carbn nanotubes interaction with bacterial cell

7/30/2019 Carbn Nanotubes Interaction With Bacterial Cell

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Interaction of Carbon Nanotubeswith Bacterial Cells

Menachem Elimelech

Department of Chemical Engineering

Environmental Engineering Program

Yale University

UCLA/CNSI workshop Bio-physicochemical

Interactions of Engineered Nanomaterials,

September 10, 2007
http://www.yale.edu/env/elimelech/publication-pdf/Kang_et_al_LANGMUIR_2007.pdfhttp://www.yale.edu/env/elimelech/publication-pdf/Kang_et_al_LANGMUIR_2007.pdfhttp://www.yale.edu/env/elimelech/publication-pdf/Kang_et_al_LANGMUIR_2007.pdf


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Richard Smalley (2005): These nanotubesare so beautiful that they must be useful for

something. . .

! Drug delivery! Biomaterials

! Sensors

! Semiconductors

! Novel materials! Photonics

! Catalytic support

! Environmental applications

Single-Walled Carbon Nanotubes


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Biocompatibility of Single-Walled

Carbon Nanotubes (SWNTs)

Numerous proposed biological applications

of SWNTs, e.g., biosensors, drug delivery,

and novel biomaterialsIncreased potential for encounters between

SWNTs and humans and ecosystem

Concerns about SWNT toxicity


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Can SWNT apparent biotoxicity be

used for beneficial applications, e.g.,antimicrobial surfaces?

ObjectivesTo study the interaction of SWNTs with

bacterial cells

To determine whether SWNTs possess

antibacterial properties


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Preparation of Well-Defined Single-

Walled Carbon Nanotubes

Silica template

MCM-41 (D=2.8 nm)

3% Co incorporated

Purification

Template removal byNaOH

Co removal by reflux

in HCl

Growth

Reduced in hydrogenat 975 K

CO disproportionation

at 6 atm and 1125 K

MCM-41

Template


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SWNT Properties

Physical characteristics: Diameter: 0.9 nm (0.75 -

1.2 nm)

Length: 1 - 3 m

Chemical characteristics: Metal content: 0.8 %

(w/w) Co

Negligible amorphous

carbon

No significant changes

during purification

(Raman)

0 500 1000 1500 2000

0

2000

4000

6000

8000

10000

Intensity(a.u.

)

Raman shift (cm-1)

SWNTs as produced

purified SWNTs


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Model Bacterium

E. coliK12

Grown in LB broth; harvested at

exponential growth phaseWashed twice with 0.9 % NaCl (isotonic

solution)

Enumerated by OD600nm and cell countingchamber


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Viability Assay

Suspended SWNTs

0.9 %NaCl

SWNT(5 mg/L) Cells(5x107/mL)

Incubation

for 1 hr

0.9 %NaCl

PI(50 g/mL) DAPI(3 g/mL)

Free swimming

Attached


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Viability Assay

Deposited SWNTs

Vacuum filtration

of 4 mg SWNT

Incubation

PI(50 g/mL)

DAPI(3 g/mL)

Filtration of cells

(2x106 cells)


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Viability Assay

Metabolic activity 5-cyano-2,3-ditolyl-tetrazolium chloride (CTC)

Filtration of cells

(2x106 cells) DAPI(after 1 hr)

Incubation

for 30 min.

CTC(50 g/mL)

Minimal medium

with glucose

Incubation

for 1 hr


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Biotoxicity of SWNTs

SWNT aggregates Total cells (stained with both)

Damaged cells (PI stained) Free swimming cells

100 m


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Control SWNT Control SWNT0

20

40

60

80

100

B

iotoxicity

(%)

Suspended Deposited


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Metabolic activity (CTC-staining) with andwithout SWNTs

Control SWNT0

20

40

60

80

100

Activ

eCells(%)


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Cell Membrane Damage

Morphological change: SEM images

Control (without SWNT) SWNT


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Control SWNT

0

100

200

300

400

DNACo

nc.

(ng/mL)

Cell Membrane Damage

Efflux of intracellular materials (plasmidDNA) into solution


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Concluding Remarks

SWNTs exhibit strong antibacterial

activity

Direct contact of bacteria with SWNTs isnecessary for inactivation

Severe cell membrane damage after

contact with SWNTs


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Acknowledgments

Prof. Lisa Pfefferle

Steve Kang (post-doc)

Funding: NSF

carbn nanotubes interaction with bacterial cell

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