Gelatin hydrogels are naturally derived scaffolds useful for tissue engineering because of their cytocompatibility and controllable degradability. However, they are brittle and inflexible when dry, which limits their use for in utero tissue engineering in large animal models. Therefore, in this study, we attempted to generate flexible gelatin sheets by adding various plasticizers with different molecular weights (MW). We systematically evaluated the flexibility, sustainability, and potential clinical utility of the resulting flexible gelatin sheets. Gelatin sheets with low‐MW plasticizers, such as monosaccharides or sugar alcohols, showed a reduced tensile modulus in dynamic viscoelasticity, which reflected their actual flexibility. Wet gelatin sheets containing plasticizers showed higher tensile strength than the nonplasticizer control, although wet gelatin sheets under all conditions had a much lower tensile strength than dry gelatin sheets. In a functional study, gelatin sheets containing glycerol, which has the lowest MW among sugar alcohols, showed encouraging results, such as good fit to the curvature of the experimental animal, biocompatibility, and suitability for endoscopic approaches. The findings of this study should enable the expansion of future applications for flexible gelatin sheets.
Rheological properties of dextran solutions in 1-butyl-3-methylimidazolium acetate were examined up to the concentration (c) of 4.1 × 10 2 kgm −3. A high molecular weight (≈ 2 × 10 6) dextran with a degree of divergence of 4 % was used. The zero-shear viscosity estimated from the flow behavior indicated that dextran chains in the solutions entangle each other at c ≥ 1.7 × 10 2 kgm −3. In fact the plateau modulus (G 0 N) was obtained from the G′ and G″ curves for c ≥ 2.6 × 10 2 kgm −3. However, the anomalous results were obtained regarding entanglement of dextran chains: The molecular weight between entanglements was constant against c at 2.3 × 10 4 , so that a large number of entanglements per chain was expected in spite of the subtle rubbery plateau that was actually observed. It was proposed that the dextran has the main structure of long branches and each branch is densely sub-branched.
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