Researchers at the University of Orenburg have tested the effect of various carbon nanoparticles on bacteria. It was discovered that the bacteria-growth-inhibiting properties of nanotubes declined as the quality of purification lowered; the bacteria were neutral towards fullerenes unless the latter were modified by amine groups.
Over 1.800 different nanomaterials are currently available in the market. Broader use could lead to polluting of natural ecosystems and human habitat. Physicochemical properties of nanoparticles differ from those of large crystals; and their interaction with living systems is virtually unexplored. The group of researchers led by Dmitry Deryabin at Orenburg State University studied the influence of various carbon nanoparticles on Escherichia coli bacteria (colon bacillus). The research is to be published in issue 11-12 of the Russian Nanotechnologies magazine.
Four samples of single-shell carbon nanotubes of various purification efficiency levels as well as multi-shell carbon tubes, fullerenes and chemically modified fullerenes (containing carboxyl and amine groups) were used for the experiment. The nanoparticle suspension was mixed with the bacterial suspension in proportion of 1:4 and kept at 37°С for an hour; later the mixture was dried and examined using the atomic-force microscopy method. In addition, the bactericidal effect was assessed by plating the microorganisms that had contacted with nanoparticles into the nutrient medium and comparing the number of viable individuals in the experimental and the reference groups.
The researchers provided detailed description of peculiarities of each carbon nanomaterial sample. In general, poorly purified nanotubes demonstrated the most effective bactericidal action. Microscopic research showed that the cells of bacteria incubated in contact with the tubes decreased in size (178 nanometer vs. 201 nanometer) and had flat fragments free of cell content. The scientists believe that the damage of the surface bacterial structures is more probably associated with the effect of admixtures (amorphous carbon, metallic catalysts) rather than with the action of the carbon tubes themselves. The study of purified nanoparticles showed that they also contacted with the surface of the bacterial cells but the researchers did not identify reliable effect on the culture viability. The fullerenes and their carboxyl modification had no influence on the viability and morphology of the bacteria whereas the fullerene modified with amine groups (-NH2) was actively interacting with the bacteria and had an evident bactericidal effect. The substance showed a high level of bacterial cell wall affinity as about 97 per cent of nanoparticles got bound with it, and only 3 per cent of particles were preserved in the solution. As a result, a characteristic nanoparticle graininess emerged on the surface of the bacteria accompanied with the changes in the cell length, width and height. After contacting with fullerene modified with amine groups, 60 per cent of bacteria were dead, as compared to the reference group.
The research was supported by the Scientific and Pedagogical Personnel in Innovative Russia Federal Task Program.
Source of information: D. G. Deryabin, А. S. Vasilchenko, Е. S. Aleshina, А. S. Tlyagulova, А. N. Nikiyan. “Studying the Interaction Between Carbon Nanomaterials and Escherichia coli Cells Using Atomic-Force Microscopy.” The Russian Nanotechnologies, 2010, #11-12.
Further information: Dmitry Deryabin, head of the Microbiology department at the Chemico-Biological faculty, Orenburg State University. +7(3532)37-24-81, email@example.com