Myoglobin immobilized on LaF3 doped CeO2 and ionic liquid composite film for nitrite biosensor

This study described a simple and reliable method for the electrochemical determination of nitrite based on the immobilization of myoglobin (Mb) on LaF3 doped CeO2 (LaF3-DP-CeO2) and ionic liquid (IL) composite film. Meantime, ultraviolet visible spectra (UV–vis), Fourier transform infrared spectra (FT-IR) and circular dichroism spectra (CD) were utilized to characterize the composite film. The results demonstrated that Mb in the composite membrane retained its secondary structure similar to the native state. Furthermore, the LaF3-DP-CeO2 provided a biocompatible microenvironment for protein immobilization and a suitable electron transfer distance between Mb and electrode surface. Amperometric responses showed that the biosensor exhibited a fast response time (within 5 s), good stability and a broad linear range of nitrite (NO2−) concentration from 5 μM to 4650 μM with a detection limit of 2 μM (S/N = 3). The low value of Michaelis–Menten constant KM (2.19 mM) indicated a high affinity of Mb to NO2−. The attractive features of LaF3-DP-CeO2 could provide potential applications in sensor and biosensor design.