ABSTRACT
Objective To study the effects of nano silver (Ag) and titanium dioxide (TiO2) on the content of nucleic acid in staphylococcus aureus in order to explore their antibacterial mechanisms.Methods After preparation of beef extract peptone liquid cultures,the effects of minimal inhibitory concentrations (MICs) of nano Ag and TiO2 on staphylococcus aureus strains were determined.With the 1/2 MICs nano Ag and TiO2,the contents of DNA and RNA macromolecules from staphylococcus aureus cultures were measured to determine the damage degree of staphylococcus aureus cell membranes by ultraviolet spectrophotometer,and then the fluorescence intensities of the staphylococcus aureus cells were observed under fluorescence microscope and the fluorescence values were tested by fluorescence spectrophotometer to determine the contents of nucleic acid DNA and RNA.Results The MICs of nano Ag and TiO2 were 1.6 mg/mL and 5.781 μg/mL.After treatment with the 1/2 MICs nano Ag and TiO2,nano Ag group and TiO2 group were compared with the control group (culture fluid without adding antibacterial agent),respectively,and there were no significant differences in the contents of DNA and RNA macromolecules from staphylococcus aureus cultures between n anoAg group and control group as well as between TiO2 group and control group were (P＞0.05),and there were significant decreases in fluorescence intensities and the contents of nucleic acid DNA and RNA (P＜0.01).Conclusions Nano Ag and TiO2 had obvious antibacterial effects on staphylococcus aureus and the antibacterial properties of nano Ag was stronger than that of TiO2.The antibacterial mechanisms of nano Ag and TiO2 against staphylococcus aureus may be associated with the inhibition of the synthesis of nucleic acid DNA and RNA,inhibiting protein synthesis and then bacterial growth.
