Biotechnology 15
surface with specific ‘molecular traps’ that bind the
chosen target molecules. Once bound, the target
molecules would change the colours that the device
absorbs and scatters, alerting the sensor to their
presence.
The team’s next step is to test whether the pair of
nanostructures can detect chosen substances in lab
experiments.
Professor Maier concludes: “This study is a
beautiful example of how concepts from different
areas of physics fertilise each other.”
Meanwhile, the German Federal Ministry of
Education and Research (BMBF) has just approved a
joint project under leadership of Forschungszentrum
Dresden-Rossendorf (FZD) and in collaboration with
the University of Rostock, Proaqua in Mainz and the
Helmholtz Centre for Environmental Research (UFZ).
The project is part of the Bionic Innovations for
Sustainable Products and Technologies (BIONA)
research programme. It will use the natural
nanostructures of bacterial coat proteins to fix
aptamers onto sensor surfaces in a controlled manner.
The UFZ is to develop aptamers that are capable
of detecting certain organic substances, such as
undesirable pharmaceutical residues, that enter the
environment through wastewater (Fig. 1).
The term aptamer means something like “fitting
pieces” (from the Latin word aptus, meaning to
fit, and the Greek word meros, meaning piece).
Fig. 2. BARC has the potential to detect 64 different target analytes.
Aptamers consist of nucleic acids and have a 3D
structure that enables them to identify and bind diagnostics, food safety, environmental testing, and
certain target molecules. These binding abilities allow, national security.
for instance, tracing, detecting and measuring certain NRL has developed a highly sensitive, portable
substances. Hence their potential as biosensors. biosensor system called the compact bead array sensor
The challenge is to identify the right aptamer for a system (cBASS). This innovative instrument utilises a
particular target molecule. Such target molecules can be special integrated sensor chip, called the Bead ARray
very complex structures, like whole cells or organisms, or Counter (BARC), which contains an embedded array of
tiny molecules consisting of just a few atoms. giant magnetoresistive sensors. With 64 200 µm diameter
This selection method is called systematic evolution of sensors on the chip, BARC has the potential to detect 64
ligands by exponential enrichment (SELEX). different target analytes (Fig. 2).
Scientists at the UFZ’s biosensor laboratory have The technology has already been licensed to Seahawk
developed two different modifications of the SELEX Biosystems Corporation in Rockville, Maryland, for further
method. One of these is known as FluMag SELEX. The development in veterinary diagnostic, clinical diagnostic,
‘Flu’ stands for fluorescence and refers to the fact that a and environmental applications.
fluorescence molecule is added to the nucleic acids during Researchers at NRL began working on the
the SELEX procedure to make them visible. In this manner magnetoelectronic biosensor concept more than a decade
the molecules can always be found again and researchers ago, under the leadership of Richard Colton and former
can measure the enrichment of those which exhibit best NRL researcher David Baselt.
binding and detecting abilities to the given target. The Baselt used a quantum-mechanical effect called giant
‘Mag’ refers to magnetic beads. These are dust-mote-sized magnetoresistance (GMR). In simplistic terms, GMR
magnetic beads onto which the scientists stick the even materials are magnetic field-dependent resistors - their
smaller target molecules to make them more manageable resistance changes when subjected to an externally
applied magnetic field. GMR devices are typically
Novel naval assays]
constructed of alternating magnetic and non-magnetic
Naval Research Laboratory scientists in the US are also metal thin-film multilayers that are only nanometers in
partnering with industry to develop a sensor system for thickness.
biomolecules that could make a significant contribution Baselt looked specifically at a type of GMR called
to a variety of fields such as healthcare, veterinary multilayer GMR in which the resistance of two thin
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