摘要
聚羟基脂肪酸酯(polyhydroxyalkanoate, PHA)是一系列由微生物合成的天然高分子材料,目前已发现有超过150种组成单体不相同的PHA聚合物。由于最常见也是研究最广泛的PHA——聚3‒羟基丁酸(PHB)具有优良的生物相容性和生物可降解性,且其降解产物3‒羟基丁酸(3HB)对多种疾病具有潜在的治疗功能,PHA相关材料在组织修复与再生领域得到广泛的关注。介绍了不同单体组成的PHA在修复骨缺损、愈合皮肤伤口、重建神经和递送药物等不同组织工程领域的应用,总结了对应的材料制备方法及组织修复机制,为后续PHA的生物医疗应用提供新的思路。
聚羟基脂肪酸酯(PHA)是一系列微生物在过量碳源和有限的氮/磷源存在的不利生长条件下,作为碳源、能量和还原力的存储物质在细胞内合成和积累的微生物线性聚
PHA材料表现出十分优越的材料性能,包括优良的热塑加工性、可调节的机械性能,以及在组织工程领域最值得关注的生物相容性和生物可降解
最常见也是研究最广泛的PHA——聚3‒羟基丁酸酯(PHB)以及其他含有3‒羟基丁酸(3HB)单元的共聚物还具有另一个突出优点:该类聚合物的降解产物3HB具有多种生物活性功能。3HB是哺乳动物酮体的重要组成部分,能够在极端条件下(如长时间运动、饥饿等)为机体提供能
基于以上优势,PHA材料已被广泛用于组织工程、植入材料、药物缓释、医疗保健等多个领域
本文将针对PHA材料在骨、皮肤、神经等组织工程中的应用进行介绍,并简述PHA作为药物载体的应用前景(
组织工程类型 | 具体例子 | 参考文献 |
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骨组织工程 | PHB/羟基磷灰石复合支架 |
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PHBV/磷酸盐玻璃复合材料 |
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PHBHHx 3D支架 |
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P34HB/氧化石墨烯多孔纳米纤维支架 |
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皮肤组织工程 | P34HB静电纺膜作伤口辅料 |
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微流控3D打印仿生P34HB/聚己内酯支架 |
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孔隙可调节的不对称PHA抗菌纤维支架 |
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神经组织工程 | 添加施万细胞或诱导多能干细胞的PHB神经导管 |
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PHBV微球 |
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药物载体 | 装载玫瑰树碱的PHBV纳米粒 |
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装载多西紫杉醇的PHB纳米载体 |
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包封抗生素的PHA微球 |
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携带含GFP基因腺病毒的PHBHHx微球 |
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含有增殖干细胞的可注射PHA高度开放多孔微球 |
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负载肉桂醛的PHBV基介孔生物活性玻璃纳米颗粒 |
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由于PHA材料良好的力学性质和生物相容性等,许多基于PHA(如PHB, PHBHHx,PHBV和P34HB)的支架已被应用于骨组织工程
PHA材料在皮肤组织工程中的修复应用也有较为广泛的研究。Volova等人通过溶剂浇铸和静电纺丝技术分别制备了P34HB膜和由超细纤维组成的无纺布静电纺膜,作为伤口敷料,分别测试了两者促进皮肤修复和再生的能力。在磷酸盐缓冲液中,两种膜没有显著膨胀,也没有快速水解,但P34HB本身的生物降解性保证了它们可以在血液中缓慢生物降解的同时保留其应有的机械强度。相对于传统的溶剂蒸发法得到的P34HB薄膜,静电纺丝膜更有利于干细胞的增殖并向成纤维细胞进行分化,而敷料上存在的成纤维细胞可同时促进伤口愈合、血管形成和再生。同时,细胞分泌的细胞外基质蛋白还可以在静电纺丝膜表面形成一层基质,促进表皮细胞向伤口周围的邻近组织迁
基于以上原理,具有细胞外基质模拟结构(ECM)的仿生支架已在伤口愈合应用中得到广泛研究,但它们不足的机械强度和有限的生物活性仍然是临床应用的主要挑战。为解决这一缺陷,近期一项研究制备了一种微流控3D打印仿生PHA支架。该支架主要由P34HB和聚己内酯(PCL)组成,具备优异的拉伸强度(2.99 MPa)和降解性。它的ECM模拟分层多孔结构允许骨髓间充质干细胞(BMSCs)和人脐静脉内皮细胞(HUVEC)增殖并黏附在支架上。此外,负载BMSCs和HUVEC的各向异性复合支架可以显著促进大鼠伤口缺损中的再上皮化、胶原沉积和毛细血管形成,其表明具有令人满意的体内组织再生活
通过湿法诱导相分离技术,Marcano团队开发了一种孔隙可调节的不对称PHA纤维支架。在抗菌实验中,当细菌与支架接触时,高达33%的表皮葡萄球菌的生物膜形成受到抑制,而26%的已形成的生物膜会被破坏。这种抗菌性能对于解决皮肤组织修复愈合中的感染问题十分有
以上结果均表明了基于PHA的敷料或仿生支架用于皮肤修复和再生的可行性,为皮肤组织工程应用提供了有效的治疗策略和新的应用前景。
神经组织损伤后的神经再生是医学领域的一个重要难题,而PHA基生物材料有望为其提供解决方
动物实验中,Young等人研究了PHB神经导管在兔腓总神经损伤模型中桥接长神经间隙(高达4 cm)的潜力。术后第63天,再生轴突在自体神经移植组和PHB导管组中已经桥接了所有长度的神经间隙,且PHB组的免疫染色再生纤维面积甚至大于自体神经移植组。因此,PHB导管支持周围神经再生的能力至少长达63天,并且适合于长间隙神经损伤修
而在一项具有前瞻性的临床研究中,PHB导管作为神经外缝合的一种替代方法,用于治疗手腕到前臂水平的周围神经损伤。12名有不同程度损伤的患者通过PHB导管或显微外科神经外端缝合进行治疗。在经过18个月的临床、神经生理学、形态学和生理学评估后,大多数结果显示PHB组患者与传统治疗组间不存在显著差异,亦未报告与PHB相关的任何不良事件或并发症。因此,PHB导管可被视为显微外科神经外缝合的安全替代方
除在上述组织工程中的应用外,PHA还可以用作药物载体搭载包括小分子药物、蛋白质、RNA和细胞在内的生物活性物质(BAS)。基于PHA的纳米粒子已广泛用于BAS递送,尤其是用于肿瘤治疗的药
由于局部注射方便且无不良反应,PHA微球在抗肿瘤治疗和组织再生方面具有巨大潜
为了避免使用支架移植进行大型开放手术,已经开发出小型细胞载体并用于修复复杂的组织缺损。Wei等人成功制造了直径为300~360 μm的PHA高度开放多孔微球(OPMs),用作含有增殖干细胞的可注射载
本文系统性地总结了不同种类、不同材料形式的PHA在骨、皮肤和神经修复及药物递送中的应用和进展,充分展示了PHA材料在组织工程中的能力和潜在价值。未来的研究将更多地集中在开发不同单聚或共聚的PHA,应用不同的改性手段使它们适用于新的组织工程场景,并逐步走向临床和市场。
作者贡献声明
陈国强:制定选题,文章撰写与修改。
刘心怡:文献搜集及文章撰写。
刘 絮:文章修改润色。
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