Analysis of gelatin secondary structure in gelatin/keratin-based biomaterials

The possibility of using protein-based materials as cellular scaffold strongly depends on protein conformation, and several attempts have been made by researchers to obtain scaffold with morphology miming the extracellular matrix. It is widely recognized that the secondary structure of proteins affects the mechanical and biological properties of protein-based scaffolds. However, few studies have been published, and an exhaustive explanation is still missing. In this work the study of the gelatin structure in gelatin-based materials and the investigation of the possible correlations between structure, mechanical and biological features is reported. We have examined how the secondary structure of gelatin is affected (i) by the process used to obtain the biomaterials (solvent casting vs. electrospinning), (ii) by the concentration of cross linker (3-(Glycidyloxypropyl)trimethoxysilane) (GPTMS), and (iii) by the raw keratin extract added. Gelatin electrospun materials have shown a content of ordered structure higher than gelatin casted films, likely due to the random coil – α-helix transition occuring during electrospinning. GPTMS gives a decrease of ordered structures in gelatin casted films (random structure increasing from 20% to 60%), while it does not affect the percentage of ordered structure in electrospun samples. In the gelatin/keratin electrospun biomaterials, the presence of keratin produces a decrease of α-helix content from 31% to 2–15% and an increase of β-structures, promoting the conversion from antiparallel to parallel β-sheet. The structure of gelatin affects the mechanical performances of biomaterials. In gelatin/keratin electrospun biomaterials we have found a positive correlation between failure strain and helix conformation and a negative correlation with β-structures. Elastic modulus has opposite correlations. All gelatin-based biomaterials have been tested as scaffold for pre-osteoblastic cells showing good biocompatibility for both casted films and electrospun biomaterials.