Browsing by Subject "Carbon nanotubes"

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    Effects of Carbon Nanotubes in Barrier Epithelial Cells via Effects on Lipid Bilayers
    (Office of the Vice Chancellor for Research, 2013-04-05) Lewis, Shanta; Petrache, Horia I.; Blazer-Yost, Bonnie L.; Witzmann, Frank
    Carbon nanotubes (CNTs) are one of many nanoparticles (NP) which are being developed as part of the burgeoning nanotechnology. The tubes have similar physical properties to known toxic materials, such as asbestos; yet there is a lack of evidence showing that they may be hazardous to humans, specifically to our barrier epithelial cells. We measured the effects of CNTs on human airway epithelial cells (Calu-3 cell line) using electrophysiology. This is a technique which measures transepithelial electrical resistance (TEER), a measure of monolayer integrity; and short circuit current (SCC) a measure of net ion transport across the cell. Exposed cells showed significant decreases in TEER when incubated for 48 hours with physiologically relevant concentrations of 4μg/cm2 - 0.4ng/cm2 of multi-wall (MW) and 4μg/cm2 - 0.04ng/cm2 single-wall (SW) CNT. TEER is a measure of barrier function which is important in cells that maintain separate compartments in the body. The impaired barrier function, despite sustained cell viability, led us to investigate the mechanism by which the CNT were interacting with the cell when applied topically. Model lipid membranes connected to an ion channel amplifier, Planar Bilayer Workstation (BLM), were used. Membranes were formed using the neutral diphytanoylphosphatidylcholine (DPhPC) and negatively charged diphytanoyl phosphatidylserine (DPhPS) lipids. CNTs caused random, transient currents ranging from 0pA to 6479pA to traverse the membrane. In the presence of Gramicidin A, an ion channel reporter protein, the tubes induced increased gramicidin channel formation in the membrane to saturation level and then membrane lysis. This CNT- lipid interaction indicated that short MWCNTs permits unregulated ion movement across the lipid membrane. Disruption in the selective permeability of the plasmalemma may impact the tissue’s barrier function.
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    Effects of carbon nanotubes on barrier epithelial cells via effects on lipid bilayers
    (2013) Lewis, Shanta; Blazer-Yost, Bonnie; Petrache, Horia; Witzmann, F. A. (Frank A.); Atkinson, Simon
    Carbon nanotubes (CNTs) are one of the most common nanoparticles (NP) found in workplace air. Therefore, there is a strong chance that these NP will enter the human body. They have similar physical properties to asbestos, a known toxic material, yet there is limited evidence showing that CNTs may be hazardous to human barrier epithelia. In previous studies done in our laboratory, the effects of CNTs on the barrier function in the human airway epithelial cell line (Calu-3) were measured. Measurements were done using electrophysiology, a technique which measures both transepithelial electrical resistance (TEER), a measure of monolayer integrity, and short circuit current (SCC) which is a measure of vectorial ion transport across the cell monolayer. The research findings showed that select physiologically relevant concentrations of long single-wall (SW) and multi-wall (MW) CNTs significantly decreased the stimulated SCC of the Calu-3 cells compared to untreated cultures. Calu-3 cells showed decreases in TEER when incubated for 48 hours (h) with concentrations of MWCNT ranging from 4µg/cm2 to 0.4ng/cm2 and SWCNT ranging from 4µg/cm2 to 0.04ng/cm2. The impaired cellular function, despite sustained cell viability, led us to investigate the mechanism by which the CNTs were affecting the cell membrane. We investigated the interaction of short MWCNTs with model lipid membranes using an ion channel amplifier, Planar Bilayer Workstation. Membranes were synthesized using neutral diphytanoylphosphatidylcholine (DPhPC) and negatively charged diphytanoylphosphatidylserine (DPhPS) lipids. Gramicidin A (GA), an ion channel reporter protein, was used to measure changes in ion channel conductance due to CNT exposures. Synthetic membranes exposed to CNTs allowed bursts of currents to cross the membrane when they were added to the membrane buffer system. When added to the membrane in the presence of GA, they distorted channel formation and reduced membrane stability.