Novel Nanocomposite Formulation for Highly Effective Oral Insulin Delivery

描述（由申请人提供）：大约2080万美国人被诊断患有糖尿病。此外，美国有近5400万人被诊断为糖尿病前期，这意味着血糖水平升高。据估计，到2030年，全球糖尿病患者人数将增加3.5亿以上。目前，糖尿病是通过肌肉注射或皮下注射胰岛素治疗的。由于患者依从性差，人们一直致力于开发口服胰岛素制剂，这种制剂也有可能模仿非糖尿病患者的生理胰岛素分泌。然而，口服胰岛素递送会遇到两大障碍：导致胰岛素快速降解的酶屏障[1]和限制胰岛素生物利用度的粘膜屏障[2]。目前，通过同时使用蛋白酶抑制剂或将胰岛素包封在保护性载体中，已经在一定程度上绕过了酶屏障，但粘膜屏障仍然是开发有效口服胰岛素递送系统的一个挑战。最近发现的一类细胞穿透肽，广泛称为蛋白质转导结构域（PTD）肽，为最终克服细胞膜屏障提供了一种工具。细胞培养和动物研究都表明，通过将PTD与几乎任何类型的货物，包括大蛋白（MW > 150kda）共价连接，PTD能够将附着的货物运送到所有类型的器官组织中。在这项SBIR拨款申请中，我们提出了一种创新的口服胰岛素递送方法，可能同时克服酶和粘膜障碍。该系统的主要组成部分将是硅-海藻酸盐纳米复合材料，用于保护胰岛素免受降解，靶向胰岛素释放到胃肠道，并控制药物释放速度。胰岛素首先通过化学方法与LMWP（一种已被证实的PTD肽）偶联，然后将偶联物封装到硅-海藻酸盐纳米复合网络中。口服后，复合材料的网状结构可以保护包裹的胰岛素不被胃肠道中的蛋白酶降解，而海藻酸盐表面的黏附功能可以使载体吸附到肠粘膜上。一旦在粘膜部位积累，LMWP强大的细胞穿透活性将允许释放的LMWP-胰岛素偶联物快速穿过上皮细胞层，将具有生物活性的胰岛素直接运送到门静脉循环中。有希望的初步体外研究结果令人信服地表明了所提出系统的可行性。在第一阶段的研究中，我们计划进行决定性的概念验证动物研究，以充分证明该系统的可行性。鉴于糖尿病对经济和社会的巨大影响，所提出的口服胰岛素给药技术的价值是深远的。公共卫生相关性：2002年美国糖尿病协会的一项评估表明，当年糖尿病造成的费用约为1 320亿美元；包括920亿美元的直接医疗支出和400亿美元因生产力损失造成的间接支出。由于几乎所有I型糖尿病患者都需要胰岛素治疗，并且现在也越来越多地用于治疗II型糖尿病患者（目前高达35%的II型糖尿病患者需要胰岛素治疗），有效的胰岛素输送已成为糖尿病临床管理的最终目标。因此，这种高效的胰岛素输送技术的发展不仅会对医疗保健和社会生活产生巨大影响，而且会给这个国家的整体经济带来巨大的利益。

DESCRIPTION (provided by applicant): Approximately 20.8 million Americans are diagnosed with diabetes. Additionally, nearly 54 million people in the U.S. are diagnosed as being pre-diabetic, meaning to suffer from elevated blood glucose levels. Worldwide, the number of people with diabetes has been estimated to increase over 350 million by 2030. Presently, diabetes is treated with insulin injected either intramuscularly or subcutaneously. Because of poor patient compliance, a strong effort has been aimed at developing oral insulin formulations, which also has the potential to mimic physiological insulin secretion seen in non-diabetic individuals. Nevertheless, oral insulin delivery encounters two major barriers: [1] the enzyme barrier that leads to rapid insulin degradation, and [2] the mucosal barrier that limits insulin's bioavailability. Presently, the enzyme barrier has been circumvented to a certain degree by concurrent administration of protease inhibitors or encapsulation of insulin into protective carriers, yet the mucosal barrier remains as a challenge in developing an effective oral insulin delivery system. The recent discovery of a class of cell-penetrating peptides, widely termed as protein transduction domain (PTD) peptides, has provided a tool for finally overcoming the cell membrane barrier. Both cell culture and animal studies demonstrate that by covalently linking PTD to almost any type of cargo, including large proteins (MW >150 kDa), PTD was able to ferry the attached cargo into all types of organ tissues. In this SBIR grant application, we propose an innovative oral insulin delivery approach that could potentially prevail over both the enzyme and mucosal barriers concomitantly. A major component of this system will be a silica-alginate nanocomposite that serves to protect insulin from degradation, target insulin release to the GI tract, and also control drug release rate. Insulin will first be conjugated to LMWP (a proven PTD peptide) by chemical method, and the conjugates will then be encapsulated into a silica-alginate nanocomposite network. Following oral administration, the network structure of the composite would protect entrapped insulin from degradation by proteases in the GI track, whereas the mucoadhesive function of alginate on the surface would provide adsorption of the carriers onto intestinal mucosa. Once accumulated at the mucosal site, the potent cell-penetrating activity of LMWP would allow the released LMWP-insulin conjugates to rapidly cross over the epithelial cell layer, transporting biologically active insulin directly into portal circulation. Promising initial in vitro findings convincingly suggest the plausibility of the proposed system. In this Phase I research, we plan to carry out decisive proof-of-concept animal studies to fully demonstrate the feasibility of this system. Based on the unmatched economical and social impacts of diabetes, the value of the proposed oral insulin delivery technology is far-reaching. PUBLIC HEALTH RELEVANCE: An assessment made by the American Diabetes Association in 2002 indicated that costs attributable to diabetes in that year were approximately $132 billion; including $92 billion in direct medical expenditures and $40 billion in indirect expenditures resulting from lost productivity. Because insulin therapy is required by virtually all patients with type I diabetes, and is also now increasingly used in treating patients with type II diabetes (right now up to 35% of patients with type II diabetes require insulin treatment), effective insulin delivery has become the ultimate goal in clinical management of diabetes. Therefore, the development of this highly effective insulin delivery technology would not only impart tremendous impact on healthcare and social lives but also offer significant benefit to the overall economy of this country.