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A study of the mechanical behaviour and stability of Nanomaterial-Hydrogel composites for Soft Tissue Applications

par Vadakken Gigimon, Anet
Président du jury Scheid, Benoît
Promoteur Hendrick, Patrick
Co-Promoteur Iorio, Carlo Saverio
Publication Non publié, 2026-06-15

Thèse de doctorat

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Résumé :

Hydrogels with protein-polysaccharide combinations are widely used in diverse engineering fields, including tissue engineering, agriculture, cosmetics, the food industry, and, relevant to space-based applications, the space industry. They are widely used as scaffolds because they can mimic the in vivo environments of native tissues, particularly the extracellular matrix (ECM) of soft tissues, such as fat, muscles, blood vessels, nerves, tendons, and ligaments. Recent studies have identified significant gaps in the Ashby chart (a visual tool for material selection) for soft biological tissues. This study addressed this challenge and developed a one-pot, easily scalable fabrication strategy for a gelatin-sodium alginate (Gel-Alg) hydrogel that meets the protein-polysaccharide design criteria of soft-tissue ECM, with a modulus < 1 MPa. However, achieving stability and mechanical properties comparable to those of tissues using only natural polymers and physical crosslinking remains a challenge due to the inherent structural weaknesses of these polymers. Therefore, magnetite (Fe3O4), graphene oxide (GO), and laponite (nanoclay) nanomaterials were incorporated into the Gel-Alg hydrogel to enhance network stability and structural integrity. Characterization tests showed that the shape, dispersion, and interactions of the nanomaterial with the polymer matrix independently influence the tensile and viscoelastic properties. The addition of nanomaterials resulted in nanomaterial-hydrogel composites with modified network stiffness and improved stability at both 25 °C and physiological temperature (37°C) compared to Gel-Alg gel. Graphene oxide, with the highest aspect ratio, displays the highest storage modulus and thus the greatest network stability, indicating improved temperature tolerance under oscillatory shear stress. In terms of tensile stress, the laponite-embedded composite demonstrates the highest stiffness of 0.16 ± 0.03 MPa at low concentrations, but this decreases significantly as the concentration increases. This confirms a low threshold concentration of laponite nanomaterials in Gel-Alg hydrogel compared to GO and magnetite. Magnetite shows a relatively high threshold concentration and greater flexibility due to its spherical shape. In resisting swelling and degradation, magnetite outperforms the other nanomaterials, indicating a higher stabilizing effect in aqueous environments and at physiological pH. The results demonstrate that integrating magnetite (Fe3O4), graphene oxide (GO), and laponite nanoparticles with polyampholytic gelatin and the polysaccharide alginate enables precise control of tensile, viscoelastic, and structural stability in a hydrated environment, thereby facilitating their use as acellular matrices or scaffolds for soft-tissue applications.