A Colorimetric Probe for the Selective Detection of Norepinephrine Based on a Double Molecular Recognition with Functionalized Gold Nanoparticles

A simple colorimetric probe for the selective and sensitive detection of neurotransmitter norepinephrine (NE), an important biomarker in the detection of tumors such as pheochromocytoma and paraganglioma, is described. The sensing strategy is based on the use of spherical gold nanoparticles functionalized with benzaldehyde and boronic acid-terminated moieties. A double molecular recognition involving on one hand the aromatic aldehyde and the aminoalcohol group of NE, and on the other hand the boronic acid and the catechol moiety of the neurotransmitter, results in analyte triggered aggregation of the gold nanoparticles, leading to a bathochromic shift of the SPR band in the UV–vis spectrum of the probe and a clear change in the color of the solution from red to blue. Probe P1 shows a remarkable selectivity toward NE versus other catecholamine neurotransmitters (dopamine and epinephrine) and selected biomolecules (5-HIAA, l-Tyr, glucose, uric acid, Lys and glutamic acid). Moreover, a linear response to NE in the 0–1 μM concentration range was observed and a limit of detection of 0.07 μM in aqueous media was determined by UV–vis spectroscopy. The sensitivity of the probe toward NE in synthetic urine was also evaluated. In this medium, a limit of detection of 0.09 μM was obtained which falls within the range of clinical interest.