Presidential Young Investigator Award: Membrane Science

将生物活性物质包封成膜已成为一个具有巨大工业应用潜力的重要研究领域。这些系统允许被捕获的物质在体内受到保护，免于失活或降解，也允许延迟或控制释放动力学。采用天然存在的物质作为载体的系统，如磷脂囊泡和再密封的红细胞膜，在生物相容性方面具有一定的优势。然而，这些载体系统的一个主要缺点是它们在递送部位缺乏特异性。如果这个问题能得到解决，它们的使用将会取得巨大的进步。影响这些系统在体内存活和靶向的两个最重要的物理特性是可变形性和粘附性。研究表明，大的磷脂囊泡被困在静脉注射后到达的第一个毛细血管床上，它们也难以从循环中移动到间隙中。这些问题可能是由于它们缺乏可变形性。完整的红细胞在通过毛细血管进入间隙时能够变形。然而，有可能这些细胞的形态在分子掺入重新密封的红细胞后发生剧烈变化。到目前为止，这些系统的变形特性还没有被量化。这些载体在体内对特定细胞的靶向也在很大程度上取决于通过循环传播过程中载体-内皮细胞的相互作用以及外渗到组织空间后载体-细胞的相互作用。这些相互作用强烈地依赖于系统的粘附特性。因此，有可能通过改变载体的粘附特性来实现特异性靶向。目前的研究主要集中在正常细胞和转基因细胞的变形性和粘附性的研究上。该实验室配备了最先进的视频显微镜系统，该系统采用微移液管吸入技术和微观流动室，分别量化膜的变形和粘附特性。最近的研究结果表明，基因改变正常成纤维细胞，可以改变膜的粘附性和变形性。目前正在使用生化分析对这些细胞进行测试，以确定导致所观察到的特性的粘附分子和结构特征。在PYI奖期间，细胞膜方面的专业知识将用于研究再密封红细胞膜和磷脂囊泡的粘附、变形和运输特性，最终目标是生产最佳的载体系统。

The encapsulation of biologically active substances into membranes has emerged as an important research area with great potential for industrial applications. These systems permit entrapped substances to be protected in vivo from inactivation or degradation and also permit delayed or controlled kinetics of release. Systems which employ naturally occurring substances as carriers, such as phospholipid vesicles and resealed erythrocyte membranes, have certain advantages with respect to biocompatibility. However, a major drawback of these carrier systems is their lack of specificity in site of delivery. If this could be solved, great strides in their use would be made. Two of the most important physical properties that can effect in vivo survival and targeting of these systems are deformability and adhesion. It has been shown that large phospholipid vesicles become entrapped in the first capillary bed reached after i.v. administration and they also have difficulty in moving from the circulation into the interstitial space. It is possible that these problems could be attributed to their lack of deformability. Intact erythrocytes are able to deform during passage through capillaries and into the interstitial space. However, it is possible that the morphology of these cells change drastically following the incorporation of molecules into the resealed erythrocyte. To date, the deformation characteristics of these systems have not been quantified. Targeting of these carriers to specific cells in vivo also depends a great deal on carrier-endothelial cell interactions during dissemination through the circulation and carrier-cell interactions following extravasation into the tissue space. These interactions are strongly dependent on the adhesion properties of the systems. Hence, it is possible that specific targeting could be accomplished by modifying the adhesion properties of the carriers. Current research is focused on the investigation of deformability and adhesion properties of both normal and genetically altered cells. The laboratory is equipped with a state-of-the-art video microscopy system that employs the micropipette aspiration technique and a microscopic flow chamber to quantify both deformation and adhesion properties of membranes, respectively. Recent results show that genetically altering normal fibroblast cells, modify membrane adhesion and deformability properties. The cells are currently being tested, using biochemical assays, to determine the adhesion molecules and structural characteristics responsible for the properties observed. During the period of the PYI award, expertise in cellular membranes will be employed to investigate adhesion, deformation and transport properties of resealed erythrocytes membranes and phospholipid vesicles with the ultimate goal of producing optimal carrier systems.