3D Co-doped Ni-based conductive MOFs modified electrochemical sensor for highly sensitive detection of l-tryptophan.

L-tryptophan (Trp) is an essential amino acid for humans and plays crucial roles in many metabolic functions. Trp levels can be used for diagnosing different kinds of metabolic disorders and the symptoms associated with those diseases. Herein, a novel, simple and sensitive sensor based on 3D peony-like bimetallic conductive MOFs (Co-Ni-MOFs) was fabricated for the electrochemical determination of Trp. The bimetallic conductive MOFs were synthesized by a facile one-pot hydrothermal process. On account of the synergy between the Ni and Co ions, the bimetallic Co-Ni-MOFs showed excellent electrochemical performance, including good conductivity, large effective surface areas, and high electrocatalytic reactivity toward the oxidation of Trp. Consequently, the Co-Ni-MOFs-modified electrodes obtained a wide linear range from 10 nmol L to 300 μmol L and a low detection limit of 8.7 nmol L (S/N = 3) for Trp. Additionally, the prepared sensor also displayed high selectivity, long-term stability and reproducibility. Moreover, the proposed sensor was successfully applied to determine the levels of Trp in the plasma of mice after cadmium intoxication.