Radical free crosslinking of direct-write 3D printed hydrogels through a base catalyzed thiol-Michael reaction

In this work we describe a method of fabricating 3D printed hydrogels which are mechanically stabilized without the use of potentially cytotoxic radical chemistry. To achieve this, we utilized a thiol-Michael reaction catalyzed by basic (pH 8.2) phosphate buffered saline (PBS) between diacrylated Pluronic F127 and multifunctional thiol crosslinkers. We showed that the print resolution could be conserved due to stabilization of Pluronic micelles as a result of the ionic strength of the buffer. These hydrogels exhibited high stretchability (similar to 750%) as well as tunable mechanical properties. We demonstrated that micelle-based free-standing 3D objects can be fabricated through non-radical pathways by stabilizing the micelles in solutions with increased ionic strength.