Purification And Immobilization Of His-Tagged Organophosphohydrolase On Yolk-Shell Co/C@Sio2@Ni/C Nanoparticles For Cascade Degradation And Detection Of Organophosphates

The synthesis or decomposition of complex substances through the combination of metals and enzymes is desirable but still a huge challenge. A kind of yolk-shell structured Co/C@SiO2@Ni/C nanocomposites were prepared by the polyhedral ZIF-67@SiO2 composite as a precursor through the extended stober method and subsequent carbonization treatment. The SiO2 as an intermediate protective layer stabilized the morphology and structure of the carbonized products. The metallic nickel nanoparticles were uniformly distributed on the surface of Co/C@SiO2 @Ni/C for highly specific absorption of His-tagged organophosphohydrolase (OpdA) from cell lysates via affinity, and therefore an integrated nanocatalyst (INC) named OpdA@Co/C@SiO2@Ni/C was successfully prepared. The prepared INC was applied to achieve a one-pot chemoenzymatic cascade degradation of organophosphates (OPs) to p-aminophenol (PAP) within 30 min. In addition, the INC proved to be a simple and high-sensitivity nanocatalyst for the detection of methyl-parathion with a low limit of detection (0.30 mu M). The INC exhibited improved pH stability, thermal stability, SDS resistance, and storage stability compared to that of free enzymes. When OpdA@Co/C@SiO2@Ni/C was reused for 7 cycles, the cascade degradation efficiency of methyl-parathion could retain more than 60 %. This study provides a strategy for constructing a multifunctional nanocatalyst, and further demonstrated its potential in biocatalysis, accurate detection of OPs and remediation of environmental pollution.