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    Cyto and genotoxicities of graphene oxide and reduced graphene oxide sheets on spermatozoa

    , Article RSC Advances ; Vol. 4, issue. 52 , May , 2014 , pp. 27213-27223 ; ISSN: 20462069 Hashemi, E ; Akhavan, O ; Shamsara, M ; Rahighi, R ; Esfandiar, A ; Tayefeh, A. R ; Sharif University of Technology
    Concentration-dependent cyto and genotoxicities of graphene oxide (GO) and reduced GO (rGO) sheets on spermatozoa were studied. rGO sheets with various surface chemical states were achieved using hydrazine (N2H 4) hydrothermal (HT) reactions and green tea polyphenols (GTPs). Although 0.1 μg mL-1 graphene could not change sperm viability and kinetic parameters, <40% and 20% of spermatozoa were viable and progressively motile, after 2 h incubation with 400 μg mL-1 GO or rGO, respectively. All the graphene nanomaterials induced concentration- dependent reductions of adenosine triphosphate and NAD+/NADH produced by spermatozoa for motility and metabolic activity. While GO, N 2H4-rGO, and HT-rGO... 

    Escherichia coli bacteria reduce graphene oxide to bactericidal graphene in a self-limiting manner

    , Article Carbon ; Volume 50, Issue 5 , 2012 , Pages 1853-1860 ; 00086223 (ISSN) Akhavan, O ; Ghaderi, E ; Sharif University of Technology
    Interactions of chemically exfoliated graphene oxide (GO) nanosheets and Escherichia coli bacteria living in mixed-acid fermentation with an anaerobic condition were investigated for different exposure times. X-ray photoelectron spectroscopy showed that as the exposure time increased (from 0 to 48 h), the oxygen-containing functional groups of the GO decreased by ∼60%, indicating a relative chemical reduction of the sheets by interaction with the bacteria. Raman spectroscopy and current-voltage measurement confirmed the reduction of the GO exposed to the bacteria. The reduction was believed to be due to the metabolic activity of the surviving bacteria through their glycolysis process. It was... 

    Use of the freely-swimming, Serratia marcescens bacteria to enhance mixing in microfluidic systems

    , Article ASME 2009 International Mechanical Engineering Congress and Exposition, 13 November 2009 through 19 November 2009 ; Volume 12, Issue PART A , 2010 , Pages 463-467 ; 9780791843857 (ISBN) Peysepar, M ; Shafii, M. B ; Rasoulian, R ; Jamalifar, H ; Fazeli, M. R ; Sharif University of Technology
    American Society of Mechanical Engineers (ASME) 
    Mixing has become a challenge in micro-fluidic systems because of the low Reynolds number in micro-channels. The method which is implemented in this paper is to use freely-swimming bacteria to enhance the mixing process. Accordingly, the Serratia marcescens bacteria were used for this matter. The mixing performance of the system is quantified by measuring the diffusion rate of Rhodamine B in a particular section of a channel connected to a chamber with varying Rhodamine B concentration. The concentration of Rhodamine B was measured using the Laser Induced Fluorescence (LIF) technique. The channel is in the form of a pipe and is closed on the extending side. In this paper, it is demonstrated... 

    3D Bioprinting of oxygenated cell-laden gelatin methacryloyl constructs

    , Article Advanced Healthcare Materials ; Volume 9, Issue 15 , 2020 Erdem, A ; Darabi, M. A ; Nasiri, R ; Sangabathuni, S ; Ertas, Y. N ; Alem, H ; Hosseini, V ; Shamloo, A ; Nasr, A. S ; Ahadian, S ; Dokmeci, M. R ; Khademhosseini, A ; Ashammakhi, N ; Sharif University of Technology
    Wiley-VCH Verlag  2020
    Cell survival during the early stages of transplantation and before new blood vessels formation is a major challenge in translational applications of 3D bioprinted tissues. Supplementing oxygen (O2) to transplanted cells via an O2 generating source such as calcium peroxide (CPO) is an attractive approach to ensure cell viability. Calcium peroxide also produces calcium hydroxide that reduces the viscosity of bioinks, which is a limiting factor for bioprinting. Therefore, adapting this solution into 3D bioprinting is of significant importance. In this study, a gelatin methacryloyl (GelMA) bioink that is optimized in terms of pH and viscosity is developed. The improved rheological properties...