Gene delivery using dendrimer-entrapped gold nanoparticles as nonviral vectors

Development of highly efficient nonviral gene delivery vectors still remains a great challenge. In this study, we report a new gene delivery vector based on dendrimer-entrapped gold nanoparticles (Au DENPs) with significantly higher gene transfection efficiency than that of dendrimers without AuNPs entrapped. Amine-terminated generation 5 poly(amidoamine) (PAMAM) dendrimers (G5.NH₂) were utilized as templates to synthesize AuNPs with different Au atom/dendrimer molar ratios (25:1, 50:1, 75:1, and 100:1, respectively). The formed Au DENPs were used to complex two different pDNAs encoding luciferase (Luc) and enhanced green fluorescent protein (EGFP), respectively for gene transfection studies. The Au DENPs/pDNA polyplexes with different N/P ratios and compositions of Au DENPs were characterized by gel retardation assay, light scattering, zeta potential measurements, and atomic force microscopic imaging. We show that the Au DENPs can effectively compact the pDNA, allowing for highly efficient gene transfection into the selected cell lines as demonstrated by both Luc assay and fluorescence microscopic imaging of the EGFP expression. The transfection efficiency of Au DENPs with Au atom/dendrimer molar ratio of 25:1 was at least 100 times higher than that of G5.NH₂ dendrimers without AuNPs entrapped at the N/P ratio of 2.5:1. The higher gene transfection efficiency of Au DENPs is primarily due to the fact that the entrapment of AuNPs helps preserve the 3-dimensional spherical morphology of dendrimers, allowing for more efficient interaction between dendrimers and DNA. With the less cytotoxicity than that of G5.NH₂ dendrimers demonstrated by thiazoyl blue tetrazolium bromide assay and higher gene transfection efficiency, it is expected that Au DENPs may be used as a new gene delivery vector for highly efficient transfection of different genes for various biomedical applications.     

基因强化骨组织工程中的病毒载体

背景：不同的基因输送策略也被应用到骨组织工程中以修复破坏的骨组织,作为最有效率的基因转运载体,病毒载体在骨组织工程中的应用方兴未艾。 目的：系统回顾和讨论目前基因强化骨组织工程中常用的病毒载体相关应用。 方法：利用PubMed数据库对2002年1月至2015年1月的相关文献进行了检索,检索的文章主要聚焦在病毒载体基因转导方法和其在骨组织工程中的应用。对腺病毒、反转录病毒、腺相关病毒和嵌合病毒在骨组织工程的相关应用及不足进行了讨论。总共24篇相关文献被纳入此篇综述。 结果与结论：总结了近年来病毒载体联合基因治疗促进骨组织再生的研究工作。讨论了包括装载目的基因的病毒载体联合种子细胞例如间充质干细胞植入支架材料修复骨缺损。研究表明,基因强化的骨组织工程比传统组织工程具有更多的优点;病毒载体介导的基因转染效率比普通载体更高;病毒载体介导的基因强化骨组织工程用于人体的安全性仍需要漫长的临床观察研究。病毒载体系统仍然是最有效的将外源基因转入种子细胞的手段之一。 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：     

Non-viral gene delivery to mesenchymal stem cells: methods, strategies and application in bone tissue engineering and regeneration

Mesenchymal stem cells (MSCs) can be isolated from several tissues in the body, have the ability to self-renewal, show immune suppressive properties and are multipotent, being able to generate various cell types. At present, due to their intrinsic characteristics, MSCs are considered very promising in the area of tissue engineering and regenerative medicine. In this context, genetic modification can be a powerful tool to control the behavior and fate of these cells and be used in the design of new cellular therapies. Viral systems are very effective in the introduction of exogenous genes inside MSCs. However, the risks associated with their use are leading to an increasing search for non-viral approaches to attain the same purpose, even if MSCs have been shown to be more difficult to transfect in this way. In the past few years, progress was made in the development of chemical and physical methods for non-viral gene delivery. Herein, an overview of the application of those methods specifically to MSCs is given and their use in tissue engineering and regenerative medicine therapeutic strategies highlighted using the example of bone tissue. Key issues and future directions in non-viral gene delivery to MSCs are also critically addressed.     

Bisphosphonate-based strategies for bone tissue engineering and orthopedic implants

Bisphosphonates (BPs) are a group of well-established drugs that are applied in the development of metabolic bone disorder-related therapies. There is increasing interest also in the application of BPs in the context of bone tissue engineering, which is the topic of this review, in which an extensive overview of published studies on the development and applications of BPs-based strategies for bone regeneration is provided with special focus on the rationale for the use of different BPs in three-dimensional (3D) bone tissue scaffolds. The different alternatives that are investigated to address the delivery and sustained release of these therapeutic drugs in the nearby tissues are comprehensively discussed, and the most significant published approaches on bisphosphonate-conjugated drugs in multifunctional 3D scaffolds as well as the role of BPs within coatings for the improved fixation of orthopedic implants are presented and critically evaluated. Finally, the authors' views regarding the remaining challenges in the fields and directions for future research efforts are highlighted.     

胶原水凝胶在软骨与骨组织工程中的研究进展

胶原水凝胶因其具有优良的生物相容性、生物力学性能，在软骨与骨组织工程、生物填充材料、创伤修复、药物缓释和细胞培养等医学领域获得广泛的关注和应用。本文重点介绍了胶原水凝胶在软骨与骨组织工程方面的研究进展，详细阐述了胶原水凝胶的性能、交联方法和类型，并对胶原水凝胶在软骨与骨组织工程中的研究现状进行了讨论，对其应用前景进行了展望。     

组织工程学中骨修复材料的研究热点与进展

BACKGROUND: With the improvement in medical level, the clinical demand for bone repair materials is gradually increasing, and the requirements are also getting more and more.     

丝素在骨组织工程中的应用及进展

蚕丝作为缝合线应用于临床已有多年历史,其中的丝素具有良好的生物相容性。丝素可制备成不同性状的新型生物材料如溶液、粉末、薄膜等,用其修复骨缺损的实验研究已相继开展。本文主婪对丝素在骨组织工程中修复骨缺损的应用及前景进行了综述。     

可注射型组织工程骨支架材料的研究进展

可注射型组织工程骨支架材料是一种具有一定形态和机械强度的支架材料,可与种子细胞复合,以流体的形式注射到骨组织缺损部位,最终形成新骨,达到结构恢复和功能重建的目的.此材料具有创伤小、可塑性好的特点,可以修复形态不规则的骨缺损,能够很好地复合生长因子,是目前较为理想的骨组织缺损的修复方式.在众多可注射骨组织工程材料中,生物陶瓷材料、高分子材料等被证明有高度的生物相容性和良好的机械性能,已成为骨组织工程材料方面的研究重点.旨在对生物陶瓷材料、高分子材料、生物陶瓷与高分子复合材料的发展与应用作一综述.     

用组织工程学技术修复骨缺损研究进展

本文从种子细胞、生物材料、纳米科技的应用、组织工程化骨的构建及临床应用等方面对 骨组织工程学研究的进展进行了综述,指出了目前存在的问题和今后的研究方向。     

Cytokine delivery and tissue engineering

Tissue engineering has been applied to various tissues, and particularly significant progress has been made in the areas of skin, cartilage, and bone regeneration. Inclusion of bioactive factors into the synthetic scaffolds has been suggested as one of the possible tissue engineering strategies. The growth factors are polypeptides that transmit signals to modulate cellular activities. They have short half-lives, for example, platelet-derived growth factor (PDGF), isolated from platelets, has a half life of less than 2 minutes when injected intravenously. Extended biological activity and the controlled release of growth factor are achieved by incorporating growth factor into the polymeric device. This review will focus on growth factor delivery for tissue engineering. Particular examples will be given whereby growth factors are delivered from a tissue-engineered device to facilitate wound healing and tissue repair.     

Role of adult mesenchymal stem cells in bone tissue engineering applications: current status and future prospects

Mesenchymal stem cells (MSCs) have been demonstrated as an attractive cell source for tissue-engineering applications because of their ability to be easily isolated and expanded from adult bone marrow aspirates and their versatility for pluripotent differentiation into mesenchymal tissues. This review highlights advances and progress in bone reconstruction techniques for both the repair of site-specific bone defects and the attenuation of musculoskeletal disease symptoms associated with osteoporosis and osteogenesis imperfecta. Despite the enormous potential benefits of MSCs within these approaches, conventional tissue culture methods limit the clinical utility of these cells because of the gradual loss of both their proliferative and differentiation potential during ex vivo expansion. Novel strategies to overcome these limitations are discussed including cultivation in the presence of basic fibroblastic growth factor 2, induction of ectopotic telomerase expression, and ex vivo expansion on various collagenous biomaterials. In addition, this review also outlines mechanistic theories on the potential role of MSC-extracellular matrix interactions in mediating the retention of MSC proliferative and differentiation capacity after ex vivo expansion on collagenous biomaterials.     

基于组织工程应用的生长因子/高分子纳米粒子传递系统的研究进展

有效运载和传递生长因子以调控细胞在支架上的生长行为是组织工程研究中的一个关键问题.高分子纳米粒子是包载生长因子的候选载体之一.介绍了组织工程研究中若干常用生长因子的生物学特性,对包载生长因子用的高分子材料的种类及其纳米粒子的制备方法进行了总结,分析了不同种类材料和制备工艺的优势与缺点;并在此基础上对多种包载生长因子的高分子纳米粒子的研究现状和发展趋势作了综合评述和展望.     

基于组织工程应用的生长因子/高分子纳米粒子传递系统的研究进展

有效运载和传递生长因子以调控细胞在支架上的生长行为是组织工程研究中的一个关键问题.高分子纳米粒子是包载生长因子的候选载体之一.介绍了组织工程研究中若干常用生长因子的生物学特性,对包载生长因子用的高分子材料的种类及其纳米粒子的制备方法进行了总结,分析了不同种类材料和制备工艺的优势与缺点;并在此基础上对多种包载生长因子的高...     

Electrospinning: applications in drug delivery and tissue engineering

Despite its long history and some preliminary work in tissue engineering nearly 30 years ago, electrospinning has not gained widespread interest as a potential polymer processing technique for applications in tissue engineering and drug delivery until the last 5-10 years. This renewed interest can be attributed to electrospinning's relative ease of use, adaptability, and the ability to fabricate fibers with diameters on the nanometer size scale. Furthermore, the electrospinning process affords the opportunity to engineer scaffolds with micro to nanoscale topography and high porosity similar to the natural extracellular matrix (ECM). The inherently high surface to volume ratio of electrospun scaffolds can enhance cell attachment, drug loading, and mass transfer properties. Various materials can be electrospun including: biodegradable, non-degradable, and natural materials. Electrospun fibers can be oriented or arranged randomly, giving control over both the bulk mechanical properties and the biological response to the scaffold. Drugs ranging from antibiotics and anticancer agents to proteins, DNA, and RNA can be incorporated into electrospun scaffolds. Suspensions containing living cells have even been electrospun successfully. The applications of electrospinning in tissue engineering and drug delivery are nearly limitless. This review summarizes the most recent and state of the art work in electrospinning and its uses in tissue engineering and drug delivery.     

Sequential growth factor delivery from complexed microspheres for bone tissue engineering

Aim of the study was to design a 3D tissue-engineering scaffold capable of sequentially delivering two bone morphogenetic proteins (BMP). The novel delivery system consisted of microspheres of polyelectrolyte complexes of poly(4-vinyl pyridine) (P(4)VN) and alginic acid loaded with the growth factors BMP-2 and BMP-7 which themselves were loaded into the scaffolds constructed of PLGA. Microspheres carrying the growth factors were prepared using polyelectrolyte solutions with different concentrations (4-10%) to control the growth factor release rate. Release kinetics was studied using albumin as the model drug and the populations that release their contents very early and very late in the release study were selected to carry BMP-2 and BMP-7, respectively. Foam porosity changed when the microspheres were loaded. Bone marrow derived stem cells (BMSC) from rats were seeded into these foams. Alkaline phosphatase (ALP) activities were found to be lowest and cell proliferation was highest at all time points with foams carrying both the microsphere populations, regardless of BMP presence. With the present doses used neither BMP-2 nor BMP-7 delivery had any direct effect on proliferation, however, they enhanced osteogenic differentiation. Co-administration of BMP enhanced osteogenic differentiation to a higher degree than with their single administration.     

干细胞外泌体治疗骨再生的研究现状与展望

骨再生是复杂的、受精密调控的生理过程,除正常的骨代谢平衡外,骨再生亦发生于骨损伤或骨疾病后的修复过程中。临床上,骨缺损的治疗往往需要通过干预来诱导骨再生,实现的技术手段包括骨移植、生长因子给药、牵引成骨术等。作为近年来新兴的研究领域,外泌体在包括骨缺损在内的一系列适应证中均取得了显著的治疗效果。然而,由于外泌体复杂的化学组成 （由磷脂双分子层包裹的一系列核酸及蛋白质）,其机理研究、样品制备和临床应用均存在一系列障碍。特别是在骨缺损治疗中,外泌体如何通过受体蛋白进入细胞并在细胞内发挥作用,仍存在较多尚未阐明的科学问题。 本篇综述将简要介绍骨缺损相关治疗方法及外泌体相关的基本概念,讨论干细胞来源外泌体在骨缺损治疗中的分子机理, 并介绍 CRISPR-Cas 基因编辑技术等前沿技术手段在研究骨缺损的外泌体治疗中的作用,最后对本领域的未来趋势进行展望。     

骨组织工程支架材料及其相关的研究进展

骨缺损的修复一直是长期以来不断深入研究的重点课题之一.随着组织工程学的兴起,组织工程的原理和技术逐步被应用于人工骨的构建.本文综述了骨组织工程支架材料的种类及复合支架材料的性能、生物学效应和生物安全性评价方法,同时简介了一种新型的具有三维空间网络结构的纳米支架材料--细菌纤维素,其与羟基磷灰石的复合材料作为骨修复和重建材料具有更好的应用前景.     

Biodegradable,phosphate-containing,dual-gelling macromers for cellular delivery in bone tissue engineering

Injectable, biodegradable, dual-gelling macromer solutions were used to encapsulate mesenchymal stem cells (MSCs) within stable hydrogels when elevated to physiologic temperature. Pendant phosphate groups were incorporated in the N-isopropyl acrylamide-based macromers to improve biointegration and facilitate hydrogel degradation. The MSCs were shown to survive the encapsulation process, and live cells were detected within the hydrogels for up to 28 days in vitro. Cell-laden hydrogels were shown to undergo significant mineralization in osteogenic medium. Cell-laden and acellular hydrogels were implanted into a critical-size rat cranial defect for 4 and 12 weeks. Both cell-laden and acellular hydrogels were shown to degrade in vivo and help to facilitate bone growth into the defect. Improved bone bridging of the defect was seen with the incorporation of cells, as well as with higher phosphate content of the macromer. Furthermore, direct bone-to-hydrogel contact was observed in the majority of implants, which is not commonly seen in this model. The ability of these macromers to deliver stem cells while forming in situ and subsequently degrade while facilitating bone ingrowth into the defect makes this class of macromers a promising material for craniofacial bone tissue engineering.     

骨组织工程支架材料--陶瓷化骨

陶瓷化骨作为骨移植材料 ,得到广泛的研究 ,并已应用于临床。由于其具有天然的骨小梁结构 ,可降解 ,无免疫原性 ,是骨组织工程比较理想的支架材料 ,因此越来越受到重视。本文主要综述陶瓷化骨的理化性质、生物学特性及在骨组织工程中的应用     

生物陶瓷与骨组织工程

为修复创伤及病理因素导致的骨缺损 ,骨组织工程是一项迅速发展、不断革新的课题。本文重点综述了国外就生物陶瓷的材料学及其作为骨组织工程细胞支架方面的研究。在分子水平对生物陶瓷理化性质、生物功能以及与细胞间相互作用的认识 ,势必加深对生物陶瓷本身及骨组织工程技术的理解。