Biological Sensing
using Novel Magnetic Materials
Gil Lee, Schools of Chemical and Biomedical Engineering
Won-Suk Chang, Postdoctoral Fellow
Kyung Jae Jeong, Ph.D. Candidate
Dong Myung Oh, Ph.D. Candidate, Physics
Alex Fung, Undergraduate ChmE
David Janes, School of Electrical and Computer Engineering
Sugata Bhattacharya, Ph.D. Candidate
Ajit K Mahapatro, Postdoctoral Fellow
INACMCW 2005
1
Background
Force Amplified Biosensor (FABS)
Challenges of Biosensing
1. Measurements must be made in extremely
Microparticles
complex environments, eg. blood, urine, or
Signalsaliva.
Piezolever
2. Relevant analytes are present in extremely small
quantities, eg, bacteria can be lethal at single
organism levels.
3. Measurement must be completed
quickly, ie., <
Reference
Piezolever
1 hr.
Batch 1:
4.
Multiple
analytes
must
often
be
analyzed
Permanent NdBFe Magnets
300 x 100 x 1 um
Anti-HelmHotz Coils
orsimultaneously.
electromagnet (B)
(dB/dx(t))
K = 0.0073 N/m
7000 G
100 G/mm
D. Baselt, et al, J.Vac. Sci. 1996; D. Baselt, et al, Proc. IEEE
1997; D. Baselt, et al , Biosensor Bioelect 1998; G. Lee, et al,
Bioanalytical Chem., 2000.
INACMCW 2005
fr = 3.75 kHz
dR/R = 0.21 1/nm
sensitivity ~ 0.42 pN
2
Integrated Approach to Sensing with
Nanonparticles
1
AreaR1: Enhance
Mass1 Transport=- New Material
=
overall
A new
class
ofcomagnetic
gold-iron nanoparticles
been created by
1/ R
1/ hCo + 1/ konChas
nvection + 1/ Rreaction
r Co
Dr. W.S. Chang and Dong Myung Oh. These particles will allow the
analyte to be efficiently
collected
Surfaces
h ~ 10-8and
m/s reacted with a surface.
Sphere h > 10 -5 m/s
Probe DNA-Analytes
Area 2: Enhance Reaction Kinetics – Surface
Chemistries
modified
colloids
The reaction kinetics of nanoparticles with gold
surfaces
has been studied
Probe DNAby K. Jeong and A. Fung. Optimized surface chemistries will allow us
modified gold
to quickly and
efficiently capture nanoparticles on surfaces using
electrode
specific molecular reactions.
Area 3: Enhance Signal - Surface Chemistries and
Microfabrication
The conductivity of the double-stranded DNA and DNA coated
Microfluidic
nanoparticles assembled
on break junctions have been studied by A.
Channel
Mahapatro and S. Bhattacharya.
INACMCW 2005
3
Area 1 - Gold-Iron Alloy Nanoparticles
Anodized Al Membrane
Electrochemical Deposition
Au-Fe alloyed
particles
Al sheet
1st Anodizing
Annealing at 650°C for 3hr
Stripping
Stripping Anodized Membrane
Disperse in water
2nd Anodizing
Pore size 60~70nm
W.S. Chang, et al, Nanoletters 2005.
INACMCW 2005
4
Synthesis Results
Mesoporous Alumina Membrane
Fabricated by Anodic Oxidation
INACMCW 2005
Partially Released Au-Fe Alloy
Particles
5
Characterization
TEM Images of Au-Fe Alloy Particles
EDS (25: 75 Fe:Au)
160
Counts
120
80
40
Fe
Au
Cu
0
0
E-Chem
500
1000
1500
Energy (keV)
PLD
Optical Spectra
20.0
18.0
1
PLD
Au
Fe3O4
Absorbance
Distribution (%)
16.0
14.0
12.0
10.0
8.0
6.0
0.8
0.6
0.4
0.2
4.0
0
200
2.0
0.0
45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61
Particle size (nm)
INACMCW 2005
300
400
500
Wavelength (nm)
600
700
6
Magnetic Properties
Force Magnetometry
40
Magnetization (emu/g)
35
Fe-Au Particles
Amplitude
Amplitude
1E-11
(2)
(1)
30
25
20
15
10
5
0
1E-12
0
1000
2000
3000
4000
5000
6000
Magnetic Field Strength
1E-13
1E-14
5
15
25
35
45
Frequency (kHz)
INACMCW 2005
7
Demonstration of DNA Sensing with AuFe Nanoparticles
a
b
c
d
Absorption Difference
b/w Complementary and Noncomplementary
Absorption Difference
4x10
Au/Fe 20%
-2
3
Au/Fe 10%
2
1
Au/Fe 2%
0
Au/Fe 1%
a. Au/Fe + Au + target DNA
500
b. Separate and c. remove Au
550
Wavelength (nm)
600
d. Redispersion of Au/Fe-Au assembly in
water and separation of Au/Fe
INACMCW 2005
8
Area 2 - Forces Controlling Assembly of
Nanoparticles on Surfaces
Relative Color Density
1.2
1
0.8
0.6
0.4
0.2
0
Complementary Complementary Non-Comp w/
w/ MCH
w/o MCH
MCH
INACMCW 2005
Non-Comp w/o
MCH
9
Immobilization of Gold-DNA
Nanoparticles on Surfaces with
Polycations
Relative Color Density
1.2
1
0.8
0.6
0.4
0.2
0
Complementary
comp-buffer
comp-water
comp-1.0mM
spermidine
comp-0.1mM
spermidine
INACMCW 2005
Noncomplementary
comp-10uM
spermidine
non-compbuffer
non-comp1.0mM
10
Area 3 - Magnetic Nanoparticle Sensor
Design
DNA Sensor
Hybridize the Fe-Au particles with the target
Apply a current in the interdigitated fingers to
produce an magnetic field
Sense the presence of the particle by direct electrical
measurement
B’
A’
Target Sequence
A
B
I(t)
V(t)
I(t)
INACMCW 2005
11
ds-DNA Oxidation Damaging
First Scan
-10
Current (in Amp.)
10
Second Scan
-11
10
-12
10
Third Scan
-13
10
-14
10
0
0.5
1.0
Voltage(in Volts)
1.5
2.0
Au/GC-rich-ds-DNA(0.137mM)/Au
INACMCW 2005
12
Microscopic photograph of Step
Junction
Au Pad
Au Pad
Au step
INACMCW 2005
13
Step Junction Results
INACMCW 2005
14
Normalized Frequency
Summary of Step Junction Results
0.8
0.6
Complementary
0.4
0.2
0.0
2
3
Normalized Frequency
10
4
10
10
Current (pA)
5
10
0.8
0.6
Noncomplementary
0.4
0.2
0.0
2
10
3
4
10
10
Current (pA)
5
10
Average Current = 144pA
INACMCW 2005
15
Conclusions
1. We have create a Fe-Au nanometer scale magnetic particles that we
believe will allow us to efficiently collect an analyte and react it with a
surface. The technique we are using will allow us to create a wide range
of sizes and shapes.
2. We have optimized a ligand immobilization surface chemistry to allow
nanoparticles baring receptors to efficiently react with surfaces.
3. Break junction work confirms that double stranded DNA is a poor
conductor and that it’s conductance is highly dependent on the manner
in which the DNA is attached to the surface and nucleic acid base
content.
3. Step junction work is underway that will allow us to measure the
conductance of single gold nanoparticles attached to surfaces through
double-stranded DNA.
INACMCW 2005
16