微囊化移植的研究进展

微囊移植技术能起有效的免疫隔离作用，为解决排斥反应、供体缺乏等问题提供了新思路。目前以海藻酸钠-多聚赖氨酸-海藻酸钠(APA)微囊发展最为成熟，但最近海藻酸-钡交联微囊也受到众多研究者的好评。微囊具有良好的免疫隔离作用，可使移植物较长时间存活，并维持良好功能。猪胰岛已经成为人们公认的良好供体。微囊移植虽尚不适于临床，但经不断完善必将在临床上有广泛的应用前景。     

微囊化组织细胞移植的研究进展

微囊化包被组织细胞移植可发挥免疫隔离作用 ,为解决治疗疾病中的免疫排斥反应和移植物来源短缺提供了新途径。海藻酸钠 /多聚赖氨酸 /海藻酸钠 (APA)微囊是目前最成熟的微囊化技术 ,其高度的生物相容性和良好的免疫隔离作用 ,使得异种组织细胞或基因工程细胞移植成为可能 ,在神经内分泌及代谢疾病方面的研究取得了可喜的进展 ,具有广阔的应用前景。     

海藻酸钠微囊制备方法及应用的研究

经过研究者们几十年的不懈努力，海藻酸钠微囊化免疫隔离技术已日臻完善。大量研究已经证实了微囊的免疫隔离作用，用它包被组织细胞进行移植可以减少或消除移植中的免疫排斥反应，避免使用副作用大的免疫抑制药物，并且扩大了组织细胞移植来源的种属范围。近些年来，微囊化免疫隔离技术在治疗多种疾病的过程中获得了突破性进展，但若想将其应用于临床治疗中，尚有待于进一步的研究探索。     

人工膜与胰岛移植

人工膜是目前应用于组织移植和细胞移植领域中一种免疫隔离物质.包括渗透性小腔、中空纤维管、海藻酸钠—多聚赖氨酸—海藻酸钠微囊三种.它们均在一定程度上对免疫细胞、淋巴因子及自身抗体起到免疫隔离作用,其中以海藻酸钠微囊应用比较广泛.微囊化胰岛在同种及异种胰岛移植中,可有效地控制糖尿病模型的血糖浓度,延长移植物存活时间.     

APA微囊移植免疫隔离效果的研究

目的：探讨海藻酸钠-多聚赖氨酸-海藻酸钠(APA)微囊在宿主体内的免疫隔离作用。方法：分别将APA空微囊、牛嗜铬细胞(BCCs)和APA微囊化BCCs(APA-BCCs)移植到绵羊的蛛网膜下腔中，观察宿主细胞免疫指标和组织形态学的变化。结果：各组移植后血中淋巴细胞数量无明显变化；APA微囊包裹可明显阻止BCCs移植引起的血中CD4^ T淋巴细胞比例、CD4^ ／CD8^ 值和脑脊液中淋巴细胞数量的增加；APA微囊包裹可减轻羊移植区组织反应，延长移植物的存活。结论：APA微囊具有免疫隔离效果，可有效地阻止细胞免疫排斥反应。     

应用微囊化转基因细胞进行小鼠腹腔移植的实验研究

目的:探讨微囊化转基因细胞用于异体细胞移植治疗的可能性。方法:使用静电液滴技术制备海藻酸钠-壳聚糖微胶囊,包埋转入癌胚抗原部分基因的人成纤维样骨髓基质细胞,进行实验小鼠腹腔移植。结果:微囊化人源细胞移植到小鼠腹腔3个月内,细胞可以继续生长、增殖并提高小鼠的兔疫功能。结论:海藻酸钠-壳聚糖作为成囊材料具有良好的生物相容性、囊膜强度和免疫隔离作用;微囊化细胞移植有助于扩大异体移植的细胞来源,并为构建微囊化转基因细胞疫苗治疗恶性肿瘤的研究提供了可靠的依据。     

微囊化细胞移植的研究进展

微囊技术为组织 /细胞移植开辟了新途径 ,它有效地避免了移植后的免疫排斥反应 ,并解决了移植物来源稀少的问题。微囊的包裹材料有多种 ,以海藻酸钠—多聚赖氨酸—海藻酸钠 (APA)应用最为广泛 ,可通过提高其生物相容性 ,从而减弱免疫排斥反应。微囊具有良好的免疫隔离作用 ,体现在对免疫活性细胞及部分细胞因子的阻挡作用 ,使移植物能存活下来并能发挥其功能。目前对微囊化人工细胞的研究取得了很大的进展 ,特别是基因工程细胞日益成为研究的焦点。微囊技术是一新兴的、尚需进一步改进的技术 ,它在异体组织 /细胞移植等方面必将有广阔的应用前景     

微囊化细胞移植的研究进展

微囊技术为组织／细胞移植开辟了新途径,它有产地避免了移植后的免疫排斥反应,并解决了移植物来源稀少的问题。微囊的包裹材料有多种,以海藻酸钠－多聚赖氨酸－海藻酸钠（APA）应用最为广泛,可通过提高其生物相容性,从而减弱免疫排斥反应。微囊具有良好的免疫隔离作用。体现在对免疫活性细胞及部分细胞因子的阻挡作用,使移植物能存活下来并能发挥其功能,目前对微囊化人工细胞的研究取得了很大的进展,特别是基因工程细胞日益成为研究的焦点。微囊技术是一新兴的,尚需进一步改进的技术,它在异体组织／细胞移植等方面必将有广阔的应用前景。     

APA微囊细胞移植的免疫隔离作用

随着器官移植研究的深入,诸如移植物排斥反应、供体缺乏等一系列问题出现在人们面前。1980年,Lim等[1]首次采用微囊免疫隔离技术进行胰岛微囊化移植研究,为人类解决这些问题提供了新思路。微囊化免疫隔离技术近些年取得了众多成就,目前研究表明由海藻酸钠—多聚赖氨酸—海藻酸钠(APA)构成的微胶囊具有制作简便、体积小、生物相容性好等优点,是应用前景较好的免疫隔离膜[2]。本文将就其免疫隔离效果的研究进展作如下综述。1发展史60年代Chang[3]首次提出人工细胞的概念,即用具有生物相容性的半透膜包裹组织细胞,该膜允许小分子营养物、代谢…     

胰岛移植用免疫隔离微胶囊的牢固度、生物相容性和通透性研究

目的为了探讨用于胰岛移植的海藻酸钠-聚赖氨酸-海藻酸钠（APA）生物膜的免疫隔离效果。方法采用高压静电成囊装置,制备APA微胶囊和微囊化胰岛,微囊直径为0.25～0.55mm;取空微囊,利用恒温振荡仪振荡后测定其破损率;将空微囊移植至小鼠腹腔,分别于不同时间由腹腔中灌洗出微胶囊,记数并观察其形态;取一定量空微囊分别与IgG、BSA和胰蛋白酶孵育,测量其浓度变化确定APA微胶囊的通透性。结果采用高压静电成囊技术制成的APA微胶囊呈球形,大小均匀、表面光滑,具有较好的生物相容性;粒径为0.25～0.35mm的微胶囊其牢固度大于粒径为0.45～0.55mm的微胶囊;葡萄糖、胰岛素等小分子物质能够自由通过微囊膜,胰蛋白酶也可通过,但速度较慢;大分子物质牛血清白蛋白和免疫球蛋白则不能透入APA微囊。结论采用高压静电成囊技术可制备高质量粒径为0.25～0.35mm的微胶囊;这是具有良好免疫隔离性能的APA微胶囊。     

Modeling and optimization of membrane preparation conditions of the alginate-based microcapsules with response surface methodology

Microencapsulation has been a promising approach for drug delivery, cell implantation, cell-based gene therapy and large-scale cell culture. To make use of microcapsules more effectively, it is important to accurately construct the microcapsule membranes with desired properties including a certain thickness, strength, and so forth. To date single factor experiments have been widely used, however, they are time-consuming to obtain the desired membrane preparation conditions. Response surface methodology (RSM) is a mathematical and statistical technique for building empirical models that gained importance for optimizing reacting conditions. In this study, three signifficant effect factors that affect alginate-based microcapsule membrane properties, including membrane thickness, swelling degree, and mechanical stability, were determined with Plackett-Burman method, and then three empirical models were built to optimize the preparation conditions of the microcapsule membranes according to the responses of these three signifficant effect factors respectively with RSM. These models can be used to predict the characteristics of microcapsules under different membrane preparation conditions, which provide a guide for optimizing the microencapsulation technology.     

Optimization of microencapsulated recombinant CHO cell growth, endostatin production, and stability of microcapsule in vivo

Microencapsulation of recombinant cells secreting endostatin offers a promising approach to tumor gene therapy in which therapeutic protein is delivered in a sustainable and long-term fashion by encapsulated recombinant cells. However, the studies of cell growth and protein production in vivo are very limited. In this study, the effects of microencapsulation parameters on in vivo cell growth, endostatin production, and microcapsule stability after implantation in the peritoneal cavity of mice were for the first time investigated. Microcapsules with liquid core reached higher cell density and endostatin production at day 18 than microcapsules with solid core. There was no significant difference in stability whether the core of the microcapsule was solid or liquid. Decrease in microcapsule size increased the stability of microcapsule. The microcapsules kept intact in the peritoneal cavity of mice after 36 days of implantation when the microcapsules size was 240 microm in diameter, which gave rise to high endostatin production as well. The optimized microencapsulation conditions for in vivo implantation are liquid core and 240 microm in diameter. This study provides useful information for antiangiogenic gene therapy to tumors using microencapsulated recombinant cells.     

Prevention of lethality and suppression of proinflammatory cytokines in experimental septic shock by microencapsulated CNI-1493.

CNI-1493, a newly developed, water-soluble tetravalent guanylhydrazone, is a powerful inhibitor of tumor necrosis factor (TNF) and interleukin-1 (IL-1) synthesis. Microencapsulation of drugs into microcapsules that target macrophages has improved the effectiveness of both TNF and IL-1 neutralizing antibodies in experimental models of septic shock. It is the purpose of this study to determine if microencapsulation of CNI-1493 will improve cytokine inhibition. CNI-1493 was microencapsulated using albumin into 1 microm spheres. Comparable amounts of CNI-1493 in solution and in microencapsulated form were added to 1 ml aliquots of whole blood along with 100 ng of endotoxin. TNF and IL-1 were measured by ELISA. Microencapsulated CNI-1493 was also given to rats with endotoxic shock (15 mg/kg Escherichia coli endotoxin) and rats with peritonitis induced by peritoneally injecting 10(10) CFU E. coli. Equivalent amounts of encapsulated and solution CN I-493 were given intravenously. Endotoxin 15 mg/kg was also given to rats 6 and 24 h after a dose of encapsulated CNI-1493 to determine the duration of action of encapsulated drug. The microencapsulated CNI-1493 produced significantly greater inhibition of TNF and IL-1 at all doses in the whole blood model. There was significantly improved survival and cytokine inhibition in the endotoxic shock model as well as the peritonitis model in rats treated with microencapsulated CNI-1493. There was also 83% survival in rats given endotoxin 24 h after a dose of encapsulated CNI-1493. From these data, we conclude that CNI-1493 is a potent inhibitor of cytokine production and is greatly potentiated by microencapsulation, which transports the drug to macrophages.     

Encapsulated cell grafts to treat cellular deficiencies and dysfunction

Cell transplantation provides a therapeutic alternative to whole organ transplantation in the management of diseases arising from the absence or failure of specialized cells. Though allogenic transplantation is favorable in terms of graft acceptance, xenotransplantation can provide a potentially unlimited source of cells and can overcome shortage of human donors. Effective immunoisolation of the xenografts is critical for their long term survival and function. Encapsulation of cells in polymeric matrices, organic or inorganic, provides a physical selectively permeable barrier between the host and the graft, thereby immunoisolating the graft. Microencapsulation of cells in alginate hydrogels has been pervasive, but this approach does not provide precise control over porosity, whereas micro- and nano-fabrication technologies can provide precise and reproducible control over porosity. We highlight both encapsulation approaches in this review, with their relative advantages and challenges. We also highlight the therapeutic potential of encapsulated cells for treating a variety of diseases, detailing the xenotransplantation of pancreatic islets in diabetes therapy as well as the grafting of engineered cells that facilitate localized enzyme-prodrug therapy of pancreatic cancer.     

原位定型微囊化载体制剂在糖尿病大鼠皮肤溃疡中的作用

背景：原位定型微囊化载体制剂成分之一胰岛素可以促进溃疡愈合。 目的：观察原位定型微囊化载体制剂在糖尿病大鼠皮肤溃疡中的疗效。 方法：腹腔内注射链脲佐菌素建立糖尿病大鼠模型,应用外科方法建立全层皮肤缺损模型。根据皮肤溃疡处干预方式将实验动物分为4组。①空白对照组用生理盐水处理创面。②一般制剂组应用甲硝唑+山莨菪硷1+普通短效胰岛素处理创面。③单纯微囊组创面外敷不含有效药物成分的微囊化载体膜。④微囊化有效制剂组溃疡处外涂微囊化载体制剂膜,内含药物成分与一般制剂组相同。定时测量溃疡面积,记录溃疡愈合时间,取创面全层组织进行组织学观察,测定表皮生长因子受体、纤维连接蛋白阳性细胞数量。 结果与结论：微囊化有效制剂组大鼠溃疡愈合时间短于其他3组(P < 0.05或P < 0.01),微囊化有效制剂组表皮生长因子受体和纤维连接蛋白阳性细胞数目高于其他各组(P < 0.05或P < 0.01)。结果表明,原位定型微囊化载体制剂能够缩短愈合时间和促进糖尿病大鼠皮肤溃疡愈合。     

Alginate-based microcapsules generated with the coaxial electrospray method for clinical application

Alginate-based microencapsulation of cells has made a significant impact on the fields of regenerative medicine and tissue engineering mainly because of its ability to provide immunoisolation for the encapsulated material. This characteristic has allowed for the successful transplantation of non-autologous cells in several clinical trials for life threatening conditions, such as diabetes, myocardial infarction, and neurodegenerative disorders. Methods for alginate hydrogel microencapsulation have been well developed for various types of cells and can generate microcapsules of different diameters, degradation time, and composition. It appears the most prominent and successful method in clinical applications is the coaxial electrospray method, which can be used to generate both homogenous and non-homogeneous microcapsules with uniform size on the order of 100 μm. The present review aims to discuss why alginate hydrogel is an ideal biomaterial for the encapsulation of cells, how alginate-based microcapsules are generated, and methods of modifying the microcapsules for specific clinical treatments. This review will also discuss clinical applications that have utilized alginate-based microencapsulation in the treatment of diabetes, ischemic heart disease, and neurodegenerative diseases.     

Microfabricated airflow nozzle for microencapsulation of living cells into 150 micrometer microcapsules

Microencapsulation of genetically engineered cells has attracted much attention as an alternative nonviral strategy to gene therapy. Though smaller microcapsules (i.e. less than 300 μm) theoretically have various advantages, technical limitations made it difficult to prove this notion. We have developed a novel microfabricated device, namely a micro-airflow-nozzle (MAN), to produce 100 to 300 μm alginate microcapsules with a narrow size distribution. The MAN is composed of a nozzle with a 60 μm internal diameter for an alginate solution channel and airflow channels next to the nozzle. An alginate solution extruded through the nozzle was sheared by the airflow. The resulting alginate droplets fell directly into a CaCl₂ solution, and calcium alginate beads were formed. The device enabled us to successfully encapsulate living cells into 150 μm microcapsules, as well as control microcapsule size by simply changing the airflow rate. The encapsulated cells had a higher growth rate and greater secretion activity of marker protein in 150 μm microcapsules compared to larger microcapsules prepared by conventional methods because of their high diffusion efficiency and effective scaffold surface area. The advantages of smaller microcapsules offer new prospects for the advancement of microencapsulation technology.     

A three-dimensional microfluidic approach to scaling up microencapsulation of cells

Current applications of the microencapsulation technique include the use of encapsulated islet cells to treat Type 1 diabetes, and encapsulated hepatocytes for providing temporary but adequate metabolic support to allow spontaneous liver regeneration, or as a bridge to liver transplantation for patients with chronic liver disease. Also, microcapsules can be used for controlled delivery of therapeutic drugs. The two most widely used devices for microencapsulation are the air-syringe pump droplet generator and the electrostatic bead generator, each of which is fitted with a single needle through which droplets of cells suspended in alginate solution are produced and cross-linked into microbeads. A major drawback in the design of these instruments is that they are incapable of producing sufficient numbers of microcapsules in a short-time period to permit mass production of encapsulated and viable cells for transplantation in large animals and humans. We present in this paper a microfluidic approach to scaling up cell and protein encapsulations. The microfluidic chip consists of a 3D air supply and multi-nozzle outlet for microcapsule generation. It has one alginate inlet and one compressed air intlet. The outlet has 8 nozzles, each having 380 micrometers inner diameter, which produce hydrogel microspheres ranging from 500 to 700 μm in diameter. These nozzles are concentrically surrounded by air nozzles with 2 mm inner diameter. There are two tubes connected at the top to allow the air to escape as the alginate solution fills up the chamber. A variable flow pump 115 V is used to pump alginate solution and Tygon? tubing is used to connect in-house air supply to the air channel and peristaltic/syringe pump to the alginate chamber. A pressure regulator is used to control the flow rate of air. We have encapsulated islets and proteins with this high throughput device, which is expected to improve product quality control in microencapsulation of cells, and hence the outcome of their transplantation.     

细胞微囊化技术的研究进展

细胞微囊化是将目的细胞包裹于一种或几种生物相容性良好且具有半透膜特性的材料内,既可实现免疫隔离、防止大分子免疫物质和免疫细胞攻击,又允许代谢产物、小分子营养物及细胞活性物质自由出入微囊.随着跨学科技术的不断进步,细胞微囊化技术显示出越来越广阔的应用前景,有望用于弥补器官移植的多种局限.同时随着细胞微囊化技术的日益发展和成熟,其在再生医学方面不断显示出强大的优势,必将推动人工细胞和人工器官领域快速发展.对细胞微囊的制作、微囊外膜对免疫大分子物质和细胞因子的作用、微囊外膜的免疫原性及细胞微囊化技术的代表性应用作一综述.     

Islet encapsulation with living cells for improvement of biocompatibility

Bioartificial pancreas, microencapsulation of islets of Langerhans (islets) within devices has been studied as a safe and simple technique for islet transplantation without the need for immuno-suppressive therapy. Various types of bioartificial pancreas have been proposed and developed such as microcapsule, macrocapsule and diffusion chamber types. However, these materials comprising a bioartificial pancreas are not completely inert and may induce foreign body and inflammatory reactions. The residual materials would be a problem in human body. Here we propose an alternative method for microencapsulation of islets with a layer of living cells. We immobilized HEK293 cells (human endoderm kidney cell line) to the islet surface using amphiphilic poly(ethylene glycol)-conjugated phospholid derivative and biotin/streptavidin reaction and encapsulated islets with a cell layer by culture. No necrosis of islet cells at the center was seen after microencapsulation with a layer of living cells. Insulin secretion ability by glucose stimulation was well maintained on these cell-encapsulated islets.