Design of polyanionic nanocarriers based on modified poly (aspartic acid)s for oral administration: synthesis and characterization

Abstract

This study designed a series of polyanionic nanocarriers based on biodegradable and biocompatible poly (aspartic acid)s for oral administration. First, polysuccinimide (PSI) was synthesized from L-aspartic acid using acid-catalyzed bulk thermal polycondensation and acid-catalyzed thermal polycondensation in a mixture of mesitylene/sulfolane. PSI-C16 was then synthesized by aminolysis with nucleophile, hexadecylamine to react with PSI known as nucleophilic addition. Finally, a series of partially esterified poly (aspartic acid)s was produced by alkaline treatment to afford an amphiphilic polyanion, poly (sodium aspartate-g-hexadecyl aspartate) (Na-PASP-g-C16-PASP). 1HNMR, FTIR, DSC and GPC were utilized to demonstrate and characterize the polymers. The synthesized polyanion could be self-assembled into the nano-scaled micelles and be independent of pH in phosphoric buffer solutions. The hydrodynamic diameter and zeta potential were measured using the dynamic light scattering (DLS) method, and the critical micelle concentration (CMC) was determined using the fluorescence spectrophotometer. The micellar morphologies were examined using transmission electron microscopy (TEM), and atomic force microscopy (AFM) to present the nano-dimensional sphere. The stability of size transition at different pH levels, from strong acid to alkaline, proved that the micelles could stably transport from the stomach to intestinal lumen prior to arriving in the epithelium of the small intestine.