Sandwich immunoassay of Cry1Ab.

<p><b>A.</b> Standard curve obtained with purified Cry1Ab protoxin in sandwich immunoassay using mAb#120 passively adsorbed on microplates as capture antibody and AChE-labeled mAb#95 as tracer. Mean +/− SD is represented. Each point is the result of duplicate measurements, except NSB (EIA buffer alone, n = 8). The limit of detection, defined as the lowest concentration of standard Cry1Ab inducing a signal statistically significantly higher than NSB (i.e. mean+3σ<i>_n</i>₋₁) is shown in the insert as a black line. <b>B.</b> Extracts from reference maize powders containing MON810 maize mass fraction level of 0.5% (●), 1% (▼) or 2.5% (◆) (2- to 250-fold dilutions) or standard Cry1Ab (10 ng/mL, 2- to 128-fold dilutions, ○) were assayed using this sandwich immunoassay. All dilution points were assayed in duplicate. Results are expressed as mean of absorbance values (mAU at 414 nm) +/− SD. No signal was detected for non-GM reference maize (not shown).