Enhancing hyaluronan pseudoplasticity via 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride-mediated conjugation with short alkyl moieties

• Alkyl derivatives were synthesized with accurate control from 1% to 50% substitution.
• Reaction kinetic of DMTMM-mediated amidation was determined.
• DMTMM is a viable tool for tuning hyaluronan rheological properties.
• Hyaluronan pseudoplasticity was enhanced with minimal modification.

Hyaluronan (HA) is widely used in the clinical practice and in biomedical research. Through chemical modification, HA shear-thinning properties, essential for injectability and additive manufacturing, can be optimized. In this study, we employed 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (DMTMM) for grafting propylamine and butylamine to HA. A parametric study was performed to identify the optimal reaction conditions. Results showed that DMTMM amidation gives reproducible and accurate control over a range of degrees of substitution (DS) from 1% to 50% and proved reliable to tune viscoelasticity. At DS = 3.0% for HA-propylamine and 3.7% for HA-butylamine a maximum for storage modulus and pseudoplasticity was found, whereas above or below this DS, rheological features go back to baseline values of pristine HA. Due to their singular rheological profiles, these derivatives are valuable biomaterials candidates for preparing bioinks and hydrogels for drug delivery and regenerative medicine.