The repair of severed nerves poses a significant clinical problem although it is recognized that the peripheral nervous system is capable of repair. Over recent years it has been established that the attachment of the distal and proximal stumps of the nerve into either end of a tube can greatly increase the degree of regeneration and performance of the repaired nerve [1]. Silicone rubber has once been a kind of biomaterial which acts as a guidance channel to guide nerve regeneration [2]. However, recently electrically conducting materials are found to be capable of enhancing nerve regeneration. It is demonstrated that poled polyvinylidene fluoride [3, 4] and poled polyterafluoroethylene [5] can enhance neurite outgrowth. And piezoelectric polymer materials such as poly(vinylidene fluoride) and vinylidede fluoride-trifluoridthylene copolymer have also enhanced neural regeneration in mice [1]. The further research has shown that electromagnetic fields have an important influence on neurite extension and regeneration of transected nerve ends [6, 7]. Now, conducting polymers are becoming important materials because the molecular operation produces useful properties: the addition of charged sidegroups to the polymer backbone, alteration of the texture or morphology of the polymeric substrate and adsorption or covalent immoboilization of biologically relevant proteins and peptides to the polymer [8]. Polypyrrole is an interesting polymer because of its easy preparation, stability, wettability and charge density. Certainly, surface properties of the latter two can be reversibly changed with applied electrical potential. In this work, we devised a new system to prepare the polypyrrole tube, and attempted to apply the polypyrrole tube to nerve regeneration. Prior to use, yellow-brown pyrrole (Aldrich Chemical Company, USA) was vacuum-distilled at 129– 131◦C and became a kind of colorless liquid, and then was stored in a sealed-ampoule at 4 ◦C in the absence of light. The silicone tubes in ethyl alcohol were placed in a supersonic bath for 20 min. In the present experiments, the polypyrrole tube on the inner surface of the silicone tube was made by electropolymerization in aqueous solution, which contained 0.2 M freshly distilled pyrrole monomer and 0.1 M potassium chloride. Fig. 1 shows the setup of the experiment system, which includes four parts: the first part is a computer, continuously showing the i-v dynamic curve; the second part is an electrochemistry station (USA), continuously recording the i-v dynamic curve; the third part is a HL-2 constant-flow pump; the forth part is a flow cell. The main body of the cell contains a silicone tube, two stainless steel rings (the working electrode and the counter electrode) and a saturated calomel reference electrode (SCE). The silicone tube is oriented vertically and acts as a backstop of the template synthesis of the polypyrrole tube. Two electrodes are put into either end of the inner surface of the silicone tube respectively and painted by 704-silicone rubber except the parts of rings for insulation. The electrolyte solution containing pyrrole monomer is pumped through the cell by the HL-2 constant-flow pump. The polypyrrole tube is easily formed potentiostatically at 10 V (vs. SCE) from working electrode to counter electrode. In the past experiments, polypyrrole’s biocompatibility with nervous tissue was tested in our laboratory and the results were satisfactory. Research of sciatic nerve regeneration was our destination in this investigation. After the polypyrrole tubes were rinsed in distilled water for 30 min, they were packed with clean white cloth and sterilized by autoclave under 1.3 MPa for 30 min. Then they were dried naturally and stored in dry conditions. Sprague-Dawley (SD) rats weighing approximately 250 g were anaesthetized with 0.6 ml pentobarbital anaesthesia and injected intraperitoneally. The right sciatic nerve was exposed and a part, about 14 mm long, was cut with special pliers. The distal and proximal
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Jun 25, 2014
Peng Bai + 6
Open Access