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NANOSILVER MOVEMENT THROUGH BIOLOGICAL BARRIERS RELATES TO PHYSICOCHEMICAL PROPERTIES
Citation:
VERONESI, B., N. Nazo, A. Tennant, S. Simmons, B. Baruwat, AND R. Varma. NANOSILVER MOVEMENT THROUGH BIOLOGICAL BARRIERS RELATES TO PHYSICOCHEMICAL PROPERTIES. Presented at Society of Toxicology (OST) Annual Meeting, Washington, DC, March 06 - 10, 2011.
Impact/Purpose:
This research relates the biological activity (i.e., translocation through biological barriers) of nanosilver (a high volume engineered nanomaterial) with its physicochemical properties. Such information helps in the design of safer and more efficacious nanomaterials and more importantly, are needed for effective risk assessment.
Description:
Linking the physicochemical (PC) properties of engineered nanomaterials (NM) to their biological activity is critical for identifying their (toxic) mode of action, and developing appropriate and effective risk assessment guidelines. Particle surface charge (zeta potential), surface coating and "redox" activity are PC properties thought to influence NM uptake and movement (i.e., translocation) through cellular barriers. Nanosilver (nanoAg) is used in water purification, antiseptics, biocides, medical devices and a variety of consumer and manufactured products. Efforts to reduce its environmental burden and enhance its bioavailability favor "green chemistry" synthesis and the surface coating of particle with benign materials. Since ingestion is a dominant route of exposure, studies were conducted to examine how such PC properties affected nanoAg movement across in vitro models of biological barrier cells. Monolayers of human intestinal (Caco-2) or rat blood brain barrier (RBE4) cells were exposed (3.12-6.25 ppm) to commercially available, capped (citrate or PVP) or uncapped nanoAg particles (10nm and 70 nm). Another sample of nanoAg was synthesized, using a borohydride reduction method, and tested as uncoated particles (50-75 nm) or those coated with glutathione (GSH) or green tea (GT). Microscopy (confocal, TEM) indicated that nanoAg particles translocated barrier cells rapidly <15 min) and without disrupting their tight junctions. Changes in transcellular electrical resistance (TERS) suggested that surface coatings (citrate>PVP; GSH=GT), an electronegative zeta potential and low aggregate size were PC properties that enhanced nanoAg's cellular movement. Future studies will use high through put techniques to confirm these relationships and will also examine how different surface coatings of nanoAg particles affect their cellular uptake, retention and clearance. (This abstract has been reviewed by NHEERL and does not necessarily reflects EPA policy