Search for: microscopy--electron--transmission
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    Preparation and characterization of starch-based composite films reinforced by cellulose nanofibers

    , Article International Journal of Biological Macromolecules ; Volume 116 , 2018 , Pages 272-280 ; 01418130 (ISSN) Fazeli, M ; Keley, M ; Biazar, E ; Sharif University of Technology
    Elsevier B.V  2018
    The current study deals with the preparation and characterization of polysaccharide-based biocomposite films acquired by the incorporation of cellulose nanofiber within glycerol plasticized matrix formed by starch. The application of starch-based films is limited due to highly hydrophilic nature and poor mechanical properties. These problems are solved by forming a nanocomposite of thermoplastic starch (TPS) as matrix and cellulose nanofiber (CNF) as reinforcement. CNF is successfully prepared from short henequen fibers which consist of almost 60% cellulose by a chemo-mechanical process. TPS/CNF composite films are prepared by the polymer solution casting method, and their characterizations... 

    Apatite-coated Ag/AgBr/TiO2 visible-light photocatalyst for destruction of bacteria

    , Article Journal of the American Chemical Society ; Volume 129, Issue 31 , 2007 , Pages 9552-9553 ; 00027863 (ISSN) Elahifard, M. R ; Rahimnejad, S ; Haghighi, S ; Gholami, M. R ; Sharif University of Technology
    Apatite-coated Ag/AgBr/TiO2 was prepared by deposition of Ag as novel metal to generate electron-hole pairs by extending the excitation wavelength to the visible-light region, AgBr, and hydroxy apatite as photosensitive material and adsorption bioceramic, respectively. The energy dispersive X-ray spectrometry clearly showed the presence of Ti, Ag, Ca, and P elements on the surface of catalyst. The bactericidal experiments in dark media indicated that only the novel catalyst shows inhibiting growth of bacteria in this case. A transmission electron microscopy image illustrated that catalyst nanoparticles adhere to the outer membrane of the cell and act as an inhibitor to the nourishment of... 

    Temperature: the "ignored" factor at the nanobio interface

    , Article ACS Nano ; Volume 7, Issue 8 , 2013 , Pages 6555-6562 ; 19360851 (ISSN) Mahmoudi, M ; Abdelmonem, A. M ; Behzadi, S ; Clement, J. H ; Dutz, S ; Ejtehadi, M. R ; Hartmann, R ; Kantner, K ; Linne, U ; Maffre, P ; Metzler, S ; Moghadam, M. K ; Pfeiffer, C ; Rezaei, M ; Ruiz-Lozano, P ; Serpooshan, V ; Shokrgozar, M. A ; Nienhaus, G. U ; Parak, W. J ; Sharif University of Technology
    Upon incorporation of nanoparticles (NPs) into the body, they are exposed to biological fluids, and their interaction with the dissolved biomolecules leads to the formation of the so-called protein corona on the surface of the NPs. The composition of the corona plays a crucial role in the biological fate of the NPs. While the effects of various physicochemical parameters on the composition of the corona have been explored in depth, the role of temperature upon its formation has received much less attention. In this work, we have probed the effect of temperature on the protein composition on the surface of a set of NPs with various surface chemistries and electric charges. Our results... 

    Removal of toxic heavy metal ions from waste water by functionalized magnetic core-zeolitic shell nanocomposites as adsorbents

    , Article Environmental Science and Pollution Research ; Volume 20, Issue 6 , 2013 , Pages 3900-3909 ; 09441344 (ISSN) Padervand, M ; Gholami, M. R ; Sharif University of Technology
    Functionalized magnetic core-zeolitic shell nanocomposites were prepared via hydrothermal and precipitation methods. The products were characterized by vibrating sample magnetometer, X-ray powder diffraction, Fourier transform infrared spectroscopy, nitrogen adsorption-desorption isotherms, and transmission electron microscopy analysis. The growth of mordenite nanocrystals on the outer surface of silica-coated magnetic nanoparticles at the presence of organic templates was well approved. The removal performance and the selectivity of mixed metal ions (Pb2+ and Cd2+) in aqueous solution were investigated via the sorption process. The batch method was employed to study the sorption kinetic,... 

    Artificial neural network assisted kinetic spectrophotometric technique for simultaneous determination of paracetamol and p-aminophenol in pharmaceutical samples using localized surface plasmon resonance band of silver nanoparticles

    , Article Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy ; Volume 138 , March , 2015 , Pages 474-480 ; 13861425 (ISSN) Khodaveisi, J ; Dadfarnia, S ; Haji Shabani, A. M ; Rohani Moghadam, M ; Hormozi Nezhad, M. R ; Sharif University of Technology
    Elsevier  2015
    Spectrophotometric analysis method based on the combination of the principal component analysis (PCA) with the feed-forward neural network (FFNN) and the radial basis function network (RBFN) was proposed for the simultaneous determination of paracetamol (PAC) and p-aminophenol (PAP). This technique relies on the difference between the kinetic rates of the reactions between analytes and silver nitrate as the oxidizing agent in the presence of polyvinylpyrrolidone (PVP) which is the stabilizer. The reactions are monitored at the analytical wavelength of 420 nm of the localized surface plasmon resonance (LSPR) band of the formed silver nanoparticles (Ag-NPs). Under the optimized conditions, the... 

    Simultaneous detection and identification of thiometon, phosalone, and prothioconazole pesticides using a nanoplasmonic sensor array

    , Article Food and Chemical Toxicology ; Volume 151 , 2021 ; 02786915 (ISSN) Koushkestani, M ; Abbasi Moayed, S ; Ghasemi, F ; Mahdavi, V ; Hormozi Nezhad, M. R ; Sharif University of Technology
    Elsevier Ltd  2021
    In this work, a colorimetric sensor array has been designed for the identification and discrimination of thiometon (TM) and phosalone (PS) as organophosphate pesticides and prothioconazole (PC) as a triazole pesticide. For this purpose, two different plasmonic nanoparticles including unmodified gold nanoparticles (AuNPs) and unmodified silver nanoparticles (AgNPs) were used as sensing elements. The principle of the proposed strategy relied on the aggregation AuNPs and AgNPs through the cross-reactive interaction between the target pesticides and plasmonic nanoparticles. Therefore, these aggregation-induced UV–Vis spectra changes were utilized to discriminate the target pesticides with the... 

    Nanoscale characterization of the biomolecular corona by cryo-electron microscopy, cryo-electron tomography, and image simulation

    , Article Nature Communications ; Volume 12, Issue 1 , 2021 ; 20411723 (ISSN) Sheibani, S ; Basu, K ; Farnudi, A ; Ashkarran, A ; Ichikawa, M ; Presley, J. F ; Bui, K. H ; Ejtehadi, M. R ; Vali, H ; Mahmoudi, M ; Sharif University of Technology
    Nature Research  2021
    The biological identity of nanoparticles (NPs) is established by their interactions with a wide range of biomolecules around their surfaces after exposure to biological media. Understanding the true nature of the biomolecular corona (BC) in its native state is, therefore, essential for its safe and efficient application in clinical settings. The fundamental challenge is to visualize the biomolecules within the corona and their relationship/association to the surface of the NPs. Using a synergistic application of cryo-electron microscopy, cryo-electron tomography, and three-dimensional reconstruction, we revealed the unique morphological details of the biomolecules and their... 

    Poly-L-lysine/hyaluronan nanocarriers as a novel nanosystem for gene delivery

    , Article Journal of Microscopy ; Volume 287, Issue 1 , 2022 , Pages 32-44 ; 00222720 (ISSN) Souri, M ; Bagherzadeh, M. A ; Mofazzal Jahromi, M. A ; Mohammad-Beigi, H ; Abdoli, A ; Mir, H ; Roustazadeh, A ; Pirestani, M ; Sahandi Zangabad, P ; Kiani, J ; Bakhshayesh, A ; Jahani, M ; Joghataei, M. T ; Karimi, M ; Sharif University of Technology
    John Wiley and Sons Inc  2022
    The present research comes up with a novel DNA-loaded poly-L-lysine (PLL)/hyaluronan (HA) nanocarrier (DNA-loaded PLL/HA NCs) for gene delivery applications, as a promising candidate for gene delivery into diverse cells. A straightforward approach was employed to prepare such a nanosystem through masking DNA-loaded PLL molecules by HA. Fourier-transform infrared (FTIR) spectroscopy, dynamic light scattering (DLS), field emission-scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) were used to analyse the interaction of the molecules as well as the physicochemical properties of the NCs. The NCs showed a negative charge of –24 ± 3 mV, with an average size of 138 ±... 

    Fabrication of a modified electrode based on Fe3 O4 NPs/MWCNT nanocomposite: Application to simultaneous determination of guanine and adenine in DNA

    , Article Bioelectrochemistry ; Volume 86 , 2012 , Pages 78-86 ; 15675394 (ISSN) Shahrokhian, S ; Rastgar, S ; Amini, M. K ; Adeli, M ; Sharif University of Technology
    Multi-walled carbon nanotubes decorated with Fe 3O 4 nanoparticles (Fe 3O 4NPs/MWCNT) were prepared and used to construct a novel biosensor for the simultaneous detection of adenine and guanine. The direct electro-oxidation of adenine and guanine on the modified electrode were investigated by linear sweep voltammetry. The results indicate a remarkable increase in the oxidation peak currents together with negative shift in the oxidation peak potentials for both adenine and guanine, in comparison to the bare glassy carbon electrode (GCE). The surface morphology and nature of the composite film deposited on GCE were characterized by transmission electron microscopy, atomic force microscopy,... 

    Nano reengineering of horseradish peroxidase with dendritic macromolecules for stability enhancement

    , Article Enzyme and Microbial Technology ; Volume 50, Issue 1 , 2012 , Pages 10-16 ; 01410229 (ISSN) Khosravi, A ; Vossoughi, M ; Shahrokhian, S ; Alemzadeh, I ; Sharif University of Technology
    A simple bio-conjugation procedure to surround a single horseradish peroxidase (HRP) enzyme molecule with dendritic polyester macromolecules (polyester-32-hydroxyl-1-carboxyl bis-MPA dendron, generation 5) was proposed. The characterization of resultant nanoparticles entitled HRP dendrozyme, was performed by transmission electron microscopy, dynamic light scattering, gel permeation chromatography and Fourier transform infrared spectroscopy. The results showed that HRP nanoparticles were spherical in shape and have an average size of 14 ± 2. nm in diameter. Furthermore, bio-conformational characterization of HRP dendrozyme was performed by means of circular dichroism and fluorescence... 

    A colorimetric sensor array for detection and discrimination of biothiols based on aggregation of gold nanoparticles

    , Article Analytica Chimica Acta ; Volume 882 , July , 2015 , Pages 58-67 ; 00032670 (ISSN) Ghasemi, F ; Hormozi-Nezhad, M.R ; Mahmoudi, M ; Sharif University of Technology
    Elsevier  2015
    Developments of sensitive, rapid, and cheap systems for identification of a wide range of biomolecules have been recognized as a critical need in the biology field. Here, we introduce a simple colorimetric sensor array for detection of biological thiols, based on aggregation of three types of surface engineered gold nanoparticles (AuNPs). The low-molecular-weight biological thiols show high affinity to the surface of AuNPs; this causes replacement of AuNPs' shells with thiol containing target molecules leading to the aggregation of the AuNPs through intermolecular electrostatic interaction or hydrogen-bonding. As a result of the predetermined aggregation, color and UV-vis spectra of AuNPs... 

    MicroRNA profiling reveals important functions of miR-125b and let-7a during human retinal pigment epithelial cell differentiation

    , Article Experimental Eye Research ; Volume 190 , 2020 Shahriari, F ; Satarian, L ; Moradi, S ; Sharifi Zarchi, A ; Günther, S ; Kamal, A ; Totonchi, M ; Mowla, S. J ; Braun, T ; Baharvand, H ; Sharif University of Technology
    Academic Press  2020
    Retinal pigment epithelial (RPE) cells are indispensable for eye organogenesis and vision. To realize the therapeutic potential of in vitro-generated RPE cells for cell-replacement therapy of RPE-related retinopathies, molecular mechanisms of RPE specification and maturation need to be investigated. So far, many attempts have been made to decipher the regulatory networks involved in the differentiation of human pluripotent stem cells into RPE cells. Here, we exploited a highly-efficient RPE differentiation protocol to determine global expression patterns of microRNAs (miRNAs) during human embryonic stem cell (hESC) differentiation into RPE using small RNA sequencing. Our results revealed a... 

    Design of pH-responsive nanoparticles of terpolymer of poly(methacrylic acid), polysorbate 80 and starch for delivery of doxorubicin

    , Article Colloids and Surfaces B: Biointerfaces ; Volume 101 , January , 2013 , Pages 405-413 ; 09277765 (ISSN) Shalviri, A ; Chan, H. K ; Raval, G ; Abdekhodaie, M. J ; Liu, Q ; Heerklotz, H ; Wu, X. Y ; Sharif University of Technology
    This work focused on the design of new pH-responsive nanoparticles for controlled delivery of anticancer drug doxorubicin (Dox). Nanoparticles of poly(methacrylic acid)-polysorbate 80-grafted starch (PMAA-PS 80-g-St) were synthesized by using a one-pot method that enabled simultaneous grafting of PMAA and PS 80 onto starch and nanoparticle formation in an aqueous medium. The particles were characterized by FTIR, 1H NMR, TEM, DLS, and potentiometric titration. Dox loading and in vitro release from the nanoparticles were investigated. The FTIR and 1H NMR confirmed the chemical composition of the graft terpolymer. The nanoparticles were relatively spherical with narrow size distribution and... 

    Voltammetric studies of sumatriptan on the surface of pyrolytic graphite electrode modified with multi-walled carbon nanotubes decorated with silver nanoparticles

    , Article Talanta ; Volume 80, Issue 1 , 2009 , Pages 31-38 ; 00399140 (ISSN) Ghalkhani, M ; Shahrokhian, S ; Ghorbani Bidkorbeh, F ; Sharif University of Technology
    Multi-walled carbon nanotube decorated with silver nanoparticles (AgNPs-MWCNT) is used as an effective strategy for modification of the surface of pyrolytic graphite electrode (PGE). This modification procedure improved colloidal dispersion of the decorated MWCNTs in water, affording uniform and stable thin films for altering the surface properties of the working electrode. Robust electrode for sensing applications is obtained in a simple solvent evaporation process. The electrochemical behavior of sumatriptan (Sum) at the bare PGE and AgNPs-MWCNT modified PGE is investigated. The results indicate that the AgNPs-MWCNT modified PGE significantly enhanced the oxidation peak current of Sum. A... 

    Biomimetic proteoglycan nanoparticles for growth factor immobilization and delivery

    , Article Biomaterials Science ; Volume 8, Issue 4 , 2020 , Pages 1127-1136 Zandi, N ; Mostafavi, E ; Shokrgozar, M. A ; Tamjid, E ; Webster, T. J ; Annabi, N ; Simchi, A ; Sharif University of Technology
    Royal Society of Chemistry  2020
    The delivery of growth factors is often challenging due to their short half-life, low stability, and rapid deactivation. In native tissues, the sulfated residual of glycosaminoglycan (GAG) polymer chains of proteoglycans immobilizes growth factors through the proteoglycans'/proteins' complexation with nanoscale organization. These biological assemblies can influence growth factor-cell surface receptor interactions, cell differentiation, cell-cell signaling, and mechanical properties of the tissues. Here, we introduce a facile procedure to prepare novel biomimetic proteoglycan nanocarriers, based on naturally derived polymers, for the immobilization and controlled release of growth factors.... 

    Synthesis and cytotoxicity assessment of superparamagnetic iron-gold core-shell nanoparticles coated with polyglycerol

    , Article Journal of Colloid and Interface Science ; Volume 345, Issue 1 , 2010 , Pages 64-71 ; 00219797 (ISSN) Jafari, T ; Simchi, A ; Khakpash, N ; Sharif University of Technology
    Core-shell iron-gold (Fe@Au) nanoparticles were synthesized by a facile reverse micelle procedure and the effect of water to surfactant molar ratio (w) on the size, size distribution and magnetic properties of the nanoparticles was studied. MTT assay was utilized to evaluate the cell toxicity of the nanoparticles. To functionalize the particles for MRI imaging and targeted drug delivery, the particles were coated by polyglycerol through capping with thiol followed by polymerization of glycidol. The characteristics of the particles were examined by X-ray diffraction (XRD), transmission electron microscopy (TEM), vibrating sample magnetometere (VSM), UV-visible spectroscopy, and Fourier... 

    An in vitro study of bare and poly(ethylene glycol)-co-fumarate-coated superparamagnetic iron oxide nanoparticles: A new toxicity identification procedure

    , Article Nanotechnology ; Volume 20, Issue 22 , 2009 ; 09574484 (ISSN) Mahmoudi, M ; Simchi, A ; Imani, M ; Milani, A. S ; Stroeve, P ; Sharif University of Technology
    As the use of superparamagnetic iron oxide nanoparticles (SPION) in biomedical applications increases (e.g. for targeting drug delivery and imaging), patients are likely to be exposed to products containing SPION. Despite their high biomedical importance, toxicity data for SPION are limited to date. The aim of this study is to investigate the cytotoxicity of SPION and its ability to change cell medium components. Bare and poly(ethylene glycol)-co-fumarate (PEGF)-coated SPION with narrow size distributions were synthesized. The particles were prepared by co-precipitation using ferric and ferrous salts with a molar Fe3+/Fe2+ ratio of 2. Dulbecco's modified Eagle's medium (DMEM) and primary...