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Novel nanohybrids of silver particles on clay platelets for inhibiting silver-resistant bacteria.

Su HL, Lin SH, Wei JC, Pao IC, Chiao SH, Huang CC, Lin SZ, Lin JJ - PLoS ONE (2011)

Bottom Line: The geographic shape of the NSPs concentrates AgNPs but impedes their penetration into attached cells, mitigating the detrimental effect of silver ion deposition in applied tissues.Moreover, the tightly tethered AgNPs on NSP surface achieve a stronger biocidal effect than silver nitrate, but bypassing Ag(+) mechanism, on silver-resistant bacteria.This nanohybrid presents an effective and safe antimicrobial agent in a new perspective.

View Article: PubMed Central - PubMed

Affiliation: Department of Life Sciences, National Chung Hsing University, Taichung, Taiwan. suhonglin@gmail.com

ABSTRACT
We develop a novel nanohybrid showing a strong antibacterial activity on all of the tested pathogens, including methicillin-resistant Staphylococcus auerus and silver-resistant E. coli. The nanohybrid consists of silver nanoparticles (AgNPs) supported on 1 nm-thick silicate platelets (NSPs). The AgNP/NSP nanohybrid enables to encapsulate bacteria and triggers death signals from the cell membrane. The geographic shape of the NSPs concentrates AgNPs but impedes their penetration into attached cells, mitigating the detrimental effect of silver ion deposition in applied tissues. Moreover, the tightly tethered AgNPs on NSP surface achieve a stronger biocidal effect than silver nitrate, but bypassing Ag(+) mechanism, on silver-resistant bacteria. This nanohybrid presents an effective and safe antimicrobial agent in a new perspective.

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The biocidal pathway in AgNP/NSP treated cells.E. coli were cultured with NSPs or AgNP/NSP for 4 hr and subjected to biochemical analysis. The glucose uptake (A), ATP production (B) and intracellular ROS production (C) were determined by the incorporation of 2-NDBG, the luciferase-luciferin reaction and the H2DCF-DCF conversion, respectively. Ratios of 2-NDBG+ and DCF+ cells were determined by FACS analysis. For the ROS test, 1% H2O2 was used as positive control. U83836E, 50 µM. Tempol, 50 µM. Before the seeding of E. coli, 50 µl glutathione (10 mM) was applied on the AgNP/Clay containing agar plates (D). The number of bacterial colonies was counted and these data were obtained from three independent results. *, p-values<0.05, Student's t-test.
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pone-0021125-g005: The biocidal pathway in AgNP/NSP treated cells.E. coli were cultured with NSPs or AgNP/NSP for 4 hr and subjected to biochemical analysis. The glucose uptake (A), ATP production (B) and intracellular ROS production (C) were determined by the incorporation of 2-NDBG, the luciferase-luciferin reaction and the H2DCF-DCF conversion, respectively. Ratios of 2-NDBG+ and DCF+ cells were determined by FACS analysis. For the ROS test, 1% H2O2 was used as positive control. U83836E, 50 µM. Tempol, 50 µM. Before the seeding of E. coli, 50 µl glutathione (10 mM) was applied on the AgNP/Clay containing agar plates (D). The number of bacterial colonies was counted and these data were obtained from three independent results. *, p-values<0.05, Student's t-test.

Mentions: Severe membrane disruption may affect the nutrient uptake, electronic transport and ROS production. By feeding E. coli with a fluorescein-labelled glucose analog, 2-NBDG, almost all bacteria became green fluorescent (Fig. 5A). FACS analysis showed that the glucose uptake was dramatically impaired in AgNP/NSP-treated E. coli (36%) after the 4 hr incubation in comparison to those in nanomaterials-untreated control (96%) and NSP-treated cells (79%) (Fig. 5A). In addition, the intracellular ATP content was also significantly reduced in a dose-dependent manner at 4 hr post-treatment in AgNP/NSP-treated E. coli, compared to that of NSP-treated cells (Fig. 5B). Using the H2DCF staining and FACS analysis, robust ROS production was confirmed in 36.0±9.9% and 69.3±3.3% of the cells during the 4 hr incubation in which E. coli were treated with 0.02 wt% and 0.05 wt% nanohybrids, respectively (p<0.05 in both). In contrast, 0.05 wt% NSPs steered only a limited amount of DCF+ cells (7.0±0.8%, Fig. 5C). Furthermore, the pretreatment of ROS scavengers, such as lipid peroxidation inhibitor U83836E and a superoxide dismutase mimetic Tempol, limited the AgNP/NSP-steered ROS production (Fig. 5C). Glutathione, a well-known cellular anti-oxidant [34], successfully rescued the AgNP/NSP-induced cell death (Fig. 5D and Fig. S1), demonstrating the critical role of ROS in this biocidal pathway. These results emphasize that the AgNP/NSP nanohybrid, but not NSP alone, constitutively disrupts the integrity of membrane, impedes the nutrient uptake and produces detrimental free radicals on the encountered cells.


Novel nanohybrids of silver particles on clay platelets for inhibiting silver-resistant bacteria.

Su HL, Lin SH, Wei JC, Pao IC, Chiao SH, Huang CC, Lin SZ, Lin JJ - PLoS ONE (2011)

The biocidal pathway in AgNP/NSP treated cells.E. coli were cultured with NSPs or AgNP/NSP for 4 hr and subjected to biochemical analysis. The glucose uptake (A), ATP production (B) and intracellular ROS production (C) were determined by the incorporation of 2-NDBG, the luciferase-luciferin reaction and the H2DCF-DCF conversion, respectively. Ratios of 2-NDBG+ and DCF+ cells were determined by FACS analysis. For the ROS test, 1% H2O2 was used as positive control. U83836E, 50 µM. Tempol, 50 µM. Before the seeding of E. coli, 50 µl glutathione (10 mM) was applied on the AgNP/Clay containing agar plates (D). The number of bacterial colonies was counted and these data were obtained from three independent results. *, p-values<0.05, Student's t-test.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3117870&req=5

pone-0021125-g005: The biocidal pathway in AgNP/NSP treated cells.E. coli were cultured with NSPs or AgNP/NSP for 4 hr and subjected to biochemical analysis. The glucose uptake (A), ATP production (B) and intracellular ROS production (C) were determined by the incorporation of 2-NDBG, the luciferase-luciferin reaction and the H2DCF-DCF conversion, respectively. Ratios of 2-NDBG+ and DCF+ cells were determined by FACS analysis. For the ROS test, 1% H2O2 was used as positive control. U83836E, 50 µM. Tempol, 50 µM. Before the seeding of E. coli, 50 µl glutathione (10 mM) was applied on the AgNP/Clay containing agar plates (D). The number of bacterial colonies was counted and these data were obtained from three independent results. *, p-values<0.05, Student's t-test.
Mentions: Severe membrane disruption may affect the nutrient uptake, electronic transport and ROS production. By feeding E. coli with a fluorescein-labelled glucose analog, 2-NBDG, almost all bacteria became green fluorescent (Fig. 5A). FACS analysis showed that the glucose uptake was dramatically impaired in AgNP/NSP-treated E. coli (36%) after the 4 hr incubation in comparison to those in nanomaterials-untreated control (96%) and NSP-treated cells (79%) (Fig. 5A). In addition, the intracellular ATP content was also significantly reduced in a dose-dependent manner at 4 hr post-treatment in AgNP/NSP-treated E. coli, compared to that of NSP-treated cells (Fig. 5B). Using the H2DCF staining and FACS analysis, robust ROS production was confirmed in 36.0±9.9% and 69.3±3.3% of the cells during the 4 hr incubation in which E. coli were treated with 0.02 wt% and 0.05 wt% nanohybrids, respectively (p<0.05 in both). In contrast, 0.05 wt% NSPs steered only a limited amount of DCF+ cells (7.0±0.8%, Fig. 5C). Furthermore, the pretreatment of ROS scavengers, such as lipid peroxidation inhibitor U83836E and a superoxide dismutase mimetic Tempol, limited the AgNP/NSP-steered ROS production (Fig. 5C). Glutathione, a well-known cellular anti-oxidant [34], successfully rescued the AgNP/NSP-induced cell death (Fig. 5D and Fig. S1), demonstrating the critical role of ROS in this biocidal pathway. These results emphasize that the AgNP/NSP nanohybrid, but not NSP alone, constitutively disrupts the integrity of membrane, impedes the nutrient uptake and produces detrimental free radicals on the encountered cells.

Bottom Line: The geographic shape of the NSPs concentrates AgNPs but impedes their penetration into attached cells, mitigating the detrimental effect of silver ion deposition in applied tissues.Moreover, the tightly tethered AgNPs on NSP surface achieve a stronger biocidal effect than silver nitrate, but bypassing Ag(+) mechanism, on silver-resistant bacteria.This nanohybrid presents an effective and safe antimicrobial agent in a new perspective.

View Article: PubMed Central - PubMed

Affiliation: Department of Life Sciences, National Chung Hsing University, Taichung, Taiwan. suhonglin@gmail.com

ABSTRACT
We develop a novel nanohybrid showing a strong antibacterial activity on all of the tested pathogens, including methicillin-resistant Staphylococcus auerus and silver-resistant E. coli. The nanohybrid consists of silver nanoparticles (AgNPs) supported on 1 nm-thick silicate platelets (NSPs). The AgNP/NSP nanohybrid enables to encapsulate bacteria and triggers death signals from the cell membrane. The geographic shape of the NSPs concentrates AgNPs but impedes their penetration into attached cells, mitigating the detrimental effect of silver ion deposition in applied tissues. Moreover, the tightly tethered AgNPs on NSP surface achieve a stronger biocidal effect than silver nitrate, but bypassing Ag(+) mechanism, on silver-resistant bacteria. This nanohybrid presents an effective and safe antimicrobial agent in a new perspective.

Show MeSH
Related in: MedlinePlus