Department of Bioengineering, Graduate School of Engineering, The University of Tokyo
Hydrogels are water-filled materials with characteristics similar to those of biological soft tissues and have broad application as biomaterials. However, the safety of hydrogels is difficult to guarantee throughout the full life cycle in vivo due to the inevitability of degradation-induced swelling. Indeed, the swelling pressure exerted by conventional hydrogels is sufficiently large to cause severe adverse reactions to surrounding tissues. In this respect, we report here a new class of in situ forming hydrogels that guarantee safety throughout the full life cycle. The oligo-TetraPEG hydrogel has an extremely high water content and a polymer content of only 4.0 g/L, resulting in an exceptionally low swelling pressure. The oligo-TetraPEG hydrogel was successfully injected and gelled inside a living body within a clinically relevant manipulation time and little cytotoxicity. The oligo-TetraPEG hydrogel exhibited an appropriate stiffness, similar to that of soft tissue, with extremely low swelling pressure thus being compatible with living tissues. The oligo-TetraPEG hydrogel functioned as an artificial vitreous body for over a year without any adverse effects, and was effective for treating retinal detachment as an intravitreous tamponade material． The present concept provides new guidance for the safety of biomaterials in vivo.