Jan 6 2011
Chemists at the University of Rostock have developed a new biosensor that can far more easily deduct genetic traces in corn flour.
As the researchers team headed by Gerd-Uwe Flechsig has demonstrated in a study, their electrochemical DNA analysis on a gold chip provides much faster results than conventional techniques. In a corn flour sample, it could reliably detect traces of GM corn that were under the legal limit of 0.9 percent. Products over this threshold must be correspondingly labelled. The demand for GM detection systems has risen following the adoption of strict legal requirements in Germany.The test from Rostock is expected to arrive on the market in around two years. Genetically modified plants can only be grown in Germany if farmers adhere to strict safety standards. This stance was confirmed last week in the Federal Constitutional Court. The judges in Karlsruhe judged the strict Gene Technology Act to be constitutional. A central aspect of the law concerns liability: Therein, a farmer growing GM crops will be liable for economic damages suffered by neighbouring farmers pursuing conventional cultivation if the GM portion in the neighbouring harvest rises above 0.9 percent. Furthermore, all products must be specially labelled when the proportion of GM material in the total content is more than 0.9 percent.
DNA emits electrical signals
Appropriate detection methods that can reliable detect traces of genetic material in plants are required to be able to check threshold values. “The conventional molecular biological tests are complicated and relatively slow,” says Gerd-Uwe Flechsig from the Institute of Chemistry at the University of Rostock. The standard approach is to take a representative sample of more than 1000 corn grains and grind them into a flour, from which genetic material is purified. Using polymerase chain reaction (PCR), a process for copying DNA, a particular gene segment in the sample is duplicated. “This is followed by the most expensive and slow stage: In most cases, the highly copied gene segments are made visible using optical methods,” says Flechsig.
In conjunction with the company Gensoric, spun off in 2009 from the University of Rostock, his team has now developed a faster high-tech technique that uses an electrochemical approach. The trick: “Instead of dyes, we mark our DNA with metal complexes. When these molecular counterparts dock to DNA, they emit electrons instead of light. We can directly measure these electrical signals,” says Flechsig.
Centimetre-wide gold chip
As a biosensor, researchers use a centimetre-wide chip made of gold, which is populated with snippets of electrochemically-marked DNA. To illustrate the procedure, Flechsig uses the well-worn example of the search for a needle in a haystack. “Whereas other search methods reproduce the needle in order to find them, we hold a magnet against the haystack.” The procedure has now been successfully tested in maize flour samples, added to which are varying quantities of the GM maize MON810. The technique was indeed able to quickly and reliably detect even GM proportions of less than 0.9 percent. After just 15 minutes, the researchers had usable results on their chip. “The next challenge for us, alongside the speed, will be to optimise the detection limit of the technique, so that we can detect even minute amounts of genetically modified corn,” says Maren Mix, one of the team of researchers in Rostock. The scientists are work closely with genetic engineering expert Inge Broer (read more about her on her profile here) from the University of Rostock.
Hunting for multi-resistant germs
Together with the company Gensoric, the researchers hope to develop a practical test system. It is expected to be marketable in two years. The Rostock-based inventors hope to ultimately create a portable biosensor device, which could possibly also be used in field operations. However, the electrochemical DNA test is not suitable for the analysis of traces of green genetic engineering. From January 2011, in the framework of a project funded by the Federal Ministry of Education and Research (BMBF), Gensoric will also be developing a high-throughput test for the detection of multidrug-resistant strains of bacteria. This is intended to assist in the daily activities of doctors in hospitals, or at doctors’ practices.
Source: http://www.uni-rostock.de/