Network for catching viruses

Scientists caught viruses with carbon nanotubes

Oleg Lischuk, N+1

American scientists have developed a configurable micro device that captures viruses in samples with low levels and contaminated with foreign impurities. The results of the work are published in the journal Science Advances (Yeh et al., Tunable and label-free virus enhancement for ultrasensitive virus detection using carbon nanotube arrays).

Avian influenza viruses in nanotubes (Penn State University)

Identification of the species and specific strains of pathogenic viruses plays a key role in the study, diagnosis, treatment and prevention of infections caused by them. The development of modern methods of analysis, such as polymerase chain reaction (PCR) and nucleic acid sequencing, has greatly facilitated this task. However, when working with field samples containing a minuscule number of virus particles, their determination is often difficult. Ultracentrifugation and ultrafiltration are used to isolate viruses in such samples, but these methods are inconvenient to use and their possibilities are limited.

To solve this problem, the staff of the University of Pennsylvania has developed a system for enriching infected samples using a filter of parallel nitrogen-containing multi-walled carbon nanotubes. These nanotubes were grown directly on the silicon substrate of a microfluidic device called CNT-STEM (carbon nanotube size-tunable enrichment microdevice, a custom-sized enrichment micro-device made of carbon nanotubes). As the name suggests, the technology allows for the growth of adjusting the size of the gaps between the nanotubes using different patterns of iron catalyst on the substrate. The range of these sizes is from 17 to 325 nanometers, which allows them to be precisely adjusted to different types of viruses.

Different catalyst patterns and corresponding nanotube sizes (Science Advances)

Carbon nanotubes were chosen for the filter because they are durable, biologically neutral, and in addition, delayed viruses are easily separated from them.

During the analysis, a suspension is prepared from the sample, which is passed through a membrane filter with pores with a diameter of 220 to 450 nanometers to remove cells and other relatively large objects. The suspension prepared in this way is passed through CNT-STEM, and the nanotubes trap viruses, passing through smaller impurities. After that, the virus concentrate is removed from the nanotubes and examined by conventional methods.

The principle of operation of CNT-STEM (Science Advances)

In experiments with fluorescent molecules, polystyrene microspheres of various diameters and a low pathogenic strain of H5N2 avian influenza (A/chicken/PA/7659/1985), scientists managed to achieve about a hundredfold degree of enrichment of the initial samples and purification of them from impurities. Also, the device was successfully tested on real field samples: swabs taken in 2012 from the cloacals of five ducks and turkey tissue samples taken in 2014. Sequencing of the enriched biomaterials revealed previously unknown strains of avian influenza virus, which received the designation H11N9 (A/duck/PA/02099/2012), and infectious avian bursitis, named IBDV/turkey/PA/00924/14.

"Since our device isolates and concentrates viruses based only on their size, we can catch pathogens whose biological properties are not known — there is no need for antibodies or other molecular markers. When the virus is captured and concentrated, it can be characterized by genome—wide sequencing and other methods," explained one of the authors of the work, Mauricio Terrones.

Carbon nanotubes are one or more graphene planes rolled into a cylinder. Due to their exceptional mechanical, electrical, optical and other properties, they are constantly finding new applications. So, on their basis, highly efficient transistors, superconductors, a direct light-to-electricity converter, a "fishing rod" for cells and macromolecules, a sensor for determining the freshness of meat and much more have been created.

Portal "Eternal Youth" http://vechnayamolodost.ru  10.10.2016