People with congenital phenylketonuria, a condition in which the amino acid phenylalanine is overproduced, have to undergo regular blood testing. This is important in part because maintaining a proper diet can reduce phenylalanine levels, so gauging the effectiveness of one’s diet can help control the condition. Currently, though, blood samples have to be sent out to the lab and the results are received a few days later, which is inconvenient and can be too slow for many.
Now researchers at Max Planck Institute for Medical Research in Heidelberg, Germany and the École Polytechnique Fédérale de Lausanne, Switzerland have developed a paper-based device that can quickly measure concentration of phenylalanine in a small sample of blood. Moreover, the same technology should be applicable to many other clinically important blood metabolites, including glucose and glutamate.
To test for phenylalanine, a blood sample from a finger prick is mixed with a reaction buffer and the mixture is dropped onto the specially prepared paper test. The paper starts as blue when the liquid is applied, but changes to red the more phenylalanine is in the sample. To measure the ratio of blue to red, a simple smartphone app is provided that takes a picture of the test paper and displays the result. This was already successfully tried on patient samples from two different hospitals.
“We introduce a fundamentally new mechanism to measure metabolites for blood analysis,” says Qiuliyang Yu, first author of the paper and scientist at the Department of Chemical Biology at the Max Planck Institute in Heidelberg. “Instead of miniaturizing available technologies for POC applications, we developed a new molecular tool.”
Here’s a video from the Max Planck Society with the researchers showing their work: