Facile Oriented Immobilization and Purification of His-Tagged Organophosphohydrolase on Viruslike Mesoporous Silica Nanoparticles for Organophosphate Bioremediation

In this study, nickel-nitrilotriacetic acid-modified viruslike mesoporous silica nanoparticles (Ni-NTA-VMSN) were fabricated by a facile method for the first time. The Ni2+ ions on the surface of Ni-NTA-VMSN provided abundant anchoring sites for directly selective oriented immobilization of His-tagged proteins from crude enzymes. By incubation of the Ni-NTA-VMSN in the His-tagged organophosphohydrolase (OpdA)-contained cell lysates, a nanobiocatalyst, OpdA@Ni-NTA-VMSN, could be constructed. At the optimal immobilization conditions, the specific activity of OpdA@Ni-NTA-VMSN was 353.0 U/gprotein, which was slightly higher than that of free OpdA in cell lysates. The substrate's affinity capacity of OpdA became higher after oriented immobilization, and the OpdA@Ni-NTA-VMSN exhibited excellent catalytic activity and stability. In addition, when OpdA@Ni-NTA-VMSN was applied in a plug-flow reactor, the degradation percent of methyl parathion could be maintained at more than 90% with the injection of 20 mL of reaction mixture. Thus, the Ni-NTA-VMSN will be a promising material for purifying and immobilizing His-tagged enzymes. The proposed OpdA@Ni-NTA-VMSN will be an excellent nanobiocatalyst for biodegradation of organophosphorus pesticides.