A biosensor based on gold nanoparticles stabilized in poly(allylamine hydrochloride) and decorated with laccase for determination of dopamine

Gold nanoparticles stabilized in poly(allylamine hydrochloride) (AuNP-PAH) were used as a support for the immobilization of the enzyme laccase obtained from genetically-modified microorganisms (Aspergillus oryzae) and successfully applied in the development of a new biosensor for the determination of dopamine by square-wave voltammetry. The electrochemical characterization of the biosensor was performed by cyclic voltammetry and electrochemical impedance spectroscopy and indicated that the nanomaterial used for the electrode modification facilitated the electron transfer. Under optimized conditions, the calibration curve showed a linear range for dopamine from 0.49 to 23.0 mu mol L-1, with a limit of detection of 0.26 mu mol L-1. The biosensor demonstrated suitable selectivity and stability, good intra-day and inter-day repeatability and electrode-to-electrode repeatability, with relative standard deviations of 4.95, 4.85 and 4.21%, respectively. The proposed biosensor was successfully applied to the determination of dopamine in pharmaceutical samples and the results were in agreement with those obtained using a spectrophotometric method. The recoveries of 97.6 to 105.5% obtained for the samples demonstrate that the proposed method is suitable for practical applications. The good analytical performance of the proposed method can be attributed to the efficient immobilization of laccase in the nanomaterial and the facilitation of electron transfer between the protein and the electrode surface due to the presence of the Au nanoparticles and the PAH polymer.