Transcript Document 7435905

Biosensors and
Carbon Nanotubes
Lakshmi Jagannathan
Enzyme-Coated Carbon Nanotubes
as Single-Molecule Bionsensors1
 Introduction and Motivation
 Physical Immobilization of Protein


Method/Experimentation
Result/Evidence of Immobilization (AFM)
 Electrical Characteristics


Method/Experimentation
Results and Electrical Characteristics
 Conclusion
1Koen
Besteman, Jeong-O Lee, Frank G. M. Wiertz, Hendrik A. Heering,
and Cees Dekker, Nano Letters, 2003, Vol. 3, No. 6, 727-730.
Introduction and Motivation
 Unique properties of single-wall carbon
nanotubes can be used for biosensors
 Detection of Glucose Oxidase:
 important enzyme that catalyzes glucose
 necessary to detect the presence of glucose in
body fluids
 enzyme as an electrode to detect current
 Potential applications: highly sensitive, cheap,
and smaller glucose monitors and other
applications
Physical Immobilization- Method
 LINKING MOLECULE:
1-Pyrenebutanoic acid
succinimidyl ester–
absorbing into the
SWNT when left in DMF
or dimethylformamide
(van der Waals
coupling)
 Amine bond in protein
Source: Chen, R. J.; Zhang, Y.; Wang, D.;
Dai, H. J. Am. Chem. Soc. 2001, 123, 3838.
reacts with amide group
from linking molecule
and immobilizes
(covalent bond)
Physical Immobilization- Results (AFM)
 A and C: Laser-ablated
and CVD growth,
respectively; before GOX
immobilization
 B and D: After
immobilization of GOXdifference in height before
and after= height of GOX
molecule
Electrical Measurements- Method
 Electrolyte-gated carbon
nanotube transistors
 Measurements done in
aqueous solution at room
temperature
 Liquid gate voltage
applied between an
Ag/AgCl 3M NaCl
standard reference
electrode and SWNT
 Conductance:
Source: Rosenblatt, S.; Yaish, Y.; Park,
J.; Gore, J.; Sazonova, V.; McEuen,
P. L. Nano Lett. 2002, 2, 869.
Electrical Characteristics- Results
 Black: bare SWNT
 Green/Red: 2h and 4h
in DMF

Electron-donating
power of DMF
 Dark Blue: With linking
molecule on surface
 Light Blue: After Gox
immobilization
Electrical Characteristics- Results
 SWNT as an excellent
nanosize pH sensor
 Without Gox Immobilization,
cannnot tell difference
between different pH
 After Gox, conductance
increases for higher pH
 Gate voltage changes by
20mV- conductance
changes
 Sensitivity due to charged
groups on Gox that
become more negative
with increasing pH
Electrical Characteristics- Results
 Real time electronic
response
 Adding water  no
conductance shift
Adding Glucose and
after activity of Gox
conductance shifts
 Inset a– another device
 Inset b– bare SWNT
without immobilization
of Gox, but just the
addition of glucose
Conclusion
 SWNT can be used as an enzymatic-activity
sensor
 SWNT can also be used as a pH sensor
 This first demonstration of biosensors
provides a new tool for enzymatic studies and
highlights the potential for SWNT to be used
for biomolecular diagnostics
References
 Besteman, K.; Lee, J.; Wiertz, F. G. M. ;
Heering, H. A.; Dekker, C.; Nano Letters,
2003, Vol. 3, No. 6, 727-730.
 Rosenblatt, S.; Yaish, Y.; Park, J.; Gore, J.;
Sazonova, V.; McEuen, P. L. Nano Lett. 2002,
2, 869.
 Chen, R. J.; Zhang, Y.; Wang, D.; Dai, H. J.
Am. Chem. Soc. 2001, 123, 3838.
Thank You!
Questions?
Extra Slides
 pH sensor:
Figure 3. The pH was set by using 0.1 mM HCl
in milli-Q water (pH 4) and 0.1 mM KCl in
milli-Q water (pH 5.5). For all measurements
the source-drain voltage was kept at 9.1 mV.
It is seen that the conductance increases with
increasing pH and that pH changes induce a
reversible change in the conductance.