NER: Nanoscale Sensing and Control of Biological ProcessesNER: Nanoscale Sensing and Control of Biological Processes

Objective:

To provide a microelectronic and microfluidic environment as a test bed for nanoelectronic / biological interfaces; to sense and control low-level charge signals arising from redox events at nanoelectrode complexes in solution

Approaches and Contributions:

Design and calibration of a micro-cyclic voltammetry flow-chip prototype

Target DNA hybridization detection at the micro-cyclic voltammetry flow-chip

Molecular assembly of a redox enzyme system by a metallized peptide at the three-microelectrode cell

Development and characterization of nanoelectrode array grown on a Si substrate

Flow-through nanopore membrance design for efficient in situ electrochemical synthesis and detection

Gold Nanotubes as Flow-Through Bioreactors for Microfluidic Networks

Napat Triroj and Rod Beresford Napat Triroj and Rod Beresford Brown University, Providence, RIBrown University, Providence, RI

Micro cyclic voltammetry measurement

Molecular assembly of Npx system

Analyte solution: 10 mM K3Fe(CN)6 in 1 M KNO3

0.6 0.3 0.0 -0.3 -0.6

-2

-1

0

1

2

100 mV/s 200 mV/s 500 mV/s 1 V/s

Curr

ent (n

A)

Potential vs. Ag/AgCl (V)

0.2 0.4 0.6 0.8 1.0

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

Pea

k c

urr

ent

(nA

)

(Scan rate)1/2 (V/s)1/2

cathodic

anodic

DNA hybridization detection

0.0 -0.1 -0.2 -0.3 -0.4 -0.5

-0.1

0.0

0.1

0.2

0.3

0.4

0.5

thiolated ssDNA hybridization with target DNA

Cu

rren

t (n

A)

Potential vs. Ag/AgCl (V)

0.8 0.6 0.4 0.2 0.0 -0.2-2.5

-2.0

-1.5

-1.0

-0.5

0.0

0.5

Npx-PepCo-AuNP in KAc

Npx-PepCo-AuNP in KAc + H2O2

NPx-PepCo-AuNP in KAc + NADH

Npx-AuNP in KAcC

urr

en

t (n

A)

Potential vs. Ag/AgCl (V)

Nanoelectrode array fabrication onto working electrode

Analyte I/O

Digital I/O

The functionality of the microfluidic three- electrode cell is confirmed:

- formal potential is close to the literature values

- peak current is proportional to (scan rate)1/2

An increase in the electrocatalytic charge upon hybridization of the target DNA present at low-concentration

Analyte: 27 µM Ru(NH3)63+ and 2 mM Fe(CN)6

3-

2 µM thiolated ssDNA, 500 nM target DNA

Current density: 3.9 mA/cm2 compared to 0.21 mA/cm2 at a bulk gold electrode

In collaboration with Prof. Joanne Yeh at University of Pittsburgh Medical Center

Collaboration with Prof. Shana O. Kelley, University of Toronto

A self-assembled system consists of NADH peroxidase (Npx) enzyme, a metallized peptide, and a gold nanoparticle onto a microfluidic three-electrode cell

Detection of the changes in redox signals in the presence of H2O2 and NADH

Electrode array process

Assemble PDMS gasket to electrode substrate

Cl2 plasma treatment to convert part of Ag to AgCl

Etch Si3N4 using CF4 plasma

PECVD of Si3N4

E-beam evaporation of Ti/Au and lift-off PR

After Cl2 plasma of Ag and lift-off

Working electrode surface area: 9 µm2

30 µm

Fabrication results

Micro cyclic voltammetry flow-chip prototype fabrication

Mask design

Completed flow-cell chip

Integration: Chip package Si signal processors nanoelectrode array self-assembled linker system biomolecular target

Collaboration with Prof. Jimmy Xu at Brown Univ.

An on-chip “biology-to-digital" sensing and control system

Nanowire array grown in FIB-patterned Al2O3; wire diameter less than 50 nm

Nanocrystal array grown from Co catalyst in FIB-patterned Al2O3

Silicon microelectronic signal processing and control

Flow network chip

Flip and bond

Biosensor electronic chip

Flow-channel network

Electrochemical sensing module

In situ monitoring, sensing, control, and actuation of biomolecular reactions

Collaboration with Hitomi Mukaibo and Charles R. Martin, University of Florida

Andres Jaramillo (undergraduate), Florida State University

Collaborators:

Jimmy Xu, Brown University ~ Charles R. Martin, University of Florida ~ Shana O. Kelley, University of Toronto ~ Joanne I. Yeh, University of Pittsburgh

1 μm

Au dot

Collaboration with P. Jaroenapibal,University of Pennsylvania

Ultra-sensitive integrated enzymatic detector arrays

• In a conically shaped nanotube, flow from base to tip is continually focused to the tube wall, resulting in high conversion efficiency

• Resistance to flow can be adjusted at will by controlling the base opening, tip diameter, and cone angle

Base opening

Tip opening

• Conical nanopore PET membrane fabricated by Martin group

• Membrane sections captured between orthogonal channels in the chip assembly process

• Electrical connection to continuous deposited Au film on the PET membrane

• Planar working electrode also in each channel as a control

• Coupled channels: analyze → synthesize → analyze

membranecontact pad

Electrode cell in glass:channel depth = 12 μmarea of WE = 2.5 x 10-5 cm2

Continuity of Au trace into channel

Modeling and Simulation of Nanoelectrochemistry

r00 0.2 0.4 0.6 0.8 1 1.2 1.4

-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

Time

Vol

tage

TVo

ltag

e

Electrocatalytic model design

YOZRf

b

k

k

ReO

Time

Voltage, RT/F

Cu

rre

nt

de

nsi

ty,

FD

C/r

T = 107

20-20 -15 -10 -5 0 5 10 15

0

2

4

6

8

10

12

ZO = +3+2+1

0−1

− 2− 3

Voltage, RT/F

-20 -15 -10 -5 0 5 10

Cu

rre

nt

de

nsi

ty,

FD

C/r

ZZ = −3

2015

0

2

4

6

8

10

12

14

ZZ = 0

Large and positive charge number of O enhances migration current at nanoelectrode

Large and negative charge number of Z suppresses the current plateau and enhances cathodic peak

Outlet

PET membrane

Glass channel

PDMS channel

Inlet