SURFACE PLASMON RESONANCE APTA-SENSOR
FOR FOOD ALLERGEN DETECTION
J. POLLET1, F. DELPORT1, D. T. TRAN1, H. PFEIFFER2, M. WEVERS2, J.
LAMMERTYN1
K.U. Leuven, Department of Biosystems – MeBioS, Willem de Croylaan 42, BE-3000
Belgium, Jeroen.Lammertyn@biw.kuleuven.be
2
K.U. Leuven, Department of Metallurgy and Materials Engineering, Kasteelpark Arenberg
44, BE-3000 Belgium, Martine.Wevers@mtm.kuleuven.be
1
The widespread incidence of food allergies presents an important challenge for the food
industry. Accurate and reliable product information is essential to inform a rising number of
food allergic patients. Tracing allergens, however, is not obvious, since they generally occur
in very low quantities, hidden in a food matrix. In this research, we aim to develop a costeffective surface plasmon resonance (SPR) probe for the label-free detection of food
allergens.
SPR is probably the best known method for online detection of biological binding reactions.
Nevertheless, SPR is rarely used outside research centers, because most commercial available
systems are expensive and require specialized staff. In the search for more convenient SPRsensors, we have replaced the traditional prism based systems by a fiber optic design. In the
setup, replaceable and interchangeable sensing probes can be affixed onto the end of a
bifurcated optical fiber. The fiber probe is attached to a computer-controlled CNC machine in
order to make repeatable measurements fast and easy. (Figure 1)
Figure 1 A) Sketch of SPR fiber; B) SPR fiber; C) Automated sensor platform; D) SPR transmission output signal
To our knowledge, it is the first time that a SPR probe is combined with the versatile
aptamer-technology. Aptamers are nucleic acids which have the potential to bind with high
affinity to specific target molecules. These selective oligonucleotides are produced in our lab
through a selection process based on systematic evolution of ligands by the exponential
enrichment (SELEX). Their most pronounced advantages over antibodies are stability to
biodegradation and low production cost. Our objective is to utilize this high stability of the
DNA aptamers to develop reusable and cost-effective biosensors with detection limits close
the sensitivity of the classic SPR platforms.
The sensor surface chemistry is a primary research topic in this project. A mixture of
mercapto poly-ethylene glycol and different length mercapto alcohol chains is used as a
ground layer. On this layer, streptavidin is immobilized by 1-Ethyl-3-[3-dimethyl
aminopropyl]carbodiimide hydrochloride. Finally, biotinilated aptamers are attached onto the
streptavidin. Our results illustrated that this surface design prevents non-specific binding and
is very stable, which is important for regeneration.
In a proof of principle, we coated our fibers with DNA-aptamers against human
Immunoglobulin E (IgE). This target protein plays an important role in many allergic
reactions in the human body. The sensitivity of this type of sensors proved to be sufficiently
accurate to monitor the different immobilization steps of the bio-recognition layer (Figure 2).
Results showed that 100 nM of the IgE target shifted the resonance wavelength approximately
3 nm. The dynamic range goes from 10 to 500 nM, depending on the amount of aptamers
immobilized on the sensor surface. We regenerated the sensors using a 1M NaCl, 0.1 mM
NaOH buffer. No shift was visible in the sensorgram when the same experiment was repeated
with IgG. In the near future we will repeat these experiments in real blood serum samples.
Figure 2 Left) The immobilization of the aptamers A. MES buffer, B.Binding curve of Streptavidin in MES buffer, C. MES buffer after
immobilization, D. TRIS buffer, E. Binding curve of biotinilated DNA, F. TRIS buffer after immobilization; Right) Calibration curve for
the IgE protein
In the next step of the project, the probe will be coated with aptamers against different types
of food allergens, more specific to the egg-allergens ovomucoid and lysozyme and the peanutallergens Arah1 and Arah2. Results for lysozyme are soon to be expected.