In situ formation of polymer–protein hybrid spherical aggregates from (nitrilotriacetic acid)-end-functionalized polystyrenes and His-tagged proteins

Polymer–protein hybrid nanostructures are important for their potential applications in pharmaceuticals and biotechnology, and new methods to generate hybrid nanostructures would be advantageous in the above fields. In this study, we present a simple method for the construction and control of polymer–protein hybrid spherical aggregates in situ from nickel complexed (nitrilotriacetic acid)-end-functionalized polystyrene (Ni-NTA-PS) and histidine-tagged green fluorescent protein (His-tagged GFP) through NTA-Ni–His interaction in water–DMF (DMF 4 vol.%) at physiological pH. The generality of the approach was demonstrated using His-tagged GFP and His-tagged lipases. Transmission electron microscopy (TEM) and dynamic light scattering (DLS) measurements revealed that hybrid aggregates of His-tagged GFP were stable up to 15 days. The size of hybrid aggregates depended on the molecular weight of polymers, concentration of polymers, concentration of protein, and also the rate of addition of polymer to the solvent containing protein. After formation of hybrid aggregates, removal of DMF by dialysis from the system resulted in the aggregation and phase separation of aggregates over time. The size of polymer–protein hybrid aggregates decreased with excess of imidazole addition. A possible mechanism for the formation of such polymer–protein hybrid aggregates is also described.