Preparation of Enzyme-Degradable Dendritic Macromolecules

以l -赖氨酸为起始材料制备的树状大分子有望成为生物相容性和可生物降解的纳米材料，用于生物医学应用，如药物传递和基因治疗。分支结构通常由α和ε-氨基与赖氨酸的羧基偶联而成。由于ε-氨基在生物识别中起着重要作用，ε-氨基的缺失降低了赖氨酸树状大分子被酶降解的能力。可降解性的降低可能导致赖氨酸树突状物在注射到活体时的积累。该研究项目旨在生产用于生物医学应用的新型酶降解树状大分子。为了达到这一目的，制备了一系列保留赖氨酸ε-氨基的赖氨酸树状大分子。研究了新型赖氨酸树状大分子的酶降解，并评价了ε-氨基对酶降解的影响。设计了由甘氨酸和赖氨酸组成的三聚体和二聚体作为新型赖氨酸树状大分子的构建单元。采用常规固相法在酸敏三烷基树脂上制备了多肽低聚物。肽低聚物的α-氨基和ε-氨基分别被9-氟酰甲氧羰基（Fmoc）和t-丁氧羰基（BOC）保护。通过核磁共振和MALDI-TOF质谱测定证实了肽低聚物的结构。以多肽低聚物为基元，在wang -树脂上采用Fmoc固相合成策略制备了赖氨酸树状大分子。三氟乙酸对其进行最终裂解，形成了去保护赖氨酸树状大分子，每个构建单元上都有ε-氨基。制备型高效液相色谱纯化的第一代和第二代树状大分子在分析型高效液相色谱中呈单峰。用MALDI-TOF质谱测定了树状大分子的分子量。还观察到，与常规肽合成中银基团的脱保护情况相比，中银基团的裂解需要更长的反应时间。由于多肽低聚物难以大规模生产，因此从多肽低聚物制备高代树状大分子和酶降解研究一直被推迟。虽然这个科研资助项目的期限已经结束，但为了创造新的酶降解树状大分子，这个项目一直在继续进行。少

Lysine Dendrimers prepared from L-lysine as a starting material are expected to be biocompatible and biodegradable nano materials for biomedical applications, such as drug delivery and gene therapy. The branching architecture is usually prepared by the coupling reaction of both α-and ε-amino groups with the carboxylic group of lysine. Since the ε-amino group plays important roles in biological recognition, the luck of ε-amino group reduces the degradability of the lysine dendrimers by enzymes. The reduced degradability may cause the accumulation of the lysine dendrimer when injected to a living body. The research project aims to produce new enzyme-degradable dendrimers for biomedical application. In order to achieve the goal, a series of lysine dendrimers which remain the ε-amino group of each lysine was prepared. The study on the degradation of the novel lysine dendrimers by enzymes was also planned to evaluate the effect of the ε-amino group on enzymatic degradation.The trimer and te … More tramer composed of glycine and lysine were designed as building blocks for the novel lysine dendrimers. The peptide oligomers were prepared by conventional solid-phase synthesis on the acid sensitive trityl-resin. The α-and ε-amino groups of the peptide oligomers were protected by 9-fluorenylmethoxycarbonyl (Fmoc) and t-butoxycarbonyl (BOC) groups, respectively. The structure of the peptide oligomers was confirmed by NMR and MALDI-TOF MS spectroscopic measurements. The lysine dendrimers were prepared using the peptide oligomers as building blocks by Fmoc solid-phase synthetic strategy on Wang-resin. The final cleavage by trifluoroacetic acid resulted in the formation of the deprotected lysine dendrimers which had the ε-amino groups on each building unit. The each generation one and two dendrimer purified by preparative HPLC showed a single peak by analytical HPLC. The molecular weight of the dendrimers was confirmed by the MALDI-TOF MS measurement. It was also observed that the cleavage of the BOC groups required prolonged reaction time in comparison with the case of deprotection of BOC groups for conventional peptide syntheses. The preparation of high-generation dendrimers from the peptide oligomers and the enzymatic degradation study have been postponed due to the difficulty in mass production of the peptide oligomer. Although the term of this research project supported by Grand-in-Aid for scientific research c was finished, the project has continuously been pursued in order to create new enzyme-degradable dendrimers. Less