Synthesis and self-assembly behavior of novel polyaspartamide derivatives for anti-tumor drug delivery

A series of amphiphilic graft copolymers based on polyaspartamide were synthesized by a successive aminolysis reaction of polysuccinimide using 2-diisopropylaminoethyl (DIP) and laurylamine as a pH sensitive and hydrophobic group, respectively. The pH-dependent self-assembly behavior of the aqueous copolymer solution was investigated. Nano-aggregation occurred at a pH in the vicinity of the pKa of the DIP group, which was induced by a hydrophilic–hydrophobic shift of the DIP group in solution. The mean diameter of the nano-aggregate could be modulated by changing the composition of both pendants. The mean diameter of the nanoparticles increased with increasing solution pH from 6.5 to 8. At pH 8, the mean diameter of the nanoparticles increased rapidly at the temperature above 45 °C, probably due to the change in hydrophilic–hydrophobic balance of the pH-sensitive DIP moiety. The dissolution of paclitaxel (PTX) into this amphiphilic nanoparticle was attempted and the pH-dependent release behavior was examined with the stability study of the particle. The results showed significantly faster release of PTX at pH 6.5, which is a tumoral acidic pH, than in a neutral physiological pH. These thermo- and pH-sensitive polyaspartamide derivatives have potential use as a tumor-targeting delivery.