Reversible His-Tagged Enzyme Immobilization on Functionalized Carbon Nanotubes as Nanoscale Biocatalyst

Common enzyme immobilization methods on nanomaterials (adsorption, covalent binding, crosslinking, encapsulation) often generate problems in enzyme leaching, 3D structure change and diffusion resistance. We show here a detailed site-specific enzyme immobilization method that overcomes the foresaid limitations. It is based on the specific interaction between His-tagged enzyme and single-walled carbon nanotubes modified with N _α ,N _α -bis(carboxymethyl)-l -lysine hydrate. This method does not require enzyme purification and the resulting nanoscale biocatalyst can maintain high enzyme activity and stability. The enzyme-loading capacity is also comparable with the reported immobilization capacity on carbon nanotubes by either covalent binding or adsorption. Furthermore, the immobilization is reversible for several cycles while maintaining high enzyme activity and the nanoscale biocatalyst can be regenerated easily.