journal of Optics (United Kingdom) ; Volume 14, Issue 12 , 2012 ; 20408978 (ISSN) ; Bahrampour, A ; Zandi, M. H ; Sharif University of Technology
Abstract
Human cardiac troponin I (cTnI) is a specific biomarker for diagnosis of acute myocardial infarction (AMI). In this paper, a composite sensing system of an optical microsphere resonator and silver nanoparticles based on surface enhanced Raman scattering (SERS) and stimulated Raman scattering (SRS) techniques towards a point of care diagnostic system for AMI using the cTnI biomarker in HEPES buffered solution (HBS) is proposed. Pump and Raman signals enter the optical fiber coupling into the microsphere, and then SRS occurs in the microsphere. The presence of silver nanoparticles on the microsphere surface provides a tremendous enhancement of the resulting Raman signal through an...
Mesoporous submicrometer TiO 2 hollow spheres as scatterers in dye-sensitized solar cells
, Article ACS Applied Materials and Interfaces ; Volume 4, Issue 6 , 2012 , Pages 2964-2968 ; 19448244 (ISSN) ; Tajabadi, F ; Taghavinia, N ; Sharif University of Technology
2012
Abstract
Hierarchical submicrometer TiO 2 hollow spheres with outer diameter of 300-700 nm and shell thickness of 200 nm are synthesized by liquid phase deposition of TiO 2 over carbon microspheres as sacrificial templates. The final TiO 2 hollow spheres are applied as a scattering layer on top of a transparent nanocrystalline TiO 2 film, serving as the photoanode of a dye-sensitized solar cell (DSC). In addition to efficient light scattering, the mesoporous structure of TiO 2 hollow spheres provides a high surface area, 74 m 2/g, which allows for higher dye loading. This dual functioning suggests that TiO 2 hollow spheres may be good replacements for conventional TiO 2 spheres as scatterers in DSCs....
Granulated copper oxide nanocatalyst: A mild and efficient reusable catalyst for the one-pot synthesis of 4-amino-5-pyrimidinecarbonitriles under aqueous conditions
, Article Monatshefte fur Chemie ; Volume 142, Issue 11 , November , 2011 , Pages 1163-1168 ; 00269247 (ISSN) ; Sadjadi, S ; Hosseinpour, M ; Sharif University of Technology
2011
Abstract
An efficient method for the synthesis of 4-amino-5-pyrimidinecarbonitriles by the three-component reaction of malononitrile, aldehydes, and N-unsubstituted amidines under aqueous conditions using CuO microspheres as catalyst is reported. The catalyst exhibited remarkable reusable activity. Graphical abstract: [Figure not available: see fulltext.]
Effect of formulation factors on the bioactivity of glucose oxidase encapsulated chitosan-alginate microspheres: In vitro investigation and mathematical model prediction
, Article Chemical Engineering Science ; Volume 125 , March , 2015 , Pages 4-12 ; 00092509 (ISSN) ; Cheng, J ; Wu, X. Y ; Sharif University of Technology
Elsevier Ltd
2015
Abstract
Higher reactive oxygen species (ROS) levels in cancer cells than normal cells have long been recognized, which makes cancer cells more susceptible to excess ROS. Thus oxidation (also called pro-oxidant) therapy has been explored as new cancer therapy regimens. To produce additional ROS, e.g. H2O2 in situ within tumor, we encapsulated glucose oxidase in chitosan-coated alginate-calcium microspheres (GOX-MS) for locoregional treatment and demonstrated its efficacy against cancer cells in vitro and in vivo. Owing to the complex biological functions of ROS, the production rate and amount of H2O2 are critical to achieve therapeutic benefits without causing normal tissue toxicity. This work was...
Study of synergistic toughening in a bimodal epoxy nanocomposite
, Article Journal of Reinforced Plastics and Composites ; Volume 34, Issue 4 , February , 2015 , Pages 281-292 ; 07316844 (ISSN) ; Khamesinia, A ; Bagheri, R ; Kouchakzadeh, M. A ; Abadyan, M ; Sharif University of Technology
SAGE Publications Ltd
2015
Abstract
Toughening of epoxy with different types of modifiers produces a bimodal blend that might show better fracture resistance in comparison with single-modified ones. In this research, bimodal epoxy formulations including mixtures of glass microsphere and silica nanoparticles are explored for possible synergistic toughening. The influence of composition on the glass transition temperature (Tg), tensile characteristics, and fracture toughness (KIC) is investigated. Interestingly, a synergism in fracture toughness is observed when mixtures of modifiers were incorporated. For the fixed overall modifier content, KIC is higher when the volume fraction of glass microsphere is lesser than the volume...
synergistic toughening in ternary silica/hollow glass spheres/epoxy nanocomposites
, Article Polymer - Plastics Technology and Engineering ; Volume 54, Issue 6 , 2015 , Pages 581-593 ; 03602559 (ISSN) ; Bagheri, R ; Kouchakzadeh, M. A ; Abadyan, M ; Sharif University of Technology
Taylor and Francis Inc
2015
Abstract
Herein, the fracture toughness of ternary epoxy systems containing nanosilica and hollow glass microspheres (HGMS) is investigated. The experimental measurements reveal synergistic fracture toughness in some hybrid compositions: The incorporation of 10 phr of HGMS and nanosilica alone modify the fracture toughness of epoxy by 39% and 91%, respectively. However, use of 10 phr hybrid modifier can enhance the fracture toughness of the resin up to 120%. Observations reveal different toughening mechanisms for the blends i.e., plastic deformation for silica nanoparticles and crack bifurcation for HGMS. Both of these toughening mechanisms additively contribute to the synergism in ternary epoxies
Synthesis and characterization of a bentonite-alginate microspherical adsorbent for removal of uranyl ions from aqueous Solutions
, Article Separation Science and Technology ; Volume 45, Issue 2 , 2010 , Pages 288-298 ; 01496395 (ISSN) ; Khanchi, A ; Ghofrani, M.B ; Outokesh, M ; Sharif University of Technogy
2010
Abstract
A novel microspherical adsorbent for the removal of uranium from aqueous solutions was developed by immobilizing of natural bentonite in the polymeric matrix of calcium alginate. Different uptake properties of the prepared microspheres were examined using batch, stirred and column methods. The adsorbent showed high affinity toward uranium ions, especially at pHs above 3. Major uptake mechanisms included ion exchange, chelating of the (UO2)2+ ions to the -OH groups of alginate, and surface complexation with bentonite. Surprisingly, the capacity of microspheres was higher than both its constituents, revealing that a synergetic effect occurs. Adsorption kinetics was controlled by slow chemical...