Thermogels based on biocompatible OEGMA-MEGMA diblock copolymers

Abstract

A series of biocompatible thermoresponsive copolymers were successfully synthesised via group transfer polymerisation (GTP) from methoxy ethylene glycol methacrylate (MEGMA) and methoxy oligo (ethylene glycol) methacrylate (OEGMA, Mn = 300 g mol -1). Statistical and diblock copolymers with molar mass around 8100 g mol−1 and various compositions were investigated. Specifically, the content in OEGMA and MEGMA was varied from 80 to 20, 70–30, 60–40, to 50–50 w/w%. The thermoresponsive and self-assembly behaviour of the copolymers was investigated throughvisual tests, rheology, dynamic light scattering (DLS) and transmission electron microscopy (TEM). Interestingly, the diblock copolymers with higher MEGMA content were able to form gels at relatively low concentrations (as low as 5% w/w) when increasing the temperature, something that is reported for the first time for linear ethylene glycol based copolymers. A transition of spherical micelle to worm-like micelle was observed in these diblock copolymers that promotes gelation. Furthermore, these in-house synthesised polymers were mixed with Pluronic® F127. It was found that the gelation area of Pluronic® F127 was broadened by the addition of the synthesised copolymers with one formulation, specifically a combination of 12.5% w/w Pluronic® F127 and 12.5% w/w of a statistical OEGMA-co-MEGMA, forming a stable gel from 34 °C to 48 °C that is a desirable temperature range for biological applications. Finally, cell viability experiments were performed for the three most promising diblock copolymers and they were confirmed to be non-toxic.