A supramolecular protein-binding system based on multivalent interactions was investigated using β-cyclodextrin-grafted chitosan (BCC) and insulin. 1H NMR and fluorescence analyses revealed that BCC binds to insulin through electrostatic and hostâguest interactions. The binding constant KBCC for the hostâguest interaction between cyclodextrin (CyD) residues in BCC and Tyr and Phe residues in insulin was 478.7 Mâ1 in acetate buffer at pH 3.6, which was ca. 3-fold greater than the Kchi attributed to electrostatic interactions between chitosan and the Tyr residues of insulin. Furthermore, KBCC was â¼10 times greater than that of β-CyD (KCyD), suggesting that multivalent interactions composed of electrostatic and hostâguest interactions strongly enhance the hostâguest interaction, similar to enzymes and antibodies in living systems. Enhanced hostâguest interactions resulted in effective insulin binding over a wide pH range (3.6â7.4) as well as stabilization against digestive enzymes. BCC and insulin formed supramolecular aggregates with significantly different morphologies depending on the buffer species used: a network structure in acetate buffer, nanoparticles in citrate buffer, and large aggregates in phosphate buffer. The network structure formed in acetate buffer was maintained even after dilution with phosphate buffer, a situation that mimics the environment after oral administration. In addition, the structure was fragmented easily after application of a mild force, which could be an important property for achieving absorption of proteinâpeptide drugs from the gastrointestinal tract. This study provides new insights for the development of CyD-based nanoarchitectures suitable for application as proteinâpeptide carriers for oral drug delivery.
基于多价相互作用的超分子蛋白质结合系统已通过β-
环糊精接枝
壳聚糖(BCC)和
胰岛素进行了研究。1H NMR和荧光分析表明,BCC通过静电和主客体相互作用与
胰岛素结合。在pH 3.6的
醋酸盐缓冲液中,BCC中的
环糊精(CyD)残基与
胰岛素中的
酪氨酸和苯丙
氨酸残基之间主客体相互作用的结合常数KBCC为478.7 M⁻¹,大约是巯基之间静电相互作用结合常数Kchi的3倍。此外,KBCC大约是β-CyD(KCyD)的10倍,这表明静电和主客体相互作用组成的多价相互作用强烈增强了主客体相互作用,类似于生命系统中的酶和
抗体。增强的主客体相互作用导致
胰岛素在广泛的pH范围(3.6-7.4)内有效结合以及抵抗消化酶的稳定性。BCC和
胰岛素根据使用的缓冲液种类不同,形成了具有显著不同形态的超分子聚集体:
醋酸盐缓冲液中的网络结构,
柠檬酸盐缓冲液中的纳米颗粒,以及
磷酸盐缓冲液中的大聚集体。在
醋酸盐缓冲液中形成的网络结构甚至在用
磷酸盐缓冲液稀释后仍保持不变,这种情况模拟了口服给药后的环境。此外,该结构在施加轻微力后易于破碎,这可能是蛋白质-肽药物从胃肠道吸收的重要特性。这项研究为开发适用于口服药物递送的蛋白质-肽载体提供了新的纳米建筑设计思路。