Ammonia-etched hollow Prussian blue@Au nanoframes performing ultrasensitive pyruvate monitoring in fermentation

Pyruvate is one of the most important intermediate metabolites in the fermentation process, thereby making it a potential indicator for monitoring and regulating the fermentation process. Since the fermentation broth is usually complex, including microorganisms, various ions, organic compounds, etc., it is necessary to develop a highly selective method for detecting pyruvate. Therefore, in this work, we proposed an ultrasensitive electrochemical enzymatic biosensor for pyruvate determination at a low working potential through constructing Prussian blue@Au nanoframes (PB@Au NFs) with improved conductivity and high electrocatalytic ability. Due to the strong catalytic ability of PB nanoframes for the reduction of H 2 O 2 , the as-prepared sensor initially demonstrated extremely 2.7-fold sensitivity toward H 2 O 2 than the non-frame structured PB nanocubes. Furthermore, after the conditions for pyruvate detection were systematically optimized, the fabricated sensor was able to effectively identify pyruvate ranging from 5   μM to 0.895   mM at -0.2   V which represented an orders-of-magnitude improvement in sensitivity over existing sensors. Meanwhile, the low working potential and the highly precise recognition ability of pyruvate oxidase ensured the high selectivity of the prepared sensor, and the sensor also showed excellent reproducibility and long-term stability. Finally, our biosensor was employed to detect pyruvate in the real microbial fermentation liquid, giving an excellent accuracy with RSD values of 1.44% - 4.64%. This work provides a new strategy approach for the design and establishment of stable pyruvate sensors and offered a usefulness approach for the pyruvate detection with high performance.