Development of a Biomimetic Lung Surfactant Replacement

我们建议开发一种新型的生物材料，称为“多肽”，或聚n取代甘氨酸，并将其应用于特定的生物医学问题：需要更有效的合成，功能模拟人类肺表面活性蛋白SP-B和SP-C。肺表面活性剂（LS）是一种表面活性物质，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实现呼吸。LS由95%的表面活性脂质和5%的表面活性剂特异性蛋白质组成；脂质和蛋白质组分都是其功能所必需的。其中两种表面活性剂特异性蛋白，SP- B和SP- c，具有特别的表面活性，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、螺旋状的、两亲性蛋白（分别为79和35个氨基酸）；本质上，就是缩氨酸。妊娠约30周前出生的早产儿出生时肺不成熟，缺乏表面活性剂，需要在出生时提供外源性肺表面活性剂替代品以实现机械通气。目前，最有效的LS替代制剂是动物源性制剂，因此，与任何直接来自动物的药物一样，人们对其纯度水平、制剂一致性和病原体传播的可能性感到担忧。虽然合成的LS替代品确实存在，但它们的效果不如动物源性表面活性剂替代品，主要是因为这些配方缺乏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，这是一种序列特异性异聚物，以类似于合成多肽的方式合成，通过简单的自动化固相协议。类肽具有蛋白酶抗性、仿生螺旋二级结构、低免疫原性和低成本等优点。基于肽的SP-mimics将被合成、纯化，其二级结构和生物物理表面活性将通过体外圆二色光谱和平衡和动态表面测定法进行分析。初步工作证明了这些新型SP-模拟的可行性。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.