Preparation of Submicron Silver Colloid by Ultrasonic Photocatalysis and Its Bacteriostatic Properties

OBJECTIVE To study the genotoxicity, bacteriostasis and diffusion ability of submicron silver colloid. METHODS Under the action of ultrasonic cleaner and high pressure mercury lamp, AgNO₃ was used as silver source and PVP as dispersant to prepare silver colloid in aqueous solution. TEM, UV-Vis, XRD were used for characterization and analysis. Colloidal silver was divided into high, medium and low dose groups(500, 50, 5 mg·L^-1), negative control group(stroke- physiological saline solution) and positive control group(cyclophosphamide). The micronucleus rate of bone marrow cells in mice was observed at the same site(femur). With oxytetracycline and fluconazole used as positive control and deionized water as negative control, eight kinds of bacteria and fungi(Candida albicans) including Shigella castellani, Salmonella enterica, Escherichia coli, Proteus, Staphylococcus aureus, Staphylococcus albicans, Staphylococcus lemonis and Bacillus subtilis were tested by silver colloid. MIC was performed by constant broth dilution method. RESULTS Compared with the negative control group, the micronucleus rate of bone marrow cells in the high and medium dose groups increased significantly, but there was no significant difference in the low dose groups. There was a dose-response relationship between the micronucleus rate of bone marrow cells and the concentration of silver colloid in mice. The results were positive and statistically significant. The silver colloid showed dose-dependent genetic toxicity. The silver colloid bacteriostatic circle was found to be clearer and the bacteriostatic effect was more thorough through the bacteriostatic circle test. MIC test showed that the minimum inhibitory concentration of the silver colloid to Staphylococcus albicans was 0.6 mg·L^-1, and to Candida albicans was 5 mg·L^-1. CONCLUSION The silver colloid with uniform particle size is successfully prepared. As a bacteriostatic agent, it has stable properties and good bacteriostasis effect. However, it is not suitable for direct use in vivo because of its genotoxicity in oral administration.