Preparation and characterization of electrospun PLGA/gelatin nanofibers as a drug delivery system by emulsion electrospinning

Novel biocompatible poly(lactide-co-glycolide) (PLGA) nanofiber mats with favorable biocompatibility and good mechanical strength were prepared, which could serve as an innovative type of tissue engineering scaffold or an ideal controllable drug delivery system. Both hydrophobic and hydrophilic drugs, Cefradine and 5-fluorouracil were successfully loaded into PLGA nanofiber mats by emulsion electrospinning. The natural bioactive protein gelatin (GE) was incorporated into the nanofiber mats to improve the surface properties of the materials for cell adhesion. Nanofibrous scaffolds were characterized by scanning electron microscopy, X-ray diffraction, differential scanning calorimetry, contact angle and tensile measurements. Emulsion electrospun fibers with GE had perfect hydrophilic and good mechanical property. The in vitro release test showed thedrugs released from emulsion electrospun fibers, which achieved lower burst release. The cells cytotoxicity experiment indicated that emulsion electrospun fibers were less toxic and tended to promote fibroblasts cells attachment and proliferation, which implied that the electrospun fibers had promising potential application in tissue engineering or drug delivery.     

静电纺纳米纤维基组织工程大孔支架的研究进展

静电纺丝作为一种纳米纤维支架的仿生构建方法,已在组织工程和再生医学领域中得到越来越多的应用和关注。但是,静电纺支架的主要问题是密集排列的纳米纤维之间的空隙很小,阻碍细胞的长入和三维(3 D)组织的形成。为了解决这一问题,近年来已发展了许多用于扩大静电纺纳米纤维支架孔尺寸的制备方法。首先概述组织工程支架中大孔对细胞行为的影响,然后对静电纺纳米纤维3 D大孔支架的制备方法和技术研究进展进行综述,讨论这些3 D大孔支架促进细胞长入的效果,最后对静电纺3 D大孔支架在组织工程中应用的主要挑战和前景,提出了看法。     

静电纺丝伤口修复载药体系：组分的选择及构建策略

文题释义：静电纺丝伤口修复载药体系：是基于静电纺丝技术制备的一类负载药物的纳米纤维膜。作为伤口敷料或屏障材料,这种纤维膜/药物复合体系具有良好的机械性能、透气性和生物相容性,能够有效隔绝外界刺激保护伤口。进一步地,载药体系可选择负载多样化的活性成分用以促进组织恢复,最终达到促进伤口愈合的效果。该类材料是一类灵活度高、个性化强、可靠有效的伤口组织工程材料。促愈合活性成分：是能够发挥促进伤口组织修复、加速伤口愈合的多类活性物质的合称,包括但不限于具有修复功能的细胞,各种促进组织愈合的生长因子或酶,维生素抗生素等促进或保护伤口的小分子药物,具有抗菌或抗炎作用的金属成分以及其他复杂的天然动植物成分等。这类活性成分的了解和选择常是构建伤口组织工程材料的关键。   摘要背景：静电纺丝纤维膜作为近年来出现的一类性质优良的材料,为促进伤口软组织的愈合提供了新的途径。受益于其纤维基底和活性组分的多样性,静电纺丝伤口修复载药体系构建策略十分灵活。 目的：综述现阶段静电纺丝纤维载药体系的研究进展,依照静电纺丝纤维膜载药体系组分进行机制和功能特点的总结。 方法：利用互联网在Web of Science、PubMed、CNKI、万方数据库中进行检索,中、英文检索关键词为“静电纺丝,伤口敷料,纳米纤维,伤口愈合和药物递送;electrospinning,wound dressing,nanofibers,wound healing,drug deliver”,最终纳入105篇文献进入综述。结果与结论：静电纺丝伤口修复载药体系组成灵活且构建策略多样。通过静电纺丝、不同作用导向的纤维聚合物、干细胞成分及纳米金属颗粒等各具功能生物活性“药物”,能构建多种有效的复合材料体系。该体系可针对伤口愈合过程中的各个环节进行作用,最终达到促进伤口软组织愈合的目的。这种优秀的载药体系/载药思路开拓了整个伤口治疗研究方向的视野,相比传统的凝胶和辅料治疗用品,其多机制、多功能、多可能性的特性使其成为更加先进的伤口处理生物材料。ORCID: 0000-0003-4277-1623(刘艳华) 中国组织工程研究杂志出版内容重点：生物材料;骨生物材料; 口腔生物材料; 纳米材料; 缓释材料; 材料相容性;组织工程     

PCL and PCL-based materials in biomedical applications

Abstract

Biodegradable polymers have met with an increasing demand in medical usage over the last decades. One of such polymers is poly(ε-caprolactone) (PCL), which is a polyester that has been widely used in tissue engineering field for its availability, relatively inexpensive price and suitability for modification. Its chemical and biological properties, physicochemical state, degradability and mechanical strength can be adjusted, and therefore, it can be used under harsh mechanical, physical and chemical conditions without significant loss of its properties. Degradation time of PCL is quite long, thus it is used mainly in the replacement of hard tissues in the body where healing also takes an extended period of time. It is also used at load-bearing tissues of the body by enhancing its stiffness. However, due to its tailorability, use of PCL is not restricted to one type of tissue and it can be extended to engineering of soft tissues by decreasing its molecular weight and degradation time. This review outlines the basic properties of PCL, its composites, blends and copolymers. We report on various techniques for the production of different forms, and provide examples of medical applications such as tissue engineering and drug delivery systems covering the studies performed in the last decades.     

Novel controlled drug delivery system for multiple drugs based on electrospun nanofibers containing nanomicelles

This research described a novel composite electrospun nanofibers, which were consisted of MPEG-b-PLA micelles, chitosan, and PEO, realizing controlled release of both hydrophobic and hydrophilic drugs. 5-FU and Cefradine used as model drugs were successfully loaded in the nanofibers. The in vitro studies showed there was a low initial burst release of 5-FU from micelles-loaded nanofibers, and the final release proportion was about 91.4% after continually releasing for 109?h. In vitro cytotoxicity studies revealed that 5-FU-loaded nanofibers restrained HepG-2 cells efficiently, and the cell viability was 45.9% after three days of cultivation in solutions containing micelles-loaded nanofibers with 21.6?μg 5-FU. All results suggested that micelles-loaded nanofibers with two kinds of drugs can be used as an effective controlled drug delivery vehicle and may have a bright future in cancer chemotherapy or clinical treatments.     

Hierarchical mesoporous silica nanofibers as multifunctional scaffolds for bone tissue regeneration

Mesoporous materials with pore sizes between 2 and 50?nm have elicited widespread interest in catalysis, separation, adsorption, sensors, and drug delivery applications due to its highly ordered pore size along with high hydrothermal stability and easily modifiable surface functionalities. Fabricating these mesoporous materials as continuous fibers offers exciting vistas for biomedical applications especially in tissue engineering. The aim of the present study was to fabricate, characterize, and evaluate the cellular and gene expression of mesoporous silica with a long ordered fibrous morphology to support regeneration of bone tissue. Tetraethyl orthosilicate, polyvinyl pyrrolidone, and the tri-block copolymer P-123 were subjected to electrospinning to fabricate continuous ordered mesoporous silica nanofibers by optimizing solution and operation parameters. Mesoporous silica fibers with an average diameter of 470?nm and mesopores of dimension 5.97?nm were obtained. The combination of micropores, mesopores, macropores, and the nanofibrous morphology imparted excellent bioactivity to the mesoporous silica fibrous scaffolds as demonstrated by the proliferation of human osteoblast-like cells (MG63) and by the maintenance of its phenotype. The upregulation of collagen I, alkaline phosphatase, osteocalcin, osteopontin, and bone sialoprotein signifies the maturation of MG63 cells on the silica scaffold. Hence, these novel scaffolds are promising new biomaterials for orthopaedic applications.     

In vitro and in vivo evaluation of the chitosan/Tur composite film for wound healing applications

We have developed tourmaline/chitosan (Tur/CS) composite films for wound healing applications. The characteristics of composite films were studied by optical microscope, infrared spectra and X-ray diffraction. Tur particles were uniformly distributed in the CS film and the crystal structure of CS was not remarkably changed except the decrease of crystallinity. The influence of Tur on wound healing applications was characterized by modulating Tur concentrations in the Tur/CS composite film prepared by loading Tur powder into CS matrix with different proportion (0, 1/40 and 1/10). Then L929 cells were co-cultured on the composite films to access the cytotoxicity in vitro. Tur concentrations strongly influenced cell process extension. Tur/CS composite film with 1/40 mass ratio could promote the cell adhesion and proliferation. Fewer and shorter processes were observed at high Tur density. When the composite films were transplanted on porcine full-thickness burn wounds, histological results demonstrated that the Tur/CS group with 1/40 mass ratio had a significantly higher number of newly-formed and mature blood vessels, and fastest regeneration of dermis. Based on the observed facts these films can be tailored for their potential utilization in wound healing and skin tissue engineering applications.     

高分子纳米纤维在组织工程支架材料研究中的应用

介绍了高分子纳米纤维的特点、合成方法、生物相容性以及表明修饰,阐明其作为新型支架材料在骨组织工程中的应用价值。     

Molecularly imprinted composite bacterial cellulose nanofibers for antibiotic release

The aim of this work is to develop drug carrier system with high loading capacity and controlled drug release profile for antibiotic release. For this purpose, composite molecularly imprinted nanofibers were prepared via in-situ graft polymerization of methacrylic acid as a monomer, N,N’-methylene bisacrylamide as a crosslinker and gentamicin sulfate as a template molecule onto surface-modified bacterial cellulose nanofibers. Gentamicin imprinted microparticles were fabricated onto bacterial cellulose nanofibers resulting in the formation of composite BC nanofibers. Thus, the composite nanofibers incorporated with gentamicin imprinted microparticles were achieved to fabricated. The in-vitro drug release tests were performed to evaluate the release performance of the resultant composite nanofibers at 37?°C. Also, kinetic models were applied to the drug release data. It was determined that the drug release from the composite molecularly imprinted nanofibers fit well in the Korsmeyer-Peppas model.     

扩张器周围构建自体复合皮修复原位皮肤缺损

背景：目前组织工程皮肤构建时间长,价格贵,修复效果不佳,而且抗原的消除以及疾病传播问题也没有彻底解决。在理想的组织工程皮肤诞生之前,如何利用现有的成熟技术来解决自体皮源奇缺患者的创面修复难题？ 目的：观察扩张器周围构建的自体复合皮用于修复皮肤缺损创面的效果。 方法：取大耳白兔10只,于其背部中线两侧对称部位皮下各埋植一球形硅胶扩张器,待扩张器周围形成纤维包囊后,分别向其中注入原代培养的自体皮肤上皮细胞悬液(实验组)或生理盐水(对照组),4周后取出扩张器,可见实验组形成上皮化的纤维包囊,即自体复合皮。沿扩张囊周边切除扩张器顶部皮肤及部分纤维包膜,而扩张器底面和顶部周边的纤维包囊予以保留,形成自体复合皮覆盖的创面,而对照组创面为非上皮化的纤维包囊覆盖,每日观察创面的愈合状况直至痊愈。 结果与结论：实验组创面红润洁净,分泌物少,平均愈合时间为(14.0±0.4) d,镜下可见上皮层厚而规整;对照组创面分泌物较多,平均愈合时间为(27.0±0.7) d,镜下见上皮层薄且细胞排列不规整。说明应用扩张器周围构建的自体复合皮能明显促进创面愈合。 中国组织工程研究杂志出版内容重点：组织构建;骨细胞;软骨细胞;细胞培养;成纤维细胞;血管内皮细胞;骨质疏松;组织工程全文链接：     

Human cardiomyocyte interaction with electrospun fibrinogen/gelatin nanofibers for myocardial regeneration

Myocardial infarction is the major cause of death in many industrialized nations as it leads to end-stage heart failure. Tissue engineering (TE) approaches for treatment of the infarcted tissue have gained huge attention over the recent years and research in this direction mainly aims for the optimization of a biomaterial scaffold with suitable cell source for tissue regeneration. In this regard, we fabricated completely natural polymeric scaffolds using fibrinogen and gelatin in two different weight ratios and performed cross-linking [Fib/Gel(1:4)-CL; Fib/Gel(2:3)-CL] while cross-linked fibrinogen scaffolds were used as the control. The fiber diameters of the fabricated scaffolds were obtained in the range of 150–300?nm. Chemical characterization of the scaffolds confirmed the presence of both the proteins and showed the absence of any chemical reactions between them. The tensile strength and the stiffness values of Fib/Gel(1:4)-CL matrices were found to be 0.0125 and 0.46?MPa, respectively, which were much similar to the innate properties of the native myocardium. Cell culture studies using human cardiomyocytes revealed higher cell proliferation on Fib/Gel(1:4)-CL scaffolds compared to cell proliferation on Fib/Gel(2:3)-CL scaffolds, which was even higher than the cell proliferation on cross-linked fibrinogen scaffolds. Moreover, the cardiomyocytes seeded on composite substrates expressed the typical functional cardiac proteins such as alpha-actinin, troponin I, connexin-43, and myosin heavy chain, and could be potential for application in cardiac TE.     

组织工程化人工皮肤的构建与应用

体外培养表皮细胞构建组织工程化人工皮肤是促进皮肤缺损创面愈合、提高创面修复质量的新途径。本文就人工皮肤种子细胞研究现状、真皮支架材料的研制、复合人工皮肤的构建与应用作一综述     

Regulation of endothelial cell activation and angiogenesis by injectable peptide nanofibers

RAD16-II peptide nanofibers are promising for vascular tissue engineering and were shown to enhance angiogenesis in vitro and in vivo, although the mechanism remains unknown. We hypothesized that the pro-angiogenic effect of RAD16-II results from low-affinity integrin-dependent interactions of microvascular endothelial cells (MVECs) with RAD motifs. Mouse MVECs were cultured on RAD16-II with or without integrin and MAPK/ERK pathway inhibitors, and angiogenic responses were quantified. The results were validated in vivo using a mouse diabetic wound healing model with impaired neovascularization. RAD16-II stimulated spontaneous capillary morphogenesis, and increased β₃ integrin phosphorylation and VEGF expression in MVECs. These responses were abrogated in the presence of β₃ and MAPK/ERK pathway inhibitors or on the control peptide without RAD motifs. Wide-spectrum integrin inhibitor echistatin completely abolished RAD16-II-mediated capillary morphogenesis in vitro and neovascularization and VEGF expression in the wound in vivo. The addition of the RGD motif to RAD16-II did not change nanofiber architecture or mechanical properties, but resulted in significant decrease in capillary morphogenesis. Overall, these results suggest that low-affinity non-specific interactions between cells and RAD motifs can trigger angiogenic responses via phosphorylation of β₃ integrin and MAPK/ERK pathway, indicating that low-affinity sequences can be used to functionalize biocompatible materials for the regulation of cell migration and angiogenesis, thus expanding the current pool of available motifs that can be used for such functionalization. Incorporation of RAD or similar motifs into protein engineered or hybrid peptide scaffolds may represent a novel strategy for vascular tissue engineering and will further enhance design opportunities for new scaffold materials.     

Genipin-Cross-linked Electrospun Collagen Fibers

The fabrication of a fibrous collagen scaffold using electrospinning is desirable for tissue-engineering applications. Previously, electrospun collagen fibers were shown to be unstable in aqueous environments and, therefore, cross-linking is essential to stabilize these fibers. In this study genipin, a significantly less cytotoxic cross-linking agent compared to glutaraldehyde, was used to cross-link electrospun collagen fibers. The significance of this research lies in the use of four alcohol/water solvent systems to carry out the crosslinking reaction to maintain fibrous morphology during cross-linking. The four cross-linking conditions established were: (1) ethanol, 5% water and 3 days, (2) ethanol, 3% water and 5 days, (3) ethanol, 5% water and 5 days, and (4) isopropanol, 5% water and 5 days at a genipin concentration of 0.03 M. Results illustrated that genipin-cross-linking was effective in maintaining collagen fiber integrity in aqueous and cell culture media environments for up to 7 days. In addition, it was shown that fiber swelling could be controlled by using different cross-linking conditions. Swelling of cross-linked fibers immersed in Dulbecco's modified eagle medium for 7 days ranged from 0 to 59 ± 4%. The cross-linked fibers were analyzed using scanning electron microscopy, Fourier transform infrared spectroscopy and ninhydrin assay. Finally, studies using primary human fibroblasts indicated good cell adhesion to these scaffolds. Overall, our data suggest that these stabilized fibrous collagen scaffolds provide a promising environment for tissue-regeneration applications.     

Preparation and characterization of electrospun in-situ cross-linked gelatin-graphite oxide nanofibers

Electrospun gelatin(Gel) nanofibers scaffold has such defects as poor mechanical property and quick degradation due to high solubility. In this study, the in situ cross-linked electrospinning technique was used for the production of gelatin nanofibers. Deionized water was chosen as the spinning solvent and graphite oxide (GO) was chosen as the enhancer. The morphological structure, porosity, thermal property, moisture absorption, and moisture retention performance, hydrolysis resistance, mechanical property, and biocompatibility of the produced nanofibers were investigated. Compared with in situ cross-linked gelatin nanofibers scaffold, in situ cross-linked Gel-GO nanofibers scaffold has the following features: (1) the hydrophilicity, moisture absorption, and moisture retention performance slightly reduce, while the hydrolysis resistance is improved; (2) the breaking strength, breaking elongation, and Young’s modulus are significantly improved; (3) the porosity slightly reduces while the biocompatibility considerably increases. The in situ cross-linked Gel-GO nanofibers scaffold is likely to be applied in such fields as drug delivery and scaffold for skin tissue engineering.     

天然-人工合成聚合物混合纳米纤维在生物医学领域中的应用

多组分人工合成纳米纤维是纳米技术、材料学与生物学等多学科相结合的产物,代表一类经典的纳米结构,能够充分模拟体内纤维微环境,同时提供必要的拓扑结构、生物力学与生物化学因素来促进组织再生与创伤愈合。这种纤维通过混合天然与人工合成聚合物制备而成,能够产生各组分在力学性质、生物学响应以及材料结构的协同效果,在组织工程与药物释放领域应用中发挥重要的作用。     

A concise review on drug-loaded electrospun nanofibres as promising wound dressings

The diversity of wound types has gathered momentum to develop a wide range of wound dressings to improve different aspects of the wound healing process. Wound healing is a dynamic, complex and highly regulated mechanism of tissue repair and regeneration. The wound dressing should encourage regeneration and prevent possible infection or scaring. Wound dressings are different from the bandages as they come in direct contact with the wound and are used to absorb exudates and accelerate healing. Wound dressings can have a variety of functions, depending upon the type, severity, and position of the wound. In this review, we have studied the properties of nanofibrous wound dresses and possible approaches to load biological components into them for wound healing improvement.     

Chitosan nanoparticle/PCL nanofiber composite for wound dressing and drug delivery

Many investigations of wound dressings equipped with drug delivery systems have recently been conducted. Chitosan is widely used not only as a material for wound dressing by the efficacy of its own, but also as a nanoparticle for drug delivery. In this study, an electrospun polycaprolactone nanofiber composite with chitosan nanoparticles (ChiNP–PCLNF) was fabricated and then evaluated for its drug release and biocompatibility to skin fibroblasts. ChiNP–PCLNF complexes showed no cytotoxicity and nanoparticles adsorbed by van der Waals force were released into aquatic environments and then penetrated into rat primary fibroblasts. Our studies demonstrate the potential for application of ChiNP–PCLNF as a wound dressing system with drug delivery for skin wound healing without side effects.