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Single Plasmonic Nanoparticles as Biosensors
Jan Becker, Carsten Sönnichsen
Plasmonic nanostructures for applications in the lif e sciences
Single Plasmonic Nanoparticles as Biosensors
�Sensing properties of plasmonic particles
�Darkfield-microscopy (fastSPS)
�Protein-membrane interaction
�Improvement of Sensors
550 600 650 7000
1
0.2
0.4
0.6
0.8
Wavelength [nm]scat
terin
g ef
ficen
cy [a
rb.u
]400 600500 700
0
1
0.2
0.6
0.4
0.80.8
Wavelength [nm]
scat
terin
g ef
ficen
cy [a
rb.u
.]
λλλλ
Qsca
400 nm 700 nm λλλλ
Qsca
400 nm 700 nm
Optical Properties Depend on:
Material Shape Surrounding refractive index
�Resonance Position
�Linewidth (FWHM)
n=1.33 n=1.5
silver goldsphere
Darkfield Microscopy
objective
direct light
sample
DF condenser
scatteredlight
CCDspectrometer
grating
Entrance slit/pinhole
100 nm
TEM
CCDspectrometer
grating
Entrance slit/pinhole
Real color image
10 µm
Concept of single particle plasmon sensors
Statistics very important
Shift in resonancewavelength
For stochastic process investigation
λλλλ
Iscat
Single Plasmonic Nanoparticles as Biosensors
�Sensing properties of plasmonic particles
�Darkfield-microscopy (fastSPS)
�Protein-membrane interaction
�Improvement of Sensors
Conventional Method to Measure Single-Particle Spectra
400 450 500 550 600 650 700 7500
200
400
600
800
1000
Wavelength [nm]C
ou
nts/
10
sec/
11B
insSelect one particle
Disperse lightCapture the spectrum
serial process ���� very slow!
CCD
The Scanning Method
wavelength
���� still slow!
Entrance Slit
The fastSPS Method
wavelength
LCD
���� many particles auto-matically observable in parallel
CCDspectrometer
grating
Entrance slit/pinhole
CCDspectrometer
grating
Entrance slit/pinholeLCD
fastSPS: fast Single Particle Spectroscopy
Nano Lett. (2007), 7, 1664
Single Plasmonic Nanoparticles as Biosensors
�Sensing properties of plasmonic particles
�Darkfield-microscopy (fastSPS)
�Protein-membrane interaction
�Improvement of Sensors
Au rods as Biosensor for Protein Binding
0 50 100 150 200 250 300655
660
665
Time [min]
Res
onan
ce W
avel
engt
h [n
m] Lipids STV TritonBuffer
0 50 100 150 200 250 300655
660
665
Time [min]
Res
onan
ce W
avel
engt
h [n
m] Lipids STV TritonBuffer
Nano Lett. (2008), 8, 1724
n=1.5H2O (n=1.33)
glass
FastSPS gives statistics with only one experiment
0 50 100 150 200 250 300655
660
665
Time [min]
Res
onan
ce W
avel
engt
h [n
m] Lipids STV TritonBuffer
0 50 100 150 200 250 300655
660
665
Time [min]
Res
onan
ce W
avel
engt
h [n
m] Lipids STV TritonBuffer
Single particle spectra:
-5 0 5 100
0.2
0.4
0.6
0.8
1.0
Shift [nm]C
umul
ativ
e P
roba
bilit
y add STV
∆=2.9nm
lipid
∆=3.6nm
triton
∆=0.5nm
Statistics on 29 particles
Nano Lett. (2008), 8, 1724
Sensitive detection of small spacer length
No biotin∆=1.2 ± 0.1nm
Incl. biotin:∆=5.3 ± 0.7nm
Incl. spacer∆=2.4 ± 0.4nm
glass
H2O
glass
H2O
glass
H2O
� smaller shift with longer spacer
� Membrane suppresses nonspecific interactions
-2 0 2 4 6 8 100
0.2
0.4
0.6
0.8
1
Shift to membrane coated rod[nm]
Cum
ula
tive
Pro
ba
bilit
y
Shift due to streptavidin binding:
Nano Lett. (2008), 8, 1724
Single Plasmonic Nanoparticles as Biosensors
�Sensing properties of plasmonic particles
�Darkfield-microscopy (fastSPS)
�Protein-membrane interaction
�Improvement of Sensors�Reduction of Single Particle Linewidth
�Increasing Plasmon Sensitivity
Sensor Improvement
λλλλ
Iscat
n=1.33 n=1.5
∆λ∆λ∆λ∆λ
� Reduction of single particle linewidth increases resolution
∆λ∆λ∆λ∆λ
λλλλ
n=1.33 n=1.5
Iscat
Ag Coating Reduces Single Particle Linewidth
Nano Lett. (2008), 8, 1719
550 600 650 700
30
40
50
60
Resonance wavelength (nm)
Lin
ew
idth
(n
m)
550 600 650 700
λres
FWHM
λres
FWHM
a 0 30 50 80 110 140 160 µM
b
Distance (nm)
Cou
nts
in 1
08
0 20 40
0
2
4
6
8
Ag
Au
Particle Characterization
Sensor Improvement
λλλλ
Iscat
n=1.33 n=1.5
∆λ∆λ∆λ∆λ
� Reduction of single particle linewidth increases resolution
� Increased plasmon sensitivity results in larger wavelength shifts
∆λ∆λ∆λ∆λ
λλλλ
n=1.33 n=1.5
∆λ∆λ∆λ∆λ’
λλλλ
n=1.33 n=1.5
∆λ∆λ∆λ∆λ
λλλλ
n=1.33 n=1.5
Iscat
Iscat Iscat
Gold Nanorattles Show Improved Sensitivity
1.32 1.34 1.36 1.38
580
600
620
640
660
λλλλres ~185 n
Pla
smon
wav
elen
gth
λ res
[nm
]
Refractive index n [RIU]
λλλλres ~ 231 n
λλλλres ~ 227 n
Pla
smon
sen
stiv
ity Ю
[nm
/RIU
]
Starting plasmon wavelength 8res [nm]
550 600 6500
40
80
120
160
200
240
[1]
[2]
[2]
[3]
JACS, submitted
[1] Raschke et al. Nano Lett. (2003), 3, 935[2] Chen et al. Langmuir (2008), 24, 5233[3] Raschke et al. Nano Lett. (2004), 4, 1853
0 100 200 300 4000
0.2
0.4
0.6
0.8
1.0
Yu [nm/RIU]
Cum
ulat
ive
Pro
babi
lity
Ю
0 100 200 300 400Yu [nm]
∆Ю = 30nm/RIU
Plasmonic sensitivity Ю [nm/RIU]
Ю [nm/RIU]
50nm
Conclusions
� fastSPS allows continuous observation of many (up to 30) nano-particles in parallel
� Membrane and protein binding can be detected by shift in resonance wavelength of single nanorods
� Simple functionalizability of membranes (many different headgroups available) � ideal characterization tool for biomolecules
� Ag coating of Au rods reduces the single particle linewidth (at same resonance wavelength)
� Gold Nanorattles show improved sensitivity on changes in refractive index
wavelength
LCD
-5 0 5 100
0.2
0.4
0.6
0.8
1.0
Shift [nm]
Cum
ulat
ive
Pro
babi
lity add STV
∆=2.9nm
lipid
∆=3.6nm
triton0.5nm
-5 0 5 100
0.2
0.4
0.6
0.8
1.0
Shift [nm]
Cum
ulat
ive
Pro
babi
lity add STV
∆=2.9nm
lipid
∆=3.6nm
triton0.5nm
add STV
∆=2.9nm
add STV
∆=2.9nm
lipid
∆=3.6nm
lipid
∆=3.6nm
triton0.5nm
triton0.5nm
550 600 650 700
30
40
50
60
Resonance wavelength (nm)
Lin
ew
idth
(n
m)
550 600 650 700550 600 650 700
Pla
smon
sen
stiv
ity Ю
[nm
/RIU
]
Starting plasmon wavelength 8res [nm]
550 600 6500
40
80
120
160
200
240
[1]
[2]
[2]
[3]
Acknowledgement
Carsten Sönnichsen
CollaboratorsAndreas Janshoff, Cristina Baciu
Carl-Zeiss-Foundation
www.nano-bio-tech.de
Financial Support
More information:
I. Ament L. Carbone
I. ZinsC. RosmanS. Pierrat
Y. KhalavkaA. JakabA. Henkel
O. Schubert
A. Jakab