title: Bactericidal mechanisms revealed for rapid water disinfection by superabsorbent cryogels decorated with silver nanoparticles.
abstract: The authors have recently reported the fabrication of superabsorbent cryogels decorated with silver nanoparticles (PSA/AgNP cryogels) that demonstrate rapid water disinfection. This paper provides a systematic elucidation of the bactericidal mechanisms of AgNPs (silver nanoparticles), both generally and in the specific context of cryogels. Direct contact between the PSA/AgNP cryogel interface and the bacterial cells is required to accomplish disinfection. Specifically, the disinfection efficacy is closely correlated to the cell-bound Ag concentration, which constitutes >90% of the Ag released. Cells exposed to PSA/AgNP cryogels show a significant depletion of intracellular adenosine triphosphate (ATP) content and cell-membrane lesions. A positive ROS (reactive oxygen species) scavenging test confirms the involvement of ROS (·O2(-), H2O2, and ·OH) in the bactericidal mechanism. Furthermore, exposed bacterial cells show an enhanced level of thiobarbituric acid reactive substances, indicating the occurrence of cell-membrane peroxidation mediated by ROS. In addition, this study reveals that both Ag(+) and Ag(0) are involved in the bactericidal mechanism of AgNPs via tests conducted using PSA cryogels with bound Ag(+) ions (or PSA/Ag(+) cryogels without reducing Ag(+) to Ag(0)). Significantly, bacterial cells exposed to PSA/Ag(+) cryogels did not show any cell-membrane damage even though the former had a higher cell-bound Ag concentration than that of the PSA/AgNP cryogels, thus indicating the differential action of Ag(+) and Ag(0).
authors: Singapore Membrane Technology Centre, Nanyang Environment and Water Research Institute, Nanyang Technological University , 1 Cleantech Loop, CleanTech One, #05-05, Singapore 637141, Singapore.
authors: Siew-Leng
authors: SL
authors: Loo
authors: William B
authors: WB
authors: Krantz
authors: Anthony G
authors: AG
authors: Fane
authors: Yiben
authors: Y
authors: Gao
authors: Teik-Thye
authors: TT
authors: Lim
authors: Xiao
authors: X
authors: Hu
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry* / Q000494:pharmacology; D002462:Cell Membrane / Q000187:drug effects; D059985:Cryogels / Q000737:chemistry*; D004203:Disinfection / Q000379:methods*; D006861:Hydrogen Peroxide / Q000737:chemistry; D053768:Metal Nanoparticles / Q000737:chemistry*; D017382:Reactive Oxygen Species; D012834:Silver / Q000493:pharmacokinetics; D014867:Water / Q000737:chemistry; D014871:Water Microbiology; D018508:Water Purification / Q000379:methods
chemical_list: D000900:Anti-Bacterial Agents; D059985:Cryogels; D017382:Reactive Oxygen Species; D014867:Water; D012834:Silver; D006861:Hydrogen Peroxide