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 reacts with amide group from linking molecule and immobilizes (covalent bond)Source: Chen, R. J.; Zhang, Y.; Wang, D.;

Dai, H. J. Am. Chem. Soc. 2001, 123, 3838.

Physical Immobilization- Results (AFM)

A and C: Laser-ablated

and CVD growth,

respectively; before GOX

immobilization

B and D: After

immobilization of GOX-

difference 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.