Effect of Ethanol Post-Treatments over Sericin Scaffolds for Tissue Engineering Applications

Protein-based biomaterials are excellent candidates for biomedical applications since they have similar properties to the extracellular matrix. Recently, the use of sericin (SS), a protein present in the silk cocoon, can be used as biomaterial. To improve their properties, SS biomaterials must be subject to treatments after their manufacturing. Ethanol post-treatments by immersion and solvent vapor, are used for increasing their crystallinity, mechanical and water stability. In this work, the effect of ethanol post-treatment on the properties of SS scaffolds elaborated by the lyophilization technique was evaluated. Four post-treatments were carried out on the samples: immersed in absolute ethanol for 5 min (SS/EtOH 5 min) and for 1 h (SS/EtOH 1 h); and exposition in a saturated ethanol vapor environment for 1 h (SS/VapEtOH 1 h) and for 24 h (SS/VapEtOH 24 h). The scaffolds were characterized by X-ray diffraction (XRD) and Fourier‑transform infrared spectroscopy (ATR-FTIR), scanning electron microscopy (SEM), water absorption, degradation in a phosphate-buffered saline solution, sericin release from the scaffolds, and the cytotoxicity test. The ATR-FTIR results showed an increment in the relative content of β-sheet structures and an increment in the crystallinity. SEM images revealed that the post-treatment process induces changes in treated materials to present morphological changes. The treatment materials were more water-stable. The excipients of the SS scaffolds evaluated in human epithelial fibroblasts do not generate an acute cytotoxic effect. The results suggest that ethanol post-treatments induce conformational transitions and morphological changes, which should be considered for selecting the post-treatment conditions according to developing materials for wound regeneration.