To reproduce the organism, a virus undergoes an adsorption process (connection) of its particles to the infected cells, connecting to cell membrane receptors. In order to prevent this connection and hence infection, researchers from the National Center for Research in Energy and Materials (CNPEM) developed a strategy that uses nanoparticles loaded chemical groups able to attract the virus by binding to them and taking adsorption pathways that would be used in mobile receivers.
Thus, the viruses, Now surface occupied by their chemical groups carried by the nanoparticles, it is unable to make connections with the cells of the organism. The innovative strategy of viral inactivation was developed within the research "nanoparticle functionalization: increasing the biological interaction" held with the support of FAPESP and coordinated by Mateus Borba Cardoso.
This is the first study demonstrating viral inactivation based on functionalized nanoparticle surface chemistry.
"This viral inhibition mechanism is through the modification of nanoparticles in the laboratory, assigning functions to the surface by adding chemical groups capable of attracting the viral particles and connect to them. This steric effect related to the fact that each atom within a molecule occupies a certain amount of space on the surface prevents the virus from reaching the target cells and bind to it, because it is now 'busy' for nanoparticle " says Cardoso.
The researchers synthesized silica nanoparticles, chemical component of various minerals with distinct surface properties and their biocompatibility evaluated with both types of virus. The antiviral efficacy was evaluated in vitro tests with the HIV virus and VSV-G - causing vesicular stomatitis - infecting type HEK 293 cells, a cell culture originally composed of a kidney cell belongs to a human embryo. Viral particles were prepared to express a fluorescent protein which changes the color of the infected cells, allowing researchers to "follow" the infection.
Innovation follows the same strategy already adopted by researchers in the functionalization of nanoparticles that carry chemotherapeutic drugs in high concentrations to the cancer cells, preventing the healthy are met and minimizing the adverse effects of chemotherapy (read more in agencia.fapesp.br/23210 ).
The silica nanoparticles were selected once again on account of its porosity, which allows a good functionalization of the surface by the addition of chemical groups in their pores. Once synthesized, these particles undergo reactions required that its surface is functionalized in accordance with the chemical affinity of the virus. Specific chemical groups were placed on the surface of particles for the viral proteins are naturally attracted by them.
After this process, the researchers began the characterization of nanoparticles, performing size measurements and checking if the functionalization was correct. For this use an arsenal of techniques, from a microscopy analysis zeta potential of - the surface charge of the particles. Having the information on the load it was possible to correlate it to data already known to the viral envelope, the chemical composition of which is the virus surface, increasing the chances of the nanoparticles are anchored in certain areas of it.
It was also used to ray scattering technique X at low angles (SAXS, its acronym in English). Through radiation generated by the particle accelerator of the National Synchrotron Light Laboratory (LNLS), a member of CNPEM, researchers use the technique to see and study the shape and spatial arrangement of objects on nanometric scale - in this case, the nanoparticles functionalized silica.
"The properly functionalized nanoparticles and viral particles passed, then, for an incubation time so that interact with each other in terms of both surface properties. When there is much attraction caused by the chemical groups on the surface of the nanoparticles, preferably the virus is to bind them, not to cells, "said Cardoso.
After the functionalization of nanoparticles, studies on their charge and other properties, and the incubation period, the investigators performed in vitro tests infecting HEK 293 cells with HIV and VSV-G virus prepared to express fluorescent protein. By means of fluorescence microscopy it was possible to follow the infection and also the cells that were not affected by it. Using flow cytometry technology capable of simultaneously analyzing several parameters cells or particles, the researchers were able to count positive cells and negative after exposure to the virus: the nanoparticles reached reduce viral infection by 50%, demonstrating the efficiency strategy.
"This result could reach 100% if we increase the amount of functionalized nanoparticles in the incubation period but the tests are performed in an optimized range of viral inactivation so that they can be observed the effects on the cells affected by virus, highlighting the differences comparison purposes, "says the researcher.
Tests have also allowed to verify that during the process the cellular morphology is maintained, without the nanoparticles to influence.
According to Cardoso, the strategy could be used, for example, detection and elimination of virus in blood bags before transfusion. For this, the researcher, magnetic nanoparticles are being studied that, once inside the blood medium contained in the bag, would bind to viruses, inactivating them and being subsequently separated from the blood by a magnet, carrying the viral particles. The affinity between chemical groups carried by the viral particles and nanoparticles could also serve for the development of new techniques for detection of HIV and other viruses.
The research results were published in the journal Applied Materials & Interfaces. Article Viral Inhibition Mechanism Mediated by Surface-Modified Silica Nanoparticles is signed by Juliana Martins de Souza e Silva, Talita Diniz Melo Hanchuk, Murilo Izidoro Santos, Jörg Kobarg and Marcio Chaim Bajgelman, and Cardoso, and can be accessed at pubs.acs .org / doi / abs / 10.1021 / acsami.6b03342.
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