Preparation and characterization of nanoparticles formed through stereocomplexation between enantiomeric poly(γ-glutamic acid)-graft-poly(lactide) copolymers

Abstract

Novel amphiphilic graft copolymers composed of poly(γ-glutamic acid) (γ-PGA) as a hydrophilic backbone and enantiomeric poly(lactide) (PLA) as hydrophobic side chains were successfully synthesized by using 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC) as the coupling agent. The number of poly(L-lactide) (PLLA) or poly(D-lactide) (PDLA) chains grafted onto the γ-PGA main chain was enhanced by increasing the feed ratio of PLA to γ-PGA in the reaction system. Nanoparticles (NPs) self-assembled from γ-PGA-graft-PLLA, γ-PGA-graft-PDLA and equal molar mixtures of enantiomeric γ-PGA-graft-PLLA and γ-PGA-graft-PDLA copolymers were formed in aqueous solution. The mean diameters of the NPs formed by equal molar mixtures of enantiomeric γ-PGA-graft-PLLA and γ-PGA-graft-PDLA copolymers (stereocomplex NPs) were in the range from 150 to 250 nm, and these NPs with reactive functional groups would have great potential to be used as stable delivery vehicles for pharmaceutical and biomedical applications. Novel amphiphilic graft copolymers composed of poly(γ-glutamic acid) (γ-PGA) as a hydrophilic backbone and enantiomeric PLA as hydrophobic side chains were successfully synthesized by using carbodiimide as the coupling agent. The enantiomeric γ-PGA-graft-PLLA (γ-PGA-g-PLLA) and γ-PGA-graft-PDLA (γ-PGA-g-PDLA) copolymers could form NPs, and stereocomplex crystallites were formed in the case of the mixture of γ-PGA-g-PLLA and γ-PGA-g-PDLA copolymers. These NPs with reactive functional groups would have great potential to be used as stable delivery vehicles for pharmaceutical and biomedical applications.