Biomaterials
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In some types of tracheal disease, tracheal resection is required. For patients with tracheal resection, artificial grafts, made from collagen sponge with a spiral polypropylene stent and mesh, have been clinically used by our group. However, epithelial regeneration was confirmed to be slow. ⋯ The bioengineered scaffolds containing GFBs were covered with tracheal epithelial cells after 1 week, and highly ciliated epithelium was formed after 2 weeks of transplantation. The bioengineered scaffold containing ASCs induced thick epithelium, and then pseudostratified epithelium containing goblet cells was formed. Furthermore, the application of both GFBs and ASCs had synergistic effects on tracheal epithelial regeneration, suggesting that bioengineered scaffolds containing GFBs and ASCs are useful for hastening tracheal epithelial regeneration.
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The objective of our study was to test alternative polymer-on-polymer articulations for cervical total disc arthroplasty with favourable biotribological properties and the benefit of radiolucency in comparison to the clinically well established metal-on-polyethylene coupling. In vitro wear simulation was performed according to ISO 18192-1:2008 (E) with the clinically introduced activ C cervical artificial disc (Aesculap AG Tuttlingen, Germany) made of UHMWPE/CoCr29Mo6 in a direct comparison to experimental disc articulations made of PEEK, CFR-PEEK and PEK. Each material combination was tested for 10 million cycles with a customised 6 station spinal wear simulator (EndoLab Thansau, Germany). ⋯ In conclusion, a number of different candidate materials for total cervical disc arthroplasty were compared using the same disc design. Whereas the polymer-on-polymer articulation of PEK showed no substantial benefit in comparison to polyethylene-on-cobalt-chromium and whereas natural PEEK tends towards pitting and delamination, the carbon fibre reinforced PEEK demonstrated an excellent wear behaviour with a reduction in order of a magnitude. Therefore, the CFR-PEEK based polymer-on-polymer articulations may be an alternative to polyethylene-on-metal and have a high potential for next generation disc replacements.
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Peripheral nerve regeneration for long-term delayed injuries is usually unsatisfied. Here we attempted to use a chitosan/polyglycolic acid (PGA) artificial nerve graft to bridge a long-term delayed 10-mm defect in SD rats based on the previous studies on the graft used for immediate repair of 30-mm-long dog sciatic nerve defects and for clinical treatment of a 35-mm-long median nerve defect at elbow of a human patient. In this study, for experimental groups, the rat sciatic nerve had been transected leaving a 10-mm defect, which was maintained for 3 or 6 months before implantation with the chitosan/PGA artificial nerve graft. ⋯ In experiment groups, nerve regeneration with functional recovery was achieved as measured by electrophysiological and histological techniques, although differences in the quantity and the quality of the regenerated nerve were observed between the 3- and 6-month delayed subgroups. The results showed that: (1) a few denervated Schwann cells survived and sustained their ability to myelinate axons at least 6 months, and (2) the atrophic denervated muscle could be reinnervated by regenerated axons through new muscle-nerve connections. These observations provide the possibility of guiding regenerated axons from survived axotomized neurons to distal nerve stump by the chitosan/PGA artificial nerve graft.
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Sensorineural hearing loss is associated with gradual degeneration of spiral ganglion neurons (SGNs), compromising hearing outcomes with cochlear implant use. Combination of neurotrophin delivery to the cochlea and electrical stimulation from a cochlear implant protects SGNs, prompting research into neurotrophin-eluting polymer electrode coatings. The electrically conducting polypyrrole/para-toluene sulfonate containing neurotrophin-3 (Ppy/pTS/NT3) was applied to 1.7 mm2 cochlear implant electrodes. ⋯ However, guinea pigs implanted with electrically stimulated Ppy/pTS/NT3-coated electrodes had lower electrically-evoked auditory brainstem response thresholds and greater SGN densities in implanted cochleae compared to non-implanted cochleae and compared to animals implanted with Ppy/pTS-coated electrodes (p<0.05). Ppy/pTS/NT3 did not exacerbate fibrous tissue formation and did not affect electrode impedance. Drug-eluting conducting polymer coatings on cochlear implant electrodes present a clinically viable method to promote preservation of SGNs without adversely affecting the function of the cochlear implant.
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Bone morphogenetic proteins (BMPs) have been widely investigated for their clinical use in bone repair and it is known that a suitable carrier matrix to deliver them is essential for optimal bone regeneration within a specific defect site. Fused deposited modeling (FDM) allows for the fabrication of medical grade poly epsilon-caprolactone/tricalcium phosphate (mPCL-TCP) scaffolds with high reproducibility and tailor designed dimensions. Here we loaded FDM fabricated mPCL-TCP/collagen scaffolds with 5 microg recombinant human (rh)BMP-2 and evaluated bone healing within a rat calvarial critical-sized defect. ⋯ A significant up-regulation of the osteogenic proteins, type I collagen and osteocalcin, was evident at both time points in rhBMP-2 groups. Although mineral apposition rates at 15 weeks were statistically equivalent amongst treatment groups, micro-compression and push-out strengths indicated superior bone quality at 15 weeks for defects treated with mPCL-TCP/collagen/rhBMP-2. Consistently over all modalities, the progression of healing was from empty defect