Particle-induced artifacts in the MTT and LDH viability assays.
In vitro testing is a common first step in assessing combustion-generated and engineered nanoparticle-related health hazards. Commercially available viability assays are frequently used to compare the toxicity of different particle types and to generate dose-response data. Nanoparticles, well-known for having large surface areas and chemically active surfaces, may interfere with viability assays, producing a false assessment of toxicity and making it difficult to compare toxicity data. The objective of this study is to measure the extent of particle interference in two common viability assays, the MTT reduction and the lactate dehydrogenase (LDH) release assays. Diesel particles, activated carbon, flame soot, oxidized flame soot, and titanium dioxide particles are assessed for interactions with the MTT and LDH assay under cell-free conditions. Diesel particles, at concentrations as low as 0.05 μg/mL, reduce MTT. Other particle types reduce MTT only at a concentration of 50 μg/mL and higher. The activated carbon, soot, and oxidized soot particles bind LDH to varying extents, reducing the concentration measured in the LDH assay. The interfering effects of the particles explain in part the different toxicities measured in human bronchial epithelial cells (16HBE14o). We conclude that valid particle toxicity assessments can only be assured after first performing controls to verify that the particles under investigation do not interfere with a specific assay at the expected concentrations.
Division of Environmental Health Sciences, University of California, Berkeley, CA 94720, USA.
Amara L
AL
Holder
Regine
R
Goth-Goldstein
Donald
D
Lucas
Catherine P
CP
Koshland
D000393:Air Pollutants / Q000737:chemistry* / Q000633:toxicity; D016477:Artifacts; D001681:Biological Assay / Q000592:standards; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D006801:Humans; D007770:L-Lactate Dehydrogenase / Q000378:metabolism*; D053758:Nanoparticles / Q000737:chemistry / Q000633:toxicity; D052638:Particulate Matter / Q000737:chemistry* / Q000633:toxicity; D012680:Sensitivity and Specificity; D053260:Soot / Q000737:chemistry / Q000633:toxicity; D013778:Tetrazolium Salts / Q000737:chemistry* / Q000378:metabolism; D013844:Thiazoles / Q000737:chemistry* / Q000378:metabolism; D014025:Titanium / Q000737:chemistry / Q000633:toxicity
D000393:Air Pollutants; D052638:Particulate Matter; D053260:Soot; D013778:Tetrazolium Salts; D013844:Thiazoles; C009495:titanium dioxide; D014025:Titanium; D007770:L-Lactate Dehydrogenase; C022616:thiazolyl blue