EFFECTS OF MAGNETITE NANOPARTICLES ON MICROORGANISMS

A.N. Belousov, T.P. Osolodchenko, Ye.Yu. Belousova

 

Abstract: The performed microbiological studies of the effects produced by magnetite nanoparticles (MNPs) on microorganisms have revealed the following facts: 1) pronounced changes in sensitivity of pathogenic microorganisms to antibiotics, widely used in clinical practice, towards in crease of their antibacterial activity; 2) a distinct bacteriastatic effect of these MNPs along with absence of any normoflora pathologies in microbiocenosia of human mucous membranes; 3) data of the parallelism in the study with the alternative ferrocolloidal non-magnetite nanoparticles enable us to draw conclusions about the effect of the influence exerted by a magnetic field on microorganisms from the side of colloidal particles of the magnetite in the above MNPs.

Keywords: magnetite nanoparticles; microorganisms; microbiological; antibacterial activity; bacteriastatic effect; normoflora.

 

Studies of the effects produced by magnetic fields on biological objects were started long ago, and now they are urgent. But the majority of experimental data are varied and contradictory, therefore regularities and mechanisms of their action have-not been formulated yet. Recent achievements in the fields of physical and colloidal chemistry as well as medicine have enabled creation of new magnetic structures, ferrocolloidal or magnetic fluids in particular, which are adapted to biological media of a living organism [1].

Their wide introduction has contributed to development of principally new technological processes and equipment not only in engineering but also for medicobiological researches. Effects of magnetic fields on microorganisms attracted much attention, but such investigations were unidirectional and carried on mostly with Escherichia coli and Staphylococcus. We have not met any reports about effects on bacteria in the home and foreign literature, though a number of authors point out in their researches that a magnetic field can change efficacy of the action of remedies in an organism.

Taking into account all above mentioned, as well as an increased interest to the influence exerted by magnetic fields on a living cell, we have decided to study effects of magnetite nanoparticles (MNPs) on microorganisms causing various supportive-inflammatory processes in humans. It should be also mentioned that in order to reveal the real effects of the magnetic field action on microorganisms we have also synthesized a ferrocolloidal solution which has no magnetic sensitivity.

The research was made on the following objects: Staphylococcus aureus, Pseudomonas aeruginosa. Corynebacterium diphtheria, fungi from the genus of Candida.

During the study with the method of disks, we revealed increases in diameters of the areas of delayed growth of microorganism strains, treated with the above MNPs, in comparison with "pure" strains.

Another characteristic feature was the fact that under the effect of MNPs the bacteria demonstrated a higher sensitivity to antibiotics than the bacteria under the effect: of the ferrocollold which has no magnetic properties.

It is worth mentioning that some strains of microorganisms, that were isolated from patients with supportive-inflammatory diseases and possessed resistance to the majority of antibiotics, began to demonstrate sensitivity to these antibiotics, in particular to penicillin, ampicillin, tetracyclin and gentamycin, after 24-hours' exposure to the above MNPs.

Thus three strains of Pseudomonas aeruginosa, isolated from foci of a supportive wound, were resistant to 24 investigated antibiotics from the groups of penicillins cephalosporina, aminoglycosides, rifampicins, and others, except for zanocin, amicacin and cyproorphloxacin. After 24-hours' treatment with MNPs these strains were resistant only to 16 antibiotics, but became sensitive even to antibiotics of the penicillin line - carbenicillin and azlocillin.

The minimum inhibitory concentration of antibiotics, producing the effect on pathogenic flora, was significantly decreased. Later, our investigations were directed to see changes in the microorganisms under the effect of MNPs, particularly their antimicrobial activity with respect to the antibiotics which are widely used in clinical practice.

The standard suspension of microorganisms and fungi, amounting to 1 milliard per 1 ml of the physiological solution, was treated with MNPs at, respectively, 0.9 ml and 0.1 ml of the suspension of the bacteria. The exposure lasted 1 hour, 3 hours, 24 hours, and 48 hours at 37°C. Then cultures of the microorganisms and fungi were inoculated on solid nutrient (agar) media, there with taking into account how some biological properties changed under the effect of MNPs.

Exposure of the bacteria and fungi to MNPs for 1 hour and 3 hours had a negative effect only on growth of cell populations. No cultural, morphological and biochemical properties were changed. Moreover, areas of haemolysis in the microorganisms with haemolytic properties constricted.

Exposure to MNPs during 24 hours resulted in a significant inhibition of growth properties of the microorganisms (only growth of single colonies was observed), changes in cultural and morphological tests, deceleration of biochemical reactions, in particular fermentation of carbohydrates and utilization of urea. Complete registration of biochemical reactions was performed only after 48 hours.

Exposure to MNPs for 48 hours resulted in the bacteriostatic effect. Within the first 24 hours any growth of the microorganisms was actually absent, except for growth of single colonies of clinical strains. Growth of microflora on the nutrient media was revealed only on the 2nd day. There was a significant decrease in biochemical activity and changes of cultural and morphological properties there. Studies of antibacterial activity of MNPs themselves were performed by standard methods (the method of wells or disks). The investigation has revealed that the given MNPs only weak activity to reference strains of Staphylococcus and fungi from the genus of Candida. The above MNPs produced no effect on gram-negative aerobic flora and diphtheria bacilli, as well as on clinical strains of the microorganisms. But in haemolytic colonies their areas of haemolysis were practically absent or very insignificant. Pseudomonas aeruginosa had no pigment. The size of most colonies web diminished. Any other significant differences in biological properties between the reference and clinical strains after their exposure to MNPs were not observed. Consequently, it should be noted that a prolonged influence of the given MNPs on the clinical strains did not result in any pronounced bacteriastatic effect. Weak growth of the microorganisms was noticed within the 1st day after inoculation on the nutrient media.

The opportunity of using MNPs as sorbents has enabled us to study their effects on the microflora, which constitutes normal microbiocenosia of human mucous membranes in humans, in particular on Bifidobacterium and Lactobacterium. As it is known, normoflora takes part in metabolism and synthesis of various acids and vitamins, stimulates the lymphoid apparatus to form immunoglobulins and for phagocytosis, participates in renewal of cells in the mucous membranes thereby forming their resistance. Therefore, dysfunction of the normal microflora under effect of some substances results in weakening of specific factors of protection of the organism, it enabling invasion of toxins and allergens into the blood stream.

Results of the study have shown that even a prolonged exposure to MNPs does not cause any changes in biological properties of the normoflora, except for an insignificant inhibition of the growth ones. But the response of inhibition of the normoflora growth was only short-term and 24 hours later the microflora resumed its vitality. A weak response of Bifidobacterium and Lactobacterium to the effects of MNPs was apparently caused by metabolism of these bacteria, since they represent the anaerobic group of bacteria.

Parallel investigations with the non-magnetic ferrocolloidal fluid have demonstrated that this preparation possesses pronounced antimicrobial activity both to the pathogenic flora and representatives of the normoflora. Particularly, we observed inhibition of growth properties in Bifidobacteria constituting the intestinal normobiocenosis.

Consequently, the performed microbiological studies of the effects produced by MNPs  on microorganisms have revealed the following facts: I) pronounced changes in sensitivity of pathogenic microorganisms to antibiotics, widely used in clinical practice, towards increase of their antibacterial activity; 2) a distinct bacteriastatic effect of these MNPs along with absence of any normoflora pathologies in microbiocenosia of human mucous membranes; 3) data of the parallelism in the study with the alternative ferrocolloidal non-magnetite nanoparticles us to draw conclusions about the effect of the influence exerted by a magnetic field on microorganisms from the side of colloidal particles of the magnetite In the above MNPs.

 


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