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

• A sensitive electrochemical method for the detection of Cu2+ was presented.
• Neurokinin B was employed for the specific recognition of Cu2+.
• Polymerized ionic liquid was adopted for neurokinin B loadings.
• This methodology realized the assessment of Cu2+ levels in AD rat brains.

An efficient ratiometric electrochemical biosensor for Cu2+ 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 m2/g for the sufficient loading of biomolecules. The specific recognition of Cu2+ was accomplished by employing neurokinin B (NKB) for the first time, which could bind to Cu2+ to form a [CuII(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 Cu2+ 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 Cu2+ levels in normal and AD rats.