Background: Lactic acid bacteria are considered important probiotics for prevention of some infections. The aim of this work was to investigate the effect of selenium dioxide on the antifungal activity of Lactobacillus plantarum and L. johnsonii against Candida albicans. Methods: Lactobacillus plantarum and L. johnsonii cells, grown in the presence and absence of selenium dioxide, and their cell-free spent culture media were tested for antifungal activity against C. albicans ATCC 14053 by a hole-plate diffusion method and a time-kill assay. Results: Both L. plantarum and L. johnsonii reduced selenium dioxide to cell-associated elemental selenium nanoparticles. The cell-free spent culture media, from both Lactobacillus species that had been grown with selenium dioxide for 48 h, showed enhanced antifungal activity against C. albicans. Enhanced antifungal activity of cell biomass against C. albicans was also observed in cultures grown with selenium dioxide. Conclusions: Selenium dioxide-treated Lactobacillus spp. or their cell-free spent broth inhibited the growth of C. albicans and should be investigated for possible use in anti-Candida probiotic formulations in future.

Some undesired nanoparticles, such as malformed structures or incomplete core/shell Fe₃O₄-Au nanocomposites, might be formed when Fe₃O₄-Au core/shell nanocomposites are being synthesized. These impurities should be separated before any applications are performed. In this investigation, magnetic cores (Fe₃O₄) were synthesized using a conventional fabrication method involving coprecipitation of Fe²⁺ and Fe³⁺. Carboxyl-capped magnetite-gold composite nanoparticles, measuring ≤50 nm, were then synthesized using a plant extract (Eucalyptus camaldulensis). The prepared carboxyl-capped magnetite-gold composite nanoparticles were further subjected to acid treatment for 18 h and characterized with different instrumentation methods. The results of the investigation showed that acid treatment can be applied successfully to separate defect-free Fe₃O₄-Au core/shell nanoparticles from different types of Fe₃O₄-Au nanocomposites, without any considerable changes in their physiochemical properties.

In the present research study, ciprofloxacincoated zinc oxide nanoparticles were prepared using a precipitation method. The nature of interactions between zinc oxide nanoparticles and ciprofloxacin (CAS 85721-33-1) was studied by Fourier transform infrared spectroscopy. The results show that the carbonyl group in ciprofloxacin is actively involved in forming chemical – rather than physical – bonds with zinc oxide nanoparticles. Also the antibacterial activity of free zinc oxide nanoparticles and ciprofloxacin-coated zinc oxide nanoparticles have been evaluated against different clinical isolates of Staphylococcus aureus and Escherichia coli. The free zinc oxide nanoparticles did not show potent antibacterial activity against all test strains. In contrast, only the low concentrations of ciprofloxacincoated zinc oxide nanoparticles (equivalent to the sub-minimum inhibitory concentrations of pure ciprofloxacin) considerably enhanced the antibacterial activity of zinc oxide nanoparticles against different isolates of Staphylococcus aureus and Escherichia coli (4 to 32 fold increase). The result is of particular value, since it demonstrates that, by using biocompatible zinc oxide nanoparticles in combination therapy, lower amounts of antibiotics may be needed.