Using gene scissors to detect diseases

Short molecules known as microRNA (miRNA) are coded in the genome, but unlike other RNA sequences, they are not translated into proteins. In some diseases, such as cancer or the neurodegenerative disease, Alzheimer's, increased levels of miRNA can be detected in the blood. Doctors are already using miRNAs as a biomarker for certain types of cancer. Only the detection of a multitude of such signaling molecules allows an appropriate diagnosis. The researchers are now working on a version of the biosensor that recognizes up to eight different RNA markers simultaneously.

The CRISPR biosensor works as follows: A drop of serum is mixed with reaction solution and dropped onto the sensor. If it contains the target RNA, this molecule binds with a protein complex in the solution and activates the gene scissors -- in a way similar to a key opening a door lock. Thus activated, the CRISPR protein cuts off, or cleaves, the reporter RNAs that are attached to signaling molecules, generating an electrical current. The cleavage results in a reduction of the current signals which can be measured electrochemically and indicates if the miRNA that is being sought is present in the sample. "What's special about our system is that it works without the replication of miRNA, because in that case, specialized devices and chemicals would be required. That makes our system low-cost and considerably faster than other techniques or methods," explains Dincer. He is working on new sensor technologies at the Freiburg Center for Interactive Materials and Bioinspired Technologies (FIT) and together with Prof. Dr. Gerald Urban at the Department of Microsystems Engineering (IMTEK).

Weber, a professor of synthetic biology at the cluster of excellence CIBSS -- the Centre for Integrative Biological Signalling Studies of the University of Freiburg -- emphasizes how important the interdisciplinary environment at CIBSS is for such a development: "The biologists at Freiburg work together on these technologies with their colleagues from the engineering and materials sciences. That opens new, exciting routes to solutions." The researchers are aiming to further develop the system in about five to ten years to become the first rapid test for diseases with established microRNA markers that can be used right at the doctor's office. "The laboratory equipment must nevertheless become easier to handle," says Weber.