纳米生物材料的应用

纳米生物材料是纳米材料和生物材料交叉而成的一个全新领域。纳米尺度的特殊生物效应使得纳米生物材料具有广泛的应用前景。文章按照纳米材料技术在材料领域的最新应用和经典材料的分类方法,对纳米金属生物材料、纳米无机非金属生物材料、纳米高分子生物材料、纳米复合生物材料的研究现状及应用作了综述。     

组织工程用生物材料与系统

当今以工程科学、生命科学原理开发修复、维持或改善组织功能的生物取代物为目标的组织工程正引起先进国家官、产、学各方面的关注，此高新技术不仅能显著提高对疾患的诊治水平，更能形成组织工程产品市场。本文结合１９９６年在加拿大多伦多举行的第５届世界生物材料大会期间举办的组织工程科学展示会为经纬，介绍相关的研究与开发进展。     

磷酸钙纳米生物材料的合成及烧结研究进展

纳米磷酸钙陶瓷由于其独特的纳米效应,力学性能和生物活性大幅度提升,成为生物医用材料领域研究热点。纳米磷酸钙陶瓷制备的两大难点在于纳米粉体的合成和陶瓷的烧结。对现有的纳米磷酸钙粉体合成和纳米陶瓷烧结工艺进行了全面的综述,归纳分析了不同过程工艺参数对纳米粉体和陶瓷晶粒的影响,并对今后的研究进行了展望。     

生物材料的仿生表面工程

组织工程是迅速发展的交叉学科，材料的细胞亲和性改进是其研究的核心之一。文中从生物材料表面的工程化设计及实现方法的角度出发，评述了组织工程中生物材料的一些进展，并探讨了这类材料的发展方向。     

胶原基生物材料制备与应用研究进展

胶原因具有良好的亲水性、柔韧性和趋化性、生物相容性、生物降解性,被认为是改善组织再生最重要的生物材料之一,并广泛应用于食品、化妆品以及再生医学领域。但是,在提取过程中,胶原的结构和自然交联键会遭到破坏,导致其机械强度、热稳定性和抗酶解能力都低于自然状态。受到天然胶原在组织重塑和修复过程中自然交联的启发,研究人员通过引入外源性交联（化学、物理和生物）来优化胶原基材料的机械强度和稳定性。目前,外源性化学、物理或生物交联已被用于修饰胶原的分子结构,通过这些方法制备的胶原基支架材料的刚度、抗张强度和压缩模量都明显提高,但是材料的延展性降低。这些方法主要是通过限制胶原三螺旋结构分子间α链的自由度,防止胶原微纤维排列的破坏,从而提高胶原的热稳定性和机械强度。另外,通过分子间交联掩盖胶原的酶切割位点,能够提高胶原对酶促降解的抵抗力。但是这些方法仍然有一些缺陷,如存在细胞毒性和降低胶原的活性等。研究者们制备了不同物理结构的胶原基材料（脱细胞基质、海绵、水凝胶、自组装纤维、膜、管和多孔球等）,以更好地促进不同组织或器官的再生。因此,了解胶原基材料的交联方法和制备技术进展,对开发新型的胶原基生物支架材料至...     

高分子生物材料的研究进展

综述了含酯锭和酰胺锭以及酯锭和酰胺锭混合锭的高分子生物材料的合成、改性以及生物相容性等方面的研究成果。富含亲水基团的可降解以及降解产物可被生物体吸收或代谢的高分子材料可满足组织工程的需要,含可偶联蛋白分子、药物分子活性基团的高分子生物材料将有更大的应用潜力．     

生物材料表面灭菌研究进展

综述了近年来生物材料表面灭菌的研究进展,讨论了材料表面细菌形成的原因及主要影响因素,重点阐述了一种新型的材料表面灭菌法的机理,效果及应用前景。     

纳米生物材料及其界面特性对成骨细胞生长影响的研究进展

目前传统生物材料并没有诱发适当的细胞响应,进而再生足够的骨以便使材料/器械维持相当长时间.纳米生物材料可能成为骨修复植入材料的另一选择.从拓扑结构、表面化学和表面亲/疏水性等方面综述了新型纳米材料的界面特性对成骨细胞生长和功能表达的影响.讨论了在骨修复应用中使用纳米生物材料潜在的挑战.     

聚氨酯抗菌生物材料的研究进展

生物材料的植入为细菌粘附提供位点,常引发感染等并发症。聚氨酯材料被称为是理想的生物材料,对它的抗菌改性是近年来的研究热点之一。按照改性方法的不同,综述了10年来聚氨酯生物材料在抗菌改性上的研究进展,并对抗菌抗感染聚氨酯材料的未来发展做出展望。     

中枢神经再生材料研究进展

首先介绍了目前中枢神经再生面临的问题和应对策略,然后系统地综述了脑再生和脊髓再生修复材料的发展。研究发现,成人中枢神经系统内存的神经干细胞和具有特定分化方向的前体细胞具有潜在的、巨大的修复功能;生物支架材料与神经干细胞的联合使用能够较好地控制细胞微环境,有望提高细胞移植后的存活状况,促进中枢神经再生。最后,结合现在中枢神经再生的研究热点——神经干细胞,阐述了中枢神经再生材料调控干细胞的研究进展和潜能,为联合应用生物材料与干细胞促进中枢再生提供了参考。     

Scaffolds for central nervous system tissue engineering

Traumatic injuries to the brain and spinal cord of the central nervous system (CNS) lead to severe and permanent neurological deficits and to date there is no universally accepted treatment. Owing to the profound impact, extensive studies have been carried out aiming at reducing inflammatory responses and overcoming the inhibitory environment in the CNS after injury so as to enhance regeneration. Artificial scaffolds may provide a suitable environment for axonal regeneration and functional recovery, and are of particular importance in cases in which the injury has resulted in a cavitary defect. In this review we discuss development of scaffolds for CNS tissue engineering, focusing on mechanism of CNS injuries, various biomaterials that have been used in studies, and current strategies for designing and fabricating scaffolds.     

Efficient Delivery of Nerve Growth Factors to the Central Nervous System for Neural Regeneration

The central nervous system (CNS) plays a central role in the control of sensory and motor functions, and the disruption of its barriers can result in severe and debilitating neurological disorders. Neurotrophins are promising therapeutic agents for neural regeneration in the damaged CNS. However, their penetration across the blood–brain barrier remains a formidable challenge, representing a bottleneck for brain and spinal cord therapy. Herein, a nanocapsule‐based delivery system is reported that enables intravenously injected nerve growth factor (NGF) to enter the CNS in healthy mice and nonhuman primates. Under pathological conditions, the delivery of NGF enables neural regeneration, tissue remodeling, and functional recovery in mice with spinal cord injury. This technology can be utilized to deliver other neurotrophins and growth factors to the CNS, opening a new avenue for tissue engineering and the treatment of CNS disorders and neurodegenerative diseases.     

A Robust Intrinsically Green Fluorescent Poly(Amidoamine) Dendrimer for Imaging and Traceable Central Nervous System Delivery in Zebrafish

Intrinsically fluorescent poly(amidoamine) dendrimers (IF‐PAMAM) are an emerging class of versatile nanoplatforms for in vitro tracking and bio‐imaging. However, limited tissue penetration of their fluorescence and interference due to auto‐fluorescence arising from biological tissues limit its application in vivo. Herein, a green IF‐PAMAM (FGP) dendrimer is reported and its biocompatibility, circulation, biodistribution and potential role for traceable central nervous system (CNS)‐targeted delivery in zebrafish is evaluated, exploring various routes of administration. Key features of FGP include visible light excitation (488 nm), high fluorescence signal intensity, superior photostability and low interference from tissue auto‐fluorescence. After intravenous injection, FGP shows excellent imaging and tracking performance in zebrafish. Further conjugating FGP with transferrin (FGP‐Tf) significantly increases its penetration through the blood–brain barrier (BBB) and prolongs its circulation in the blood stream. When administering through local intratissue microinjection, including intracranial and intrathecal injection in zebrafish, both FGP and FGP‐Tf exhibit excellent tissue diffusion and effective cellular uptake in the brain and spinal cord, respectively. This makes FGP/FGP‐Tf attractive for in vivo tracing when transporting to the CNS is desired. The work addresses some of the major shortcomings in IF‐PAMAM and provides a promising application of these probes in the development of drug delivery in the CNS.     

A Bioinspired Platform for Effective Delivery of Protein Therapeutics to the Central Nervous System

Central nervous system (CNS) diseases are the leading cause of morbidity and mortality; their treatment, however, remains constrained by the blood–brain barrier (BBB) that impedes the access of most therapeutics to the brain. A CNS delivery platform for protein therapeutics, which is achieved by encapsulating the proteins within nanocapsules that contain choline and acetylcholine analogues, is reported herein. Mediated by nicotinic acetylcholine receptors and choline transporters, such nanocapsules can effectively penetrate the BBB and deliver the therapeutics to the CNS, as demonstrated in mice and non‐human primates. This universal platform, in general, enables the delivery of any protein therapeutics of interest to the brain, opening a new avenue for the treatment of CNS diseases.     

Systemic Delivery of Monoclonal Antibodies to the Central Nervous System for Brain Tumor Therapy

As an essential component of immunotherapy, monoclonal antibodies (mAbs) have emerged as a class of powerful therapeutics for treatment of a broad range of diseases. For central nervous system (CNS) diseases, however, the efficacy remains limited due to their inability to enter the CNS. A platform technology is reported here that enables effective delivery of mAbs to the CNS for brain tumor therapy. This is achieved by encapsulating the mAbs within nanocapsules that contain choline and acetylcholine analogues; such analogues facilitate the penetration of the nanocapsules through the brain–blood barrier and the delivery of mAbs to tumor sites. This platform technology uncages the therapeutic power of mAbs for various CNS diseases that remain poorly treated.     

Self-assembling peptide nanofiber hydrogels for central nervous system regeneration

Central nervous system (CNS) presents a complex regeneration problem due to the inability of central neurons to regenerate correct axonal and dendritic connections. However, recent advances in developmental neurobiology, cell signaling, cell--matrix interaction, and biomaterials technologies have forced a reconsideration of CNS regeneration potentials from the viewpoint of tissue engineering and regenerative medicine. The applications of a novel tissue regeneration-inducing biomaterial and stem cells are thought to be critical for the mission. The use of peptide nanofiber hydrogels in cell therapy and tissue engineering offers promising perspectives for CNS regeneration. Self-assembling peptide undergo a rapid transformation from liquid to gel upon addition of counterions or pH adjustment, directly integrating with the host tissue. The peptide nanofiber hydrogels have mechanical properties that closely match the native central nervous extracellular matrix, which could enhance axonal growth. Such materials can provide an optimal three dimensional microenvironment for encapsulated cells. These materials can also be tailored with bioactive motifs to modulate the wound environment and enhance regeneration. This review intends to detail the recent status of self-assembling peptide nanofiber hydrogels for CNS regeneration.