Martinho Nuno, Silva Liana C, Florindo Helena F, Brocchini Steve, Zloh Mire, Barata Teresa S
Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa, Lisbon, Portugal.
Department of Pharmaceutics, UCL School of Pharmacy, London.
Int J Nanomedicine. 2017 Sep 25;12:7053-7073. doi: 10.2147/IJN.S135475. eCollection 2017.
Dendrimers are hyperbranched polymers with a multifunctional architecture that can be tailored for the use in various biomedical applications. Peptide dendrimers are particularly relevant for drug delivery applications due to their versatility and safety profile. The overall lack of knowledge of their three-dimensional structure, conformational behavior and structure-activity relationship has slowed down their development. Fluorophores are often conjugated to dendrimers to study their interaction with biomolecules and provide information about their mechanism of action at the molecular level. However, these probes can change dendrimer surface properties and have a direct impact on their interactions with biomolecules and with lipid membranes. In this study, we have used computer-aided molecular design and molecular dynamics simulations to identify optimal topology of a poly(l-glutamic acid) (PG) backbone dendrimer that allows incorporation of fluorophores in the core with minimal availability for undesired interactions. Extensive all-atom molecular dynamic simulations with the CHARMM force field were carried out for different generations of PG dendrimers with the core modified with a fluorophore (nitrobenzoxadiazole and Oregon Green 488) and various surface groups (glutamic acid, lysine and tryptophan). Analysis of structural and topological features of all designed dendrimers provided information about their size, shape, internal distribution and dynamic behavior. We have found that four generations of a PG dendrimer are needed to ensure minimal exposure of a core-conjugated fluorophore to external environment and absence of undesired interactions regardless of the surface terminal groups. Our findings suggest that NBD-PG-G4 can provide a suitable scaffold to be used for biophysical studies of surface-modified dendrimers to provide a deeper understanding of their intermolecular interactions, mechanisms of action and trafficking in a biological system.
树枝状大分子是具有多功能结构的超支化聚合物，可定制用于各种生物医学应用。肽树枝状大分子因其多功能性和安全性，在药物递送应用中尤为重要。对其三维结构、构象行为和构效关系的全面了解不足，减缓了它们的发展。荧光团常与树枝状大分子共轭，以研究它们与生物分子的相互作用，并在分子水平上提供有关其作用机制的信息。然而，这些探针会改变树枝状大分子的表面性质，并直接影响它们与生物分子和脂质膜的相互作用。在本研究中，我们使用计算机辅助分子设计和分子动力学模拟，来确定聚（L-谷氨酸）（PG）主链树枝状大分子的最佳拓扑结构，该结构允许将荧光团掺入核心，同时将不期望的相互作用降至最低。使用CHARMM力场对不同代数的PG树枝状大分子进行了广泛的全原子分子动力学模拟，其核心用荧光团（硝基苯并恶二唑和俄勒冈绿488）和各种表面基团（谷氨酸、赖氨酸和色氨酸）修饰。对所有设计的树枝状大分子的结构和拓扑特征进行分析，提供了有关其大小、形状、内部分布和动态行为的信息。我们发现，需要四代PG树枝状大分子，以确保核心共轭荧光团对外部环境的暴露最小化，并且无论表面末端基团如何，都不存在不期望的相互作用。我们的研究结果表明，NBD-PG-G4可以提供一个合适的支架，用于表面修饰树枝状大分子的生物物理研究，以更深入地了解它们在生物系统中的分子间相互作用、作用机制和运输过程。
