Time-dependent evaluation of mechanical properties and in vitro cytocompatibility of experimental composite-based nerve guidance conduits

Abstract

The use of nerve guidance conduits to repair peripheral nerve discontinuities has attracted much attention from the biomaterials community, with many resorbable and non-resorbable materials in clinical use. However, a material with ideal biocompatibility, sufficient mechanical properties (to match that of the regenerating nerve) coupled with a suitable degradation rate, has yet to be realized. Recently, potential solutions (composite nerve guidance conduits) which support the emerging philosophy of allowing synthetic materials to establish key interactions with cells in ways that encourage self-repair (i.e. ionic mediators of repair such as those observed in hard tissue regeneration) have been proposed in the literature; such composites comprise specially designed bioactive phosphate-free glasses embedded in degradable polymeric matrices. Whilst much research has focussed on the optimization of such composites, there is no published literature on the performance of these experimental compositions under simulated physiological conditions. To address this key limitation, this paper explores the time-dependent variations in wet-state mechanical properties (tensile modulus and ultimate tensile strength) for NGC composites containing various compositions of PLGA (at 12.5, and 20 wt%), F127 (at 0, 2.5 and 5 wt%) and various loadings of Si-Na-Ca-Zn-Ce glass (at 0 and 20 wt%). It was observed that Young's modulus and ultimate tensile strength of these composites were in the range 5-203 MPa and 1-7 MPa respectively, indicating comparable mechanical performance to clinical materials. Furthermore, an analysis of the cytocompatibility of experimental compositions showed comparable (in some instances superior), compatibility when compared with the commercial product Neurolac(®). Based on current synthetic devices and the demands of the indication, the CNGCs examined in this work offer appropriate mechanical properties and compatibility to warrant enhanced development.