Nonetheless, this study clearly

demonstrates PF 01367338 the feasibility of using Ag NPs to impart selleckchem antiviral activity to chitosan and lower concerns about the risk of diffusion of Ag NPs in the environment. Conclusions Ag NP/Ch composites with antiviral activity against influenza A virus were synthesized in aqueous medium. The composites were obtained as yellow or brown flocs; unreacted Ag NPs were not detected in the residual solution. The particle size of the Ag NPs in the composites was similar to that of the Ag NPs used to synthesize the composites. The antiviral activity of the composites was determined from the decreased TCID50 ratio of viral suspensions after treatment with the composites. For all sizes of Ag NPs tested, Selleck QNZ the antiviral activity of the Ag NP/Ch composites increased as the amount of Ag NPs increased. Stronger antiviral activity was generally observed with composites containing smaller Ag NPs for comparable concentrations of Ag NPs. Neat chitosan did not exhibit antiviral activity, suggesting that Ag NPs are essential for the antiviral activity of the composites. Although the antiviral mechanism of the composites remains to be investigated, the experimental

results showing the relationship between antiviral activity and the concentration of Ag NPs suggest that the virions and composites interacted. Consequently, detailed studies of the antiviral mechanism of the Ag NP/Ch composites could lead to the development of practical Ag NP-containing materials that will reduce concerns about the risks of diffusion of Ag NPs into the environment. Authors’ information YMo is a technical official of the Japan Air Self-Defense Force.

MI and YMi are professors of the National Defense Medical College. TO is a research associate of the National Defense Medical College. TM is a professor of the Tokyo Metropolitan University. VQN is a graduate student of the Tokyo Metropolitan University. Acknowledgments The authors would like to thank Ms. Y. Ichiki at the Laboratory Center of the National Defense Medical College (Tokorozawa, Japan) for helping with the electron microscopy experiments. References 1. Pal S, Tak YK, Song JM: Does the antibacterial enough activity of silver nanoparticles depend on the shape of the nanoparticle? A study of the gram-negative bacterium Escherichia coli. Appl Environ Microbiol 2007, 73:1712–1720.CrossRef 2. Sondi I, Salopek-Sondi B: Silver nanoparticles as antimicrobial agent: a case study on E. coli as a model for Gram-negative bacteria. J Colloid Interface Sci 2004, 275:177–182.CrossRef 3. Morones JR, Elechiguerra JL, Camacho A, Holt K, Kouri JB, Ramirez JT, Yacaman MJ: The bactericidal effect of silver nanoparticles. Nanotechnology 2005, 16:2346–2353.CrossRef 4. Gajbhiye M, Kesharwani J, Ingle A, Gade A, Rai M: Fungus-mediated synthesis of silver nanoparticles and their activity against pathogenic fungi in combination with fluconazole.