Preparation and Properties of Polymer Micelles based on Polygalacturonic Acid

Cystamine (CYS) and deoxycholic acid (DOCA)were used as raw materials to synthesize cystamine modified deoxycholic acid (CD), and then the amino group (―NH₂) of CD and the carboxyl group (―COOH) of polygalacturonic acid (PGA) were synthesized into PGA-g-CD polymer through amidation reaction. And the polymer was self-assembled into micelles in the aqueous solution through dialysis. Doxorubicin (DOX) was used as a model drug, it was encapsulated in the hydrophobic core of the micelles. By regulating the feed ratio of n(―NH₂)∶n(―COOH), the drug-loading performance of the micelles is controlled. The polymers were characterized by ¹H nuclear magnetic resonance spectroscopy and fourier transform infrared spectroscopy, and the substitution degree (D_S) of CD in the polymer was measured in sequence. The structure, drug loading and drug release properties of the polymer micelles were tested using transmission electron microscope, dynamic light scattering and Zeta potential analyzer, etc. The optimal feed ratio is n(―NH₂)∶n(―COOH) = 1.3∶1. Under this condition, the D_S in the polymer is 31%, and the critical micelle concentration is 0.025 mg/mL. The drug loading capacity and encapsulation efficiency of the micelles reach 11.53% and 60.68%, respectively. The particle sizes of the polymer micelles and the drug-loaded micelles are (208.5±4.1) nm and (296.1±0.3) nm, respectively. And the polydispersity index values are 0.215±0.008 and 0.101±0.053, respectively. Under the reductive condition, the cumulative drug release amount within 36 h reached 78.8%, compared to 22.9% in the non-reductive environment, showing good reductive responsiveness.