The synthesis and biomedical applications of novel elastomeric, pH-responsive, biocompatible and biodegradable copolymer hydrogels based on poly(glycerol sebacate) and gelatin.

Polymers play a prominent role in daily lives; however, there is a growing concern on the depleting fossil resources triggering the research for sustainable alternatives. Here, novel wholly biobased nanocomposites are prepared from polyamide 36,36 (PA36,36) thermoplastic elastomer and cellulose nanocrystals (CNCs). Further, the influence of CNC addition and CNC loading on the morphological features, thermal and mechanical properties of PA36,36 is studied. The presence of CNC in PA36,36 affects the thermal degradation of PA36,36. The additions of 10 and 30 wt% CNCs to the PA36,36 improve the tensile strength and Young's modulus by up to 700% and 750% to 9.6 and 6.8 MPa, respectively, while still maintaining relatively high elongation at break values. The hardness of the polymer increases significantly after the inclusion of CNC. The PA36,36/CNC nanocomposites also show relatively good resilience when exposed to 100% strain. Overall, these biobased thermoplastic elastomer nanocomposites can be potential alternatives for some existing rubbers with low or medium hardness.

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Elastomeric hydrogels are promising in soft tissue applications due to their biomimetic mechanical and physical behaviors. In this study, we design and synthesize a poly­(glycerol sebacate)-based polyurethane-clay nanocomposite hydrogel system with controllable mechanical, swelling, drug release, and biodegradation behaviors. The polymer-clay nanocomposites are synthesized by in situ polymerization in the presence of a solvent, which facilitates the dispersion of clay within the polymer matrix and their bonding. The nanocomposite hydrogels exhibit higher water swelling ratios in comparison to the neat polymer. The fully swollen hydrogels are capable of enduring complex mechanical deformations such as stretching and knotting, while the tensile moduli of the hydrogels mimic various soft tissues in human body. The mechanical behavior of hydrogels is significantly enhanced by the addition of no more than 3 phr clay, showing higher stiffness, strength, ductility, and toughness. The drug loading and release behavior of the hydrogels is investigated with three model drugs, showing selective drug loading capacity and sustained release, based on the Coulombic interaction between the clay and drug molecules. Biodegradation tests under a simulated body condition reveal a highly tunable degradation rate by the clay content in the nanocomposite hydrogels. Good cytocompatibility by the cell metabolic assay with mouse fibroblasts in vitro is also demonstrated. Finally, three-dimensional microporous foam is manufactured as a proof-of-concept study.