Deconstructing culture media reveals a key role of oxyanion salts on the physicochemical properties of ortho -aminomethyl-phenylboronic acid/glucamine hydrogels in aqueous environments

Dynamic hydrogels are important materials for recreating the viscoelastic properties of the extracellular matrix in 3D cell culture and tissue engineering applications. However, dynamic crosslinking reactions are often sensitive to their chemical environment, and surprisingly little is known about how the composition of common aqueous solutions and culture media affects the properties of dynamic hydrogels. In this context, we investigated the effect of various common aqueous media on the formation, stiffness and stability of dynamic hydrogels based on boronate ester (BE) crosslinking. By deconstructing different aqueous media, we demonstrated that oxyanion salts play a central role in the properties of BE hydrogels in aqueous environments. In particular, we demonstrated that phosphate ions are primarily responsible for the formation, stiffness, and long-term stability of these hydrogels. We also showed that bicarbonate ions transiently stiffen BE hydrogels, while nitrate ions cause a decrease in the mass of BE hydrogels. We further demonstrated that these results correlate with alterations to BE association constants in the presence of oxyanions, thereby expanding our knowledge of the sensitivity of BE chemical equilibria. Together, our findings revealed previously unknown chemical interactions between oxyanions and BE precursors and/or products, with significant implications for the design of BE hydrogels and their biomedical applications.