Nanoparticles for Trace Analysis of Toxins: Present and Future Scenario - Advanced Materials for Agriculture, Food and Environmental Safety - page 191

and demonstrated for a variety of applications. h e ability of array bio-
sensors to analyze multiple samples simultaneously for multiple analytes
of ers a signii cant advantage over other types of biosensors. In particular,
a rapid, multianalyte array biosensor developed by Ngundi et al. [60] at the
Naval Research Laboratory of Washington D.C., USA, has demonstrated
the potential to be used as a screening and monitoring device for clinical,
food and environmental samples. h e device, which is portable and fully
automated, can be used with dif erent immunoassay formats. One interest-
ing application is the development of a competitive immunoassay for the
detection and quantii cation of ochratoxin A in a variety of spiked food
and beverage samples. A simple extraction procedure was employed with
no need for clean-up or preconcentration of the sample extract. h is is the
i rst demonstration that a rapid biosensor can be used in a competitive
assay format to detect a mycotoxin in extracts of relevant foods. However,
further work aimed at developing a dual-analyte assay for deoxynivalenol
and ochratoxin A showed that improvements are still necessary to reduce
the analysis time and increase the sensitivity.
Carbon nanotubes were used for the determination of zearalenone in
urine samples by Andres et al. [61]. Multiwalled carbon nanotubes were
modii ed with an enzyme, al atoxin detoxii zyme. h e MWCNTs were used
for enzyme immobilization of al atoxins detoxii zyem (APTZ) and for the
determination of sterigmatocystin [62] and also carbon nanotubes i eld
ef ect transistors (FET) that had been functionalized with protein G and
IgG to detect Aspergillus l avus in contaminated milled rice [63]. Optical
sensors based on nanomaterials have been applied much less for the detec-
tion of analytes of interest in the food industry. Quantum dots (QD) are
practically the only nanomaterial. h ey are nanocrystals of inorganic semi-
conductors that are somewhat restricted to a spherical shape of around
2 to 8 nm diameter [64]. h eir l uorescent properties are size-dependent
and, therefore, they can be tuned to emit at desired wavelengths (between
400 and 2000 nm) if synthesized in dif erent composition and size. In this
way, QDs of dif erent sizes can be excited with a single wavelength and
emission controlled at dif erent wavelengths, thus providing for simultane-
ous detection. h is, together with their highly robust emission properties,
makes them more advantageous for labeling and optical detection than
conventional organic dyes [65]. h eir high quantum yields and their nar-
row emission bands produce sharper colors, leading to higher sensitivity
and the possibility of multiplexing of analysis [66, 67]. Costa et al. [68]
have reviewed the progress in exploiting these novel probes in optical sens-
ing, as well as their still unexploited sensing capabilities. In the analytical
chemistry i eld their major application has been as l uorescent labels, while