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Haupt, Bar, Gheber, Appl. Phys. Lett. 94(194103),
1-3, (2009).
Kantarovich,
Tsarfati, Gheber, Haupt, Bar, Anal. Chem. 81,
5686-5690, (2009).
Kantarovich,
Tsarfati, Gheber, Haupt, Bar, Biosens.
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De Wilde, Haupt, Biosens. Bioelectron. 25(3),
568-571, (2009).
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Label-free
detection methods are important in (bio)sensing, since without
them, "on-line" monitoring is not possible. Indeed label-free
detection methods exist, most notably
Surface Plasmon Resonance (SPR) and
Quartz Crystal
Microbalance (QCM). The problem with these methods is that
they are not specific: they report on accumulation of material
on the sensor surface.
Raman
spectroscopy provides chemical information about specific bonds,
and is thus a very attractive method for specific label-free
detection. To test the limits of sensitivity of this approach we
monitored spots of MIP imprinted against propranolol, using a
confocal Raman setup. We first characterized the spectrum of
each component of the MIP, and confirmed that the target
molecule (propranolol) has a distinct fingerprint. Using this
fact, we were able to measure quantitatively the amount of bound
propranolol. Moreover, we demonstrated the selectivity of the
MIP, for the isoforms (S and R) of propranolol. |
Surface
Enhanced Raman Spectroscopy (SERS) makes use of the enhancement
provided by metallic surfaces (usually Gold), especially in the
vicinity of sharp features, to provide superior sensitivity.
We used
surfaces specially designed for SERS ("Klarite"
now from Renishaw) and our NFP technique to deposit drops of
MIP on these surfaces, and study the signal enhancement.
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a - DPAP
(initiator)
b- TRIM and MMA
c- Monomers and
porogen
d-
R-propranolol
e- Monomers and
R-propranolol
f- Monomers,
R-propranolol and porogen |
a - MIP as
synthesized
b -
Extracted MIP
c - Non
Imprinted Polymer (NIP - control)
d -
R-Propranolol
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Circles - R-propranolol (the template molecule)
Squares - S-propranolol |
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a- 3D AFM image
of MIP drop on top of Klarite
b- 2D AFM image
of the drop in a
c- Optical
image of drop. SERS spectra were collected along the
line indicated.
d- Height
profile along the line in b (the same as the one
in c), along which SERS spectra were collected. |
SERS spectra collected
along the line indicated in the AFM and optical images.
a - l, from the top of the drop, downhill. It is visible
how the spectra are losing the fingerprint of the MIP
with the distance from the edge of the drop. |
Next, we deposited minuscule drops of MIP
using Nano Fountain Pen (NFP) onto Klarite, to test the
ultimate detection sensitivity of very small MIP
quantities.
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This page was last updated
31-Dec-12
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