Katana Dzana, Jayasinghe Suwan N, Trbojevic Sara, Yin Casey M, Rodgers Vanessa R, Almarza Alejandro J, Marra Kacey G
Department of Plastic Surgery, University of Pittsburgh, Pittsburgh, PA, United States of America.
Department of Mechanical Engineering, University College London, London, United Kingdom.
J Neural Eng. 2024 Dec 23;21(6). doi: 10.1088/1741-2552/ad995c.
Peripheral nerve injuries (PNI) represent the most common type of nervous system injuries, resulting in 5 million injuries per year. Current gold standard, autografts, still carry several limitations, including the inappropriate type, size, and function matches in grafted nerves, lack of autologous donor sites, neuroma formation, and secondary surgery incisions. Polymeric nerve conduits, also known as nerve guides, can help overcome the aforementioned issues that limit nerve recovery and regeneration by reducing tissue fibrosis, misdirection of regenerating axons, and the inability to maintain long- distance axonal growth. Polymer-based double-walled microspheres (DWMSs) are designed to locally and in a sustainable fashion deliver bioactive agents. Lysozyme is a natural antimicrobial protein that shares similar physical and chemical properties to glial cell line-derived neurotrophic factor, making it an ideal surrogate molecule to evaluate the release kinetics of encapsulated bioagent from polymeric biodegradable microspheres embedded in polycaprolactone and polycaprolactone/polyurethane blend nerve conduits.Lysozyme was encapsulated in poly(lactic-co-glycolic acid)/poly(L-lactide) DWMSs fabricated through a modified water-oil-water emulsion solvent evaporation method. Lysozyme-loaded DWMS were further embedded in PCL and PCL-PU based nerve guides constructed via polymer dip-coating and electrospinning method respectively. Lysozyme DWMS and nerve guides were imaged using scanning electron microscopy (SEM). Released lysozyme concentration was determined by using a colorimetric micro-BCA protein assay and spectrophotometric quantitation. Tensile and suture pull-out tests were utilized to evaluate the mechanical properties of both dip-coated and electrospun nerve guides, embedded and free of lysozyme DWMS.The study revealed significant distinctions in the lysozyme release profiles, and mechanical properties of the manufactured polymer nerve guides. Both PCL dip-coated and PCL/PU electrospun DWMS-embedded nerve guides revealed biphasic protein release profiles. PCL/PU electrospun and PCL dip-coated nerve guides released 16% and 29% of the total protein concentration within 72 h, plateauing at week 16 and week 8, respectively. SEM analysis of the nerve guides confirmed the homogeneity and integrity of the polymer nerve guides' structures. The electrospun guides were found to be more flexible with a higher extension under stress bending, while the dip-coated PCL nerve guides displayed more rigid behavior.This study provides useful insights on how to optimize nerve guide design and fabrication to enhance recovery progress of PNI.
周围神经损伤（PNI）是最常见的神经系统损伤类型，每年导致500万例损伤。当前的金标准——自体移植，仍存在一些局限性，包括移植神经的类型、大小和功能匹配不当、缺乏自体供体部位、神经瘤形成以及二次手术切口。聚合物神经导管，也称为神经导向器，可以通过减少组织纤维化、再生轴突的误定向以及无法维持长距离轴突生长等问题，帮助克服限制神经恢复和再生的上述问题。基于聚合物的双壁微球（DWMSs）旨在以局部和可持续的方式递送生物活性剂。溶菌酶是一种天然抗菌蛋白，其物理和化学性质与胶质细胞系衍生的神经营养因子相似，使其成为评估包裹在聚己内酯和聚己内酯/聚氨酯混合神经导管中的聚合物可生物降解微球中封装生物制剂释放动力学的理想替代分子。通过改进的水包油包水乳液溶剂蒸发法制备的聚（乳酸-共-乙醇酸）/聚（L-丙交酯）DWMSs中封装了溶菌酶。负载溶菌酶的DWMSs进一步分别通过聚合物浸涂和静电纺丝法嵌入基于PCL和PCL-PU的神经导向器中。使用扫描电子显微镜（SEM）对溶菌酶DWMSs和神经导向器进行成像。通过比色微量BCA蛋白测定法和分光光度法定量测定释放的溶菌酶浓度。利用拉伸和缝线拔出试验评估浸涂和静电纺丝神经导向器（嵌入和未嵌入溶菌酶DWMSs）的力学性能。该研究揭示了所制造的聚合物神经导向器在溶菌酶释放曲线和力学性能方面的显著差异。PCL浸涂和PCL/PU静电纺丝的嵌入DWMSs的神经导向器均显示出双相蛋白释放曲线。PCL/PU静电纺丝和PCL浸涂的神经导向器在72小时内分别释放了总蛋白浓度的16%和29%，分别在第16周和第8周达到平稳状态。对神经导向器的SEM分析证实了聚合物神经导向器结构的均匀性和完整性。发现静电纺丝导向器在应力弯曲下更具柔韧性且延伸性更高，而浸涂PCL神经导向器表现出更刚性的行为。这项研究为如何优化神经导向器的设计和制造以促进周围神经损伤的恢复进程提供了有用的见解。
