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Biosensors and Carbon Nanotubes. Lakshmi Jagannathan. Enzyme-Coated Carbon Nanotubes as Single-Molecule Bionsensors 1. Introduction and Motivation Physical Immobilization of Protein Method/Experimentation Result/Evidence of Immobilization (AFM) Electrical Characteristics

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Presentation Transcript
enzyme coated carbon nanotubes as single molecule bionsensors 1
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
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
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

Physical Immobilization- Results (AFM)
electrical measurements method
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
electrical characteristics results1
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
electrical characteristics results2
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

Electrical Characteristics- Results
conclusion
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
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.
extra slides
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.