High-temperature processing of meat food generates in it toxic heteroaromatic amines and nitrosamines (NAs)^1,2 causing chronic diseases including hormonal dysfunctions and cancer.³ Therefore, we devised and fabricated chemical sensors for selective determination of the N-nitroso-L-proline (Pro-NO)⁴ and N-nitroso-thiazolidine-4-carboxylic acid (NT4A) toxins in this food. We applied films of conducting polymers molecularly imprinted (MIPs) with either the Pro-NO or NT4A template as recognition units of these chemosensors. For selection of most appropriate functional monomers, we used DFT at the B3LYP/3-21G(*) level modeling to find phenolic derivative of bis(bithiophene) and a thiosalenCo(III) complex (CS)^5,6 suitable to form pre-polymerization complexes with Pro-NO and NT4A, respectively, at the 1:2 template/monomer stoichiometry. The calculated Gibbs free energy gain due to formation of these complexes with a series of NAs was proportional to the UV-vis spectroscopy determined stability constants of these complexes. These constants were relatively high equalling 3.14×10⁹ M^-2 and 2.72×10¹⁰ M^-2for Pro-NO and NT4A, respectively. Then, we electrochemically polymerized these complexes under potentiodynamic conditions. This electropolymerization resulted in depositing thin MIP films on different electrode substrates. After subsequent extraction of the Pro-NO and NT4A templates from MIPs, we used the resulting MIPs with empty imprinted cavities for determination of Pro-NO and NT4A analytes in grilled pork neck samples. We confirmed the presence and then absence of NA templates in the MIP films before and after extraction, respectively, with FTIR spectroscopy and XPS, and then characterized morphology of the films with AFM. For analytical signal transduction, we used piezoelectric microgravimetry (PM) at the Au-QCR/MIP electrodes of EQCM as well as DPV and EIS at the Pt/MIP electrodes. Limits of detection of the chemosensors were 36.9 nM Pro-NO (with EIS) and 46 nM NT4A (with DPV). The chemosensors selectively responded to the target toxins in the presence of interfering compounds of similar composition and structure. Successful selective determination of Pro-NO and NT4A in the food extract samples indicates that the chemosensors are promising as tools for determination of these toxins in food of animal origin.

References

1. Santarelli R. L. et al., Nutr. Cancer 2008, 60, 131.

2. Oostindjer, M. et al., Meat Sci. 2014, 97, 583.

3. Larsson S. C. et al., Int. J. Cancer 2006, 119, 915.

4. Lach P. et al., Chem. Eur. J.(2016) in press, DOI:10.1002/chem.201604799.

5. Pan, M.; et al., Biosens. Bioelectron. 2012, 31, 11.

6. Zhao, L.; et al., Sens. Actuators, B Chem. 2012, 171–172, 563.