PEG-based thermogels: Applicability in physiological media

Abstract

Novel biocompatible thermogels have been synthesized and characterized. The hydrogelators were synthesized by atom transfer radical copolymerization of 2-(2-methoxyethoxy)ethyl methacrylate (MEO 2MA) and oligo(ethylene glycol) methyl ether methacrylate (OEGMA 475, M n = 475 g mol − 1 or OEGMA 300, M n = 300 g mol − 1 ) in the presence of a 4-arm star poly(ethylene glycol) (PEG) macroinitiator. The formed macromolecules possess a permanently hydrophilic PEG core and thermoresponsive P(MEO 2MA- co-OEGMA) outer-blocks. These star-block architectures exhibit an inverse thermogelation behavior in aqueous medium. Typically, above their lower critical solution temperature (LCST), the thermoresponsive P(MEO 2MA- co-OEGMA) precipitate, thus forming physical crosslinks, which are stabilized in water by hydrophilic PEG bridges. This thermo-induced sol–gel transition can be adjusted within a near-physiological range of temperature by simply varying the composition of the thermoresponsive segments. Moreover, these novel hydrogelators formed free-standing gels in various buffer solutions (e.g., PBS, Tris, MOPS, bicine and HEPES) and in cell culture media. In saline solutions, a weak salting-out effect was observed. However, other components of physiological media (e.g., buffering agents, amino acids, vitamins, proteins) did not hinder the thermogelation process. Hence, these novel thermogels appear as highly attractive candidates for applications in biosciences.