Engineering Ultrathin Immunomodulatory Coatings for Islet Encapsulation

临床胰岛移植（CIT），将异体胰岛输注到肝脏中，通过提供一种基于细胞的方法来模拟对葡萄糖的正常生理反应，在长期治疗型糖尿病中显示出重大的前景。虽然很有希望，但植入后胰岛功能受损和丧失使其受到抑制。这种损失归因于对移植的强烈炎症和免疫反应，主要是由细胞表面蛋白和抗原引起的。在这个应用中，我们看到通过将胰岛封装在新型超薄聚合物层中，以最大限度地减少导致胰岛植入失败的有害宿主反应。超薄涂层是通过生物正交化学手柄功能化的生物材料的共价层接层组装而成的。通过控制胰岛细胞簇表面聚合物层的共价连接，得到的稳定胶囊比标准做法小500倍；因此，空隙体积大大减少，营养运输和葡萄糖传感不受影响。此外，这些层的组成、结构、厚度和功能可以在纳米尺度上进行复杂的控制。一旦制成，这些超薄层将成为细胞表面工程的理想平台，从而可以将能够与植入物-宿主界面动态相互作用的生物活性基序固定在一起。因此，惰性生物材料层可以转化为能够主动改变局部植入环境的生物活性表面。我们假设，共价稳定的超薄涂层，通过共价层层组装产生，将通过掩盖宿主对表面抗原和蛋白质的识别来增强胰岛的植入和功能持续时间，而不会限制营养物质或胰岛素的扩散。此外，能够指导免疫反应的生物活性药物的系缚将进一步提高移植胰岛的长期存活。为了验证这一假设，将在胰岛表面生成生物稳定的、共价连接的超薄涂层

DESCRIPTION (provided by applicant): Clinical islet transplantation (CIT), the infusion of allogeneic islets into the liver, has shown significant promise in the long-term treatment of Type diabetes by providing a cell-based means to mimic the normal physiological response to glucose. While promising, it is dampened by the impaired function and loss of islets following implantation. This loss is attributed to strong inflammatory and immunological responses to the transplant, primarily instigated by cell surface proteins and antigens. In this application, we see to minimize detrimental host responses that lead to islet engraftment failure by encapsulating the islets in novel ultrathin polymeric layers. Ultrathin coatings are generated through the covalent layer-by-layer assembly of biomaterials functionalized with bioorthogonal chemical handles. Through the controlled, covalent linking of polymers layers on the islet cell cluster surface, resulting stable capsules are on the order of 500-fold smaller than standard practices; thus, void volumes are dramatically reduced and nutritional transport and glucose sensing are unaffected. Further, the composition, structure, thickness, and function of these layers can be intricately controlled on the nanometer scale. Once fabricated, these ultrathin layers serve as ideal platforms for cell surface engineering, whereby bioactive motifs capable of dynamically interacting with implant-host interface can be tethered. As such, the inert biomaterial layer can be converted to a bioactive surface capable of actively altering the localized implant environment. We hypothesize that covalently stabilized, ultrathin coatings, generated via covalent layer-by-layer assembly, will enhance islet engraftment and functional duration by masking host recognition of surface antigens and proteins, without imparting limitations on nutrient or insulin diffusion. In addition, the tethering of bioactive agents capable of instructin immune responses will further enhance long-term survival of the transplanted islets. To test this hypothesis, biostable, covalently-linked, ultrathin coatings will be generated on the islet surface using biocompatible polymers capable of masking surface antigens and inflammatory proteins (Aim 1). Additionally, the surface of ultrathin coatings will be functionalized with immunomodulatory agents capable of directing host innate and adaptive immune responses at the transplant interface (Aim 2). Aims will be evaluated both in vitro and in diabetic murine models. The design of effective strategies to build tailored nano-thin layers on the islet surface capable of expressing active immunomodulatory agents could significantly improve the efficacy and long-term stability of islet transplants in the absence of chronic, systemic immunosuppression.