Abstract:
GOODFOOD aimed to develop new generation micro- and nanoscale
devices for safety and quality assurance in the food chain and agrofood
industry. Cranfield University, along with other partners in Worpackage 2,
was responsible for developing immunosensors for the determination of
pesticides in wines and fruit juices at analytically valid levels.
Methods and Materials
The immunosensor format was based on the use of antibodies with
binding specificity directed towards the target analytes. These were chiefly
supplied by CSIC in Barcelona. The protocol and reagents supplied were
used for detection of atrazine and 2,4,6-Trichlorophenol in various matrices.
Screen Printed Electrodes were produced, comprising carbon working and
counter electrodes and Ag/AgCl working electrode. Screen printed
electrodes can be mass-produced at low cost, and so are disposable after a
single use. A macro-scale flow-cell system was used with the screen-printed
electrodes for detection of horseradish peroxide (HRP) which is the enzyme
label for the assay (Figure 3). As part of system optimisation, three electron
acceptors were compared. Reaction time between substrate and enzyme was
also examined as a factor. As a step towards miniaturisation, HRP was
immobilised onto magnetic beads and then dilutions of the beads were
measured in order to help calibrate the system.
Activated Sepharose 4B
TM
from Pharmacia was also used as a solid
support. Small-scale Polydimethylsiloxane (PDMS) and adhesive-layer cells Dumont / DETECTION OF PESTICIDES
iv
were manufactured for optical analysis of immunoassay product. Optical
analysis was performed by an RGB reader developed in-house.
Results
The detection of atrazine and 2,4,6-TCP at nanomolar concentrations
in various matrices, using the supplied reagents was demonstrated. Of the
three electron acceptors tested, ABTS was found to be most effective.
Increased reaction time was found to increase the signal. Dilutions of
magnetic beads coated with immobilised HRP gave a proportional response
as anticipated.
Data obtained by optical analysis of assay product using the RGB-
reader followed the expected trend and showed signal intensity reduction
with increasing analyte concentration.
