Histidine-based coordinative polymers for efficient intracellular protein delivery via enhanced protein binding, cellular uptake, and endosomal escape.

Polymers are one of the most promising protein delivery carriers; however, their applications are hindered by low delivery efficacy owing to their undesirable performance in protein binding, cellular uptake and endosomal escape. Here, we designed a series of histidine-based coordinative polymers for efficient intracellular protein delivery. Coordination of metal ions such as Ni 2+ , Zn 2+ , and Cu 2+ with histidine residues on a polymer greatly improved its performance in protein binding, complex stability, cellular uptake and endosomal escape, therefore achieving highly improved protein delivery efficacy. Among the coordinative polymers, the Zn 2+ -coordinated one exhibited the highest cellular uptake, while the Cu 2+ -coordinated one exhibited the highest endosomal escape. The Ni 2+ -coordinated polymer formed large-sized aggregates with cargo proteins and showed insufficient protein release after endocytosis. The results obtained in this study provided new insight into the development of coordinative polymer-based protein delivery systems.