Long-Term In Vivo Evaluation of Chitosan Nerve Guide Properties with respect to Two Different Sterilization Methods

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.

Two-Chambered Chitosan Nerve Guides With Increased Bendability Support Recovery of Skilled Forelimb Reaching Similar to Autologous Nerve Grafts in the Rat 10 mm Median Nerve Injury and Repair Model

“…At this late time point, edema or continued inflammatory infiltrations would only be expected in case of immune responses against the artificial nerve grafts or their degradation products. This was, however, never detected in other studies evaluating chitosan-based nerve guides before (e.g., Haastert-Talini et al, 2013; Stößel et al, 2018a,b). We further did not study effects of any complementary treatment to protect peripheral nerve arrangement and to prevent development of neuropathic pain, like, e.g., daily oral administration of rosemary extracts (Pacini et al, 2010; Di Cesare Mannelli et al, 2016), because the rat median nerve transection and repair model has not been reported before to induce neuropathic pain.…”

“…Sterilization of all types of CNGs was performed by beta irradiation (11 kGy, 10 MeV) by BGS Beta-Gamma-Service GmbH & Co. KG (Wiehl, Germany) (Stößel et al, 2018a). All CNGs used for median nerve repair were rinsed in 0.9% sodium chloride solution (NaCl 0.9%, B. Braun Melsungen GmbH, Germany) for at least 20 min prior to implantation.…”

In Vivo and In Vitro Evaluation of a Novel Hyaluronic Acid–Laminin Hydrogel as Luminal Filler and Carrier System for Genetically Engineered Schwann Cells in Critical Gap Length Tubular Peripheral Nerve Graft in Rats

“…Briefly, their middle line was perforated with a sharp needle, creating six holes with 2 mm distance to each other. After inserting the CFs concentrically into the chitosan tubes, the final CNG[F]s were sterilized by beta irradiation (11 kGy, 10 MeV) by BGS Beta-Gamma-Service GmbH & Co. KG (Wiehl, Germany) 38 . To rinse all CNGs and CNG[F]s for 20 min before they were implanted, 0.9% sodium chloride solution (NaCl 0.9%, B. Braun Melsungen AG, Melsungen, Germany) was used.…”