Surface plasmon resonance sensor for norepinephrine using a monolayer of a calix[4]arene crown ether

The article describes a calix[4]arene derivative for use as a recognition element in an SPR sensor for norepinephrine (NE). The calix[4]arene carries a crown ether and a thiol group that enables the formation a self-assembled monolayer (SAM) on a gold surface. NE is recognized by the calix[4]arene via its positively charged amino group that has a high affinity for the crown moiety of the calixarene. The modified gold surface was characterized by Fourier transform infrared reflection absorption spectroscopy, atomic force microscopy, and cyclic voltammetry. The binding process to the sensor surface was monitored by SPR. Under optimized condition, the sensor has a linear response to NE in the 10 pM to 100 nM concentration range, and the detection limit is 0.12 pM.