This protocol describes a strategy for separating Caenorhabditis elegans (C. elegans) from engineered nanomaterials, a critical step for accurate quantification in uptake studies. Conventional rinsing procedures, typically comprised of water or buffer rinsing steps followed by centrifugation, have been previously tested and deemed unsuitable for this purpose, even at environmentally relevant exposure concentrations. Therefore, this protocol details the development and assessment of a unique sucrose gradient density centrifugation procedure for the efficient separation of nanoparticles and C. elegans at the end of an exposure protocol. The example outlined in this SP pertains to the measurement of gold nanoparticles (AuNPs) and C. elegans. However, this method can potentially be implemented in bioaccumulation studies involving other organisms and with different metallonanoparticles. Visit http://nist.gov/mml/np-measurement-protocols.cfm
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