A MOLECULARLY IMPRINTED POLYMER RECEPTOR FOR FURFURAL ON REMOVABLE PLASMONIC CHIPS
2Department of Engineering, University of Campania Luigi Vanvitelli
MIPs are synthetic receptors presenting several favorable distinctive features with respect to bio-receptors1. For sensors application it is particularly relevant that they can be prepared in different formats, as required by the intended application. In the case of SPR sensors a thin MIP layer must be formed over a surface plasmon resonance (SPR) interface, in close contact with it.
Here, a simple procedure has been applied to realize the layer: the prepolymeric liquid was deposited on a flat gold surface by a spin coating machine, and the in situ polymerization was carried out at 70°C in the air by inserting the platform in an oven2. As a proof of principle, a molecularly imprinted polymer (MIP) for furfural (furan-2-carbaldehyde, 2-FAL) was considered, the final aim being the development of a sensing device for the determination of 2-FAL in beverages as wine or beer. The composition of the prepolymeric liquid was as previously reported2.
The interaction between the MIP layer and the substrate was studied by SPR, using an optical platform consisting in a removable polymethylmethacrylate (PMMA) chip with a 60 nm gold film on the top3 as shown in Figure 1. MIP is deposited on the gold film over the chip, which acts as a waveguide. The transmission spectra show a plasmonic resonance at about 680 nm, which demonstrates that the refractive index of the obtained MIP layer is suitable for the determination3. The resonance wavelength is shifted to higher values (red shift) when the 2-FAL concentration increases (Figure 2), indicating that the refractive index of the MIP increases after combination of 2-FAL with the polymer.
The affinity constant of 2-FAL for the MIP layer is Kaff=106M-1, similar to that obtained by batch equilibration at low concentration. The instrumental response extends up to concentrations of about 1ppm, with a LOD of 0.03 ppm, which is suitable to 2-FAL determination in beverages. Not any further SPR signal variation is obtained even at much higher concentrations, despite of the fact that more 2-FAL has been found to be adsorbed on MIP by batch equilibration.
References
[1] L. Uzun, A.P.F. Turner (2016) Biosens. Bioelectron. 76: 131–144
[2] N. Cennamo, L. De Maria, C. Chemelli, A. Profumo, L. Zeni, M. Pesavento (2016) IEEE Sens. J. 16: 7663-7670
[3] N. Cennamo, F. Mattiello, L. Zeni (2017) Sensors 17:1488-1492
Figure 1. SPR sensor
Figure 2. Dose-response curve of 2-FAL and Hill fitting
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