BIOCOMPATIBLE MEMBRANES FOR ISLET XENOGRAFTS

用于胰岛异种移植物的生物相容性膜

基本信息

批准号：
3243669
负责人：
Peter B Dervan
金额：
$ 9.64万
依托单位：
UNIVERSITY OF TEXAS AT AUSTIN
依托单位国家：
美国
项目类别：
财政年份：
1992
资助国家：
美国
起止时间：
1992-02-01 至 1996-01-31
项目状态：
已结题

项目摘要

Membranes with enhanced biocompatibility will be developed for the immunoisolation of xenogenic islet of Langerhans transplants, and the mechanisms of bioincompatibility will be determined. In a relatively successful technique, a membrane is formed by the coacervation of a polyanionic, water-soluble, nontoxic polymer (algin, a polysaccharide) with a polycationic, water-soluble polymer (polylysine, a polyamino acid). The resulting membrane consists of a hydrogel of mutually entwined, closely interacting negatively and positively charged polymers. Proteins adsorb to this charged membrane and potentiate fibroblast adhesion, spreading, and overgrowth. This process may be initiated or accelerated by inflammation resulting from macrophage spreading and activation on the membrane, which may be stimulated by complement. A novel polymer will be synthesized that has a poly(L-lysine) (abbreviated PLL) backbone with poly(ethylene oxide) (abbreviated PEO) side arms. The polycationic backbone will interact with algin to form a hydrogel membrane, and the nonionic, hydrophilic, PEO side arms will shield the charged surface from the proteins and cells in the biological environment. The permeability and stability of membranes made from coacervates of algin and PLL-graft-PEO will be measured in vitro. Membrane permeance will be assessed by measuring the diffusion of 125I-labeled proteins relative to a mathematical model. Stability in vitro will be assessed by measuring permeance immediately after membrane formation and after 1 month incubation. The biocompatibility of these membranes will be assessed in vitro by measurement of protein adsorption, fibroblast spreading, complement activation, macrophage spreading, and macrophage synthesis of interleukin 1. This will provide insight into the mechanisms of bioincompatibility in these materials. Biocompatibility will be assessed in vivo with islet-free microcapsules in nondiabetic hamsters by measuring the appearance of peritoneal macrophages post-implantation, the attachment of cells to and collagen synthesis upon the microcapsule membranes, and the clumping and incorporation of the microcapsules into the peritoneal tissues. Stability of the capsules in vivo will be assessed by histological examination of peritoneal tissues for broken capsules and by measurement of permeability before implantation and after explantation. Rat islets will be isolated, microencapsulated, and the transplanted intraperitoneally in diabetic golden hamsters. Preliminary in vivo data of 1 month duration with microcapsules made from these materials are presented and lend support to the hypothesis that these microcapsules have enhanced biocompatibility. Microcapsules made with the PLL-graft-PEO material showed dramatically less cell attachment and inflammation than those made with ungrafted PLL.

将开发具有增强生物相容性的膜朗格汉斯移植异种胰岛的免疫分离，以及将确定生物不相容性的机制。在一个相对成功的技术，膜是通过凝聚形成的聚阴离子、水溶性、无毒聚合物（藻胶，一种多糖）聚阳离子水溶性聚合物（聚赖氨酸，聚氨基酸）。这所得膜由相互缠绕、紧密的水凝胶组成带负电和带正电的聚合物相互作用。蛋白质吸附于这种带电膜增强成纤维细胞粘附、扩散和过度生长。该过程可能由炎症启动或加速巨噬细胞在膜上扩散和激活的结果，可能受到补体的刺激。将合成一种新型聚合物，其具有聚（L-赖氨酸）（缩写为 PLL）主链，侧臂为聚环氧乙烷（缩写为 PEO）。这聚阳离子主链将与藻胶相互作用形成水凝胶膜，非离子、亲水性 PEO 侧臂将屏蔽带电生物环境中蛋白质和细胞的表面。这藻胶凝聚层制成的膜的渗透性和稳定性 PLL-graft-PEO 将在体外进行测量。膜的渗透率为通过测量 125I 标记蛋白相对于数学模型。体外稳定性将通过测量来评估膜形成后立即和 1 个月后的渗透孵化。这些膜的生物相容性将在体外通过测量蛋白质吸附、成纤维细胞扩散、补体激活、巨噬细胞扩散和巨噬细胞合成白细胞介素 1。这将深入了解白细胞介素 1 的机制这些材料的生物不相容性。将评估生物相容性通过测量，在非糖尿病仓鼠体内使用无胰岛微胶囊植入后腹膜巨噬细胞的出现，附件细胞和胶原蛋白在微胶囊膜上的合成，以及微胶囊聚集并掺入腹膜组织。胶囊在体内的稳定性将通过以下方式评估腹膜组织的组织学检查是否有破裂的囊膜植入前和移出后渗透性的测量。大鼠胰岛将被分离、微囊化并移植糖尿病金仓鼠腹膜内注射。初步体内数据由这些材料制成的微胶囊可持续 1 个月并支持这些微胶囊增强了生物相容性。 PLL-接枝-PEO材料制成的微胶囊与制造的相比，细胞附着和炎症明显减少具有未嫁接的 PLL。