Functional Bioelectronic Interfaces on Electrolessly Deposited Gold for Bioelectronic Applications

1
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
Science Michigan State University East Lansing,
Michigan
2
Presentation Outline

• Background on sensing mechanisms
• Formation of the gold interface
• Interface formation/characterization
• Lipid bilayer with membrane protein
• Bioelectronic interface with dehydrogenase
• Summary

3
Sensing Mechanisms

• Electrochemical oxidation/reduction
• Conductive substrates
• Gold
• Optical fluorescence, luminescence
• Clear substrates
• Glass
• Plastics

4
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

5
SEM-Time
(after colloidal solution)
(20 minutes seeding)
(40 minutes seeding)
(60 minutes seeding)
6
EDS-Analysis
7
Development and Characterization of Lipid Based
Interfaces

• Interface development
• Interface characterization
• Fluorescence recovery after patterned
  photobleaching (FRAPP)
• Determine mobile fraction
• Determine diffusion coefficient

8
Interface Development

• Lipid bilayer formation
• DGP 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolam
  ine- N-3-(2-pyridyldithio) propionate
• DPGP 1,2-di-O-phytanyl-sn-glycero-3-phosphoethano
  lamine
• NBD-PE 1,2-dioleoyl-sn-glycero-3-phosphoethanolam
  ine-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)
9
Fringe patterns using Ronchi ruling
(a) Bleached area
(b) Area Interrogated

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

10
FRAPP Results

• Diffusion coefficient
• 0.12 0.0610-8 cm2 s-1
• Mobile fraction
• 0.87 0.10

Wright, L. L. Palmer, A. G. Thompson, N. L.
Biophysical Journal 1988, 54, 463-470.
11
Development of Dehydrogenase Based Bioelectronic
Devices

• Interface development
• Interface characterization
• Cyclic voltammetry
• Chronoamperometry

12
Reaction Mechanism
13
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 mA mM-1
• Saturation current 60 mA

14
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 mA mM-1
• Saturation current 43 mA

15
Comparison
Hassler and Worden, Biosensors and Bioelectronics
(2005), In press
16
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

IketQexp(-kett)ketQexp(-kett)
?Q/(nFA)
http//www.chemistry.msu.edu/courses/cem837/
17
Chronoamperometry on Glass

• Potentials
• Initial 400 mV
• Final -200 mV
• Results
• Electron transfer coefficients
• ket 3.2102 s-1
• ket 3.5101 s-1
• Surface coverage
• ?? 3.010-12 mol cm-2
• ?? 3.010-12 mol cm-2

18
Chronoamperometry on Polystyrene

• Potentials
• Initial 400 mV
• Final -200 mV
• Results
• Electron transfer coefficients
• ket 4.2102 s-1
• ket 2.1102 s-1
• Surface coverage
• ?? 6.310-12 mol cm-2
• ?? 2.110-12 mol cm-2

19
Comparison
Hassler and Worden, Biosensors and Bioelectronics
(2005), In press
20
Summary

• Designed bioelectronic interfaces
• Electrolessly deposited gold
• Lipid bilayers
• Dehydrogenase enzymes
• Characterized interfaces
• Optical Techniques
• FRAPP
• Electrochemical
• Cyclic voltammetry
• Chronoamperometry

21
Acknowledgements

• Funding
• Michigan Technology Tri-Corridor
• Department of Education GAANN Fellowship
• Undergraduate participants
• Sean OBrien
• Craig Pereira

22
Thank You
23
Polyelectrolyte Multilayers

• Formation of films

• Formation of films
• Multilayer architectures
• Salt Concentration
• pH

• Formation of films
• Advantages of polyelectrolytes
• Ease of formation
• Molecule inclusion
• Controllable thickness

PAH ()
Water
Water
PAA (-)
Water
Water
24
Lipids Used
DGP
DPGP
NBD-PE
25
Technique
PAH (ve)
Glass slide
26
Cyclic Voltammetry

• Procedure
• Linear change in potential
• Plot current vs. potential
• Controlled/measured variables
• Peak current (Ip)
• Area (A)
• Scan rate (v)
• Concentration (C)

http//www.chemistry.msu.edu/courses/cem837/
27
Dehydrogenase Enzymes

• Dehydrogenase enzymes
• Catalyze electron transfer reactions
• Activity easily measured electrochemically
• Bioelectronic applications
• Often require cofactor (e.g., NAD(P))
• Challenge regenerating cofactor after reaction

cofactor
enzyme
NAD(P)H
Dehydrogenase Enzyme Reaction
28
Channel Protein Incorporation
(A)
(B)
(C)

• Bottom leaflet
• Upper leaflet
• Protein Incorporation
• 510-7 M Valinomycin in NaCl
• Equilibration Time 1 h

29
Impedance Spectroscopy

• Interface Design
• Lipid bilayer
• Lipids with valinomycin
• Interface Characterization
• Lipid bilayer
• Valinomycin containing bilayer
• Cm0.5 F cm-2
• Cdl 4.1 F cm-2
• Rm 8 K? cm2