to characterize them, both Drs. McNeil and Yuliang Zhao pointed out. “Very naively we thought five and six years ago that we could simply take an off-the-shelf kit and characterize nanomaterials, and that’s not the case. [The nanomaterials] will interfere with the assay—many nanoparticles will absorb at the same wavelength that the colorimetric assays do. Some particles are catalytic and will cleave a substrate so you get false positives,” said Dr. McNeil. Dr. Yuliang Zhao, director of the Chinese Academy of Sciences’ Key Lab for Nanosafety added that additional parameters are required when characterizing the toxicity of nanomaterials, besides mass concentration, reactivity, solubility and other standard parameters. These additional parameters include quantum effects, structure, shape, particle concentration, number, size, size distribution, surface chemistry, and tendency to aggregate or self assemble.