The need for more advanced, accurate and lower cost sensor platforms is constantly growing. However, for certain applications the already existing sensing systems based on biological recognition elements have sometimes restrictions, which limit their use. As a result, sensors with synthetic recognition elements, such as molecular imprinted polymers (MIPs), can be interesting alternatives. Molecular imprinting leads to the formation of inert polymer particles with nanocavities, which can exhibit similar selectivity and specificity to target molecules as antibodies or enzymes. It is demonstrated that MIPs can be readily incorporated into two different sensor platforms for the detection of histamine in aqueous media. The first platform is based on electrochemical impedance spectroscopy and allows for the accurate detection of histamine in the nanomolar range. The second sensing technique is based on microgravimetry and allows for the detection of histamine in the micromolar range. Using the analogous molecule histidine, it is demonstrated that both sensor platforms are specific for the detection of histamine.

Serotonin is an important signaling molecule in the human body. The detection of serotonin is commonly performed by high performance liquid chromatography (HPLC), which is costly and time consuming due to extensive sample preparation. We will show that these problems can be overcome by using molecularly imprinted polymers (MIPs) as synthetic receptors in combination with impedance spectroscopy as readout technique. The MIPs were prepared with several blends of the underlying monomers and the best performing MIP material was selected by optical batch-rebinding experiments. MIP microparticles were then integrated in an impedimetric sensor cell and dose-response curves were measured in PBS buffer and in non-diluted blood plasma. The sensor provides reliable data in the physiologically relevant concentration regime as an independent validation by HPLC measurements demonstrates. Finally, we show that the impedimetric response upon serotonin binding can be attributed to a capacitive effect at the interface between the MIP particles and the plasma.

Phone: þ32 (0)11 26 88 95, Fax: þ32 (0) 11 26 88 99 ** e-mail Evi.Bongaers@uhasselt.be, Phone: þ32 (0)11 26 88 76, Fax: þ32 (0)11 26 88 99

Molecularly imprinted polymers (MIPs) are synthetic receptors that are able to specifically bind their target molecules in complex samples, making them a versatile tool in biosensor technology. The combination of MIPs as a recognition element with quartz crystal microbalances (QCM-D with dissipation monitoring) gives a straightforward and sensitive device, which can simultaneously measure frequency and dissipation changes. In this work, bulk-polymerized L-nicotine MIPs were used to test the feasibility of L-nicotine detection in saliva and urine samples. First, L-nicotine-spiked saliva and urine were measured after dilution in demineralized water and 0.1× phosphate-buffered saline solution for proof-of-concept purposes. L-nicotine could indeed be detected specifically in the biologically relevant micromolar concentration range. After successfully testing on spiked samples, saliva was analyzed, which was collected during chewing of either nicotine tablets with different concentrations or of smokeless tobacco. The MIPs in combination with QCM-D were able to distinguish clearly between these samples: This proves the functioning of the concept with saliva, which mediates the oral uptake of nicotine as an alternative to the consumption of cigarettes.

Phone: þ32 (0) 11 26 88 95, Fax: þ32 (0) 11 26 88 99 Synthetic materials with imprinted nanocavities can act as highly selective tailor-made artificial receptors. Implementing these materials in a piezoelectric sensing device can offer fast and straightforward detection together with high sensitivity. Lnicotine, a major addictive substance in cigarettes is used as target molecule. The synthetic receptors for L-nicotine are made via the molecular imprinting technique. The target molecule is added to a monomer mixture containing initiator and this mixture is polymerized with heat. Subsequently, microparticles are obtained by crushing the bulk molecular imprinted polymers (MIPs), which are then immobilized on thin films of polyvinyl chloride. Using Quartz crystal microbalance, Lnicotine could be detected in the submicromolar range and the selectivity of the sensors was verified by reference measurements with L-cotinine. The effectiveness of the sensor was also tested for different aqueous fluids at different pH. It was found that MIPs bind 4.03 times more L-nicotine than non-imprinted polymer in water and 1.99 times more in 0.1Â phosphate buffer saline at pH 9.