Peptide nanotube/hemin composite with enhanced peroxidase activity for the detection of dopamine in food and drug samples.

Inspired by natural enzymes, artificial enzymes have been widely studied due to their ease of mass production, robustness to harsh environments and high stability. In this work, a peptide nanotube/hemin composite (KL@hemin) as an artificial enzyme was prepared by immobilizing hemin onto self-assembled peptide nanotubes (PNTs). The successful loading of hemin was determined by a series of characterizations. The multiple noncovalent interactions between the PNTs and hemin endow KL@hemin with strong stability. Subsequent enzyme activity tests showed that the prepared KL@hemin exhibited enhanced peroxidase activity. Further experiments indicate that PNTs as carriers can not only protect hemin from dimerization to maintainenzyme activity but also increase the affinity of hemin to the substrate for faster binding and accelerate mass transfer, thus promoting the whole catalytic process. Coupled with a peroxidase-catalyzed chromogenic system, a colorimetric method for dopamine detection was constructed based on KL@hemin. The strategy shows high sensitivity and selectivity and has been applied to the determination of dopamine in dopamine injection and meat samples.