Nerve conduit fabrication

In an effort to develop a nerve guiding conduit, we have specifically focused on two of the key parameters listed above, namely the material and the permeability of the conduit. We selected type I collagen from bovine Achilles tendon for nerve conduit fabrication because it causes minimal inflammation responses in humans. Type I collagen is biodegradable and can be chemically modified to alter its physicochemical, mechanical and biological properties. Thus, type I collagen is a logical material to meet the requirements for peripheral nerve repair. 

Collagen derived from bovine deep flexor (Achilles) tendon was used for nerve conduit fabrication. Tendons were first cut into thin slices and then purified by a combination of enzymatic and chemical treatments to reduce the non-collagenous moieties while retaining the integrity of the fibrillar structure for mechanical strength. Chemical analysis of this material showed a minimal level of hexosamine content indicating most of the glycoproteins were removed by the purification steps. 

The steps in nerve conduit fabrication procedure are as follows (1)... 

The fabrication of pol nneric nerve conduits loaded with nerve growth factor, and... 

In contrast, spider silk is devoid of sericin and hence does not evoke the same biological or immunological reactions. Thus, spider silk has better biocompatibility and is a preferred biomaterial for suture applications. It has also been studied as a material for regenerative nerve conduits to promote peripheral nerve regeneration [33]. Silk s unique mechanical properties coupled with its ability to be fabricated into different textile structures enable its use in tissue engineering scaffolds that mimic the mechanical properties of native tissues. For example, silk filaments have been converted into a braided rope stracture that acts as a scaffold for the regeneration of anterior cruciate ligaments (ACL) [34]. 

Yao, L., Billiar, K.L., Windebank, A.J., Pandit, A., 2010. Multichanneled collagen conduits for peripheral nerve regeneration design, fabrication, and characterization. Tissue Eng. Part C-Methods 16, 1585-1596. 

The obtained copolymer P(BHET-EOP/TC) has been fabricated into conduits to guide nerve regeneration. One day after implantation, some of the nerve guide conduit chambers (three out of four type II conduits) became filled with a solid structure that bridged the two nerve stumps (Figure 20(a)). This structure appeared as a blood clot and was loosely attached to the stumps. On day 3, the solid structure was present in all tubes examined (Figure 20(b)). By microscopic examination, small threads dis-... 

Figure 20 Macroscopic views of (a) the sciatic nerve repaired at the proximal stump with a type II PPE conduit prefilled with saline at the time of implantation, (b) A macroscopic picture of the matrix cable across 10 mm gap at 3 days in a type II PPE conduit, (c) Micrograph of a longitudinal section of the acellular fibrin matrix found at 3 days. The original magnification was x 200. (d) A regenerated nerve 3 months after surgery. A conduit, 14 mm in total length, was used to bridge a 10 mm gap. The obtained copolymer P(BHET-EOP/TC) has been fabricated into conduits to guide nerve regeneration. ...

Novel material options are being explored as matrix fdlers in NGCs. Recently, a sericin/silicone-based NGC was fabricated and used as a long-term implant in vivo. Sericin conduit wrapped with a silicone conduit was used for the bridging repair of a 5-mm gap in a rat sciatic nerve transection model. These double conduits achieved functional recovery comparable to autologous nerve graft and, importantly, positive results were mainly attributed to sericin (Xie et al., 2015). 

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