Detection of Dopamine Using an Electrochemiluminescence Biosensor Based on Iridium Nanorods

KeyWord:electrochemiluminescence  dopamine(DA)  biosensor  Ir nanorods

Abstract:

      Electrochemiluminescence(ECL) is a new analysis technique that combines electrochemistry and chemiluminescence.With various advantages of simplicity,rapidness,high sensitivity and high controllability,ECL has been widely used for the analysis in food,environment,pharmaceutical and clinical diagnosis fields.Iridium(¢ó) complex,as a new type of ECL material,exhibits excellent light stability,long luminescence life,large Stokes shift,and tunable luminous efficiency and emission wavelength.However,the weak solubility of iridium(Ir) complex in aqueous solution restricted its application in ECL field.In this paper,tris(2.phenylpyridine)iridium(¢ó)(Ir(ppy)3) was firstly functionalized with poly(styrene-maleic anhydride)(PSMA) through a simple nano-precipitation method to obtain iridium nanorods(Ir NDs) which were then characterized by transmission electron microscopy(TEM),infrared spectroscopy(IR) and X-ray electron spectroscopy(XPS).The TEM image showed that the lengths of Ir NDs were in the range of 204-1 158 nm,and the average length was 543 nm.The prepared Ir NDs had a large number of carboxyl groups on their surface,thus displaying an outstanding dispersibility in aqueous solution.Furthermore,Ir NDs also presented a strong ECL emission in the presence of the co-reactant tripropylamine(TPrA).Then,the dispersion of Ir NDs was used to modify the glassy carbon electrode(GCE) to obtain an ECL biosensor.The construction process of the biosensor was characterized by cyclic voltammetry(CV) and electrochemical impedance(EIS),and the experimental conditions including concentration of TPrA in detection solution and volume of the dispersion of Ir NDs modified on the GCE were optimized.Under the optimized experimental conditions,namely,0.75 mmol/L of TPrA and 10.0 ¦ÌL of Ir NDs,the response of the biosensor to dopamine(DA) was further explored.Based on the high quenching effect of DA on ECL emission of Ir NDs-TPrA system,a highly sensitive detection of DA was realized with a wide linear response range of 2.0¡Á10-8-4.0¡Á10-4 mol/L and a low detection limit of 6.3¡Á10-9 mol/L.The continuous scanning for 10 cycles was performed at the biosensor,with a relative standard deviation(RSD) for ECL signals of 1.7%,which indicated that the biosensor had a good stability.Four biosensors constructed from various batches were applied to the inter-assays,while four biosensors from the same batch were applied to the intra-assays,with corresponding RSDs of 1.4% and 2.8%,respectively,showing a satisfactory reproducibility.Glucose(Glu),uric acid(UA),ascorbic acid(AA),arginine(L-Arg),glycine(Gly),K+ and norepinephrine(NA) were selected as potential interfering substances to test the selectivity.It was found that the mentioned substances except NA made no interference to the determination of DA.Finally,the detection of real samples showed that the biosensor had a good practical application potential.The carboxyl-functionalized Ir NDs provided an ideal platform for application of iridium(¢ó) complexes in ECL field,and a novel method for DA detection.