Abstract
Severe peripheral nerve injuries are reconstructed either with autologous nerve grafts (gold standard) or alternatively with clinically approved artificial nerve guides. The most common method used to sterilize these medical products is ethylene oxide gassing (EO). However, this method has several disadvantages. An alternative, which has been barely studied so far, represents beta irradiation (β). In previous studies, we developed an artificial nerve guide made of chitosan (chitosan nerve guide, CNG), a biomaterial that is known to potentially retain toxic residues upon EO sterilization. Therefore, we analyzed the long-term regeneration-supporting and mechanical properties of CNGs upon their sterilization with EO or β and their following application in unilateral repair of 12 mm gaps of the rat sciatic nerve. Over a period of 76 weeks, we serially evaluated the recovery of motor functions, the possible emergence of an inflammation in the surrounding connective tissue, the regrowth of axons into the distal nerve, and possible changes in the material properties. Our first long-term evaluation did not reveal significant differences between both sterilization methods. Thus, β is as appropriate as commonly used EO for sterilization of CNGs; however, it may slightly increase the stiffness of the biomaterial over time.
Highlights
Chitosan, a random copolymer consisting of D-glucosamine units (C6H11NO4)n) and N-acetyl-D-glucosamine units (C8H13NO5)n), is a highly biocompatible, natural-derived heteropolymer that is widely used as scaffold-material in different biomedical applications [1,2,3]
We found an increased overall recovery rate of motor function in the β group, no significant differences were detected between both methods
A recovery rate of 68.8% at 12 weeks after surgery was detected upon 10 mm nerve gap repair using β-sterilized chitosan nerve guides (CNGs) in Wistar rats [6] and a recovery rate of 42.9% at 16 weeks after surgery following 15 mm nerve gap repair using either β-sterilized CNGs in Wistar rats [4] or ethylene oxide gassing (EO)-treated
Summary
A random copolymer consisting of D-glucosamine units (C6H11NO4)n) and N-acetyl-D-glucosamine units (C8H13NO5)n), is a highly biocompatible, natural-derived heteropolymer that is widely used as scaffold-material in different biomedical applications [1,2,3]. These chitosan nerve guides (CNGs) have demonstrated very good properties to support critical gap lengths (15 mm) rat sciatic nerve regeneration in acute as well as in clinically relevant delayed repair approaches [4,5,6,7,8]. Different mechanical properties were monitored, e.g., the flexibility, the compression resistance, and the degradation rates of the CNGs, to deliver the ideal implant for clinical application [6, 7]. Toxic residues might remain at the treated materials’ surfaces by irreversible alkylation of highly reactive functional groups such as the amine groups of the chitosan structure [13,14,15]
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