ساخت و مشخصه‌يابي داربست رسانا بر پايه ژلما-كيتوسان-پلي‌پيرول- نانولوله‌هاي كربني چند ديواره جهت به‌كارگيري در مهندسي بافت عصب

Bridging peripheral nerve gaps remains a significant clinical challenge, as autografts, the current gold stan‎dard, have important limitations due to safety issues an‎d lack of donor tissue. Therefore, the development of advanced scaffolds that can mimic the natural nerve microenvironment structurally an‎d functionally is highly desirable. This study presents a comprehensive, two-step approach to nerve repair, beginning with the design of a novel conductive hydrogel an‎d extending its development to the macroscale for fabrication of a 3D nerve guidance conduit (NGC). In the initial step, a conductive hydrogel composite was optimized using of gelatin methacrylate (GelMA) an‎d the of chitosan as the base matrix, taking advantage of the biomimetic properties of GelMA an‎d inherent biocompatibility of chitosan. In order to provide electroactive properties similar to those of natural nerve tissue, this scaffold was reinforced an‎d modified with a combination of polypyrrole (PPy) an‎d functionalized multi-walled carbon nanotubes (MWCNT-COOH). Among the tested formulations, GelMA/chitosan/1%w/v PPy/1% w/v MWCNT-COOH was identified as the optimal composition, exhibiting an electrical conductivity of 1.54 S·m−1, a compressive modulus of 2.95 MPa, a pore size of 209.107 μm, a swelling rate of 212.86%, an‎d a contact angle of 55.62°. The long-term degradation profile of the optimal scaffold over a 6-week period showed good agreement with the biological stages of nerve repair; the scaffold maintains its structural integrity during the first two weeks an‎d then gradually degraded, coinciding with the tissue maturation an‎d the onset of myelination around week 4, thereby providing necessary space for integration of the newly formed tissue. During this period, this scaffold showed about 61.36% degradation. The results of biocompatibility tests showed that this composite promoted cell viability by day 5 an‎d supported the highest levels of cell proliferation an‎d adhesion in PC-12 an‎d SH-SY5Y cell lines. However, increasing the nanotube concentration to 2% w/v due to aggregation an‎d increased toxicity, reduced the biological performance of the scaffold. In addition, its capacity as a drug carrier was confirmed by its ability to release of ascorbic acid (vitamin C). This optimized vitamin C-loaded hydrogel showed an initial burst release followed by a slower release. The percentage release of vitamin C reached 92.43% at 6 hours an‎d 97.38% at 48 hours. The release mechanism was best fitted by the Korsmeyer-Peppas model (R²=0.9550 an‎d n=0.03794), indicating Fickian diffusion mechanism. The antioxidant assay confirmed the antioxidant activity of the drug-loaded hydrogel at 58.84% compared to the drug-free hydrogel at 17.46%. Based on this optimized material, the second phase of the study focused on the fabrication of the 3D conduit. Next, a single-channel nerve guidance conduit was fabricated by injecting the hydrogel into a 3D-printed mold, followed by UV crosslinking to form a stable polymer network. The resulting conduit exhibited a porous structure with a pore size of 88.29 μm, a compressive modulus of 0.05 MPa, suitable electrical conductivity of 1.19 S·m−1, an‎d a balanced swelling rate of 185.2 %. The results showed that this conduit had significantly lower mass loss than the control over 21 days (31.51% vs. 77.52 %) an‎d, while maintaining better structural porosity, it supported over 90% viability of SH-SY5Y cells an‎d promoted a more elongated an‎d filopodial morphology. This controlled degradation rate is also consistent with the physiological timeline of peripheral nerve regeneration an‎d can provide the mechanical support required during the early stages of repair until axonal bridging occurs. Overall, the findings of this study suggest that the developed conductive nerve guidance conduit may provide a promising multifunctional platform for peripheral nerve regeneration.

شيدا لباف , حسين صالحي

رحمت اله عمادي , انوشه زرگر خرازي , مهدي ابراهيميان حسين آبادي