Immobilization of His-tagged proteins on NiO foams for recyclable enzymatic reactors

Highlights: • NiO foams with high surface area were synthesised. • His-tag proteins bind to the NiO foam and remain bound upon wash. • Protein binding to the foam results in microporous cavities alterations. • DFT suggests His-tags prefer stretched conformations and act as bidentate ligands. • Immobilized His-tag enzyme remains active and the support is recyclable. We report for the first time the use of NiO foams for specific protein binding. These affordable porous materials, with high surface area, possess the features required as supports for enzymatic catalysis. A physicochemical and computational characterization of the interaction between this support and a model His-tagged sulfotransferase was performed as a first approach to the use of NiO foams for specific protein binding. Results confirm that the His-tag binds the NiO foam and remains bound when the support is washed. The foam microporous cavities undergo marked rearrangement upon protein binding and removal, in agreement with the successful immobilization and posterior removal of the protein on the foam. Computational results suggest that the His-tag prefers a stretched conformation, acting as a bidentate ligand. Enzymatic activity of the immobilized protein was confirmed, as well as the ability to recycle the support. These results demonstrate that NiO foams constitute an affordable and effective material for His-tag protein immobilization, with potential applications, namely protein isolation and enzymatic reactor applications. The ultimate aim of this work is to contribute to a better understanding of the kinetic activity at surface level, as well as the comparison between the experimental results and the computational output.