In this paper, a new and facile method for the electrochemical determination of L-tyrosine was designed. First, 3-mercaptopropyl trimethoxysilane-functionalized silica nanoparticles were added to a paper disc. Then, the banana peel tissue and the mediator potassium hexacyanoferrate were dropped onto the paper, respectively. The modified paper disc was placed on the top of the graphite screen printed electrode and electrochemical characterization of this biosensor was studied by cyclic voltammetry and electrochemical impedance spectroscopy methods. The effective parameters like pH, banana peel tissue percentage, and the amount of mediator loading were optimized. L-tyrosine measurements were done by differential pulse voltammetry with a little sample (3µL) for analysis. The biosensor showed a linear response for L-tyrosine in the wide concentration range of 0.05-600 µM and a low detection limit about 0.02 µM because of the co-catalytic effect of enzyme and nanoparticles. The stability of the biosensor and its selectivity were evaluated. This biosensor was applied for the voltammetric determination of L-tyrosine in the blood plasma sample. The results of the practical application study were comparable with the standard method (HPLC). In conclusion, a simple, inexpensive, rapid, sensitive and selective technique was successfully applied to the L-tyrosine analysis of the little samples.
