Abstract:
This thesis describes the development and evaluation of a number of
biosensors
for food applications.
The first part of this thesis deals with the development
of
Surface Plasmon Resonance
(SPR) biosensor systems, coupled with
Polymerase Chain Reaction (PCR) for the
detection
of GMO related amplified nucleic acids in foodstuffs.
The first SPR Biosensor described, used streptavidin-biotin linkage chemistry to attach
a
P35S nucleic acid probe on
dextran-coated SPR transducer chips.
Methodologies
were
developed for both the PCR
stage and post-PCR sample preparation for the
sensitive, rapid and cost-effective
detection
of
GMO-specific
amplified
DNA
sequences. The final
embodiment of the method was an asymmetric
PCR
amplification system with a simple sample processing step (0.3 M NaOH for 30 min
in
20 %
v/v
formamide). The developed PCR-SPR system was successfully applied to
the screening of samples of
GMO
origin.
The
second SPR biosensor
reported
herein, is based on a
SPR chip immobilised
single-stranded thiolated DNA. The thiolated probe exhibited a
hybridisation
capacity of
95 RU (Resonance Units) for 100 nM of complementary DNA target
and a
detection limit
of
5
nM.
The
potential of the current probe system
for the
detection
of symmetrically amplified
DNA
sequences of short
length
was
subsequently confirmed.
The
second part of this thesis involved
preliminary studies into the development
of simple,
disposable
screen-printed electrodes
for the electrochemical
determination
of glucose and
L-amino acids
in horticultural
products.
The
dynamic
range of the developed biosensors was up to 10 mM
for
glucose and up
to 1
mM
for L-leucine determination. The developed glucose biosensor exhibited
encouraging analytical performance in fresh fruit
samples.
However, the L-amino
acid oxidase electrodes consistently underestimated the amino acid content of the
fruit
samples. The latter
observation was
found to be
primarily
due to inhibitory
components in the matrix.