Construction of magnetic Fe3O4@NH2-MIL-100(Fe)-C18 with excellent hydrophobicity for effective protein separation and purification

Due to the appearance of amino and carboxyl groups on the surface of NH2-MIL-100(Fe), a stable Metal-Organic Frameworks (MOFs), it is ready to be modified with other functional ligands to provide versatile applications. In this study, we have successfully employed aliphatic C18 carbon chain to functionalize the magnetite-doped Fe3O4@NH2-MIL-100(Fe). The remarkable hydrophobic surface of Fe3O4@NH2-MIL-100(Fe)-C18 with a water contact angle of 98.93° allowed it to selectively form hydrophobic interaction with a protein in a high concentration of sodium chloride environment. The complex was easily harvested with a magnet, and the bound protein was able to be eluted by reducing sodium chloride concentration. The maximum protein binding capacity reached approximately 28.74 μg of BSA/mg with Fe3O4@NH2-MIL-100(Fe)-C18. Our results have demonstrated that the Dulbecco's phosphate buffer could provide a better “salt-out” effect and afford a higher resolution to separate proteins in a mixture. In addition, we have successfully employed the magnetic Fe3O4@NH2-MIL-100(Fe)-C18 in the purification of recombinant green fluoresce protein by replacing the stage of using a commercial hydrophobic interaction resin, and achieved almost the same purification efficiency. Fe3O4@NH2-MIL-100(Fe)-C18 also provides us with the higher protein binding capacity than other commercial products, reliable performance for fifteen repeat uses, and more convenient and affordable method for protein purification in laboratory.