Calcium Ion-Induced Self-Assembly of Carboxylated Polyallylamine-graft-Poly(Ethylene Glycol) in an Aqueous Medium

Double hydrophilic copolymers (DHCs) can form nano-assemblies such as micelles and vesicles in aqueous media under certain environmental conditions. These assemblies have attracted much attention in both fundamental and applied research. To date, most studies on DHC self-assemblies have focused on block copolymers rather than graft copolymers. In this study, we investigated using Ca²⁺ ions in an aqueous medium to induce the formation of carboxylated polyallylamine-graft-poly(ethylene glycol) (PAA-g-PEG) self-assemblies as a graft-type DHC. Dynamic light scattering measurements conducted under various conditions showed that the carboxylated PAA-g-PEG self-assemblies had a micellar structure with a core of Ca²⁺ ions/carboxylates surrounded by non-ionic poly(ethylene glycol) grafts. Confocal laser scanning microscopy showed that the carboxylated PAA-g-PEG self-assemblies were able to deliver Ca²⁺ ions into cells. These results show that carboxylated PAA-g-PEG self-assemblies formed in the presence of divalent metal ions have potential for future applications in the biomedical field.