Branched Amphiphilic Polylactides as a Polymer Matrix Component for Biodegradable Implants

The combination of biocompatibility, biodegradability, and high mechanical strength has provided a steady growth in interest in the synthesis and application of lactic acid-based polyesters for the creation of implants. On the other hand, the hydrophobicity of polylactide limits the possibilities of its use in biomedical fields. The ring-opening polymerization of L-lactide, catalyzed by tin (II) 2-ethylhexanoate in the presence of 2,2-bis(hydroxymethyl)propionic acid, and an ester of polyethylene glycol monomethyl ester and 2,2-bis(hydroxymethyl)propionic acid accompanied by the introduction of a pool of hydrophilic groups, that reduce the contact angle, were considered. The structures of the synthesized amphiphilic branched pegylated copolylactides were characterized by H-1 NMR spectroscopy and gel permeation chromatography. The resulting amphiphilic copolylactides, with a narrow MWD (1.14-1.22) and molecular weight of 5000-13,000, were used to prepare interpolymer mixtures with PLLA. Already, with the introduction of 10 wt% branched pegylated copolylactides, PLLA-based films had reduced brittleness, hydrophilicity, with a water contact angle of 71.9-88.5 degrees, and increased water absorption. An additional decrease in the water contact angle, of 66.1 degrees, was achieved by filling the mixed polylactide films with 20 wt% hydroxyapatite, which also led to a moderate decrease in strength and ultimate tensile elongation. At the same time, the PLLA modification did not have a significant effect on the melting point and the glass transition temperature; however, the filling with hydroxyapatite increased the thermal stability.

Automated summary

The synthesis and application of lactic acid-based polyesters for the creation of implants have gained increased interest due to their biocompatibility, biodegradability, and high mechanical strength. However, the hydrophobicity of polylactide limits its use in biomedical fields. This study focused on the synthesis of amphiphilic branched pegylated copolylactides to introduce hydrophilic groups and improve the properties of polylactide. The resulting copolylactides were used to prepare interpolymer mixtures with PLLA, leading to reduced brittleness, increased hydrophilicity, and water absorption. Furthermore, filling the polylactide films with hydroxyapatite further decreased the water contact angle and increased thermal stability.