Effects of chemical composition on the in vitro degradation of micelles prepared from poly(D,L-lactide-co-glycolide)-poly(ethylene glycol) block copolymers

Publication date: Available online 9 November 2018Source: Polymer Degradation and StabilityAuthor(s): Feng Su, Chenglong Li, Rongye Li, Peng Yun, Yuandou Wang, Laishun Xi, Yangsheng Chen, Suming LiAbstractIn this work, a series of poly(D,L-lactide-co-glycolide)-poly(ethylene glycol) (PLGA-PEG) diblock copolymers with relatively short PLGA blocks were synthesized by ring-opening polymerization of D,L-lactide and glycolide in the presence of monomethoxy PEG with Mn of 2000. Spherical micelles were obtained by self-assembly of copolymers using direct dissolution method. The degradation of the micelles was investigated under in vitro conditions at 37 °C. The effects of chemical composition on micelle degradation were evaluated from NMR, GPC, DLS and TEM measurements. The molar mass of copolymers constantly decreases during degradation in all cases. The copolymers with longer hydrophobic PLGA blocks exhibit larger molar mass decrease rate since only the PLGA block is degradable. Meanwhile, the molar mass distribution remains almost unchanged, in agreement with random chain cleavage. NMR spectra show that the final degradation products are lactic acid and glycolic acid. A pH decrease is also detected during degradation. The size of the micelle depends on the chemical composition of copolymers. Micelle size is smaller for copolymers with longer hydrophobic PLGA blocks because of more compact core structure. With the hydrolysis of the PLGA blocks, the structure of micelles becomes...

Source: Polymer Degradation and Stability - November 10, 2018 Category: Chemistry Source Type: research