Preparation of Enzyme-Degradable Dendritic Macromolecules

以L赖氨酸为原料制备的赖氨酸树枝状大分子有望成为生物相容和可生物降解的纳米材料，应用于药物输送和基因治疗等生物医学领域。支化结构通常由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的作用，ε-氨基的存在降低了赖氨酸树枝状大分子的酶降解能力。当注射到活体中时，降低的降解率可能会导致赖氨酸树枝状大分子的积累。该研究项目旨在生产用于生物医学应用的新型可酶降解树枝状大分子。为了实现这一目标，我们制备了一系列保持每个赖氨酸的ε-氨基的赖氨酸树枝状大分子。还计划对新型赖氨酸树枝状大分子的酶降解进行研究，以评价ε-氨基对酶降解的影响。三聚体和TE…设计了更多由甘氨酸和赖氨酸组成的Tramer作为新型赖氨酸树枝状大分子的构建基团。采用传统的固相合成法，在酸敏三丁基树脂上合成了多肽齐聚物。该多聚体的α-氨基和ε-氨基分别被9-荧甲氧基羰基和叔丁氧基保护。通过核磁共振和MALDI-TOF-MS光谱确证了该多肽齐聚物的结构。采用Fmoc固相合成法，以多肽齐聚物为构建基块，在Wang树脂上合成了赖氨酸树枝状大分子。最终被三氟乙酸裂解，形成去保护的赖氨酸树枝状大分子，每个构筑单元上都有ε-氨基。制备的每一代树枝状大分子和两代树枝状大分子经分析高效液相色谱分离均呈单峰。用MALDI-TOF MS测定了树枝状大分子的相对分子质量。还观察到，与常规多肽合成中BOC基团的去保护情况相比，BOC基团的裂解需要更长的反应时间。由于多肽低聚物难以规模化生产，多肽齐聚物制备高世代树枝状大分子的研究和酶降解研究一直被推迟。虽然这一科研资助项目的期限已经结束，但该项目一直在继续，以创造新的可酶降解的树枝状大分子。较少

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