Supramolecular Hydrogels with Reverse Thermal Gelation Properties from (Oligo)tyrosine Containing Block Copolymers

Abstract

Novel block copolymers comprising poly­(ethylene glycol) (PEG) and an oligo­(tyrosine) block were synthesized in different compositions by <i>N</i>-carboxyanhydride (NCA) polymerization. It was shown that PEG2000-Tyr₆ undergoes thermoresponsive hydrogelation at a low concentration range of 0.25–3.0 wt % within a temperature range of 25–50 °C. Cryogenic transmission electron microscopy (Cryo-TEM) revealed a continuous network of fibers throughout the hydrogel sample, even at concentrations as low as 0.25 wt %. Circular dichroism (CD) results suggest that better packing of the β-sheet tyrosine block at increasing temperature induces the reverse thermogelation. A preliminary assessment of the potential of the hydrogel for in vitro application confirmed the hydrogel is not cytotoxic, is biodegradable, and produced a sustained release of a small-molecule drug