In the course of our goal to carry out research leading to tangible
benefits for future generations, Imego is in the process of developing a
micro sensor system based on molecular imprints in polymeric materials
for the purpose of detecting toxic substances. The aim is to develop a
sensor capable of detecting the toxins that appear in drinking water,
agricultural products and food.
Molecularly Imprinted Polymers in sensorics
Molecularly Imprinted Polymers (MIPs) are used to specifically bind and
enrich medium and small sized molecules. MIPs can be used to detect a
wide variety of compounds and most molecules below less than
approximately 5 kDa are suitable for imprinting.
A specific MIP is designed and prepared for each molecule of interest. It
can then be used as a selective sensing material integrated in a sensoric
system. MIPs can be designed to be used in a sensor system for the
detection of the toxins that can appear in drinking water, agricultural
products and food to name some examples.
The detection part of the sensor system is fairly generic, so similar
detection techniques can be used to sense a variety of different
compounds. Imego´s strategy involves the evaluation and optimization of
several detection techniques using model imprint systems. After
identifying the optimal detection technique, we produce molecular
imprints of target analytes of commercial interest or environmental
importance then use them in our sensor system.
Principle of Molecularly
Imprinted Polymer production
Molecularly Imprinted Polymers act by specific binding of the molecule
they are made to bind. The specificity is established by the production
procedure. The molecule of interest, the blue target molecule in the
figure above, is mixed with functional monomers. The monomers bind to the
target molecule via for example hydrogen bonds, electrostatic interaction
or hydrophobic interactions. A crosslinking molecule is added and by
illuminating or heating the reaction mixture a polymerisation process is
started, linking the crosslinkers to the monomers and to each other and
locking the structure around the target molecule. The target molecules
are then washed away, leaving hollow spaces in a sponge like polymeric
network. The hollow spaces are able to encase and rebind the target
molecule if encountered with for example a water sample containing the
molecule. The rebinding has a specificity connected to both the
geometrical structure of the hollow site and the chemically functional
groups within the site.
Principles of detection
When the target molecule is absorbed by the molecularly imprinted polymer
network and binds to the tailor made hollow spaces in the polymer, the
characteristics of the polymer are altered. At Imego we evaluate two
different detection techniques for monitoring of the target binding.
It is known that the dielectric properties of the imprinted polymer with
and without the bound analyte are different. One of the detection
techniques used at Imego is based on the measurement of the frequency
dependent complex impedance of a MIP layer. We use microelectrodes
developed at Imego that are covered with a thin film MIP. See figure
"Imego developed microelectrode" below. The electric signal can be
related to the target uptake in the polymer and the concentration of the
target in the sample solution.
It is also known that some MIPs tend to expand or shrink upon target
absorption and their surface energy changes. These changes are monitored
using micro-cantilevers. The changes of volume and surface energy upon
target binding cause the cantilever to bend, see figure "Cantilever"
below. Changes in the beam curvature can be detected either optically or
using strain gauges and can be related to the target uptake and the
concentration of the target in the sample solution.
In addition to the mentioned detection techniques we use well established
sensor techniques such as Quartz Crystal Microbalance with Dissipation
monitoring and radioactivity measurements to evaluate the function of the
thin MIP layers.
Collaborations
Imego is working together with a research group at Lund University with
several years of experience and expertise in Molecularly Imprinted
Polymer production. The group at Lund University develops the MIP
chemistry and produces thin film MIPs on sensor substrates provided
and/or developed by Imego.
Imego’s expertise lies in the development of an appropriate sensoric
system, with MIPs used as the absorbing material.