Copper (II)-ploy-L-histidine functionalized multi walled carbon nanotubes as efficient mimetic enzyme for sensitive electrochemical detection of salvianic acid A

Abstract

In this work, carboxylated multi walled carbon nanotubes (CMWCNTs) were firstly prepared and functionalized with poly-L-histidine (PLH), which were then chelated with copper (II) ions to from the nanocomposites of Cu(II)-PLH-CMWCNTs. The nanocomposites could be exploited as an efficient mimic enzyme for sensitive electrochemical detection of salvianic acid A (SAA). Cu(II)-PLH-CMWCNTs owned good charge transfer property and excellent synergetic catalytic effect between the overoxidized imidazole groups and the copper redox-active units. Therefore, highly sensitive electrochemical response to SAA was achieved under optimum experimental conditions. A good linear relationship between differential pulse voltammetry (DPV) peak current and the SAA concentration was established in the range of 0.4-1000 μM. A low detection limit of 0.037 μM and a sensitivity of 0.27 μA μM^-1 cm^-2 were achieved. The developed biosensor also had advantages of good repeatability, stability and high selectivity, thus, it was successfully applied to the determination of SAA in real samples with satisfactory results, which may have great potential for further exploitation of electroanalysis applications.

Keywords: Cu(II); Differential pulse voltammetry; Mimetic enzyme; Multi walled carbon nanotubes; Poly-L-histidine; Salvianic acid A.