Search for: microsphere
Total 37 records
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
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.]
An analytical model for prediction of controlled release from bulk biodegrading polymer microspheres, Article Asian Journal of Pharmaceutical and Clinical Research ; Volume 11, Issue 3 , March , 2018 , Pages 432-437 ; 09742441 (ISSN) ; Sharif University of Technology
Innovare Academics Sciences Pvt. Ltd 2018
Objective: a convenient numerical model has been developed to predict release profile of different types of agents from bulk biodegrading polymer microspheres, including magnitude methods are less accurate than analytical methods. Usually, this study used analytical solutions for the model and compared the analytical results with numerical solution and experimental data. Methods: The objective drug controlled release profiles were modeled based on a four-phase pattern. Then, a specific formulation was considered based on Fick’s second law. After calculating various parameters, the equations were solved using an analytical method. Results: Comparison results showed that analytical solution...
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
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
, M.Sc. Thesis Sharif University of Technology ; Bahrampour, Alireza
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...
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
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...
Preparation and investigation the release behaviour of wax microspheres loaded with salicylic acid, Article Journal of Microencapsulation ; Volume 26, Issue 6 , 2009 , Pages 485-492 ; 02652048 (ISSN) ; Taghizadeh, M ; Seifkordi, A. A ; Ardjmand, M ; Sharif University of Technology
Salicylic acid-beeswax microspheres were prepared by melt dispersion technique. The effects of formulation parameters on the microscopic characteristic, drug loading and cumulative amount of released drug were investigated by experimental design. Results showed that all of the microparticles were spherical with porous surfaces. The average size of microspheres was 2448 m, the drug content was in the range of 2245 and the encapsulation efficiency was 4693. Drug loading was influenced by emulsification speed as a main factor. All the microspheres had a burst release initially. The emulsifier concentration did not have a significant effect on drug release. The release behaviour of microspheres...
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
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...
Drug release from ion-exchange microspheres: Mathematical modeling and experimental verification, Article Biomaterials ; Volume 29, Issue 11 , 2008 , Pages 1654-1663 ; 01429612 (ISSN) ; Wu, X. Y ; Sharif University of Technology
This paper presents for the first time a mathematical model for a mechanism of controlled drug release involving both ion exchange and transient counter diffusion of a drug and counterions. Numerical analysis was conducted to study the effect of different factors on drug release kinetics including environmental condition, material properties, and design parameters. The concentration profiles of counterions and drug species, the moving front of ion exchange, and three distinct regions inside a microsphere, namely unextracted region, ion-exchange region and drug diffusion region, were revealed by model prediction. The numerical results indicated that the rate of drug release increased with an...
Drug loading onto ion-exchange microspheres: Modeling study and experimental verification, Article Biomaterials ; Volume 27, Issue 19 , 2006 , Pages 3652-3662 ; 01429612 (ISSN) ; Wu, X. Y ; Sharif University of Technology
A new mathematical model was developed and an exact analytical solution without approximations of previous work was derived for the description of the kinetics and equilibrium characteristics of drug loading from a finite external solution onto ion-exchange microspheres. The influence of important parameters pertinent to material properties and loading conditions on the kinetics, efficiency, and equilibrium of drug loading was analyzed using the developed model and equations. The numerical results showed that the rate of drug loading increased with increasing initial drug concentration in the solution or with the relative volume of the external solution and the microsphere. The maximum...
Fabrication and Characterization of PVA/PLA Composites, M.Sc. Thesis Sharif University of Technology ; Frounchi, Masoud ; Dadbin, Susan
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...
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 ; Firoozbakhsh, Keykhosrow
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 ; Asghari, Mohsen
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...
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
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...
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
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
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
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
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...
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
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...
Hybrid energy storage device from binder-free zinc-cobalt sulfide decorated biomass-derived carbon microspheres and pyrolyzed polyaniline nanotube-iron oxide, Article Energy Storage Materials ; Volume 25 , March , 2020 , Pages 621-635 ; Hosseini, H ; Shahrokhian, S ; Unalan, H. E ; Sharif University of Technology
Elsevier B.V 2020
High-performance supercapacitors that merit superior power and energy densities, as well as long-term cycle durability are always of great significance as a building block of energy storage devices. Herein, an innovative strategy is developed to design hierarchical and unique porous structures of ternary metal sulfide nano-flake decorated porous hydrothermal carbon microspheres. Hierarchical microspheres of ternary zinc-cobalt sulfide nanosheet (NS) decorated biomass derived hydrothermal carbon spheres (HTCSs) are directly employed as the positive supercapacitor electrodes. In addition, composites of pyrolyzed polyaniline nanotubes (PPNTs) and iron oxide, receiving advantages from highly...
Fluidic barriers in droplet-based centrifugal microfluidics: Generation of multiple emulsions and microspheres, Article Sensors and Actuators, B: Chemical ; Volume 311 , May , 2020 ; Madou, M. J ; Dorri Nokoorani, Y ; Shamloo, A ; Martinez Chapa, S. O ; Sharif University of Technology
Elsevier B. V 2020
Droplet generation is very important in biochemical processes such as cell encapsulation, digital PCR (Polymerase Chain Reaction), and drug delivery. In the present paper, a density-based method called “fluidic barrier” is introduced to produce multiple emulsions on a centrifugal microfluidic platform or Lab-on-a-CD (LOCD). We show that the density and the viscosity of the fluids involved are important parameters for predicting the characteristics of the droplets generated with this method. Moreover, we broadened this concept by using the fluidic barriers to separate reactive chemicals. As a proof of concept, alginate and CaCl2 solutions are separated by an oil barrier to control the...
Images of finite sized spherical particles in confocal and conventional microscopes when illuminated with arbitrary polarization, Article Applied Optics ; Volume 47, Issue 3 , 2008 , Pages 453-458 ; 1559128X (ISSN) ; Massoumian, F ; Sharif University of Technology
OSA - The Optical Society 2008
We investigate the form of the image of a finite sized spherical particle in confocal and conventional microscopes when the illuminating light has an arbitrary polarization. In particular, we take the cases of radial and azimuthal polarizations and use the Mie theory to find the scattered field from differently sized particles for these cases. We present numerical results for the changes in the detected intensity when subresolution and resolvable spherical particles are illuminated with particular wavelengths and polarizations. Further, we find the limiting size of a particle for which it can be considered a point scatterer for a particular wavelength. © 2008 Optical Society of America