A novel electrochemical sensor based on Au-SH-SiO2 nanoparticles supported on metal-organic framework (Au-SH-SiO2@Cu-MOF) has been developed for electrocatalytic oxidation and determination of L-cysteine. The Au-SH-SiO2@Cu-MOF was characterized by scanning electron microscopy, transmission electron microscopy, x-ray diffraction and cyclic voltammetry. The electrochemical behavior of L-cysteine at the Au-SH-SiO2@Cu-MOF was investigated by cyclic voltammetry. The Au-SH-SiO2@Cu-MOF showed a very efficient electrocatalytic activity for the oxidation of L-cysteine in 0.1 M phosphate buffer solution (pH 5.0). The oxidation overpotentials of L-cysteine decreased significantly and their oxidation peak currents increased dramatically at Au-SH-SiO2@Cu-MOF. The potential utility of the sensor was demonstrated by applying it to the analytical determination of L-cysteine concentration. The results showed that the electrocatalytic current increased linearly with the L-cysteine concentration in the range of 0.02–300 μM and the detection limit was 0.008 μM. Finally, the sensor was applied to determine L-cysteine in water and biological samples.
