骨髓基质干细胞在IKVAV多肽纳米纤维凝胶表面增殖、黏附及向神经细胞诱导分化的研究

目的研究骨髓基质干细胞（BMSCs）与IKVAV多肽纳米纤维凝胶复合的细胞假体应用于脊髓损伤治疗的可行性。方法合成IKVAV多肽两亲性分子，进行自组装，用透射电镜检测。将IKVAV多肽纳米纤维凝胶与BMSCs复合培养，采用倒置显微镜下观察、Calcein—AM／PI染色、CCK-8法、免疫荧光双标法，检测IKVAV多肽对BMSCs增殖、黏附及向神经细胞方向诱导分化的影响。结果IKVAV多肽可成功自组装成纳米纤维凝胶，其与BMSCs复合培养细胞生长良好，活细胞数达90％以上，IKVAV多肽对BMSCs增殖没有影响，可促进BMSCs的黏附，并在诱导BMSCs向神经细胞分化过程中提高神经元分化比例。结论BMSCs在IKVAV多肽纳米纤维凝胶材料表面可良好的增殖及黏附，并可提高其向神经细胞分化过程中神经元的分化比例。     

Nanofiber technology in the ex vivo expansion of cord blood-derived hematopoietic stem cells

Umbilical cord blood (CB) can be used as an alternative source of hematopoietic stem cells (HSCs) for transplantation in hematological and non-hematological disorders. Despite several recognized advantages the limited cell number in CB one unit still restricts its clinical use. The success of transplantation greatly depends on the levels of total nucleated cell and CD34+ cell counts. Thus, many ex vivo strategies have been developed within the last decade in order to solve this obstacle, with more or less success, mainly determined by the degree of difficulty related with maintaining HSCs self-renewal and stemness properties after long-term expansion. Different research groups have developed very promising and diverse CB-derived HSC expansion strategies using nanofiber scaffolds. Here we review the state-of-the-art of nanofiber technology-based CB-derived HSC expansion.     

A bioengineered peripheral nerve construct using aligned peptide amphiphile nanofibers

Peripheral nerve injuries can result in lifelong disability. Primary coaptation is the treatment of choice when the gap between transected nerve ends is short. Long nerve gaps seen in more complex injuries often require autologous nerve grafts or nerve conduits implemented into the repair. Nerve grafts, however, cause morbidity and functional loss at donor sites, which are limited in number. Nerve conduits, in turn, lack an internal scaffold to support and guide axonal regeneration, resulting in decreased efficacy over longer nerve gap lengths. By comparison, peptide amphiphiles (PAs) are molecules that can self-assemble into nanofibers, which can be aligned to mimic the native architecture of peripheral nerve. As such, they represent a potential substrate for use in a bioengineered nerve graft substitute. To examine this, we cultured Schwann cells with bioactive PAs (RGDS-PA, IKVAV-PA) to determine their ability to attach to and proliferate within the biomaterial. Next, we devised a PA construct for use in a peripheral nerve critical sized defect model. Rat sciatic nerve defects were created and reconstructed with autologous nerve, PLGA conduits filled with various forms of aligned PAs, or left unrepaired. Motor and sensory recovery were determined and compared among groups. Our results demonstrate that Schwann cells are able to adhere to and proliferate in aligned PA gels, with greater efficacy in bioactive PAs compared to the backbone-PA alone. In vivo testing revealed recovery of motor and sensory function in animals treated with conduit/PA constructs comparable to animals treated with autologous nerve grafts. Functional recovery in conduit/PA and autologous graft groups was significantly faster than in animals treated with empty PLGA conduits. Histological examinations also demonstrated increased axonal and Schwann cell regeneration within the reconstructed nerve gap in animals treated with conduit/PA constructs. These results indicate that PA nanofibers may represent a promising biomaterial for use in bioengineered peripheral nerve repair.     

Characterization of dielectrophoresis-aligned nanofibrous silk fibroin–chitosan scaffold and its interactions with endothelial cells for tissue engineering applications

Aligned three-dimensional nanofibrous silk fibroin–chitosan (eSFCS) scaffolds were fabricated using dielectrophoresis (DEP) by investigating the effects of alternating current frequency, the presence of ions, the SF:CS ratio and the post-DEP freezing temperature. Scaffolds were characterized with polarized light microscopy to analyze SF polymer chain alignment, atomic force microscopy (AFM) to measure the apparent elastic modulus, and scanning electron microscopy and AFM to analyze scaffold topography. The interaction of human umbilical vein endothelial cells (HUVECs) with eSFCS scaffolds was assessed using immunostaining to assess cell patterning and AFM to measure the apparent elastic modulus of the cells. The eSFCS (50:50) samples prepared at 10 MHz with NaCl had the highest percentage of aligned area as compared to other conditions. As DEP frequency increased from 100 kHz to 10 MHz, fibril sizes decreased significantly. eSFCS (50:50) scaffolds fabricated at 10 MHz in the presence of 5 mM NaCl had a fibril size of 77.96 ± 4.69 nm and an apparent elastic modulus of 39.9 ± 22.4 kPa. HUVECs on eSFCS scaffolds formed aligned and branched capillary-like vascular structures. The elastic modulus of HUVEC cultured on eSFCS was 6.36 ± 2.37 kPa. DEP is a potential tool for fabrication of SFCS scaffolds with aligned nanofibrous structures that can guide vasculature in tissue engineering and repair.     

Electrospinning of polysaccharides for regenerative medicine

Electrospinning techniques enable the production of continuous fibers with dimensions on the scale of nanometers from a wide range of natural and synthetic polymers. The number of recent studies regarding electrospun polysaccharides and their derivatives, which are potentially useful for regenerative medicine, is increasing dramatically. However, difficulties regarding the processibility of the polysaccharides (e.g., poor solubility and high surface tension) have limited their application. In this review, we summarize the characteristics of various polysaccharides such as alginate, cellulose, chitin, chitosan, hyaluronic acid, starch, dextran, and heparin, which are either currently being used or have potential to be used for electrospinning. The recent progress of nanofiber matrices electrospun from polysaccharides and their biomedical applications in tissue engineering, wound dressings, drug delivery, and enzyme immobilization are discussed.     

Electrospun silk biomaterial scaffolds for regenerative medicine

Electrospinning is a versatile technique that enables the development of nanofiber-based biomaterial scaffolds. Scaffolds can be generated that are useful for tissue engineering and regenerative medicine since they mimic the nanoscale properties of certain fibrous components of the native extracellular matrix in tissues. Silk is a natural protein with excellent biocompatibility, remarkable mechanical properties as well as tailorable degradability. Integrating these protein polymer advantages with electrospinning results in scaffolds with combined biochemical, topographical and mechanical cues with versatility for a range of biomaterial, cell and tissue studies and applications. This review covers research related to electrospinning of silk, including process parameters, post treatment of the spun fibers, functionalization of nanofibers, and the potential applications for these material systems in regenerative medicine. Research challenges and future trends are also discussed.     

Stem cell impregnated nanofiber stent sleeve for on-stent production and intravascular delivery of paracrine factors

Stem cell therapies for atherosclerotic diseases are promising, but benefits remain modest with present cell delivery devices in part due to cell washout and immune attack. Many stem cell effects are believed mediated by paracrine factors (PFs) secreted by the stem cells which potentiate tissue repair via activation and enhancement of intrinsic host repair mechanisms We therefore sought to create an “intravascular paracrine factor factory” by harnessing stem cells on a stent using a nanofiber (NF) stent sleeve, and thus providing a sheltered milieu for cells to continuously produce PFs on-stent. The NF sleeve acts as a substrate on which stem cells grow, and as a semi-permeable barrier that protects cells from washout and host immune response while allowing free outward passage of PFs. NF stent sleeves were created by covering stents with electrospun poly-lactic-co-glycolic acid nanofibers and were then uniformly coated with mesenchymal stem cells (MSCs). NF sleeves blocked cell passage but did not hamper MSC attachment or proliferation, and did not alter MSC morphology or surface markers. NF sleeve MSCs continued to secrete PFs that were biologically active and successfully induced tubulogenesis in human endothelial cells. NF stent sleeves seeded with allogeneic MSCs implanted in pigs remained patent at 7 days without thrombotic occlusion or immune rejection. Our results demonstrate the feasibility of creating an intravascular PF factory using a stem cell impregnated NF stent sleeve, and pave the way for animal studies to assess the efficacy of local PF production to treat ischemic artery disease.     

纳米纤维微载体/胶原凝胶复合体系体外肝细胞培养的研究

目的 观察纳米纤维载体/胶原凝胶复合体外肝细胞培养效果.方法 超声振荡制备胶原/丝素纳米纤维载体,与胶原凝胶复合体外培养人肝癌HepG2细胞12d,测定细胞功能.结果 纳米纤维载体/胶原凝胶复合组细胞聚集于纳米纤维载体周围生长,细胞功能持续增高于第9天达到峰值后下降;胶原凝胶培养组中细胞均匀分,细胞功能至第3天达到峰值后迅速下降.结论 纳米纤维载体结合胶原凝胶复合体外肝细胞培养有利于维持肝细胞的白蛋白分泌功能及细胞活性,在生物人工肝中有一定的可行性.     

Delivery of Therapeutics from Layer-by-Layer Electrospun Nanofiber Matrix for Wound Healing: An Update

Increasing incidences of chronic wounds urge the development of effective therapeutic wound treatment. As the conventional wound dressings are found not to comply with all the requirements of an ideal wound dressing, the development of alternative and effective dressings is demanded. Over the past few years, electrospun nanofiber has been recognized as a better system for wound dressing and hence has been studied extensively. Most of the electrospun nanofiber dressings were fabricated as single-layer structure mats. However, this design is less favorable for the effective healing of wounds mainly due to its burst release effect. To address this problem and to simulate the organized skin layer's structure and function, a multilayer structure of wound dressing had been proposed. This design enables a sustained release of the therapeutic agent(s), and more resembles the natural skin extracellular matrix. Multilayer structure is also referred to layer-by-layer (LbL), which has been established as an innovative method of drug incorporation and delivery, combines a high surface area of electrospun nanofibers with the multilayer structure mat. This review focuses on LbL multilayer electrospun nanofiber as a superior strategy in designing an optimal wound dressing.