Preparation of antibacterial silver-doped silica glass microspheres by sol-gel method

摘要

Various kinds of inorganic substances doped with silver ion have been developed as antibacterial materials, and some of them are already commercialized. Colorless and more chemically durable materials which slowly release the silver ion are, however, still desired to be developed. If they take a form of microsphere less than 1 μm in diameter, they are easily mixed with organic polymers and can be formed into a thin film, fine fibers, etc. In the present study, preparation of silver-doped silica glass microsphere less than 1 μm in diameter was attempted by using sol-gel method. Tetraethoxysilane was first partially pre-hydrolyzed by water in ethanol, then aluminium triisopropoxide was added to the solution to form Si-O-Al bond, and finally, ammonia solution containing silver nitrate was added to the solution to form silica microspheres doped with silver ion together with aluminium ion. As a result, monodispersed microspheres 0.4-0.6 μm in diameter with the nominal compositions Si/Al/Ag--1/0.01-0.03/0.003-0.03, where Al/Ag=1-3.3, in molar ratio were obtained. They were colorless, highly chemically durable, and slowly released the silver ion into water at 37°C. The microspheres with the composition Si/Al/Ag=1/0.01/0.01 showed excellent antibacterial activity against Escherichia coli. The minimum inhibitory concentration (MIC) of the microspheres was 400, which is less than that (800) of commercialized antibacterial materials.