Development of a Biomimetic Lung Surfactant Replacement

我们建议开发一类新的生物材料，称为多肽，或多N-取代甘氨酸，并将它们应用于特定的生物医学问题：需要更有效的合成、功能模拟的人肺表面活性蛋白SP-B和SP-C。肺表面活性物质(LS)是一种表面活性物质，它覆盖在健康哺乳动物肺的内表面，通过降低肺泡表面的表面张力来促进呼吸。LS由95%的表面活性脂类和5%的表面活性剂特有的蛋白质组成；脂类和蛋白质都是其功能所必需的。其中两种表面活性物质特异性蛋白SP-B和SP-C尤其具有表面活性，对LS在体外和体内的正常生物物理功能至关重要。SP-B和SP-C都是小的、螺旋的两亲性蛋白质(分别为79和35个氨基酸)；本质上，只是多肽。在妊娠30周前出生的早产儿，出生时肺表面活性物质缺乏，需要在出生时给予外源性肺表面活性物质替代，以实现机械通气。目前，最有效的LS替代制剂是动物来源的，因此引起了人们对其纯度水平、配方的一致性和病原体传播潜力的担忧，任何直接来自动物的药物也是如此。虽然人工合成的LS替代品确实存在，但它们的效果不如动物来源的表面活性物质替代品，主要是因为这些配方缺乏对SP-B和SP-C蛋白的良好功能替代品。我们建议开发基于聚N-取代甘氨酸的SP-B和SP-C的功能模拟物。聚-N-取代甘氨酸是以类似于合成多肽的方式合成的序列特异性杂聚体，通过一种简单、自动化的固相方案来实现。S类肽具有抗蛋白酶、仿生螺旋二级结构、免疫原性低、成本低等优点。将合成、纯化基于多肽的SP-模拟物，并利用体外圆二色谱、平衡和动态表面测量法对其二级结构和生物物理表面活性进行分析。这些新型的SP-模拟物的可行性在初步工作中得到了验证。有希望的配方将由合作者在体内进行测试。

We propose to develop a novel class of biomaterials called "polypeptoids," or poly-N-substituted glycines, and to apply them to a specific biomedical problem: the need for more effective synthetic, functional mimics of the human lung surfactant proteins SP-B and SP-C. Lung surfactant (LS) is a surface-active material that coats the internal surfaces of healthy mammalian lungs and enables breathing, by reducing the surface tension on the alveolar surfaces. LS is composed of 95 percent surface-active lipids and 5 percent surfactant-specific proteins; both lipid and protein fractions are necessary for its functioning. Two of these surfactant-specific proteins, SP- B, and SP-C, are especially surface-active and are critical for the proper biophysical functioning of LS in vitro and in vivo. SP-B and SP-C are both small, helical, amphipathic proteins (79 and 35 amino acids, respectively); essentially, just peptides. Premature infants born before about 30 weeks of gestation are born with immature lungs lacking surfactant, and require the delivery of an exogenous lung surfactant replacement at birth to enable mechanical ventilation. At present, the most efficacious LS replacement formulations are animal- derived, and therefore raise concerns about their level of purity, their consistency of formulation, and their potential for pathogen transmission, as do any medicines sourced directly from animals. While synthetic LS replacements do exist, they do not work as well as animal- derived surfactant replacements, primarily because these formulations lack good functional replacements for SP-B and SP-C proteins. We propose to develop functional mimics of SP-B and SP-C based on poly-N-substituted glycines, which are sequence- specific heteropolymers synthesized in a similar manner to synthetic polypeptides, by a facile, automated solid-phase protocol. Peptoids offer the advantage s of protease- resistance, biomimetic helical secondary structure, low immunogenicity, and low cost. Peptoid-based SP-mimics will be synthesized, purified, and their secondary structure and biophysical surface activities will be analyzed in vitro circular dichroism spectroscopy and by equilibrium and dynamic surfactometry. The feasibility of these novel SP- mimics is demonstrated in preliminary work. Promising formulations will be tested in vivo by a collaborator.