Nanoscale Design of Biosensors for Toxicity Screening and Biomedical Applications
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Nanoscale Design of Biosensors for Toxicity Screening and Biomedical Applications James F. Rusling Departments of Chemistry & Pharmacology University of Connecticut Storrs, CT, USA. Traditional Electrochemical Biosensors. substrate. product. Enzyme, or Label on Ab/Ag Or DNA. electrode.

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Nanoscale Design of Biosensors for Toxicity Screening and Biomedical Applications

James F. Rusling

Departments of Chemistry & Pharmacology

University of Connecticut

Storrs, CT, USA


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Traditional Electrochemical Biosensors Biomedical Applications

substrate

product

Enzyme, or

Label on Ab/Ag

Or DNA

electrode

Measure current prop.

to concentration of substrate

Apply voltage

• nanoscale biosensing architecture

• patternable nanomaterials for arrays


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Layer-by-layer Biomedical Applications

Film assembly

Lvov, Decher

Lvov, Y. in Nalwa, R.W.; Ed.;

Handbook Of Surfaces And Interfaces

Of Materials, Vol. 3. Academic, 2001, pp. 170-189.

Stable, easily prepared, versatile


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toxic? Biomedical Applications

Research

goal

transducer

test chemical

Biomolecular

reporter

• ~ 30 % of drug candidates defeated by toxicity

• Early screening could save drug development costs


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In vitro Toxicity Screening Biomedical Applications

Lipophilic Molecule

Cyt P450, O2

Enzyme-activated molecule

+DNA

Damaged

DNA

Detect by electrochemical sensor

Validate by LC-MS/MS


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Collaboration with Prof. John Schenkman, Biomedical Applications

Pharmacology, Uconn Health Center

Funding from NIH, NIEHS


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Enzyme Biomedical Applications

ds-DNA

Films for Toxicity Screening

20-40 nm

PDDA or

Ru-PVP (catalyst)

(Ru(bpy)22+-PVP)

Pyrolytic Graphite


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Mass: M/A = - Biomedical ApplicationsDF/1.86 x 108

Thickness: d = -(0.016) DF


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Equipment for toxicity biosensors Biomedical Applications

potentiostat

electrode

material

insulator

reference

DNA/enzyme film

N2

inlet

counter

working electrode

E-t waveform

Square-wave

voltammetry

E, V

Electrochemical cell

I measured,

then subtracted

time

Figure1


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Screening Chemical Toxicity Biomedical Applications

Enzyme reaction - Incubate:

Reactant + H2O2-->metabolite

Analysis by catalytic SWV or

electrochemiluminescence

RuL2+ = RuL3+ + e-

RuL3+ + DNA-G --> RuL2+ + DNA-G•


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Enzyme/DNA films Biomedical Applications

Peak increase

measures damage

of DNA by enzyme-

generated

metabolite


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Nucleobase adducts Biomedical Applications


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Comparison of toxicity sensors with LC-MS Biomedical Applications

For DNA damage by methylmethane sulfonate


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Equipment for ECL toxicity sensors Biomedical Applications

potentiostat

electrode

material

insulator

reference

DNA/enzyme film

N2

inlet

counter

working electrode

ECL cell

E-t waveform

Square-wave

voltammetry

E, V

glass

Monochromator/

PM tube detector

I measured,

then subtracted

optical fiber

time

Figure1


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Incubations with styrene oxide Biomedical Applications

DNA +



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Direct ECL generation from DNA Biomedical Applications

RVP-RuL2+ = PVP-RuL3+ + e-

PVP-RuL3+ + DNA-G --> PVP-RuL2+ + DNA-G•

Then?

PVP-RuL3+ oxidizes DNA-G• to give

Photoexcited PVP-[RuL2+]*

Or

DNA-G• reduces PVP-RuL2+ to PVP-RuL+,

PVP-RuL3+ + PVP-RuL+ --> PVP-[RuL2+]*


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Arrays: Which Liver Cytochrome P450s -generate toxic Biomedical ApplicationsBenzo[a]pyrene Metabolites?


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Arrays detect in-vitro DNA damage from metabolites of Biomedical Applications

different enzymes in DNA/enzyme films

Rel. turnover rate,

1/min (nmol E)

Drug discovery

applications


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Sensors for oxidative stress via oxidized DNA Biomedical Applications

Os-PVP

PSS

Pyrolytic Graphite

Ru-PVP

ECL detection in films:

Lynn Dennany, Robert J. Forster, Blanaid White, Malcolm Smyth and James F. Rusling, Am. Chem. Soc., 2004, 126, 8835-8841.


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Summary: DNA damage Biomedical Applications

detection/toxicity sensors

• Catalytic voltammetry and ECL toxicity sensors

• sensors produce metabolites, damage DNA

• Can detect 5-10 damaged bases/10,000

• can detect DNA oxidation - 8-oxoguanine (1/6000)

• Future: extensions to many compounds, cyt P450 arrays, ECL arrays, drug toxicity


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Single-walled carbon nanotube forests as a basis for immunosensors

James F. Rusling and Xin Yu,

Depts. of Chemistry and Pharmacology, Univ. Connecticut

Maire O’Connor, Anthony Killard, Malcolm Smyth

NCSR, Dublin City University

Sang Nyon Kim, Fotis Papadimitrakopoulos

Institute of Materials Science, University of Connecticut


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Carbon Nanotubes immunosensors

  • Single walled (1.4 nm o.d.) and multi-walled

  • Highly conductive, flexible, strong, patternable

  • Commercially Available


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Single-Walled Carbon Nanotube immunosensors

Forests: Antigen-Antibody Sensing

~1.4 nm diameter, high conductivity

SPAN or

Nafion

Chattopadhyay, Galeska, Papadimitrakopoulos, J. Am. Chem. Soc. 2001, 123, 9451.

End COOH groups allow chemical attachment to proteins (antibodies)

High conductivity to conduct signal (e’s) from enzyme label to meas. circuit


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Negatively immunosensors

Experimental Procedure for SWNT Forest Assembly

Acid + U-sound

Chattopadhyay, Galeska, Papadimitrakopoulos, J. Am. Chem. Soc. 2001, 123, 9451.


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Covalently Binding Protein to SWNT immunosensors

Protein

Protein

Protein

N

H

N

H

N

H

O

O

O

N

H

N

H

N

H

HRP

g

r

a

p

h

i

t

e

s

u

r

f

a

c

e

/

S

W

N

T

/

Ends of nanotubes -COOH:

water-soluble carbodiimide (1-(3-(dimethylamino) propyl)-3-ethylcarbodiimide hydrochloride, EDC, or EDC + NHSS


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(b) immunosensors

(a)

AFM of SWNT forest with and without antibiotin attached

SWNT + antibody

(EDC coupling)

SWNT


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HRP on electrodes: + H immunosensors2O2 = current signal

Zhe Zhang, Salem Chouchane, Richard S. Magliozzo,and James F. Rusling,

"Direct Voltammetry and Enzyme Catalysis with M. tuberculosis

Catalase-Peroxidase, Peroxidases and Catalase in Lipid Films",

Anal. Chem., 2002, 74, 163-170.


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Competitive Immunoassay immunosensors

Catalytic current should be inversely proportional to the amount of non-labeled Ag, depending on binding constant, Ag was pre-bound on Ab


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Anti-biotin/biotin-HRP test system immunosensors

(H2O2 present)

No mediator

With mediator

25

with mediator

LOD ~1 pmol/mL

3

Near LOD

not all the HRP label was communicating

with the measuring circuit - soluble mediator shuttles

electrons from HRP label more efficiently


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H immunosensors2O2

HRP

HRP

HRP

HRP

HRP

HRP

Ag

Ag

Ab1

Ab1

Sandwich Assay for Human Serum Albumin

Ab2

HPR

Conductive polymer

(SPAN)

SWNT forest

Apply E measure I


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Detection of Human Serum albumin in immunosensors

10 mL drops on SWNT forest immunosensor

LOD ~ 10 pmol/mL,

~50-fold better

w/ SPAN


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Design approaches to future arrays immunosensors

Layer-by-layer approach general, simple

Stable films, complex architecture, any surface

Sensors for toxicity, oxidative stress

Ambient T solution processable

SWNT forests patterned by solution process

Excellent LOD and sensitivity using

conductive polymer bed (SPAN)

7. Possibility of automated array formation

8. Applications to proteins, pathogens, etc.


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Also, screen printed carbon arrays, Lab 901, Edinbugh immunosensors

Detection of Protein biomarkers for Cancer:

• NIH, NIDCR

• prostate, squamous cell, and breast cancers


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Thanks to NIH, NSF and ARO for funding! immunosensors

Thanks to all our coworkers and collaborators

http://web.uconn.edu/rusling/

Thanks to YOU for listening!

Thanks to intangible creative factors

+


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