Electrospun mats of biodegradable chitosan-based polyurethane urea

Polyurethane ureas (PUU) are segmented polymers where soft and hard segments are separated in microphases. Usually, the soft segment is derived from a polyol and the hard segment from a diisocyanate and a chain extender. The PUU properties can be tuned in order to obtain biodegradable scaffolds with suitable mechanical properties for tissue engineering applications [1]. Electrospinning is a convenient technique for the production of nanofibrous scaffolds from a polymeric solution that mimic the extracellular matrix, thereby supporting cell attachment and growth [2]. The physico-chemical properties of the material used and the scaffold's architecture both provide cells with cues. In this work, we synthetized a PUU based on PCL-diol using CS as chain extender (PUU-CS) [3]. Molecular structure was analyzed by ¹H NMR and FTIR. Thermogravimetric analysis was performed to examine the thermal stability. The PUU-CS was electrospun from solutions using a mixture of tetrahydrofuran and N, N-dimethylformamide as solvent. Randomly oriented and aligned fibres were collected on a static and on a rotating collector, respectively. Morphological properties were characterized by SEM and mechanical properties evaluated through tensile tests. Hydrolytic (phosphate buffer saline (PBS) solution) and enzymatic (lipase) degradation studies were carried out. The cytocompatibility of the PUU-CS fibre mats was evaluated using the extract method. A preliminary study of cell adhesion was also performed. Spectroscopic results confirmed that PUU-CS was successfully produced and is stable at least until 200 ºC. Randomly oriented and aligned fibres with different mean diameters were obtained. Both types of fibre mats showed higher Young's modulus for the thinner fibres. Elongation at break was lower for the aligned fibre mats. No mass changes were observed in the mats during 3 months in PBS while significant degradation was observed in lipase. In vitro tests didn't demonstrate any toxicity of the extracts. Cells seeded on the mats were able to adhere. These properties make nanofiber mats based on PUU-CS good candidates for soft tissue engineering.