Vibrational characterization of electrospun nanofibrous scaffolds based on silk fibroin and poly(L-lactic acid) for biomedical applications

Silk fibroin (SF) has been widely used in biomedical field for its high biocompatibility and mechanical properties. Scaffolds based on SF have been employed for tissue and bone regeneration. In this field electrospinning has proved an interesting and effective process for producing nanofibrous scaffolds usable for drug delivery, wound dressing, tissue engineering. Actually, the produced fibres have high specific surface area and high porosity with very small pore size. Therefore, the micro/nanofibres can simulate the extracellular matrix and enhance cell migration and proliferation. On the other hand, in the biomedical field, a single material hardly fulfills all the requirements of a specific biological function. Therefore, composites are designed to properly modify and tailor the materials properties according to the desired function. A common strategy consists in the preparation of composite scaffolds made from a biodegradable synthetic polymer and a natural material. In this study, composite nanofibrous scaffolds were obtained by electrospinning a solution containing regenerated Bombyx mori SF and poly(L-lactic acid) (PLLA) in a 1:1 weight ratio. Actually, PLLA is a biocompatible polymer used since a long time in many biomedical applications for its outstanding properties such as strength and controlled degradation. Optical and atomic force microscopy imaging has been employed to gather information on the length, thickness and weaving of the nanofibres in the material. Raman and IR spectroscopy have been employed to clarify the possible interactions between SF and PLLA in the composite scaffold and the structure modifications induced by these interactions. Raman and IR marker bands of the PLLA crystallinity were identified and their trend was followed as a function of the treatment. An analogous analysis was performed for the Raman and IR Amide modes of SF. The vibrational data showed that the electrospinning process caused a decrease in crystallinity in both SF and PLLA components, as also confirmed by thermoanalytical techniques such as Differential scanning calorimetry.