Conduits based on the combination of hyaluronic acid and silk fibroin: Characterization, in vitro studies and in vivo biocompatibility

Abstract

We address the production of structures intended as conduits made from natural biopolymers, capable of promoting the regeneration of axonal tracts. We combine hyaluronic acid (HA) and silk fibroin (SF) with the aim of improving mechanical and biological properties of HA. The results show that SF can be efficiently incorporated into the production process, obtaining conduits with tubular structure with a matrix of HA-SF blend. HA-SF has better mechanical properties than sole HA, which is a very soft hydrogel, facilitating manipulation. Culture of rat Schwann cells shows that cell adhesion and proliferation are higher than in pure HA, maybe due to the binding motifs contributed by the SF protein. This increased proliferation accelerates the formation of a tight cell layer, which covers the inner channel surface of the HA-SF tubes. Biocompatibility of the scaffolds was studied in immunocompetent mice. Both HA and HA-SF scaffolds were accepted by the host with no residual immune response at 8 weeks. New collagen extracellular matrix and new blood vessels were visible and they were present earlier when SF was present. The results show that incorporation of SF enhances the mechanical properties of the materials and results in promising biocompatible conduits for tubulization strategies.

Keywords: Biomaterials; Hyaluronic acid; Nerve guidance conduits; Silk fibroin; Tissue engineering.