Antibacterial activity and mechanism of Ag2Cu2O3 mixed-metal oxide

Pure phase Ag2Cu2O3 mixed-metal oxides with homogeneous morphology of short rod-like structure were synthesized through simple co-precipitation methods. The efficacious antibacterial activities of the obtained Ag2Cu2O3 against both Gram positive and Gram negative bacteria were corroborated by the minimum inhibitory concentration (4.88 mg/L for both Escherichia coli and Staphylococcus lentus) and minimum bactericidal concentration (19.53 mg/L for E. coli and 9.76 mg/L for S. lentus). In shake flask inactivation experiments, more than 99 % of bactericidal rate was achieved for both test strains within 30 min using 250 mg/L of the Ag2Cu2O3. From the results of free radical quenching experiments and electron spin resonance spectroscopy, singlet oxygen in suspension played an important role in the sterilization of the Ag2Cu2O3, but some factors other than reactive oxygen species might also make a significant contribution. Through the simulated antibacterial experiments of the leached Cu2+ and Ag+ from Ag2Cu2O3, we found that trace Ag+ exhibits strong bactericidal ability against both strains. While, trace Cu2+ displayed a more pronounced sterilization activity against S. lentus than E. coli, which explains the higher antibacterial activity of Ag2Cu2O3 against Gram positive bacteria compared with Gram negative ones.