Antimicrobial Effect of Bismuth and Silver Nanoparticles in Oral Species

Objective: Bismuth has been used as an antimicrobial agent, for treating gastrointestinal disorders, especially in the eradication of Helicobacter pylori. In addition, silver is well known for its effective antimicrobial properties. The aim of the present study was to evaluate the minimum inhibitory concentrations (MICs) of nano (5 to 20 nm) and micro particles using different bismuth chemical derivatives in comparison to the well-known colloidal silver, on eight bacterial species belonging to the normal flora of the oral cavity. Methods: Zero-valent bismuth (ZVBi NPs), bismuth oxide (Bi2O3 NPs) and silver (ZVAg NPs) colloidal nanoparticles were synthesized. In addition, their respective microcrystalline equivalent species were prepared. Different concentrations of each of the above mentioned compound were tested with pure cultures of the following bacterial strains: Aggregatibacter actinomycetemcomitans, Actinomyces israelii, Eikenella corrodens, Fusobacterium nucleatum, Parvimonas micra, Porphyromonas gingivalis, Prevotella intermedia and Streptococcus sanguinis. Results: ZVBi and Bi2O3 NPs are able to inhibit bacterial growth at 0.16 to 0.32 μM, except to S. sanguinis, which is inhibited at 1.28 μM. In contrasts, ZVBi and Bi2O3 microparticles are effective at 128 μM. Ag NPs are effective to inhibit the growing of six microbial species at 0.08 μM, except for F. nucleatum and P. gingivalis, which are inhibited at 0.16 and 0.32 μM, respectively. While the MICs, of silver microparticles, are effective at 128 μM. Conclusions:Important results were obtained, the confirmation of the antibacterial properties of Bi-based particles for other strains than the H. pyroli. Secondly, that the nano-compounds can achieve an inhibition of bacterial growth, using much lower concentrations than their respective microcrystalline compound. Confirming the notion that the characteristics or effects of an element may vary depending on whether the particle is in micro or nanometer size. Additionally, ZVBi NPs exhibit a similar antibacterial action in comparison with colloidal silver nanoparticles