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