Soft Immobilization Of Proteins Onto Single-Walled Carbon Nanotubes Through Nickel Complexed Nitrilotriacetic Acid-End Functionalized Polystyrenes

We describe the immobilization of histidine-tagged green fluorescent protein (His6-GFP) specifically and reversibly onto single-walled carbon nanotubes (SWCNTs) using nickel complexed nitrilotriacetic acid-end functionalized polystyrene (Ni-NTA-PS) by conjugation between the protein and the polymer in phosphate buffer solution (PBS). We synthesized Ni-NTA-PS by atom transfer radical polymerization (ATRP) using a nitrilotriacetic acid (NTA) initiator. The SWCNTs were dispersed in PBS along with Ni-NTA-PS and His6-GFP aided by sonication. The diameter of the dispersed SWCNTs was measured by transmission electron microscope (TEM). The immobilization of His6-GFP and dispersion of SWCNTs were controlled by addition of excess imidazole. It was found that the immobilized His6-GFP was more stable than free His6-GFP in organic solvent (PBS/DMF, 1/1, v/v).