Enzymatic biosensor based on tyrosinase and gold nanostructures for Bisphenol A determination

Gold nanostructures are versatile for a broad range of applications in various areas including catalysis, biomedicine, diagnostic and detection1. Their attractive characteristics such as high surface area, biocompatibility, high stability and potential of multifunctionality, make them suitable for the development of (bio)sensors2. In this work, we present the development and application of a tyrosinase-based biosensor for the detection of bisphenol A (BPA). Before enzyme immobilization, gold nanostructures were electrodeposited on a screen-printed carbon electrode (SPE) to improve the analytical performance of the biosensor. Leaf-shaped gold nanostructures resulted from the electrochemical reduction of tetrachloroauric acid (HAuCl4) in a 0.1 mol L-1 Na2SO4 aqueous solution through an applied potential of -0.6V for 600 s. The experiment was performed using a potentiostat/galvanostat Autolab PGSTAT128 (Ecochemie, Holland) interfaced to a computer and controlled by NOVA 2.1 software. The SEM image of the modified surface is depicted in Fig. 1a. For the enzyme immobilization, a solution containing 500 U of tyrosinase solution was dropped and left to dry. Nafion solution was also applied to prevent leaching of the enzyme into the solution. Cyclic voltammograms (CVs) were registered at different concentrations of BPA in 0.1 mol L-1 phosphate buffer solution (pH=7.3) to evaluate the performance of the biosensor. The voltammograms exhibit a welldefined irreversible peak corresponding to BPA oxidation, see in Fig. 1b. For comparison, CVs were obtained using a modified SPE without the enzyme (shown in the inset of Fig. 1b`), a higher sensitivity it is observed in the presence of tyrosinase. The optimum conditions for the biosensor, pH, pre-concentration time and scan rate were studied, from which it was possible to construct a calibration curve of BPA Fig 1c., and LOD=0,93μmol/L.