Deconstructing Culture Media Reveals a Key Role of Oxyanion Salts on the Physicochemical Properties of Ortho-Aminomethyl Phenylboronic Acid/Glucamine hydrogels in Aqueous Environments

Abstract

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 buffers 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 BE hydrogel properties 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 BE hydrogel degradation. 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 underestimated chemical interactions between oxyanions and BE precursors and/or products, with significant implications for the design of BE hydrogels and their biomedical applications.