Peripheral nerve injuries (PNI) are a large-scale problem that affects over one million people around the world. For PNI that require surgical intervention and in the case of long gap injuries, autologous nerve grafts (ANG) have been considered the gold standard for decades. However, the random efficiency of ANG is associated to several drawbacks, for instance, donor site morbidity, limited availability and nerve mismatches, leading to merely 50% rates of success.
Keratin, our selected protein, is a highly available fibrous protein found in hair, wool and feathers and it has been used as a potential scaffold material for tissue engineering procedures since it possess cell binding motifs capable of supporting cellular attachment. In this study, an innovative combination of chitosan (medical grade chitosan, Altakitin) and keratin (human air) is obtained in order to create novel materials aimed at finding applications in the treatment of PNI. Two types of biomaterials were produced: Chitosan/keratin membranes by solvent casting and nanofibers by electrospinning technique. Scaffolds were physicochemical and biologically characterized.
Keratin/chitosan membranes and nanofibers topography showed a rough surface, with ridges and pores. FTIR revealed characteristic peaks of keratin and chitosan in both membranes and electrospun nanofibers, suggesting the presence of both biomaterials in the blend solution. Regarding mechanical properties, both membranes and nanofibers showed mainly elastic behavior and a low ability to dissipate energy, but the latest showed higher stiffness.
In a preliminary screening using L929 cells in both materials, it was observed that cell viability increased with culturing time in both chitosan/keratin membranes and electrospun nanofibers. In a more specific study including several cell types relevant to peripheral nerve regeneration, such as human Schwann cells (SC), human brain microvascular endothelial cells (HBMECS) and human dermal fibroblasts (BJ), there is a significantly higher cell adhesion and metabolic activity after 14 days in chitosan membranes containing 1% keratin, comparing to 100% chitosan membranes.
These data, together with the fact that materials have appropriate physicochemical and mechanical properties, indicate the suitability of keratin containing materials for Peripheral Nerve Regeneration.