Improving the binding capacity of Ni2+ decorated porous magnetic silica spheres for histidine-rich protein separation

Biomagnetic immobilization of histidine-rich proteins based on the single-step affinity adsorption of transition metal ions continues to be a suitable practice as a cost effective and a up scaled alternative to the to multiple-step chromatographic separations. In our previous work [12], we synthesised Porous Magnetic silica (PMS) spheres by one-step hydrothermal-assisted modified-stöber method. The obtained spheres were decorated with Ni2+ and Co2+, and evaluated for the capture of a H6-Tagged green fluorescence protein (GFP-H6) protein. The binding capacity of the obtained spheres was found to be slightly higher in the case Ni2+ decorated PMS spheres (PMSNi). However, comparing with commercial products, the binding capacity was found to be lower than the expected. In this way, the present work is an attempt to improve the binding capacity of PMSNi to histidine-rich proteins. We find that increasing the amount of Ni2+ onto the surface of the PMS spheres leads to an increment of the binding capacity to GFP-H6 by a factor of two. On the other hand, we explore how the size of histidine-rich protein can affect the binding capacity comparing the results of the GFP-6H to those of the His-tagged α-galactosidase (α-GLA). Finally, we demonstrate that the optimization of the magnetophoresis parameters during washing and eluting steps can lead to an additional improvement of the binding capacity.

Porous magnetic silica spheres with a narrow size distribution were synthesized by hydrothermal-assisted modified-Stober method. Then the obtained spheres were homogeneously decorated with Ni ions and evaluated for histidine-rich protein capturation under a uniform radial gradient magnetic field.Figure optionsDownload as PowerPoint slideHighlights
► Decoration of the porous magnetic silica spheres by Ni2+.
► Enhancement of the binding capacity to histidine-rich protein.
► Binding capacity depends strongly on the amount of the adsorbed Ni2+.
► Optimization of magnetophoresis processes improves the binding capacity.
► Binding capacity is not significantly affected by the proteins size.