Antimicrobial activity of Ag nanoclusters encapsulated in porous silica nanospheres

Silica nanospheres encapsulating silver nanoclusters (denoted as Ag-SiO2) have been synthesized via a one-pot microemulsion method and their antibacterial activities have been investigated in detail. ICP-AES analysis indicated that the silver ions were continually released from the silica spheres in aqueous solution. The antibacterial properties of Ag-SiO2 against both Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus were evaluated using minimum inhibitory concentration (MIC), minimal bactericidal concentration (MBC), and the modified Kirby Bauer method. The results show that the Ag-SiO2 exhibits excellent and durable antimicrobial activities. The growth of both Gram-negative E. coli and Gram-positive S. aureus was completely inhibited during 48 h culture period. Moreover, the tested silver nanoclusters show higher activity against bacteria than the silver nanoparticles. This newly designed Ag-SiO2 may offer a rapid and constant antimicrobial solution for practical applications. (C) 2013 Elsevier Ltd and Techna Group S.r.l. All rights reserved.