Morphology controls of self-assembled nanoparticles by the secondary structures of poly(amino acid)s

Abstract

A series of amphiphilic graft copolymers, poly (2-hydroxyethyl astartamide) grafted with poly (L-lysine) with different degree of polymerization of poly (L-lysine) and various degree of substitution were synthesized. This PHEA-g-poly (L-lysine) was successfully synthesized using living polymerization of α-amino acid-N-carboxyanhydrides form of L-lysine. And self-assembled nanoparticles of PHEA-g-poly (L-lysine) in an aqueous solution were performed. The morphology changes of self-assembled nanoparticles were induced by the pH or temperature-responsive conformational transition of grafted chain, poly (L-lysine) group. The conformational transition of secondary structure of poly (L-lysine) group was confirmed by CD (circular dichroism). The morphology of self-assembled nanoparticles was studied by TEM (transmission electron microscopy) and DLS (dynamic light scattering) measurement. In this study, the further researches for investigating secondary structures of amino acids were designed. Firstly, the surface plasmon resonance (SPR) biosensor has been widely used to figure out binding event occurring on biological surfaces by the detection of a refractive index change on a gold surface without the need to label molecules. Through the SPR study, we verified physicochemical properties of conformational transition of poly (amino acid). Secondly, rheology behavior was also observed by an ARES fluid rheometer. There are certain differences depending on secondary structure of α-helix conformation or β-sheet conformation. Consequently, self-aggregates amphiphilic copolymer are affected by not only DS and DP but also secondary structure of side chain.