Fabrication and adsorption performance evaluation of flower-like Fe3O4@NiO core-shell nanospheres for efficient separation and purification of histidine-tagged proteins

Hierarchical Fe 3 O 4 @NiO core-shell nanospheres are synthesized. • High adsorption capacity of 65.83 mg/g for His-tagged proteins is obtained. • Fe 3 O 4 @NiO NSs exhibit rapid magnetic separation and good reusability (>80% after 5 cycles). • The adsorption follows pseudo-second-order kinetics and Langmuir isotherm model. Magnetic nanomaterials are highly efficient for the separation and purification of histidine-tagged (denoted as His-tagged) proteins. This article reports the facile synthesis of flower-like magnetic Fe 3 O 4 @NiO core-shell nanospheres (NSs) for that purpose. The synthesis involved the initial solvothermal preparation of Fe 3 O 4 NSs, followed by their controlled reaction with nickel chloride under alkaline condition to in-situ deposit a hierarchical NiO nanosphere shell. The unique hierarchical flower-like architecture could provide abundant accessible Ni 2+ coordination sites for protein binding. When isolating the target protein from cell lysate, Fe 3 O 4 @NiO NSs exhibited a high adsorption capacity of 65.83 mg/g toward His-tagged green fluorescent protein with an equilibrium time of 60 min, together with the merit of fast magnetic separation. Systematic adsorption studies revealed that the adsorption process of the target proteins by Fe 3 O 4 @NiO NSs followed pseudo-second-order kinetics and fitted the Langmuir isotherm model, referring to a chemisorption-dominated monolayer adsorption mechanism. Furthermore, the Fe 3 O 4 @NiO nano-adsorbent exhibited excellent stability and reusability, retaining over 80% of initial separation efficiency after five consecutive adsorption-desorption cycles. Therefore, the hierarchical Fe 3 O 4 @NiO NSs, as a kind of high-performance magnetically recoverable nano-adsorbent, could have significant potential for downstream bioseparation and protein purification applications.