Kistenuyck T.S., Skrotska O.I.

National univtrsiti of food technologies, Ukraine

Antiviral activity of cerium dioxide nanoticles

 

The scientific information on biological activity of ceria dioxide nanoparticles (CeO2) is still very fragmentary. It is known, that nanoceria interaction with biological systems is based on two principal properties of this substance: low toxicity and high reducibility [1]. These factors determines activity of nanoceria in biological redox processes, especially in inactivation of reactive oxygen species, including free radicals that are formed inside living cells.

Moreover, vacancy engineered ceria nanostructures can protect from radiation-induced cellular damage and can prevent retinal degeneration caused by ultraviolet (UV) irradiation. It should also be noted that UV-extinction coefficient of ceria is rather high; therefore this compound is considered a promising UV-filter in sunscreen cosmetics [2]. According to a recent study performed by GEMATRIA Test Lab (Germany), could be judged a key component of future sunscreen cosmetics because it protects from both sunlight and free radicals [3].

The industrial applications includes its uses as a polishing agents, ultraviolet absorbing compound in sunscreen, solid electrolytes in solid oxide fuel cells, as a fuel additive to promote combustion [4]. However, it is in the biomedical industry CeO2 is gaining much attention because of their antioxidant properties [5].

Antiviral activity of nanoceria to date been studied very little. Ukrainian scientists first showed inhubuyuchyy impact sols nanoceria, which were stabilized low molecular weight poliakrylovoy acid (PAA), the development of cytopathic effect (CPS) test vesicular stomatitis virus (BBC family Rhabdoviridae) provided 24-hour pre-contact culture reference fibroblast cell line mice (L929) and epithelial cells of embryos of pigs testicles (PST) [6].

It was found that prophylactic treatment of both cell cultures at a concentration of nanoceria zolyamy 2,0-10,0 mg/ml caused the formation of antiviral resistance of cells [7]. In these studies first showed that nanoceria stabilized by citrate also gave an inhibitory effect on the development of the CPS test virus BBC. In terms of in vitro formation of 100% antiviral resistance observed in both prophylactic and therapeutic regimens. Also found that CeO2 significantly inhibits the reproduction of viruses in model systems L929/BBC and RF/HSV-1: the virus titer reduction was 2,6-4,8 lg. These data are of great practical interest, however, in these studies revealed no possible mechanism nanoceria antiviral activity [8].

Simplified diagram of retrovirus replication in a system with agents based on cerium dioxide Nanodispersed. Extracellular virions enter the host cell, mainly by means of viral fusion proteins that interact with receptors on the plasma membrane. After adsorption of the virus on the cell surface, the virus penetrates the cell in two ways. In the first case, the virus penetrates the cell membrane by fusion with the plasma membrane, and hereditary material appears to cells (typical of herpes viruses).

In the second case, the result of endocytosis of cell penetrating vesicles containing virions. In this state, the virus is packaged in an extra shell formed by the cell membrane. From the second shell it is discharged at the confluence of vesicles from endosomes, where the acidic environment activates fusion proteins and thus contributes to the unification of the virion membrane with endosomalnoyu membrane and then released into the cytoplasm of hereditary material.

This way the most common and characteristic of many complex viruses, such as for influenza virus. After the "strip" genomic RNA is transcribed into double-stranded DNA copy that is imported into the nucleus. At the core of the viral genome DNA is integrated into the chromosome of the host cell and serves as a template for synthesis of viral mRNA. Then viral mRNAs are transported to the cytoplasm, where the synthesis of viral GAG - polyprotein and the glycoprotein shell. Then, the assembly of the virus particles, and then virus particle reaches the plasma membrane or endosomalnoyi and uses it to form new virions, which is able to participate in the next infectious cycle. The penetration of the virus into the cell causes the formation of reactive oxygen species (ROS). On the one hand, ROS play a positive role in the destruction of viruses, since cell peroxisomes (along with mitochondria) is one of the most important parts of the development stage of antiviral innate immune responses. On the other hand, the AFC supports the inflammatory process, causing destructive changes in cells and tissues, in some cases irreversible. They initiate the process of lipid peroxidation of cell membranes, resulting in loss of barrier function in tissues and organs there is structural and functional disorders.

Typically, existing antiviral drugs designed to inhibit certain stages of viral infection. Thus, a number of drugs (eg oksolin) block extracellular virions. The following drugs (Remantadun, Arbidol, Tamiflu) prevent adsorption, membrane penetration and removal of viruses. Others are able to inhibit the synthesis of viral RNA/DNA (azo-Azina oligonucleotides ribavirin) or synthesis of proteins (interferons and their inducers, protease inhibitors). A number of drugs are inhibitors of folding or prevent the release of virions offspring (interferons) [9].

Until recently, nanomaterials regarded only as a means of delivery of biologically active molecules in the center of viral infection [10]. In recent years, there have been reports of independent antiviral activity of nanoparticles without the prior modification of special structures. Yes, shows activity of titanium dioxide nanoparticles (with a particle size of 4-5 nm) with respect to influenza A virus (H3N2). According to electron microscopy after 15 min after the addition of TiO2 nanoparticles in a liquid that contains viruses, data structures adsorbed on the outer shell of viruses and cause local destruction, which in turn leads to the loss of infectious virus activity [11].

It is believed that the antiviral effect of nanoparticles can be directed to different targets in the reproduction cycle of viruses. Consider multiple mechanisms of antiviral action of cerium dioxide nanoparticles in the table.

Thus, due to the adsorption of viral proteins NDC-1) or receptors cells NDC-2) nanoparticles can block extracellular virions and hinder their adsorption on cell membranes. Viruses that enter the cell via endocytosis (eg, influenza virus), for agglutination and release of hereditary material reduces the pH content of the vesicles.

 

 

The mechanism of antiviral action of CeO2 nanoparticles

Targets the drug NDC

 

Mode of action of nanoparticles

per cell and virus

NDC -1

effect on viral receptors (nezdaten virus attach to the cell surface)

NDC -2

effect on cell receptors, what hinders virus adsorbed on the surface

NDC -3

damage to viral nucleic acids

NDC -4

інгібування транскрипції вірусної РНК

NDC -5

hinders "drawing up" virus

NDC -6

hinders release of virus from cells

 

Thus, the hemagglutinin of influenza virus at pH = 7 inactive. Fusion peptide alters conformation only in acidic medium (pH ≤ 5). This pH nanocrystalline cerium dioxide reveals are expressed oxidant properties and can damage nucleic acids virion NDC-3).

Studies show that the physico-chemical point of view CeO2 nanoparticles can non-specifically adsorbed on the surface of both the virus and provide a mechanism for blocking SIC - 1 dimensions virus can be considered as an object of near-field physics. If the virus will be located near nanochastyky CeO 2 is between the virus particle and interaction may be due to fluctuating fields (similar to Vander Waals forces). It is hoped that this interaction will lead to irreversible transformation of the system. For example, can collapse the weak chemical bonds that are part of the education of receptors the viral capsid [12, 13].

This mechanism allows two ways to reduce viral activity. On the one hand, the adsorption of the particles prevents the penetration of the virus into living cells. Firstly, thanks very stable formation of "virus - nanoparticle" can be considered that this system has the geometric characteristics that differ from the characteristics of the virus. Since the permeability of the virus through the cell membrane is largely determined by the geometric factor of virus attached nanoparticles mainly lose their ability to penetrate into cells. Secondly, due to the local field on receptors located on the surface of the virus, molecular groups of receptors can be modified up to their destruction. Indeed, because the effective susceptibility tensor can be sufficiently large values​​, the local field the viral particle is greatly enhanced. Since the virus receptors interact with relevant education on the cell membrane of the principle of complementarity (interaction type key-lock), then any damage to the receptor leads to the impossibility of the virus into the cell. Thirdly, the local field can have on the virus particle thermal effect. Due to local heating of viral capsids latter may lose their properties and activity of the virus will also be reduced [11].

In in vitro experiments, it was shown that the NDC (0.1 M the aqueous solution of colloidal CeO 2 particles with a size of 2-4 nm, stabilized sodium citrate) effectively inhibits the reproduction of influenza virus in cell culture inoculated dog kidney (MDSK) at a dose of 1.25 mM . As a comparison using drugs Tamiflu (Hoffman La Rosh USA) Remantadun (Russia) [14].

After this study, it was suggested that one of the main mechanisms of inhibition of reproduction of herpes virus is blocking nonspecific hemagglutinin and neuraminidase of the virus (NDC mechanism - 1), which affects the stages of adsorption and fusion of the virus with the cell membrane and the exit of the virus from the cell with the release of virus particles from the cell membrane after budding. Perhaps activity blockade surface antigens hemagglutinin and neuraminidase of influenza virus is due to incorporation of nanoparticles in glycoprotein structure surface antigens of influenza virus and change their conformation or due to overlapping of nanoparticles receptors hemagglutinin and neuraminidase active site of interaction with the substrate or erythrocytes.

Use of the drug reduced the severity of symptoms CeO2 to 29.0 points, which corresponds to the therapeutic effect on the level of 63.8% (p <0.05), and significantly reduced the duration of illness. At therapeutic scheme of CeO2 decreased symptoms to score 31 level, the therapeutic effect was 61.3%, duration of disease in animals was 8 days, which is statistically significant for all parameters differ from the control of herpes virus and indicates the efficacy of this dose [12 ].

Mechanisms of antiviral action сeria dioxide nanoparticles are of particular interest for further analysis because open perspective of CeO2 in the prevention and treatment of viral diseases.

 

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