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HERO ID
90608
Reference Type
Journal Article
Title
Bactericidal activity of photocatlytic TiO2 reaction: toward an understanding of its killing mechanism
Author(s)
Maness, PC; Smolinski, S; Blake, DM; Huang, Z; Wolfrum, EJ; Jacoby, WA
Year
1999
Is Peer Reviewed?
Yes
Journal
Applied and Environmental Microbiology
ISSN:
0099-2240
EISSN:
1098-5336
Volume
65
Issue
9
Page Numbers
4094-4098
Language
English
PMID
10473421
Abstract
When titanium dioxide (TiO2) is irradiated with near-UV light, this semiconductor exhibits strong bactericidal activity. In this paper, we present the first evidence that the lipid peroxidation reaction is the underlying mechanism of death of Escherichia coli K-12 cells that are irradiated in the presence of the TiO2 photocatalyst. Using production of malondialdehyde (MDA) as an index to assess cell membrane damage by lipid peroxidation, we observed that there was an exponential increase in the production of MDA, whose concentration reached 1.1 to 2.4 nmol cntdot mg (dry weight) of cells-1 after 30 min of illumination, and that the kinetics of this process paralleled cell death. Under these conditions, concomitant losses of 77 to 93% of the cell respiratory activity were also detected, as measured by both oxygen uptake and reduction of 2,3,5-triphenyltetrazolium chloride from succinate as the electron donor. The occurrence of lipid peroxidation and the simultaneous losses of both membrane-dependent respiratory activity and cell viability depended strictly on the presence of both light and TiO2. We concluded that TiO2 photocatalysis promoted peroxidation of the polyunsaturated phospholipid component of the lipid membrane initially and induced major disorder in the E. coli cell membrane. Subsequently, essential functions that rely on intact cell membrane architecture, such as respiratory activity, were lost, and cell death was inevitable.
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