Analysis of L-tyrosine based on electrocatalytic oxidative reactions via screen-printed electrodes modified with multi-walled carbon nanotubes and nanosized titanium oxide (TiO 2 ).

Method for electrochemical determination of L-tyrosine with screen-printed electrodes (SPE) modified with multi-walled CNT or CNT/TiO2 as sensing elements was used for the electroanalysis of L-tyrosine (Tyr). It was demonstrated that SPE/CNT and SPE/CNT/TiO2 exhibited high electrocatalytic activity and good analytical performance towards oxidation of L-tyrosine. The linear range of Tyr in human serum was 0.025 ÷ 1 mM with the correlation coefficient R2  = 0.97. Direct electrochemistry (without any mediator) of co-factor-free bovine serum albumin (BSA) and human serum albumin (HSA) was investigated by use of modified electrodes. Protein-ligand interactions based on the electrocatalytic oxidation of L-tyrosine during HSA interaction with hemin were analyzed by the change of peak height and oxidation peak area, corresponding to tyrosine oxidation accessibility.