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Download fileBactericidal Mechanisms Revealed for Rapid Water Disinfection by Superabsorbent Cryogels Decorated with Silver Nanoparticles
journal contribution
posted on 2015-02-17, 00:00 authored by Siew-Leng Loo, William B. Krantz, Anthony
G. Fane, Yiben Gao, Teik-Thye Lim, Xiao HuThe 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
Ag0 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
Ag0). 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 Ag0.