Self-assembly of polyion complex nanocarriers from ammonium glycyrrhizinate and monomethoxy poly(ethylene glycol)-b-poly(γ-amino-ε-caprolactone)

A novel polyion complex (PIC) drug carrier was developed via electrostatic self-assembly in aqueous media based on our previous copolymer methoxy poly(ethylene glycol)-b-poly(γ-amino-ε-caprolactone) (mPEG-b-PACL) and anti-hepatotoxic drug ammonium glycyrrhizinate (AMG). The formation and the physicochemical properties of the polyion complex nanoparticles in aqueous solution were investigated by various methods. The results demonstrated that AMG was encapsulated successfully and the nanoparticles had a core–shell or tri-layer spherical structure based on the length of the PACL. The AMG/PACL PIC also displayed a high loading capacity and encapsulation efficiency of up to 41.8% and 91.7%, respectively. Furthermore, the nanoparticles enabled a continuous and sustained in vitro AMG release and the release half time was about 3 times that of the free AMG's. Results obtained by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay, flow cytometry and fluorescence microscopy revealed that AMG loaded nanoparticles demonstrated greater prevention of liver cell apoptosis induced by lipopolysaccharide (LPS). These findings indicated that methoxy poly(ethylene glycol) (mPEG)-b-poly(γ-amino-ε-caprolactone) could be an efficient AMG carrier and could even be used as a delivery template for some other negatively charged water-soluble drugs or gene delivery systems.