Resveratrol enhancement staphylococcus aureus survival under levofloxacin and photodynamic treatments.

Reactive oxygen species (ROS) are an efficient tool to eradicate micro-organisms owing to the capacity of these species to damage almost all types of biomolecules and to kill cells. The increase in mechanisms of antimicrobial resistance has led to the exploration of new strategies to eliminate micro-organisms that involve the production of ROS such as superoxide anion (O2•-) and hydrogen peroxide (H2O2). ROS are produced during several antimicrobial treatments, including antibiotic and photodynamic therapies. Among the natural antioxidants, resveratrol (RSV) is efficient at preventing damage from ROS, and every day more people incorporate it as a dietary or cosmetic supplement. However, the consequences of the administration of RSV during antimicrobial treatment are unknown. To investigate possible antagonistic or synergistic effects of RSV during antibiotic therapy (levofloxacin) or photodynamic therapy (visible radiation and methylene blue), killing of planktonic Staphylococcus aureus bacteria was evaluated in the presence of RSV. The results showed that the antimicrobial capacity of these therapies is significantly diminished when levofloxacin or methylene blue are co-administered with RSV, indicating that consumption of RSV during antimicrobial treatment must be, at least, cautioned. Moreover, considering the ROS antimicrobial activity of antibacterial agents, the topical addition of RSV may also affect the control of pathogens of the human body. The results presented in this article highlight the importance of the evaluation of possible antagonistic effects when an antimicrobial agent with ROS-mediated action is co-administrated with RSV.

Biocompatibility of magnesium particles evaluated by in vitro cytotoxicity and genotoxicity assays.

Mg is a biodegradable biomaterial which may release particles (MP) to the environment. The possible cyto- and genotoxic effects of MP derived from magnesium powder (mesh 325) were analyzed on rat osteosarcoma UMR106 cells in order simulate the effect of Mg debris. Neutral red (NR) incorporation and acridine orange/ethidium bromide (AO/EB) staining techniques were used as endpoints to analyze the cytotoxic effects at 25-1000 µg/mL concentration range. Genotoxicity was estimated according to micronucleus (MN) formation and the Comet assay (CA). Results showed that MP size changes with time due to corrosion. Changes in lysosomal activity were observed after 24 h only at 1000 µg/mL. Accordingly, AO/EB staining showed a significant decrease in the number of living cells at 500 µg/mL. Transmission electronic microscopy showed MP internalization (60 and 200 nm diameter) in cells after 2-h treatment, whereas no MP was detected after 24 h. A significant dose-dependent increase in MN frequencies was observed at 25-100 µg/mL range (nontoxic range). DNA damage induction was assessed by CA only at 500 µg/mL. Results showed dose-dependent cytotoxic and genotoxic effects of MP on UMR106 cells with different threshold values of MP concentration.

Response of UMR 106 cells exposed to titanium oxide and aluminum oxide nanoparticles.

The cytotoxicity potential of TiO(2) and Al(2)O(3) nanoparticles (NP) in UMR 106 cells was studied by evaluating the lysosomal activity with neutral red uptake assay (NR), and the mitochondrial activity with tetrazolium MTT test. Different NP concentrations (10-300 microg/mL range) were used. A significant (p < 0.001) increase in the absorbance (stronger for TiO(2) NP) was detected in both NR and MTT assays after 24-h exposure to the NP. However, the total cell proteins and the cell proliferation rate demonstrated (p < 0.05) that the cell viability decreased after 96 h exposure to NP. The formation of NP-containing vesicles within the cells was observed by transmission electronic microscopy. Such event could explain the high cellular activity detected during the early stages of exposure not related to the increase in cell viability. Results showed that the effects of NP on cell lines are dependent on the chemical composition of the particles, their concentration, exposure time, and the type of treated cell. It can be concluded that the presence of TiO(2) and Al(2)O(3) NP in the cell surroundings can lead to cytotoxic effects. In the case of osteoblast cells, such events may induce osseointegration failures in orthopedic and dental implants that release NP.