1. Carbon Nanotube Biosensors with Aptamers as Molecular Recognition Elements
Jeong-O Lee
Fusion-Biotechnology Research Center, Korea Research Institute of Chemical Technology

2. How we fabricate nanodevices?
Fabrication of nanotube devices by patterned growth technique
Home land security (Nerve gas, blood agent, blister agent etc)
Environmental monitoring
Polymer coating
Medical sensors (cancer, drug discovery)
Bioterror (Anthrax, botulinum toxin, diphtheria toxin etc)
Antibody or aptamer
functionalization

3. Detection of thrombin
before
after
J. Am. Chem. Soc. 127, (2005)

4. Detection of Escheria coli
SELEX buffer
E. coli
After washing
(a)
(b)
E.coli
500 nm
Abrupt decrease of conductance observed from the sensor, while no changes observed with aptamer-free devices

5. Detection of Escheria coli
Selectivity of sensor
E.coli aptamer functionalized SWNT-FET does not respond to 109 cfu/ml Salmonella solution
(a)
(b)

6. Detection of Escheria coli
Microbiologists are clever.. They solved the problem with statistical method, called Most Probable Number Method (MPN)
What is MPN?
10-1
10-2
10-3
10-4
10-5
Make series dilutions of the original solution
Incubate each diluted solutions in at least three petri dishes
Choose three sets of samples before extinction
Compare with 3-tube (5, 10) MPN table
(+,+,+)
(+,+,+)
(+,+,+) 3
0.95 1
0.43
0.75
(+,-,-)
5. Multiply MPN with dilution factor
0.43×104=4.3×103 /ml E.coli
(-,-,-)

7. Detection of Escheria coli
MPN-combined with nanoFET
(+,+,+)
100
(+,-,+)
10-1
(-,-,-)
10-2
0.93×10 cfu/3 ml→0.93×10×333 cfu/ml=~3100 cfu/ml

8. Conclusions
We have immobilized aptamers specific for thrombin & E.Coli on the sidewalls of single-walled carbon nanotubes by non-specific binding.
Binding of targets with aptamers are reversible in case of thrombin, we were able to fabricate recyclable thrombin sensors with aptamer-functionalized single-walled carbon nanotubes.
Highly specific interactions observed with E.Coli and E.Coli aptamer, which shows the possibility of electronic detection platforms for the detection of microorganisms.
For samples with very low density and random distribution, pre-concentration or active attraction of targets are necessary to improve the sensitivity and detection time.

9. Acknowledgement
NBALinK (NanoBio Applications Lab in KRICT) in Fusion-Biotechnology center, KRICT; Dr. Hyunju Chang, Dr. Ki-jeong Kong, Dr. Gyoungho Bu, Dr. Hye-Mi So
Ph.D candidate; Byoung-Kye Kim, Dong-Won Park, and Eun-Kyoung Jeon.
Professor Yong Hwan Kim, Kwangwoon Univ.
Professor Beom Soo Kim, Chungbuk National Univ.
Professor Ju-Jin Kim, Chonbuk National Univ.
Dr. Sung Chun Kim, GenoProt Inc.
Mario Hofmann, Prof. Jing Kong, MIT
These works were supported by Korea Research Council for Industrial Science and Technology.