Agriculture Reference
In-Depth Information
8.4.4.2 Membrane-Based Immunoassays
Noninstrumental immunoassays based on antimycotoxin antibody principles are
LFD, dipstick tests, and
flow-through assays. In these assays, antigens or antibodies
are immobilized on carrier membranes prepared from polyvinylidene di
uoride,
nylon, or nitrocellulose. Based on the appearance of colored lines on analysis strips,
qualitative, semiquantitative, and in some cases quantitative results can be obtained
by membrane immunoassays. Concentrations of mycotoxins then correlate with the
intensity of the color. Test kits enabling both qualitative and quantitative analyses are
commercially available for routinely controlled analytes, such as
Fusarium
myco-
toxins (DON, ZON, T2 toxin, and fumonisins), a
atoxins, and OTA in many
matrices. Additionally, new antimycotoxin monoclonal antibodies have also been
developed, such as those for ZON or total fumonisins [90,91].
To document that a particular assay is
fit-for-purpose, several studies focused on
comparison between data obtained and those generated by conventional ELISA or
LC
MS techniques. Most recently, the concentrations of both DON and 3-ADON
have been assessed by both ELISA and LFD assays [92]. Although the data obtained
with LFDs were in agreement with ELISA at most of the concentrations tested, in
some cases, the recoveries of LFDs were outside the range of EU requirements (70
-
-
120%). In a study by Liu J. et al. [93], the accuracy of a new quantitative LFD for
DON determination in durum wheat, semolina, and pasta was veri
-
MS/MS analyses. The assay was shown to be capable of simple, rapid, cost-effective,
and robust on-site screening or remote quantitative analysis for ZON at concentrations
ful
ed by parallel LC
lling the worldwide legislation requirements.
Great attention has also recently been paid to the development of reliable multi-
target dipsticks. For instance, a study describing semiquantitative determination of
multiple mycotoxins in wheat, oats, and maize by multiplex indirect dipstick
immunoassay was published in 2012 [8]. In this study, two application reports on
the use of commercial dipsticks for simultaneous determination of DON, ZON, T2/
HT2 toxins and fumonisins FB1, FB2, and FB3 in cereals were described. Amethanol
and water mixture used for the extraction of samples demonstrated recoveries in the
range of 73
109% for all tested mycotoxins in all examined matrices (wheat, oats, and
maize). The complete sample preparation and extraction was performed within 10 min
and the dipstick analysis was performed in
-
30min. The reliability of these assays
∼
was con
MS analysis. The rate of false positive results, which can be
caused by cross-reactivity of structural analogs, was below 13%.
The development of these types of devices is still in progress. In particular, the use of
nanotechnologies and nanomaterials for preparation and construction of assays has been
applied and published. For instance, a quantitative LFD for measuring of OTA in maize
and wheat was developed [94], in which a ready-to-use device with antibodies labeled
with gold nanoparticles was applied. Similar establishment was also published for the
detection of a
rmed by LC
-
atoxins B1 in food [95], but in this particular case a monoclonal antibody
immobilized on nanoparticles with a silver core and a gold shell as a detection reagent
was used. The assay was evaluated with the use of naturally contaminated rice, wheat,
sun
ower, cotton, chili peppers, and almonds. Agood correlationwas obtained between
