Plasma Surface Modification of Electrospun Polymeric Scaffolds Intended for Tissue Engineering

Abstract

In an attempt to repair peripheral nerve injuries while obviating the drawbacks of autograft, artificial guidance conduits are nowadays being developed. The enhancement of nerve regeneration through these conduits strongly depends on their mechanical, topographical, and surface chemical properties1. The appropriate elasticity and strength of the copolymer poly(ethylene oxide terephthalate)/poly(butylene terephthalate) 300 55/45, commercially known as Polyactive (PA), as well as its safe use in humans, made it the material of choice in this study. The conduits were fabricated by electrospinning since the process can be tailored to produce fiber meshes mimicking the neural extracellular matrix. As a result, conduits comprised of PA fibers having an average diameter of $1.3~ \mu \mathrm {m}$ and a pore average diameter of $2.5~ \mu \mathrm {m}$ were developed. The crucial bio-activation step of such a porous structure with narrow dimensions remains a challenging task. Plasma treatment having the potential to modify the surface of complex shaped scaffolds might thus reach the central part of the porous conduits. Therefore, the conduits were subjected to a sub-atmospheric plasma treatment using an air or argon dielectric barrier discharge. Chemical and physical surface changes were examined by Xray photoelectron spectroscopy and scanning electron microscopy (SEM). Results showed that air and argon plasmas increased the oxygen content from 17% to 24% on the inner and outer conduit surface clearly showing the ability of the plasma to penetrate and modify the entire wall thickness $(140~ \mu \mathrm {m})$. In terms of the incorporated functional groups, a small difference was emphasized between both treatments. A higher incorporation of C-O and O-C=O is observed in the case of the air plasma compared to the argon plasma treatment that was shown to also incorporate a small amount of C=O. Different types of neural cells might sense these small differences thus generating detectable variances in their behavior. SEM images showed that after argon plasma treatment, the fibers retained their morphology, whereas a minor tendency of smaller fiber diameter and higher porosity is observed after air plasma treatment probably due to the more pronounced etching effect of the air plasma. Lastly, plasma technology can constitute a promising move towards the unreached goal of treating large nerve gaps.