Functionalized poly (ionic liquid) as the support to construct a ratiometric electrochemical biosensor for the selective determination of copper ions in AD rats

An efficient ratiometric electrochemical biosensor for Cu 2+ determination was constructed using dual hydroxyl-functionalized poly (ionic liquid) (DHF-PIL) as the catalyst support. The DHF-PIL exhibited typical macroporous structure, which provided a high surface area of 39.31   m 2 /g for the sufficient loading of biomolecules . The specific recognition of Cu 2+ was accomplished by employing neurokinin B (NKB) for the first time, which could bind to Cu 2+ to form a [Cu II (NKB) 2 ] complex with high specificity. Meanwhile, a common redox mediator , 2, 2′-Azinobis-(3-ethylbenzthiazoline-6-sulfonate) (ABTS) was modified into DHF-PIL by electrostatic interactions to act as an inner reference molecule, which provided a built-in correction for environmental effects and improving the detection accuracy. With this strategy, the developed electrochemical biosensor was capable of determining Cu 2+ with a linear range between 0.9 and 36.1   μM and low detection limit (LOD) and quantification limit (LOQ) of 0.24 and 0.6   μM, respectively. The sensor also displayed a satisfactory selectivity against a series of interferences in the brain, including metal ions , amino acids and other endogenous compounds . Accordingly, the present biosensor was successfully applied to evaluate Cu 2+ levels in normal and AD rats.