Preparation of Magnetic Nickel Nanoparticles and Their Use in Efficient Purification of Histidine-Tagged Fusion Proteins

Nickel nanoparticles (denoted as Ni NPs), being applicable in catalysis, battery manufacturing, and bioseparation, have garnered considerable attention due to their remarkable magnetism, crystalline anisotropy, high coercivity, and excellent chemical stability. Unlike previous studies that require multi-step surface functionalization with chelating ligands, such as nitrilotriacetic acid (abridged as NTA), to achieve histidine-tagged (denoted as His-tagged) protein binding, this study reports a one-step hydrothermal synthesis of Ni NPs with a spherical-spiky architecture that provides abundant intrinsic Ni2+ active sites. A series of synthesis experiments were conducted to systematically optimize the hydrothermal reaction conditions (solution pH, temperature, and time). The ability of Ni NPs to separate and purify His-tagged fusion proteins was evaluated in relation to their abundant Ni2+ active binding sites and robust magnetic responsiveness. It was found that Ni NPs were able to rapidly, specifically, and efficiently purify a variety of His-tagged proteins, achieving a high saturation adsorption capacity of 80.36 mg/g, significantly higher than commercial Ni-NTA resins and previously reported Ni-based adsorbents, while retaining excellent recyclability (>80% after 5 cycles). These features underscore the potential of Ni NPs as cost-effective, reusable, and high-performance nano-adsorbents for protein separation, offering distinct advantages over conventional functionalization-dependent methods.