Toxicological characteristic and bactericidal properties of Keggin-type heteropolyacids

Introduction. In modern reality the effectiveness of disinfection measures is often complicated by rapid development of microbial resistance to known disinfectants, therefore a constant search for new effective, safe disinfectants and compositions is necessary. Polyoxometallates (POMs), especially Keggin’s heteropolyacids (HPAs), are a promising class of inorganic compounds with a broad biological activity, including antiviral and antibacterial ones. So the research of HPAs toxicity and bactericidal activity for the creation of new disinfectants or optimization of known disinfectants by combining with HPAs are essential and actual. 

Materials and methods. HPAs samples H₃PW₁₂O₄₀, H₃PMo₁₂O₄₀, H₄SiW₁₂O₄₀, H₄SiMo₁₂O₄₀, H₄PMo₁₁VO₄₀, H₅PMo₁₀V₂O₄₀, H₄PW₁₁VO₄₀ were evaluated by the cytotoxicity index (IC₅₀) in three cell lines by the MTT method using MTT-reagent 3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyl-2H-tetrazolium bromide. HPAs acute toxicity in white mice (administration into the stomach and intraperitoneally) was tested in accordance with GOST 12.1.007-76. Bactericidal activity of HPAs and compositions with hydrogen peroxide was determined against test microorganisms S. aureus and E. coli by the suspension method. The results were supplemented by electron microscopic examination. 

Results. Vanadium-containing HPAs structures had higher cytotoxicity. All HPAs corresponded to hazard class III in terms of acute toxicity. Bactericidal activity of HPAs and HPAs combinations with hydrogen peroxide was revealed. The incorporation of two vanadium atoms into HPAs structure increased the bactericidal activity. Electron microscopic examination showed more pronounced morphological changes in the ultrastructure of E.coli treated with HPAs / hydrogen peroxide combinations. Mechanism of the bactericidal activity may be associated with HPAs penetration through a damaged membrane of porin channels of bacterial cells. Explanations are also given for another possible mechanism of HPAs action. 

Limitations. The study is limited to researching toxicological characteristics and bactericidal properties of HPAs, their combinations with hydrogen peroxide. The limited number of HPAs and disinfectants samples is associated with the complexity of the biological experiments. The choice of three cell lines is determined by three different sources of their origin. The suspension method for assessing the antimicrobial activity of substances was performed under the relevant GOST. Test cultures of S. aureus and E. coli were used, other pathogens were not considered. The experiments in vivo were carried out under guidelines for the protection of experimental animals, and their limited number is due to the cost of animals and current ethical views on experiments in vivo. 

Conclusion. It has been shown that prospects of both HPAs research and combining HPAs with disinfectants having a different mechanism of action in order to enhance a disinfecting effect and reduce the risk of developing microbial resistance to disinfectants. 

Contribution:

Baklanova O.V. — research concept, data collection and processing, text writing, responsibility for the integrity of all parts of the article;

Gololobova T.V. — editing;

Fedorova L.S. — responsibility for microbiological research, approval of the final version of the article;

Lopatina O.A. — research concept, collection and processing of material, text writing;

Bidevkina M.V. — responsibility for toxicological research;

Gushchina E.A. — responsibility for electron microscopic examination;

Suetina A.A. — performing cytotoxic tests;

Lisitsyn F.V. — preparation of photographic materials;

Kovalevskiy S.A. — research design, selection of HPA samples;

Dalidchik F.I. — research concept, editing;

Mezentseva M.V. — approval of the final version of the article.

Conflict of interest. The authors declare no conflict of interest.

Acknowledgement. The work was carried out within the framework of the state task on the topic “Fundamental foundations for the creation of nanostructured systems of a new generation with unique operational electrical and magnetic properties” No. 0082-2018-0003 (registration number AAAA-A18-118012390045-2).

Received: September 1, 2021 / Accepted: November 25, 2021 / Published: February 09, 2022