Raman_MIP

Raman_MIP

In collaboration with Karsten Haupt and Ilana Bar

Kantarovich, Belmont, 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. Bioelectron. 26(2), 809-814, (2010).

Bompart, Gheber, De Wilde, Haupt, Biosens. Bioelectron. 25(3), 568-571, (2009).

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.

Scanning electron microscopy (SEM) micrograph of a Klarite gold substrate taken by FEI Quanta 600F Environmental SEM (FEI Company, Hillsboro, OR, USA) under high vacuum and secondary electron mode at an accelerating voltage of 5 kV and a working distance of 10 mm

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

Circles - R-propranolol (the template molecule)

Squares - S-propranolol

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.


Printing droplets of MIP on Klarite with NFP	a- AFM image of area where MIP droplet was deposited. b - red line height profile along the white line in a (where MIP is deposited) compared with a height profile along a similar line (black line) where no MIP was deposited. c - difference between red line and black line in b, showing the height of MIP in the Klarite wells (a maximum of 250 nm).

Map of MIP volume (left) compared with Raman intensity (right) shows we can detect target in drops of a few nm³ of MIP.

This page was last updated 31-Dec-12

This page was last updated 08-Jun-2009