Faster than PCR
Russian scientists have created a fast alternative to PCR diagnostics
Recognition of DNA fragments is an indispensable method for the diagnosis of many hereditary as well as infectious diseases. But existing technologies have their drawbacks. The new development of Russian scientists gives the result many times faster than the classic PCR.
The achievement is described in a scientific article published by scientists from the Institute of Theoretical and Experimental Biophysics of the Russian Academy of Sciences in the journal Analytical Chemistry (Shlyapnikov et al., Rapid Amplification-Free Microarray-Based Ultrasensitive Detection of DNA).
DNA analysis is an important diagnostic tool. First of all, it allows you to identify hereditary ailments, but it is also used to diagnose infections. The fact is that the pathogen or parasite that causes infectious diseases has DNA sequences peculiar only to it. Therefore, the diagnosis can be made by identifying these DNA fragments in human blood.
The gold standard for DNA fragment analysis today is polymerase chain reaction (PCR). But such a diagnosis is a rather lengthy process (the analysis may take several days). In addition, it is sensitive to the presence of interfering impurities in the sample.
The new development of Russian scientists is devoid of these disadvantages, and at the same time it is close to PCR in sensitivity. It takes less than five minutes to detect DNA present only in a concentration of 10,000 fragments per 0.1 milliliter. A medical analysis can be done in 10 minutes.
Scientists have created a microchip to which short fragments of DNA (oligonucleotides) are chemically attached, complementary to those sequences that need to be captured. They play the role of a kind of traps: coming into contact with the pieces of DNA intended for them, they capture them and do not let go.
Schematic representation of the experiment. Translation of "Vesti.Science" (nauka.vesti.ru ). Illustration by ITEB RAS.
During the analysis, a flow of liquid containing substances from the sample taken from the patient flows through the microchip. Thanks to the newly applied flow microcell of a special design, any DNA fragments in this flow are deposited onto the chip using an electric field. If these are the sequences that biologists are looking for, they are associated with "DNA traps". Extraneous DNA is quickly washed off the chip.
Then the surface is scanned with magnetic beads coated with streptavidin (streptavidin). Such a ball collects the trapped DNA fragments thanks to biotin tags.
"Our method is based on the use of technologies that were previously developed for immunoassay on protein microchips. In this paper, similar technologies were used for DNA analysis. However, a significant part of the work had to be done anew, since DNA molecules have a completely different chemistry, and, for example, in order to immobilize oligonucleotides on a special substrate, it was necessary to create a new technology," said Yuri Shlyapnikov, co–author of the article, head of the Laboratory of Nanostructures and Nanotechnology at ITEB RAS, Candidate of Chemical Sciences.
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