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@SiO 2 @Ni/C nanocomposites were prepared by the polyhedral ZIF-67@SiO 2 composite as a precursor through the extended stöber method and subsequent carbonization treatment. The SiO 2 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@SiO 2 @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@SiO 2 @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 μM). The INC exhibited improved pH stability, thermal stability, SDS resistance, and storage stability compared to that of free enzymes. When OpdA@Co/C@SiO 2 @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.