Amphiphilic polymers have vivid odds in the nano-drug system for its special self-assembly character. Here the self-assembly properties of polyethylene glycol (PEG)-graft-poly(lactic acid) (PLA) (PEG-g-PLA, PPLA) were investigated to explore its potential application to drug delivery. The dissolubility of PPLA in water was (2.16～4.32)×10^－2 mg•mL^－1 according to eye judgment. The critical micelle concentration was 2.16×10^－2 mg•mL^－1 obtained from a fluorospectrophotometer. The self-assembled aggregates of PPLA in water were nanoscale spheres observed by a transmission electron microscope. The particle size and zeta potential tests by dynamic light scattering revealed that during preparation, the ratio of hydrophilicity/hydrophobicity, the aqueous medium and the pH had great influences; while dilution, freezing and pH change to basic condition had no effect after preparation, but pH change to acidic condition made the nanoparticles precipitate. The results demonstrated that the particle size and zeta potential could be easily controlled so as to control their stay in some special tissues and realize a target.

Key words: poly(lactic acid), polyethylene glycol, graft, self-assembly, nanoparticle