CONICET | Buscador de Institutos y Recursos Humanos

Gelatin gels are attractive materials due to their uses in photography, ballistic, food and pharmaceutical industries as well as to their novel applications in biomedical field. When cooling, gelatin solutions undergo a conformational transition from coil to helix and a tridimensional physical network is formed. Then, the gel is constituted by ordered triple helical collagen-like sequences (physical crosslinking points) interconnected by flexible protein chains. The amount of triple helices developed depends on several parameters such as protein source (chemical composition), molecular weight, gelatin concentration, environment (pH, salts, solvents, etc) and thermal history. It has been stated that the elastic modulus of gelatin gels is determined by the sole helix concentration- ie. a master curve has been constructed using different types of gelatin gel samples. Inspired by this study, this work explores if fracture toughness of gelatin gels is also governed by helix concentration. To this aim, several gel samples differing in gelatin concentration and source (bovine or porcine) are studied. Fracture toughness (Gc) is determined by the wire cutting method and the helix concentration is estimated trough the physical crosslinking degree. Samples are characterized by the number-average molecular weight between two crosslinking points, determined by using the Flory?Renher equation. The ultrastructures of the gels are analyzed by SEM. Increasing gelatin concentration leads to higher Gc values and porcine gelatin gels series exhibit higher fracture toughness than bovine gelatin gels ones. These results are consistent with a more physically crosslinked structure. The results obtained in our experiments identify the relevance of triple helix concentration as key parameter determining fracture toughness values of gelatin gels.

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