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Biosensors and Carbon Nanotubes

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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Biosensors and Carbon Nanotubes

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  1. Biosensors and Carbon Nanotubes Lakshmi Jagannathan

  2. 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.

  3. 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

  4. 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.

  5. 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)

  6. 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.

  7. 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

  8. 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

  9. 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

  10. 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

  11. 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.

  12. Thank You!Questions?

  13. 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.

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