Closed-loop biomaterial design: Diels-Alder hydrogels from renewable polymers for biomedical devices

Guar gum (GG), a biodegradable and biocompatible polysaccharide, exhibits limited stability in its hydrogel form. To overcome this, semi-interpenetrating polymeric networks (semi-IPN) were engineered by synthesizing a Diels-Alder (DA) polymer (Polymer 1) from a difurfuryl monomer (Di-Fur, derived from L-tartaric acid) and a dimaleimide (Di-Mal, from 1,8-diamine-3,6-dioxaoctane) within a GG solution (Polymer 2). Controlled crosslinking was achieved by introducing a novel trifunctional crosslinker (Tri-Fur), containing three furan rings and synthesized from D-ribonolactone. By optimizing the Tri-Fur concentration, maximum crosslinking degrees (Xr) of 4 % and 10 % were attained, yielding GG-Xr₄ and GG-Xr₁₀, respectively. Polymer 1 demonstrated thermal degradation at 60 °C, releasing maleimide units that undergo rapid Michael addition, indicating reversible and self-healing properties. Rheological studies confirmed that the materials were gelatinous and stable for 14 days at 25 °C, maintaining integrity from 24 to 60 °C, with complex viscosity notably increasing between 24 °C and 37 °C (e.g., GG-Xr₄: 139 to 619 Pa·s), supporting potential for injectable formulations. SEM revealed nanoporous structures (GG-Xr₄: 530 nm mean pore size). The materials retained mucoadhesive properties and enabled drug loading and release, enhancing GG's biomedical and pharmaceutical potential.