Functional Bioelectronic Interfaces on Electrolessly Deposited Gold for Bioelectronic Applications

Brian L. Hassler, Neeraj Kohli, Lavanya Parthasarathy, Robert Ofoli, Ilsoon Lee, and R. Mark Worden.

Chemical Engineering and Materials ScienceMichigan State UniversityEast Lansing, Michigan

Presentation Outline Background on sensing mechanisms Formation of the gold interface Interface formation/characterization

Lipid bilayer with membrane protein Bioelectronic interface with dehydrogenase

Summary

Sensing Mechanisms Electrochemical: oxidation/reduction

Conductive substrates Gold

Optical: fluorescence, luminescence Clear substrates

Glass Plastics

Formation of Gold Film Treat with oxygen plasma Deposit polyelectrolyte mulilayers

Poly(acrylic acid) (PAA) Poly(allylamine hydrochloride) (PAH)

Deposit colloidal gold Seed by reductive deposition of gold salt

SEM-Time

(after colloidal solution) (20 minutes seeding)

(40 minutes seeding) (60 minutes seeding)

EDS-Analysis

Au

Si Si

Development and Characterization of Lipid Based Interfaces

Interface development Interface characterization

Fluorescence recovery after patterned photobleaching (FRAPP) Determine mobile fraction Determine diffusion coefficient

Interface Development Lipid bilayer formation

DGP: 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine- N-[3-(2-pyridyldithio) propionate]

DPGP: 1,2-di-O-phytanyl-sn-glycero-3-phosphoethanolamine

NBD-PE: 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine-N-(7-nitro-2-1,3-benzoxadiazol-4-yl)

(A) Cystamine, DPGP, and DGP in ethanol (B) DPGP and NBD-PE in 0.1 M NaCl

(A) (B)

Fringe patterns using Ronchi ruling

Excitation wavelength (=488 nm) Emission (=510 nm) Bleaching time (3 1-s pulses)

(a) Bleached area (b) Area Interrogated

FRAPP Results Diffusion coefficient

0.12 ± 0.06×10-8 cm2 s-1

Mobile fraction 0.87 ± 0.10

2 2

2 2 2

8 4 1 36( ) (0) 1 (0) . 1 . exp exp

2 9

m Dt Dtf t f f

a a

Wright, L. L.; Palmer, A. G.; Thompson, N. L. Biophysical Journal 1988, 54, 463-470.

Development of Dehydrogenase Based Bioelectronic Devices

Interface development Interface characterization

Cyclic voltammetry Chronoamperometry

Reaction Mechanism

Cyclic Voltammetry on Glass Scan Parameters

Initial potential: 400 mV Final potential: -200 mV Scan rate: 100 mV s-1

Results Turnover rate= 69.8 s-1 Sensitivity= 2.0 A mM-1 Saturation current= 60 A

Cyclic Voltammetry on Polystyrene Scan Parameters

Initial potential: 400 mV Final potential: -200 mV Scan rate: 100 mV s-1

Results Turnover rate= 47.2 s-1 Sensitivity= 1.7 A mM-1 Saturation current= 43 A

Comparison

Turnover Number

(s-1)

Sensitivity

(A mM-1)

Saturation Current

(A)Glass 69.8 2.0 60.0Polystyrene 47.2 1.7 43.0Silicon 23.4 0.8 21.0

Hassler and Worden, Biosensors and Bioelectronics (2005), In press

Chronoamperometry Procedure

Step change in potential Plot current vs. time

Characterization Equation for current decay

Evaluation of constants ket= Electron transfer constant Q= Charge associated with oxidation/reduction = Surface coverage

I=k’etQ’exp(-k’ett)+k”etQ”exp(-k”ett)

=Q/(nFA)

http://www.chemistry.msu.edu/courses/cem837/

Chronoamperometry on Glass Potentials:

Initial: 400 mV Final: -200 mV

Results: Electron transfer coefficients

k’et= 3.2×102 s-1

k”et= 3.5×101 s-1

Surface coverage ’= 3.0×10-12 mol cm-2

”= 3.0×10-12 mol cm-2

Chronoamperometry on Polystyrene Potentials:

Initial: 400 mV Final: -200 mV

Results: Electron transfer coefficients

k’et= 4.2×102 s-1

k”et= 2.1×102 s-1

Surface coverage ’= 6.3×10-12 mol cm-2

”= 2.1×10-12 mol cm-2

Comparison

k'et k"et' "

Glass 3.20E+02 3.50E+02 3.00E-12 3.00E-12Polystyrene 4.20E+02 2.10E+02 6.30E-12 2.10E-12Silicon 2.40E+02 2.10E+02 2.10E-12 2.40E-12

Surface Coverage

(mol cm-2)

Kinetic Parameters

(s-1)

Hassler and Worden, Biosensors and Bioelectronics (2005), In press

Summary Designed bioelectronic interfaces

Electrolessly deposited gold Lipid bilayers Dehydrogenase enzymes

Characterized interfaces Optical Techniques

FRAPP Electrochemical

Cyclic voltammetry Chronoamperometry

Acknowledgements Funding

Michigan Technology Tri-Corridor Department of Education GAANN Fellowship

Undergraduate participants Sean O’Brien Craig Pereira

Thank You