Development of an impedimetric sensor for the label-free detection of the amino acid sarcosine with molecularly imprinted polymer receptors

© 2017 Elsevier B.V. In this article we report on the development and optimization of a biomimetic sensor for the label-free detection of the amino acid sarcosine, a molecule which is seen as a biomarker for prostate cancer. The recognition elements were sarcosine-imprinted poly-aminothiophenol (p-ATP) layers deposited by electro-polymerization onto screen-printed gold electrodes and, for comparison, onto carbon electrodes covered first with a gold-nanoparticles interlayer. Using the latter type of electrodes, we reached a detection limit below 1 nM in aqueous buffer solutions with an accessible concentration range from the nano- to the micromolar scale. This was achieved by a careful thickness optimization of the Au-nanoparticle and the p-ATP layers in combination with Faradaic impedance spectroscopy as a readout method. The sensor showed an excellent reproducibility, a good stability with time, and a surprisingly low cross-selectivity towards other proteins.