Photopolymers Based on Boronic Esters for the Enhanced Degradation of 3D-Printed Scaffolds

Lithography-basedadditive manufacturing technologies have becomea valuable tool in tissue engineering for the fabrication of biocompatibleand biodegradable bone regeneration scaffolds. Currently employedphotopolymers based on (meth)acrylates, vinyl esters, or vinyl carbonatesdisplay undesirable properties such as irritancy or cytotoxicity ofresidual monomers, degradation via autocatalytic bulk erosion leadingto implant failure, or insufficient degradation speed in vivo. This work investigates monomers containing boronic ester bondsas a potential alternative to these state-of-the-art compounds. Nextto a facile synthesis, significantly lower cytotoxicity was shownfor this generation of biocompatible allyl ether monomers comparedto commonly utilized (meth)acrylates. Photopolymerization via thethiol-ene reaction showed that rigid boronic esters led tosufficient photoreactivity for 3D structuring, and materials withreduced shrinkage and excellent mechanical properties can be obtained.Additionally, degradation studies revealed significantly accelerateddegradation via the desired surface erosion under physiological andacidic conditions. Ultimately, a 3D test structure out of a boronicester-based formulation was successfully stereolithography-printed,showing the great potential of these monomers as precursors for photopolymersused for 3D-printed implants with improved degradation behavior withoutforfeiting good mechanical properties.