Molecular Design of Hyaluronan with Polypeptide Branches of Controlled Structure

说明(申请人提供)：透明质酸(HA)是一种带电的多糖，由于其在结缔组织中的天然含量，对人体免疫系统几乎是“看不见的”。近年来，合成具有可控结构并含有接枝反应所需的末端伯胺的长多肽已成为可能。有人建议使用这一新技术将长长的多肽链偶联到高分子量HA分子的骨架上。由此得到的新型梳状支链HA衍生物有望作为软骨保护滑膜！液体补充剂，用于粘性外科和药物输送。多肽将具有窄的链长分布，并将包含疏水氨基酸(例如亮氨酸)，这些氨基酸在水条件下自组装成α螺旋结构域。由于这些疏水支链，HA衍生物将起到“缔合增稠剂”的作用，可以在注射配方中使用，在相对较低的HA含量下提高用于治疗骨关节炎(OA)的滑液的粘弹性。通过连接支链，较短的HA链可以获得等量的粘弹性增强，并且较短的HA链被认为在促进有利于OA治疗的细胞内信号通路方面更有效。在稍高的浓度下，梳状分支的HA衍生物也可以用作原位凝胶生物材料，这种材料可以低粘度注入体内，一旦进入体内，就会自组装成缔合网络。在分子模拟的指导下，通过明智地选择分支长度、分支间距和多肽化学特性，应该可以调整这些材料的物理性质(凝胶强度、粘弹性、粘度剪切变稀、渗透压)。在未来的改进中，长枝可以用来携带抗氧化剂或对治疗骨关节炎有益的多肽配体。这里提出的研究可能会导致开发更有效和更持久的注射制剂来缓解关节炎相关的疼痛，或者允许进行某些类型的手术，而不会留下更少的疤痕。

DESCRIPTION (provided by applicant): Hyaluronic acid (HA) is a charged polysaccharide that is virtually "invisible" to the body's immune system because of its natural abundance in connective tissues. Recently it has become possible to synthesize long polypeptides having controlled structure and containing terminal primary amines needed for grafting reactions. It is proposed to use this new technique to conjugate long polypeptide chains to the backbones of HA molecules of high molecular weight. The novel comb-branched HA derivatives so obtained are expected to be useful as chondroprotective synovia! fluid supplements, and for use in viscosurgery and in drug delivery. The polypeptides will have a narrow chain length distribution, and will contain hydrophobic amino acids (e.g. leucine) that serf-assemble into alpha-helical domains under aqueous conditions. Due to these hydrophobic branches, the HA derivative will function as an "associative thickener" that can be used in injected formulations to boost the viscoelasticity of synovial fluid for remediation of osteoarthritis (OA) at relatively low HA content. With attached branches, shorter HA chains can be used to obtain equivalent boost in viscoelasticity, and shorter HA chains are thought to be more effective in promoting intracellular signaling pathways beneficial to OA treatment. At somewhat higher concentrations, the comb-branched HA derivative could also be used as an in situ gelling biomaterial that could be injected into the body at low viscosity, and which would self-assemble into an associative network once in place inside the body. It should be possible to tune the physical properties of these materials (gel strength, viscoelasticity, viscosity shear-thinning, osmotic pressure) by judicious choice of branch length, branch spacing, and peptide chemical identity guided by molecular simulations. In future enhancements, the long branches could be used to carry antioxidants or peptide ligands beneficial for treatment of osteoarthritis. The research proposed here may lead to the development of more potent and long-lasting injectable formulations for alleviating the pain associated with arthritis, or allow certain types of surgery to be performed with less scarring.