BLBS102-c03 BLBS102-Simpson March 21, 2012 11:56 Trim: 276mm X 219mm Printer Name: Yet to Come
42 Part 1: Principles/Food Analysis
y y y
y y y y
y y y y
y y y y
y y
= Enzyme-labeled secondary antibody
= Enzyme-labeled analyte-specific
antibody
= Analyte-specific capture antibody
y
y
= Analyte
y
y
y= Analyte-specific antibodies
= Analyte
Direct sandwich assay Indirect sandwich assay
Figure 3.1.Sandwich ELISA with direct and indirect enzyme-labeled antibody detection.
Other techniques have been developed in recent years for
protein or allergen analysis, which utilize enzyme-labeled
antibodies for detection. These include lateral flow assays,
which are immunochromatographic tests involving movement
of immunoreactants along a test strip, and dipstick tests, which
involve immobilized capture antibodies on a test strip with an-
alyte detection by enzyme-labeled antibodies. Both techniques
are generally inexpensive, rapid, and portable, thus making them
ideal tools for online monitoring. For a detailed review of these
techniques and other methods for protein and allergen analysis,
the reader is referred to a recent review by Schubert-Ulrich et al.
(2009). The growing field of nanotechnology has opened up
other opportunities for development of enzyme-based biosen-
sors for protein analysis. A recent report captured the essence of
yy
y yyy
= Enzyme-labeled analyte
y
= Analyte-specific capture antibody
= Analyte
Direct competitive ELISA
y
y
y
y
y
y
y y
yy yy
y
y
= Analyte-specific
antibody
= Analyte
yy= Enzyme-labeled
secondary antibody
= Protein-bound
analyte
Indirect competitive ELISA
Figure 3.2.Competitive ELISA with direct and indirect enzyme-labeled antibody detection.